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With light streaming out of our cities at night, with roads and power lines etched

across most landscapes, any visitor from another planet would be well aware of

human activities long before arriving on earth. A conservation biologist might argue

that Homo sapiens is only one of many millions of species that constitute life on earth,

but there is no denying that people are a dominant life-form. As we have captured

more and more of the earth’s resources, allowing our population and biomass to

grow larger and larger, many other species have declined or even disappeared. Indeed,

you could build a strong argument that we have degraded the overall ability of the

earth to support life given the area occupied by human activity and the amount of

photosynthesis appropriated by people (Vitousek et al. 1997; Rojstaczer et al. 2001;

Sanderson et al. 2002a; Haberl et al. 2004; Imhoff et al. 2004) (Fig. 8.1).

In this chapter we will examine the various ways in which people diminish the

earth’s ability to support a diverse biota. To begin, we need to make some key distinctions,

starting with habitat versus ecosystem. A habitat is the physical and biological

environment used by an individual, a population, a species, or perhaps a group of

species (Hall et al. 1997). In other words, at the species level we can speak of blue

whale habitat and sequoia habitat, and perhaps waterfowl habitat. However, if the

group of species is too broad, the term becomes so general as to be almost meaningless.

What does “wild life habitat” mean if virtually every environment supports wild

organisms? Even a parking lot will have microbes and small invertebrates living in the

cracks in the pavement. An ecosystem is a group of organisms and their physical

environment (see Chapter 4), such as a lake or a forest, and it may or may not correspond

to the habitat of a species. A forest ecosystem may constitute the sole habitat of

a squirrel, but a frog’s habitat might include both the forest and a lake, and a bark

beetle’s habitat might only be certain species of trees spread widely across the forest.

We can also make a distinction between degradation and loss of habitats or ecosystems.

Habitat degradation is the process by which habitat quality for a given species is

diminished: for example, when contaminants reduce a species’s ability to reproduce in

an area. When habitat quality is so low that the environment is no longer usable by a

given species, then habitat loss has occurred. The line between habitat degradation

and loss will often be unclear. For example, if environmental changes prevent a

species from reproducing, but some individuals can still be found (e.g. dispersing juvenile

animals, or a few old trees that survive, but whose seeds never survive), is this

habitat loss or severe degradation? Sometimes, these differences can be clarified if we

describe the types of habitat use more explicitly: for example, by referring to breeding

CHAPTER 8

Ecosystem

Degradation and Loss

Ecosystem Degradation and Loss 151

habitat, foraging habitat, winter habitat, and so on. Note that habitat loss or degradation

for one species will probably constitute habitat gain or enhancement for some

other species. For example, cutting a forest is likely to degrade or destroy habitat for a

squirrel, but the resulting early successional ecosystem is likely to be new habitat for

at least one butterfly species. A more poignant example comes from the Everglades,

where managing the hydrological regime means choosing between the habitat of two

endangered species: wood storks (which need periods of very limited water to concentrate

their food in residual pools) and snail kites (which need long, wet periods)

(Bancroft et al. 1992; Beissinger 1995; Curnutt et al. 2000).

Ecosystem degradation occurs when alterations to an ecosystem degrade or destroy

habitat for many of the species that constitute the ecosystem. For example, when

warm water from a power plant increases the temperature of a river, causing many

temperature-sensitive species to disappear, this is ecosystem degradation by a conservation

biologist’s definition. In contrast, an ecosystem ecologist might focus on

changes in ecosystem function such as a reduction in productivity, rather than on

structural attributes such as the abundance and diversity of biota. Ecosystem loss

occurs when the changes to an ecosystem are so profound and when so many

species, particularly those that dominate the ecosystem, are lost that the ecosystem

is converted to another type. Deforestation and draining wetlands are just two of

many processes that destroy ecosystems.

Let us consider a hypothetical example to illustrate these distinctions. Imagine a

small forest park on the edge of city in which there are many dead and dying trees

Figure 8.1 This map shows the human footprint, a quantitative depiction of human influence on the land surface,

based on geographic data on human population density, land transformation, transportation and electrical power

infrastructure, and normalized to reflect the continuum of human influence across each terrestrial biome defined

within biogeographic realms. Further details are available at the “Atlas of the Human Footprint” website

(www.wcs.org/humanfootprint) and in Sanderson et al. (2002a). (Map provided by the Wildlife Conservation Society.)

(i.e. snags). The park manager might decide to make this forest safer for walkers by

removing all snags near paths. This would degrade the park’s value as a habitat for

the many species that require snags, such as woodpeckers and termites. If the manager

were very thorough and cut down every snag in the park, regardless of its location,

this would constitute habitat loss for snag-dependent species. Assuming

snag-associated species were more than a trivial portion of the forest’s biota, then loss

of snags would also lead to ecosystem degradation. Removing the forest to create a

golf course would constitute ecosystem loss.

There are many ways to degrade or destroy habitats or ecosystems, and in this chapter

we can only provide a broad overview. We will begin with two sections on what

humans add to natural environments: (1) substances that contaminate air, water, soil,

and biota; and (2) physical structures such as roads, dams, and buildings. The third section

covers some of the ways we modify physical environments by eroding soil, consuming

water, and changing fire regimes. In the fourth, fifth, and sixth sections we will

review three major processes by which ecosystems are destroyed or severely degraded:

deforestation, desertification, and the various processes afflicting wetlands and aquatic

ecosystems (e.g. draining and filling). We will not focus on two of the major causes of

ecosystem loss and species endangerment: conversion of ecosystems to urban areas and

agriculture (Czech et al. 2000; McKinney 2002). Their direct effects are so unsubtle

that they do not require much elaboration; we will discuss how to mitigate their impacts

in Chapter 12, “Managing Ecosystems.” Finally, we will discuss fragmentation, a process

by which ecosystem destruction can isolate the biota of those ecosystems that remain

intact. For the sake of simplicity we will cover each issue independently, but realize that

in the real world many problems occur simultaneously and interact with one another.

Two special forms of ecosystem degradation – overexploitation of biota and introduction

of exotic species – will be covered in Chapters 9 and 10, “Overexploitation” and

“Invasive Exotics.” Note that all these sundry threats are direct, proximate causes of loss

of biodiversity. As with so many problems, the ultimate cause is human overpopulation

and overconsumption, but we will reserve discussion of this topic until Part IV, “The

Human Factors.” One deadly enterprise merits special mention here: war. The human

dimensions of war’s tragedies are all too familiar, and it takes but a moment’s reflection

to extend its images – ravaged lands, shattered bodies – to all biota. As you read the following

chapter, realize that virtually all the activities described here can become part of

a war machine with dire and far-reaching consequences (Westing 1980; Dudley et al.

2002). Indeed, long after a war is over, elephants, rhinos, and any large, marketable

animals will continue to suffer from the widespread distribution of weaponry.

Contamination

One might define a pollutant or contaminant as a substance that is where we do not

want it to be. This suggests that substances often do not stay where we put them; they

move. There are three main media that can move pollutants – air, water, and living

organisms – and we will structure our overview of the topic by focusing on air pollution,

water pollution, and pesticides. Note that there is overlap among these media; for

example, acid rain begins as air pollutants and ends up contaminating a lake or causing

increased concentrations of heavy metals in biota. Pesticides can be distributed by air or

water, but we will focus on those that move from organism to organism in a food web.

152 Part II Threats to Biodiversity

Air Pollution

Every day huge quantities of materials are lofted into the atmosphere from our vehicles,

factories, and homes. Nitrogen oxides and sulfur oxides combine with water to

form nitric and sulfuric acids, the basis of acid rain. Chlorofluorocarbons (CFCs) and

halons rise to the upper atmosphere, where they reduce the concentration of ozone,

allowing more harmful ultraviolet radiation to reach the earth’s surface. Closer to

earth, ozone and a suite of other chemicals form toxic clouds called smog.

Through extensive research we know that these and other forms of air pollution

have impaired the health of people and domestic plants and animals (Holgate et al.

1999). We know less about the effects of air pollution on wild species, but given the

basic similarity in the physiology of domestic and wild species, it is likely that they are

also affected (Barker and Tingey 1992). Certainly severe air pollution has even killed

the majority of plant species downwind from some factories (Fig. 8.2). No doubt

many animal species also become locally extinct in these zones, but it would be hard

to know if they were directly eliminated by air pollution or simply disappeared

because of the loss of plant species. Even moderate levels of air pollution are known

to eradicate many lichen species; in fact this relationship is so well documented that

lichens are widely used to monitor air pollution (Gombert et al. 2005).

Chronic effects that diminish an individual’s health and vigor, and thereby reduce

reproductive success or longevity, are probably more common than acute effects that kill

organisms directly. For example, in parts of Belgium great tits have reduced reproductive

success that appears to be correlated to heavy metal contamination (Janssens et al. 2003).

Ecosystem Degradation and Loss 153

Figure 8.2 Fumes from a copper smelter killed most of the vegetation in the Copper

Basin, Tennessee. This photo was taken in 1945, about 25 years after the fumes were

controlled. (Photo from USDA Forest Service.)

154 Part II Threats to Biodiversity

Even species living far from the source of air pollution may be affected. Notably,

declines in some remote amphibian populations (Houlahan et al. 2000; Beebee and

Griffiths 2005) might be linked to air pollution because of its effects on the acidity of

aquatic ecosystems, global climate, pesticides, and ultraviolet radiation. For example,

some research indicates that certain amphibian species, especially those living at high

altitudes, are vulnerable to ultraviolet-B radiation (e.g. Blaustein et al. 2003); at least

one paper has directly implicated climate change in the loss of many frog species at a

Costa Rican site (Pounds et al. 1999; see Chapter 6); and Fig. 8.3 presents a case where

pesticides carried by the wind were implicated. Similarly, one of the major threats to

coral reefs can probably be traced to global climate change induced by air pollution;

Figure 8.3

Analysis of the

spatial patterns of

dominant winds

(arrows) and agricultural

lands

(shaded areas) indicated

that air pollution

by pesticides

is likely to have

played a major role

in the decline of

four species of

frogs in California

(Davidson et al.

2002). Two other

species seemed to

have been more

affected by direct

habitat loss; climate

change and

ultraviolet radiation

did not seem

important in this

system.

unusually warm water temperatures are thought to be a primary cause of “bleaching,”

the massive death of coral polyps (West and Salm 2003).

Water Pollution

The list of substances with which we pollute aquatic ecosystems is very diverse. It

includes innocuous materials such as mud and plant matter that may become

contaminants only when they reach such high concentrations that they smother the

bottom of aquatic ecosystems or use up all the oxygen as they decompose. The list

also includes chemicals such as nitrates and phosphates that are important nutrients

for aquatic plants, but can lead to an excessive growth of plants, upsetting the balance

of an aquatic ecosystem. On the other hand, there are chemicals such as dioxin

that endanger life at concentrations so low that they are measured in parts per billion.

Some pollutants are routinely discharged into aquatic ecosystems from factories and

sewage treatment plants. Others enter in a catastrophic deluge after an accident such

as the rupture of an oil tanker. Still others, such as sediments, pesticides, and fertilizers,

often seep in gradually, carried by the runoff from our agricultural fields, lawns,

and streets. When pollutants originate from broad areas, these places are called nonpoint

sources, in contrast to specific sites (e.g. factories), which are called point sources.

It may surprise you to know that nonpoint-source pollution, usually involving

sediments and nutrients and not highly toxic chemicals, is considered the leading

threat to endangered freshwater species in the United States (Richter et al. 1997).

Not surprisingly, aquatic species and ecosystems are more threatened by water pollution

than are terrestrial biota. On a local scale, there are many lakes, streams,

rivers, and bays where water pollution has eliminated so many species that it would

be fair to say that the aquatic ecosystem has been destroyed, even though a body of

water and a handful of species remain. One of Europe’s largest rivers, the Rhine,

exemplifies this problem; along substantial stretches the natural biota has been

severely altered by pollution (Table 8.1) (Broseliske et al. 1991).

Elimination of a species from a single water body may mean global extinction

because many aquatic species are found in a single lake or river system, having

evolved in isolation from their relatives in nearby water bodies. One of the most interesting

examples of this comes from Lake Victoria in East Africa, home to hundreds of

endemic cichlid fish species (Seehausen et al. 1997). Separation among these closely

related species is highly dependent on females choosing mates of the correct species;

however, with growing eutrophication the lake’s turbidity is increasing, and the

females cannot distinguish the colors they need to see to choose the correct mates.

Consequently, cichlid diversity is declining in eutrophic areas of the lake.

In contrast, water pollution is less likely to cause global extinction of species in

marine ecosystems than in freshwater ecosystems because marine ecosystems are

often too large to pollute in their entirety and because many marine species have large

geographic ranges, making it less likely that their entire range would be so polluted as

to be uninhabitable (Palumbi and Hedgecock 2005). Even though water pollution

may not be responsible for the global extinction of marine species, it still can have a

profound impact on marine biodiversity, particularly through local extirpations: for

example, when coral reefs are smothered in silt or overrun with macroalgae because

of excessive nutrients and eutrophication (Jompa and McCook 2003; Nugues and

Roberts 2003). Water pollution can also upset the equilibrium of marine food webs,

Ecosystem Degradation and Loss 155

such as when an excess of nutrients causes an explosive growth of toxin-producing

plankton known as “harmful algal blooms” (Anderson et al. 2002).

In recent years growing concern has focused on contamination from pharmaceutical

drugs such as ibuprofen and other anti-inflammatory analgesics that pass from

humans into aquatic ecosystems through waste water disposal (Tixier et al. 2003).

In one case a drug administered to cattle, diflonac, has caused kidney failure in three

species of vultures that feed on cattle carcasses, leading to widespread, catastrophic

declines in vulture populations in the Indian subcontinent (Oaks et al. 2004).

Pesticides

To capture a large portion of the earth’s resources people must compete against other

organisms, and pesticides are one of our preferred tools for doing this. We use enormous

quantities of insecticides and rodenticides to kill animals that would eat our

crops, herbicides to kill plants that would compete with our crop plants, and fungicides

to kill fungi that would decompose our food and fiber. Worldwide, over 50,000 different

pesticide products with active ingredients weighing over 2.6 million metric tons are

used each year (World Resources Institute et al. 1998). Some of these pesticides are

relatively benign. They kill only a small group of target organisms, they are used in

limited areas (e.g. food storage facilities), and after use they quickly break down into

harmless chemicals. Unfortunately, very few pesticides meet all these criteria, and

some, such as the notorious DDT, wreak havoc on a broad set of nontarget organisms

for a long period over large areas.

156 Part II Threats to Biodiversity

Upper Rhine Middle Rhine Lower Rhine

1916 1980 1916 1980 ~1900 1981–1987

Gastropoda (snails) 8 4 8 5 11 10

Lamellibranchiata (mussels) 11 4 10 4 14 7

Crustacea (crustaceans) 3 2 3 2 3 13

Heteroptera (true bugs) 2 1 1 0 1 1

Odonata (dragonflies) 2 1 1 0 3 2

Ephemeroptera (mayflies) 11 4 3 0 21 2

Plecoptera (stoneflies) 13 0 12 0 13 0

Trichoptera (caddisflies) 11 5 11 2 17 5

Total 61 21 49 13 83 40

Source: from Broseliske et al. (1991).

Table 8.1

Changes in species

richness of some

invertebrate taxa in

the Rhine.

Ecosystem Degradation and Loss 157

Croplands strewn with corpses can

mark the aftermath of pesticide use, but

more often the effects are not seen until

much later and in more subtle ways. One

example of this has garnered considerable

attention: pesticides and related chemicals

that mimic the action of the female

sex hormone estradiol (Colborn et al.

1996; National Research Council 1999;

Hayes 2004). Sterility, delayed sexual

maturity, abnormal sex organs, and an

array of other problems have been attributed

to these contaminants, which are

characterized as “endocrine disruptors”

or “hormonally active agents.” Longterm,

insidious effects of pesticides are

well documented because some of them

can persist in the tissue of living organisms,

accumulating in one individual, and

passing on to other individuals through a

food web. The most infamous example

involves a set of chemicals known as

chlorinated hydrocarbons (which

includes DDT, many other pesticides, and

some chemicals that are not pesticides,

such as PCBs, polychlorinated biphenyls).

They are soluble in fat and can take years,

even decades, to break down. This means

that they pass from prey to predators up a

food chain and can concentrate in top

predators, a process known as biomagnification

(Fig. 8.4). Populations of several

predatory birds (ospreys, brown pelicans,

bald eagles, peregrines, and others) were

dramatically reduced by chlorinated

hydrocarbons during the 1950s and

1960s. Use of these chemicals has been

sharply curtailed in many wealthier countries, and this has allowed populations of these

birds to recover somewhat (Sheail 1985). However, use of chlorinated hydrocarbon pesticides

continues in many less-developed countries, and, because of their persistence, a

wide variety of chlorinated hydrocarbons continue to contaminate the environment of

places where they have been banned (Berg et al. 1992; Gonzalez-Farias et al. 2002).

Accounts of the negative effects of pesticides typically focus on species that are most

similar to us – birds and mammals – because we tend to be more concerned about their

welfare, and because toxic effects on these species may portend toxic effects on us.

However, it is likely that the most serious effects of pesticides fall on organisms that are

most closely related to the target species. Consider the insect order Lepidoptera (butterflies

Figure 8.4 Persistent pesticides and similar compounds accumulate

in the tissues of one species and then are passed up the food

web to other species where they become more concentrated. This

process is called biomagnification or bioamplification. In this figure

DDT has entered the food web of Lake Kariba in Zimbabwe and

reached its highest levels in top predators such as crocodiles, tigerfish,

and cormorants. Numbers are parts per billion of DDT and its

derivatives in the fat of the species illustrated. (Redrawn by permission

from Berg et al. 1992.)

and moths), which includes many pest species, as well as many endangered species. It

seems reasonable to assume that attempts to control pest lepidoptera with insecticides

would jeopardize some rare lepidoptera, although in practice this has not been well documented

to date (New 1997; Pimentel and Raven 2000). Loss of nontarget insect populations

may have far-reaching consequences. In particular, there is growing concern about

the loss of pollinating insects and the consequences this may have for a wide range of

plants that require animal pollinators, for the other animals dependent on those plants,

and for human food production (Allen-Wardell et al. 1998; Kremen et al. 2002).

Roads, Dams, and Other Structures

Flying in a plane, you can easily see the hand of humanity; most landscapes are crisscrossed

with roads, railroads, fences, and utility corridors and dotted with buildings,

dams, mines, parking lots, and many other structures. The total area covered by such

structures is significant (about 3 million km2 worldwide; over 2% of the land area

[Wackernagel et al. 2002]) and represents a loss of habitat for virtually all wild species.

Looking beyond the immediate footprint of these structures,

one can see that a much larger area is affected. For example,

roads and their adjacent impact zones cover an estimated

20% of the area of the United States (Forman 2000; also

see Riitters and Wickham 2003). Thus we can list “construction

of human infrastructure” along with deforestation,

desertification, and other processes that destroy entire

ecosystems, all of which we will discuss later in this chapter.

In this section we will focus on the consequences of adding

these and other structures to the biota of entire landscapes,

especially on animals that move across landscapes.

Roads

The most ubiquitous structures created by people are roads,

and while roads facilitate the movement of people, they can

also serve as impediments to the movements of many animals

(Forman and Alexander 1998; Forman et al. 2003).

Some roads have curbs or lane dividers that are an absolute

barrier to small, flightless animals such as amphibians, small

reptiles, and various invertebrates. More commonly animals

are capable of crossing a road, but may be run down in the

process (Fig. 8.5). In a two-year study of a 3.6 km stretch of

highway in Ontario, Canada, over 32,000 vertebrate carcasses

were found (Ashley and Robinson 1996). Most of the

mortality fell on amphibians and reptiles; overland migrations

of these species to and from breeding sites make them

especially vulnerable (e.g. Gibbs and Shriver 2002; Gibbs

and Steen 2005). Nevertheless, just the mortality of birds

(62 species; 1302 individuals) and mammals (21 species;

282 individuals) in this study would extrapolate to billions of

carcasses on the world’s road system without even

158 Part II Threats to Biodiversity

Figure 8.5 Roads act as filters to the movements

of many animals, especially because of

collisions such as the one that killed this tayra in

Belize. (Photo from M. Hunter.)

attempting to measure the mortality of amphibians, reptiles, and invertebrates. Most of

the individual animals killed on roads may be of common species that are in no danger of

extinction, but even a few road deaths can be of great consequence for an endangered

species. For example, Florida scrub jay territories adjacent to roads are population sinks

because of traffic-induced mortality (Mumme et al. 2000). For some species roads are a

psychological filter; individuals are apparently reluctant to cross them even though physically

capable of doing so. In the Brazilian Amazon some bird species, especially those

found in the understory of interior forests, very rarely crossed roads, even roads where

regrowth formed a nearly intact canopy over the road (Laurance et al. 2004). If organisms

are unable or unwilling to cross a road, then the populations on either side of the

road may become isolated from one another; this has been demonstrated for amphibians

(Gibbs 1998) and beetles (Keller and Largiader 2003).

A second major problem associated with roads is the access they provide to people

who may overexploit organisms or destroy whole ecosystems. The roads penetrating

formerly remote areas of tropical forest, allowing access by poachers who overexploit

game populations and settlers who raze the tropical forests, are a particularly lamentable

example of this phenomenon. The effect of road access on habitat quality has

been well studied for some large carnivores such as wolves and tigers (Kerley et al.

2002; Theuerkauf et al. 2003).

Roads may also provide access to exotic organisms that can disrupt native populations

(Hansen and Clevenger 2005). Usually, these will be species carried, intentionally

or not, by people traveling along the highway. Sometimes, exotic species will move

along the road by themselves. In particular, weedy exotic plants seem to use the

disturbed ground of roadsides to invade a landscape (Gelbard and Belnap 2003)

(Fig. 8.6). Finally, roads have a variety of physical and chemical attributes that are

likely to affect adjacent aquatic and terrestrial ecosystems. These include various substances

such as dust, sediment, salt, heavy metals, hydrocarbons; a sunny, windy,

warm microclimate; blocking surface water runoff; and more (Trombulak and Frissell

2000; Angermeier et al. 2004). One of the most annoying physical aspects of roads for

human observers – traffic noise – was found to reduce bird population densities in a

band hundreds of meters wide in one study (Reijnen et al. 1995).

Dams

Worldwide, over 45,000 large dams (>15 meters high) have affected most of the

world’s major river systems (Nilsson et al. 2005). The damming of streams and rivers

destroys many aquatic ecosystems, flooding ecosystems upstream of the dam and

changing water flows to downstream ecosystems. We will return to these issues in a

later section; here the focus will be on the barrier effects of dams. Many animals move

up and down rivers during the course of a year, or during their life cycle, searching for

the best places to forage or breed. Some of them can fly or walk around dams (otters,

mergansers, mayflies, etc.), but for totally aquatic species dams can be very significant

barriers. Moving downstream these animals are likely to be churned to death or at

least highly stressed in turbines (Wertheimer and Evans 2005). Moving upstream

they encounter an insurmountable wall that may or may not have a fish ladder

around it, and even fish ladders work for only a portion of the population. The reservoir

behind a dam may also impede movement, especially if it has been stocked with

exotic, predatory fish. Of course, fish are the best known victims of dams, especially

Ecosystem Degradation and Loss 159

anadromous fish such as salmon that move long distances between riverine spawning

areas and marine foraging areas (Petrosky et al. 2001; Fig. 8.7). Some salmon populations

have been completely eliminated, largely by dams, despite millions of dollars

spent building fishways, trucking fish around dams, supplementing populations with

hatchery-reared stocks, and so on (Molony et al. 2003). A study of eight rivers in

Sweden suggested that the effects of dams and reservoirs on shoreline plants are also

shaped by dispersal issues: water-dispersed species with a limited ability to float were

strongly affected by damming (Jansson et al. 2000a; also see 2000b).

Other Barriers

Some landscapes are dissected by barriers specifically designed to inhibit the movement

of animals. Notably, rangeland fences stretch huge distances, controlling the

movement of both livestock and large wild mammals and sometimes severing

seasonal migrations (Berger 2004). For example, in Botswana, thousands of kilometers

of fences have been erected to isolate livestock from wild ungulates that might

harbor diseases. These fences have had catastrophic consequences for native ungulates,

especially wildebeest, that must migrate to access water during dry seasons

(Williamson et al. 1988).

160 Part II Threats to Biodiversity

Figure 8.6 Exotic and native plant species richness in plots 50 meters away from paved,

improved-surface, graded, and four-wheel-drive (4WD) roads through grasslands, shrublands,

and woodlands in southern Utah, USA (Gelbard and Belnap 2003). Error bars represent

1 SE. Different letters indicate significant differences (p < 0.05) among levels of road

improvement.

Utility corridors also dissect landscapes, potentially isolating the organisms on

either side. For example, a forest herb that spreads by means of vegetative reproduction

would be impeded by the dry, sunny environment of a power line running

through a forest. In one study even reindeer, a species usually found in open environments,

exhibited avoidance of power lines during winters in Norway (Nellemann et al.

2001). Pipelines and irrigation canals also have the potential to be direct barriers. In

the best known example of this issue – the Trans-Alaskan Pipeline and caribou

migrations – elevating the pipe kept it from being an absolute barrier but pipelines

still degrade caribou habitat quality (Cameron et al. 2005).

Most bird species can readily fly over human-made barriers, although some forest

birds are very reluctant to venture into the open, and some of the large, flightless birds

(e.g. emus and ostriches) are easily stopped by fences. Unfortunately, birds are often

killed by flying into human structures. Large numbers of migrating birds collide with

power lines, antennas, lighthouses, windmills, and similar structures (e.g. Barrios and

Rodriguez 2004); even local movements can result in a collision with a large window.

Trash and Other Things

In this final section on human-made structures we will list some of the other things

people make and then add to the natural environment that are detrimental to other

Ecosystem Degradation and Loss 161

Figure 8.7 Survival of wild, juvenile, chinook salmon migrating toward the sea before

(1966–8) and after (1970–5) completion of two dams on the Snake River in Washington.

(Redrawn by permission from Raymond 1979; also see Petrosky et al. 2001.)

organisms. Much of this material is trash, things discarded by people, perhaps intentionally

or perhaps not. Lost or discarded fishing gear is a major hazard (Coe and Rogers

1997; Derraik 2002). The worst offenders are probably lost gill nets – often called ghost

nets – which can drift for months or years, still catching fish, diving birds, seals, and

other creatures. It is difficult to estimate the extent of this mortality, but with about

21,300 km of nets (enough to reach more than halfway around the world) set nightly

to catch salmon and squid in the North Pacific alone, the total loss is likely to be enormous

(Laist 1987). Even a single strand of monofilament fishing line discarded by an

angler can ensnare an animal and kill it. Fishing sinkers made of lead and lead shot discharged

by waterfowl hunters accumulate on the bottoms of water bodies, where they

are likely to be swallowed by bottom-feeding birds and cause lead poisoning (Sanderson

and Bellrose 1986; Sidor et al. 2003). Lead shot in carcasses often poisons scavengers

such as California condors and various species of eagles (Pain et al. 2005). One of the

major causes of death among sea turtles appears to be ingesting marine debris, especially

plastic bags and balloons that they mistake for jellyfish (Derraik 2002).

Some of the problems we cause by putting human-made objects into natural environments

would be hard to predict. Consider a seemingly innocuous item, red plastic

insulators for electric fences. It turns out that large numbers of hummingbirds mistook

the insulators for flowers and electrocuted themselves until the manufacturer

withdrew the product. Street lights on beaches may make people feel safer, but they

can disorient hatchling sea turtles when they emerge from their nests and make an

already perilous trip to the sea even more dangerous (Tuxbury and Salmon 2005).

Given that six of the seven species of marine turtle are endangered to varying

degrees, any added source of mortality may be of some consequence.

Lastly, we can list the forms of motorized transport that travel across our lands and

waters without using roads, often crushing plants, colliding with animals, and compacting

and eroding soil. Collisions with motor boats are a major source of mortality for

manatees in Florida (Nowacek et al. 2004). In deserts and on beaches off-road vehicles

are a threat to sedentary or slow-moving species such as plants, hatchling birds, and

desert tortoises. Ironically, fences are a common way to control off-road vehicles (Brooks

1995, 1999), and these have their own ecological problems unless carefully designed.

Earth, Fire, Water

In this section we will consider some of the ways people modify physical environments

that may have negative consequences for biota. We will focus on three issues –

soil erosion, changing fire regimes, and water consumption – that usually degrade

ecosystems without destroying them.

Soil Erosion

Soil erosion is a natural process, an inevitable consequence of wind, rain, and gravity.

The problem is that the rate of soil erosion is often greatly accelerated by human use of

ecosystems (Fig. 8.8). Indeed, it has been estimated that collectively human activities,

such as agriculture, overgrazing by livestock, timber harvesting, and road and building

construction, erode soil at ten times the rate of all natural processes combined

(Wilkinson 2005). Under extreme circumstances, soils that took centuries to form can

be eroded in a matter of hours in a torrential rain storm.

162 Part II Threats to Biodiversity

Ecosystem Degradation and Loss 163

Soil erosion is a double-edged sword. Not only does it

produce sediments that can blanket other ecosystems,

leading to some of the water pollution problems discussed

above (Alin et al. 1999), but it also degrades the productivity

of the land from which the soil is eroded. As Lester

Brown has written, “Society can survive the exhaustion of

oil reserves, but not the continuing wholesale loss of topsoil.”

When a terrestrial ecosystem loses soil and its productivity

is diminished, what are the consequences for the

ecosystem’s biota? This is a difficult question, in part

because there is no simple relationship between productivity

and biodiversity. Some highly productive ecosystems

support a very diverse biota (e.g. tropical rain forests), and

some support relatively few species (e.g. salt marshes). In

the short term, most species are likely to be more affected

by the agent of soil disturbance – the plow, the chainsaw,

etc. – than by the subsequent soil erosion. In the long

term, diminishing the productivity of an ecosystem for

several centuries could be one more stressor that pushes a

species that is dependent on that type of ecosystem a bit

closer to extinction.

In some severe cases, ecosystems can be highly

degraded and species extirpated by soil erosion. For example,

on Round Island in the Indian Ocean, rabbits and

goats introduced to provide a food source for passing

mariners removed most of the vegetation and this led to

severe soil erosion. Two species of reptiles became extinct,

and ten species of plants, three reptiles, and a seabird

were at risk until the exotic herbivores were removed and

erosion was brought under control (North et al. 1994).

We will return to soil erosion below in our discussion on

desertification.

Fire Regimes

Few phenomena can match the ability of a large, hot forest fire to totally transform a

natural ecosystem in a short time. Volcanoes, nuclear bombs, and large meteorites

could readily match a fire, but, thankfully, these are rare events. The apparent devastation

wrought by severe fires has led to concerted efforts to control all fires. Smokey

the Bear’s “Only you can prevent forest fires!” is one of the best-known phrases in the

United States’ advertising media.

Unfortunately, the campaign has been too successful in many respects, especially

when humans reduce the frequency of fires in ecosystems where they are a natural

phenomenon (Van Lear et al. 2005). For example, most natural grasslands and shrublands,

and some types of forests (e.g. certain eucalypt forests in Australia and pine

forests of the southeastern and southwestern United States) are adapted to experiencing

low-intensity fires at frequent intervals (Whelan 1995; Bond and Keeley 2005;

Bond et al. 2005). Consequently, their vegetation changes dramatically without fires to

Figure 8.8 Soil erosion has profoundly degraded

ecosystem productivity in many regions, although it

is most noticeable in mountainous areas, as in this

photo from the Himalayas. (Photo from M. Hunter.)

inhibit the influx of fire-intolerant species. Furthermore, when low-intensity fires are

suppressed, fuel can accumulate and any fire that does get started is likely to be very

intensive. A well known example of the consequences of removing fire from a firedependent

ecosystem comes from Michigan, where fire suppression led to a shortage of

young jack pine stands, the sole habitat of the rare Kirtland’s warbler (Probst and

Donnerwright 2003). The Kirtland’s warbler almost became extinct before its habitat

needs were recognized and met through active forest management.

On the other hand, humans often burn ecosystems quite deliberately. This can be an

ecological problem if the frequency and intensity of the fires are too great. For example,

about 70% of the forests of New Zealand have been eliminated by fire; much of

this occurred soon after Polynesian colonization (Ogden et al. 1998). Undoubtedly,

the very earliest humans realized that fire often promotes grassy vegetation, and

therefore they set fires to produce food for their preferred prey animals and later for

their livestock. These practices continue in many places to this day and, when overdone,

can be a problem. This is most evident when fire is used as a tool to clear forest

for agriculture, as is happening in many countries with burgeoning human populations,

an issue we will discuss below. It might also be a problem in semiarid environments

where frequent burning allows little opportunity for the soil’s organic matter to

develop and thus can contribute to desertification (Woube 1998; Savory and

Butterfield 1999).

Water Use

Every year people directly use 4430 cubic kilometers of water (Postel et al. 1996): that

is over 700,000 liters per person. Some of it we drink. Far more of it we use to irrigate

our crops and lawns, to bathe, to flush our toilets, to manufacture sundry products

such as paper, and to cool our power plants. To be specific, an estimated 65% is used for

agriculture, 22% for industry, and 7% for domestic purposes, and 6% is lost to evaporation

from reservoirs (Postel et al. 1996). With 43,000 liters required to produce a kilogram

of beef it is not surprising that agriculture is the dominant use (Pimentel et al.

2004). Some of this water is returned to an aquatic ecosystem; most of it is returned to

the atmosphere through evaporation and transpiration. When large volumes of water

are removed from aquatic ecosystems, their biota is likely to be affected. Not surprisingly,

the effects are most dramatic in arid regions. Desert springs, streams, and wetlands

are usually rare and fragile ecosystems, often containing unique species that

have evolved in isolation (Minckley and Deacon 1991; Fagan et al. 2002). Obviously, if

most of their water is removed, these ecosystems will be degraded (Contreras-B. and

Lozano-V. 1994). Consider the lower Colorado River in the arid southwestern United

States, where water flow disruptions have had a major role in the decline of 45 endangered

species (Glenn et al. 2001).

Water scarcity can be an issue even in places where there is a great deal of water.

Most of the southern tip of Florida is essentially one huge wetland – the Everglades –

that covers many thousands of square kilometers in a sheet of water. Yet the

Everglades is so shallow, and the demands on its water from farmers and coastal communities

are so great, that the whole ecosystem is being profoundly changed by a

scarcity of water (Davis and Ogden 1994). Notably, the numbers of herons, egrets,

and other wading birds have declined sharply, in part because a reduction in freshwater

input has reduced the productivity of estuarine parts of the Everglades.

164 Part II Threats to Biodiversity

Deforestation

■ Forests cover less than 6% of the earth’s total surface area.

■ Forests are habitat for a majority of the earth’s known species.

■ Forests are being lost faster than they are growing.

These three facts highlight why many conservation biologists believe that deforestation

may be the most important direct threat to biodiversity. In this section we will

first review some of the causes, and then some of the consequences, of deforestation.

Causes of Deforestation

Forests tend to grow in places with reasonably fertile soils and benign climates, not too

dry and not too cold. These also tend to be good places for people to live and grow crops.

Consequently, millions of square kilometers of forests have been removed to make way

for our agriculture, homes, businesses, mines, and reservoirs since the beginning of

agriculture (Williams 2003). This process has slowed, stopped, or even reversed in some

areas that were extensively deforested many years ago, such as Europe, China, and eastern

North America. In some developed countries, the demand for forest land is less

because the human population has stabilized, or because the local economy has shifted

from agriculture (the single biggest cause of deforestation) to industry. In other places,

such as large parts of China, there are simply few forests left to remove. Unfortunately,

deforestation continues at an alarming pace in many tropical regions. The statistics

vary widely – an area the size of Switzerland every year, nearly 50,000 ha every day,

and so on – and we do not really have a good estimate, but the basic fact remains: forests

are disappearing, especially tropical forests (Williams 2003). The fundamental reasons

for the current spate of tropical deforestation are threefold. First, human populations

are increasing rapidly in most tropical areas. Second, many of these people are poor,

and clearing forest to open a small plot where crops can be grown is often their only

choice for survival. Third, corporations and wealthy individuals cut forests for wood

products with inadequate attention to regrowth (especially in Asia) and to open the

land for cattle ranching (especially in Latin America).

Unfortunately, poor farmers are often trapped in poverty because the lands they clear

are not really suitable for agriculture in the first place. After only a few years the soil’s fertility

is drained, and they must move on to another site and clear more forest. The process

of clearing a small patch of tropical forest, growing crops for a few years, and then moving

on to another site is called shifting cultivation and it is a traditional, sustainable practice

when human populations are low and the abandoned site is allowed to return to

forest. However, when populations are too high, then people stay at a site too long or

return to a previously used site too soon. Alternatively, they may sell the land to a wealthy

cattle rancher. Particularly in Latin America, much of the tropical forest initially cleared

for subsistence agriculture ends up as rangeland for cattle, while under some circumstances

the cattle ranchers raze the forest themselves (Fearnside 2005). In Asia, the direct

drivers of deforestation are often logging companies. Whatever the underlying reason,

abusive use of a site is likely to degrade the soil so badly that, even when it is abandoned, it

will probably take several centuries, or even millennia, for a rich forest to return. Tropical

forest soils are notorious for being easily degraded and difficult to reforest (Lal 1995).

In many people’s eyes timber harvesting is a major cause of deforestation. For example,

Pimm (1991, p. 136) wrote “consider the ultimate form of external environmental

Ecosystem Degradation and Loss 165

disturbance – total destruction of the habitat, such as might result from logging of a forest,

or an asteroid collision, or a nuclear holocaust.” This viewpoint needs to be scrutinized,

however. A forest can be profoundly disturbed by severe fires or windstorms, but in

time the forest will be restored by ecological succession. Similarly, when a forest is

clearcut, it will eventually return to a forest again if it is given enough time and freedom

from additional disturbances such as plows and cattle and real estate developers

(Fig. 8.9). It may or may not resemble a forest that was disturbed by natural phenomena,

but it will be a forest. Time is the critical issue here. Calling a clearcut forest deforested is

probably appropriate only if its recovery will take significantly longer than recovery from

a natural disturbance. Note that under some circumstances logging can negatively affect

a forest even if only a small portion of the trees are removed, but this is more appropriately

called degradation than deforestation. This issue will be covered in Chapter 9, and

in Chapter 12 we will address ways to harvest wood and maintain biodiversity.

Consequences of Deforestation

The extraordinary species diversity of forests is based on a number of factors (Hunter

1990); here are four key ones. First and most basically, the environmental conditions

that forests require – some soil and a reasonably benign climate – are favorable to life in

general. Contrast the places where forests grow to a tundra or desert. Second, the durability

of wood means that forests contain an enormous reservoir of organic matter, and

this material represents food and shelter to a large set of invertebrates, fungi, and

microorganisms. For example, just two families of wood-boring beetles – long-horned

beetles and metallic wood borers – contain twice as many species as all the world’s

bird, mammal, reptile, and amphibian species combined (Hunter 1990). Third, the

strength of wood makes forests taller, more three-dimensional, than other terrestrial

ecosystems. The height of a forest means that it contains many different microenvironments,

from the sunny, windy foliage at the top of the canopy to the cool, damp

recesses of a crack in the bark of a tree trunk, and each of these different microenvironments

may support a different set of small creatures. Fourth, forests are dynamic

ecosystems, frequently changing through the processes of disturbance and succession,

and many of these changes are marked by differences in species composition.

Among all forests, the most diverse are the tropical rain forests. Indeed, many biologists

believe that half of all the species on earth may occur in tropical rain forests (Wilson

1992). Our knowledge is too limited to corroborate this statement (as was explained in

Chapter 3), but we can consider many fragmentary bits of supporting evidence. For

example, 43 species of ants have been found on one tree in a Peruvian tropical forest,

about equal to the number that occur in all of Great Britain, and 1000 tree species were

found collectively in ten 1 ha plots in Borneo, far more than occur in all of the United

States and Canada (Wilson 1992). The reasons for the extraordinary diversity of tropical

forests are complex and not well understood (Hill and Hill 2001). Suffice it to say here

that the four factors mentioned above probably play a role (for example, tropical rain

forests are taller and have larger reservoirs of organic matter than many other types of

forest), as well as other factors such as long-term climate change.

Needless to say, when people convert a forest to another type of ecosystem, most of the

forest-dependent species are lost from that site for some period. It is easy to name forestdwelling

species that are threatened with extinction largely because of deforestation – giant

166 Part II Threats to Biodiversity

pandas, tigers, gorillas, and many many more – but, of course, these are just the tip of the

iceberg. With most of the earth’s biodiversity residing in insects and other small organisms,

and with many, perhaps most, of these small species living in tropical forests where they

remain unknown to science, we can only make gross estimates of the likely impact of

deforestation (Lawton et al. 1998). Fully acknowledging the extent of our uncertainty, it is

still clear that a large portion of the earth’s biodiversity is found in tropical forests and that

these forests are being lost to deforestation at a very high rate. Consequently, all conservation

biologists believe that protection of tropical forests must be a high priority.

Ecosystem Degradation and Loss 167

Figure 8.9

Clearcuts have a

dramatic effect on

forest biota but the

key issue is what

happens in the following

years; will

the forest regenerate

or will it be

converted to

another use, such

as housing or agriculture,

and thus

constitute deforestation?

We also

need to consider to

what extent a

clearcut does or

does not resemble

the natural disturbance

regime for a

particular type of

forest. (Photo from

Marc Adamus.)

Thus far we have focused on the biological consequences of deforestation, but

through changes in the physical environment, deforestation can have effects far

beyond the edge of the forest. We have already discussed soil erosion as a source of sediment

that can contaminate aquatic ecosystems. On a global scale, forests affect the

earth’s climate by acting as reservoirs of carbon, and when they are cut, much of the

carbon moves into the atmosphere as carbon dioxide, the major greenhouse gas

(Steininger 2004). More locally, because much of the water vapor in the atmosphere

above a forest is maintained by evaporation and transpiration, when a forest is cut,

rainfall may decrease. This makes the hot, dry conditions of a deforested site even hotter

and drier.

Desertification

When you envision a barren, nearly lifeless landscape, do you think of deserts? This

image ignores the myriad species that flourish in desert ecosystems, but nevertheless,

fewer species overall live in arid environments than in more humid ones. Therefore it

is of great concern to conservationists that the extent of arid land – currently about

35% of the earth’s land surface – is apparently increasing because of human activities

(Mainguet 1999). In particular, grasslands and woodlands (i.e. relatively dry

forests in which tree crowns do not meet to form a continuous canopy) are being

degraded until they are dominated by sparse, relatively unproductive vegetation

(Fig. 8.10). This process is called desertification.

Causes of Desertification

In most parts of the world desertification is closely associated with overgrazing

(Schlesinger et al. 1990; Asner et al. 2004). Too many cattle, sheep, goats, and other

livestock consume and trample too many plants, and this alters the species composition

and structure of the vegetation and reduces the overall biomass. With few plants

to protect the soil and with many animal hooves breaking and compacting the soil,

erosion is likely to increase. The excessive burning of grasslands, usually to provide

fodder for livestock, may further exacerbate the problem (Savory and Butterfield

1999), while suppression of natural fire regimes can lead to the encroachment of

shrubs (Asner et al. 2004).

Cultivation is also a major cause of desertification (Dregne 2002), particularly because

it generates soil erosion. Furthermore, croplands that require irrigation often face two

other problems: salinization and waterlogging (Contreras-B. and Lozano-V. 1994;

Mainguet 1994). Salinization is common when irrigation is used in arid environments

because large volumes of water evaporate, leaving behind salts that can reach toxic concentrations.

If farmers try to solve this problem by using enough water to leach the salts

lower into the soil, waterlogged soils can occur. Cutting trees in woodlands, usually for

fuelwood, can also contribute to desertification.

Over the long term, whenever cyclical changes in the earth’s orbit have led to

warmer and drier conditions, some grasslands and woodlands have become deserts

(see Chapter 6). Against this background, the relative importance of long-term climate

change and short-term droughts, natural erosion, and human-induced causes of

desertification is a complex and controversial topic. Some argue that anthropogenic

168 Part II Threats to Biodiversity

factors are paramount; others

argue for climate change; and

their relative role seems to depend

on what part of the globe you are

talking about (Geist and Lambin

2004).

Consequences of

Desertification

Desertification and its consequences

are often overlooked until

they become extreme, in part

because it is harder to recognize

the work of hungry livestock (the

cumulative impact of thousands of

small bites) than the work of a

hungry chainsaw (Fleischner

1994). A deforested site often looks

like a disaster, but an overgrazed

ecosystem where grasses have been

replaced by unpalatable brush may

not look degraded to the untrained

eye. Grasslands and woodlands

that are vulnerable to desertification

may not match the wealth of

biodiversity of forests, but they do

have a large set of unique species

that merit the attention of conservation

biologists, including such

well known species as African elephants,

cheetahs, black-footed ferrets,

both black and white rhinos,

great bustards, and African wild

dogs. Furthermore, in decrying the

loss of grasslands and woodlands

to desertification, it is important

not to imply that deserts lack biodiversity

value. Thousands of species

are found in deserts, and many of

them are highly endangered:

desert tortoises; Asian and African

wild asses; sundry species of cactus;

and a variety of antelopes

such as the addax, scimitar-horned oryx, and Arabian oryx, to name some of the better

known taxa.

Ecosystem Degradation and Loss 169

Figure 8.10 This photo from the Khyber Pass in Afghanistan reveals some

of the classic signs of desertification: virtually no ground vegetation (at

least of palatable plants), a browse line on the tree indicating how high

livestock can reach, and soil erosion. (Photo from M. Hunter.)

It is instructive to think of a continuum of decreasing ecosystem biomass and productivity

from forests to woodlands to grasslands to deserts. Ecosystems that already

fall in the desert part of this continuum are still vulnerable to being pushed further

down the continuum of decreasing productivity and biomass. This perspective raises

the possibility that some species adapted to the lower end of this continuum might

benefit from desertification by having larger areas of habitat (Whitford 1997). This

may be true of some common, highly adaptable species, but the species of greatest

concern are likely to be habitat specialists that cannot survive in degraded ecosystems

that are a human-created facsimile of natural desert.

One reason why desertification has had a significant impact on biodiversity is that

relatively few grasslands and woodlands have been protected as parks (Hoekstra et al.

2005). This is partly because these lands usually lack the amenities – lakes, mountains,

forests – that people seek for outdoor recreation. (A notable exception to this

generalization comes from eastern and southern Africa, where tourists visit arid and

semiarid parks to see the spectacular suite of large mammals.) Of course, establishing

some more parks would not be a complete solution; wiser management of all ecosystems

vulnerable to desertification must be the goal.

Draining, Dredging, Damming, etc.

Swamps and marshes, bogs and fens, lakes and ponds, rivers and streams, estuaries

and the ocean, and more: there is a wide variety of ecosystems – freshwater

ecosystems, marine ecosystems, and wetlands – in which water is a medium for life,

not just an essential nutriment. Similarly, there is a wide variety of ways in which

people destroy these ecosystems by changing their hydrology (Fig. 8.11). We will

begin by briefly reviewing some of these methods.

Filling a wet depression with material until the surface of the water table is well

below ground is an obvious way to turn a wet ecosystem into a dry one. This method

is usually too expensive to use for creating agricultural land, but it is routinely used to

create house lots, airports, parking lots, and other high-priced land. Small, shallow

wetlands are particularly vulnerable to being filled.

Draining a wet ecosystem (i.e. lowering the water table by moving the water somewhere

else) is a common practice. In its simplest form it involves digging ditches that

allow the water to drain away. Under the right circumstances, this method can be used

to drain large areas relatively easily. Occasionally, water is actually pumped out of a

wet ecosystem at great expense.

The primary impetus for both draining and filling is to acquire more land that is useful

for human enterprises. The single biggest use for land created in this fashion is agriculture,

except in urban and suburban areas where housing developments, shopping

malls, and other projects are often the key issue. Occasionally, sites are drained to

improve their ability to produce timber, and in some countries peatlands are drained so

that the peat can be mined for fuel. Clearly, it is easier to drain or fill a shallow basin

than a deep one, and thus wetlands are far more vulnerable to these losses than are

lakes, rivers, and estuaries.

Dredging involves digging up the bottom of a water body – the mud and a host of muddwelling

creatures – and depositing the material elsewhere, often in a wetland that someone

wants filled. The goal is usually to maintain a shipping channel in a river or harbor;

170 Part II Threats to Biodiversity

Ecosystem Degradation and Loss 171

the ecological result is a scarred bottom and sediment pollution. Sometimes, the sediments

contain high concentrations of toxins that are returned to the food web after dredging.

Channelizing rivers and streams means making them straighter, wider, and deeper

and replacing riparian (shoreline) vegetation with banks of stone or concrete. This

conversion from a complex of natural riverine communities to a barren canal may

meet engineering objectives, usually flood control, but is obviously an environmental

calamity. Sometimes canals are dug to connect separate water bodies; these can

become conduits that allow the mixing of formerly isolated biotas (Smith et al. 2004).

Figure 8.11 A

complex of aquatic

ecosystems before

and after human

alterations. In the

lower right a housing

development

that was previously

surrounded by

dikes is being

extended by filling

the wetland.

Nearby, the channel

is being

dredged. Upstream

the river has been

channelized and

the adjacent wetlands

ditched. A

tributary on the

right side of the

main river has

been dammed to

create a reservoir.

In the real world it

would be highly

unusual to have all

these activities in a

small area.

Damming rivers and streams can profoundly change ecosystems both upstream and

downstream (Nilsson and Berggren 2000; Bunn and Arthington 2002). First,

upstream of a dam, a flowing-water ecosystem (the technical term is lotic) is converted

to a standing-water (lentic) ecosystem, and wetland and upland ecosystems will also be

flooded and thus become part of a reservoir. Wetlands are especially likely to be extensively

flooded because their elevation is often close to that of a nearby river.

Additionally, many reservoirs are subject to dramatic fluctuations in water level

depending on changing demands for electricity and water. This means that the shores

of reservoirs are often quite barren because relatively few species can cope with being

inundated and then exposed in this manner (Jansson et al. 2000a). Second, downstream

of a dam, floodplain ecosystems are likely to be replaced by upland ecosystems

if the dam minimizes or eliminates the seasonal floods that are critical to the maintenance

of these ecosystems. In the river itself, species are likely to be challenged by flow

rates that are very unnatural: too much short-term fluctuation in response to demands

for water or electricity, or not enough annual fluctuation in response to rainy and dry

seasons. Also, the water temperature may be too warm (if drained from the top of the

reservoir) or too cold (if drained from the bottom of the reservoir) (Vaughn and Taylor

1999). A third issue, dams as barriers to the movements of aquatic species, was discussed

above in the section on roads and dams as barriers.

Diking consists of constructing earthen banks, usually called dikes or levees, along the

edges of water bodies to prevent flooding. Given that floods are natural phenomena vital

to the maintenance of many types of ecosystems, diking can easily destroy ecosystems,

especially because it is often linked with developing land for other purposes.

Obviously, the world’s oceans and seas are too large to be converted to other types of

ecosystems by filling, draining, etc., but they are not completely immune to these

processes. The bays and inlets that line oceans and seas (often these are estuaries where

salt and fresh waters meet) are small enough to be affected by these processes, especially

filling and dredging. Furthermore, sometimes our attempts to control currents in these

areas with breakwaters, jetties, and other structures can change marine ecosystems

profoundly. For example, shortsighted attempts to maintain sandy beaches by building

jetties often end up accelerating beach erosion and sand deposition somewhere else.

To discuss the consequences for biodiversity of filling, draining, dredging, channelizing,

damming, and diking, we will focus on the two groups of species that are most

vulnerable to these processes: those associated with wetlands and rivers. In the wake

of devastating tsunamis, hurricanes, and floods, the consequences of degrading

shoreline ecosystems is of great concern for human communities too, albeit beyond

our scope here. Suffice it to say that the impacts of natural disasters are much

less severe where shoreline ecosystems are intact enough to provide a buffer

(Danielsen et al. 2005).

Consequences for Wetland Biota

Stemming the loss of wetlands has become a major goal of conservationists for two

basic reasons: the rarity of wetlands and their ecological value. Wetlands cover a relatively

small portion of the earth’s total surface, roughly 1–2%, and this portion is

decreasing (Harcourt 1992). In the conterminous United States, roughly 53% of wetlands

were lost between the 1780s and 1990s (Dahl 2000), and worldwide figures

172 Part II Threats to Biodiversity

are probably roughly comparable (Dugan 1993; Mitsch and Gosselink 2000). These

facts alone make it imperative to protect remaining wetlands, given a goal of protecting

biodiversity at the ecosystem level (see Chapter 4). Furthermore, wetlands are

often keystone ecosystems, playing critical roles in a landscape through hydrological

processes, biomass production and export, removal of contaminants from polluted

water, and so forth. (See Mitsch and Gosselink 2000 for a review of this topic.)

At the species level of biodiversity, wetlands are important because they are habitat

for a diverse biota comprising three groups of species. First, there are species that are

primarily aquatic (such as many species of fish and insects) that can use the pools of

water often found in wetlands. Some may be permanent residents; some may be visitors,

coming only at high tide, or during spring or monsoonal high waters.

Second, many terrestrial species are facultative users of wetlands, with a portion of

their population found in wetlands. Wetlands can be particularly important refugia for

terrestrial species that are sensitive to human interference; this is because wetlands

tend to be too wet for humans to hunt, plow, or extract trees and too dry for them to

access by boat. For example, the mangrove swamps in the mouth of the Ganges River,

the Sunderbans, harbor one of the world’s largest remaining tiger populations.

Finally, there are many thousands of species that are uniquely adapted to the interface

of wet and dry environments found in wetlands. These include whole families of

plants (cattails, water lilies, bur-reeds, and many more) and insects (e.g. predaceous

diving beetles, water boatmen, and several families of damselflies and dragonflies)

that are almost exclusively found in wetlands. Among vertebrates, most amphibians

and turtles are wetland species.

Throughout the world the loss of wetlands has pushed many species toward

extinction. Nine of the world’s 15 species of cranes – birds that require wetlands for

breeding and often foraging – are in jeopardy. In recent years herpetologists have been

alarmed by precipitous drops in many frog populations, and wetland loss is a primary

cause (Houlahan et al. 2000; Beebee and Griffiths 2005).

Consequences for River Biota

Rivers and streams are often likened to the arteries of a landscape, and this metaphor

is apt from both an ecological and economic perspective. It is hard to imagine human

history without rivers – bringing water to our croplands and homes, driving waterwheels

and turbines, providing a transportation network, and carrying away our

wastes. Think about how many of the world’s cities are located on a river, and you

will appreciate their pivotal role.

Unfortunately, being the focus of so much attention has left many rivers badly

degraded by water pollution, channelization, and dredging, or converted to reservoirs

by dams (Malmqvist and Rundle 2002; Postel and Richter 2003). The victims

of this scarcity of clean, free-flowing rivers do not draw much public attention

because they are chiefly fish, mollusks, and insects, not the birds and mammals that

galvanize public support (Allan and Flecker 1993). Scores of riverine fish species are

threatened with extinction, but most of them are minnows and other small species

that are seldom seen. Only a few economically important fish species such as various

salmon species are likely to garner much attention. Even lower on the list of public

popularity are mussels, crayfish, and other invertebrates, even though hundreds,

Ecosystem Degradation and Loss 173

perhaps thousands, of species are endangered by river degradation and conversion.

One analysis of North American crayfishes and unionid mussels estimated that 63%

of the crayfish species (198 of 313) and 67% of the unionid mussels (201 of 300)

were either extinct or at some level of risk (Master 1990). Another analysis of the

freshwater fauna of North America demonstrated that the recent (since 1900)

extinction rate of these animals was about five times greater than that of terrestrial

vertebrates and that this difference was likely to persist in the future (Ricciardi and

Rasmussen 1999). A similarly dramatic story could be told for Asian rivers – home

to over half of the world’s large dams (over 15 meters tall) and a large portion of the

world’s freshwater crabs, snails, turtles, crocodilians, river dolphins, and fishes

(Dudgeon 2000, 2002). For example, there are 105 families of freshwater fishes in

Asia compared with 74 in Africa and 60 in South America. For many taxa we do not

even have enough information to evaluate rarity or endangerment. For example,

388 algal species were recorded in one stream in southern Ontario (Moore 1972),

but few streams have been inventoried this thoroughly, and thus virtually all of their

algal species could be eradicated without documentation of their disappearance.

Fragmentation

When early explorers of wild regions found a high vantage point from which to scan

the terrain, they often wrote of a “sea of green” to convey the unbroken vastness of

the forests and grasslands they traversed. A modern traveler, looking down from a

plane, is likely to describe a typical landscape as a “patchwork quilt” – a mosaic of pastures

and croplands, woodlots and house lots and parking lots. The process by which a

natural landscape is broken up into small parcels of natural ecosystems, isolated from

one another in a matrix of lands dominated by human activities, is called

fragmentation. Because fragmentation almost always involves both loss and isolation

of ecosystems, researchers would like to distinguish between the effects of these two

processes but it is not often practical to do so (Guerry and Hunter 2002; Fahrig 2003).

Fragmentation is a major focal point for conservation biologists, both because it has

degraded many landscapes and because many nature reserves have become isolated

fragments or are in danger of becoming so (Saunders et al. 1991). In addition, it captured

the interest of many conservation biologists because it was recognized as an issue

at about the same time that conservation biology was emerging as a new discipline; in

other words, it was new ground for conservation biology to plow. Furthermore, it

appeared to have a theoretical foundation in an intriguing body of ideas and observations

known as island biogeography (Box 8.1). It seemed reasonable to assume that the

effects of isolation on the biota of oceanic islands might provide a model for understanding

the effects of isolation on populations inhabiting patches of natural ecosystems that were

isolated in a sea of human-altered land.

Most conservation biologists have come to recognize that the applicability of island

biogeography theory to fragmentation issues is quite limited, primarily because fragmentation

“islands” are not nearly as isolated for most species as true oceanic islands

(Zimmerman and Bierregaard 1986; Debinski and Holt 2000; Haila 2002).

Nevertheless, island biogeography does provide a conceptual foundation for understanding

fragmentation and is the origin for two important ideas. Small fragments

(or islands) have fewer species than large fragments, and more isolated fragments

174 Part II Threats to Biodiversity

have fewer species than less isolated fragments. We will begin by considering these

two ideas further.

Fragment Size and Isolation

There are three main reasons why large fragments have more species than small

fragments (Fig. 8.13). First, a large fragment will almost always have a greater variety

of environments than a small fragment (e.g. different types of soil, a stream, a

rock outcrop, an area recently disturbed by fire), and each of these will provide

niches for some additional species.

Second, a large fragment is likely to have both common species and uncommon

species (i.e. species that occur at low densities), but a small fragment is likely to have

only common species. This idea is easy to grasp when we consider species that have

large home ranges; for example, it means that we are unlikely to find a bear in a tiny

fragment. However, it also applies to species that have rather limited home ranges but

still actively avoid small fragments. For example, certain small birds such as Sprague’s

pipits and grasshopper sparrows have home ranges of only a few hectares, but are

usually not found in habitat fragments less than 100 ha in size (Davis 2004). Species

that do not occur in small patches of habitat are called area-sensitive species and are

often of concern to conservationists. Furthermore, uncommon species that are not

area-sensitive (i.e. that can find habitat in a small fragment) are also unlikely to occur

in a small patch by chance alone. This last point is a subtle one that is often overlooked

(Haila 1999), but it is easily explained with an example. Imagine there was an

uncommon tree species that had an average density of one individual per 1000 ha;

all other things being equal, a 100 ha sample plot would have a 1:10 chance of

Ecosystem Degradation and Loss 175

BOX 8.1

Island biogeography theory

The fundamental idea of MacArthur and Wilson’s (1967) equilibrium theory

of island biogeography is that the number of species on an island represents

a balance between immigration and extinction. The rate of

immigration is determined largely by how isolated an island is; the more

isolated, the lower its immigration rate. This is represented in Fig. 8.12,

with the curve for remote islands (far) being lower than the curve for

islands that are near the mainland (near). Extinction rates are a function of

island size; populations on large islands tend to be larger and thus less vulnerable

to extinction. In Fig. 8.12 the extinction curve for large islands is

lower than the curve for small islands.

For any given island there is an extinction rate and an immigration rate

that will balance one another and keep the number of species relatively constant.

In this example, the numbers of species for four equilibria are represented

as follows: SFS, number of species on a far, small island; SFL, far,

large island; SNS, near, small island; SNL, near, large island. P is the total

number of species that could potentially immigrate to the island from a

nearby landmass.

Figure 8.12 A graphical representation

of island biogeography theory.

(From Hunter 1990, reprinted

by permission of Prentice-Hall,

Englewood Cliffs, New Jersey.)

176 Part II Threats to Biodiversity

containing this species, but a 10

ha plot would have only a 1:100

chance. This sampling effect, added

across many species, would mean

that a small fragment would have

fewer species than a large fragment

simply because it is a smaller sample.

To adjust for this phenomenon,

fragmentation studies should focus

on number of species per unit area

(e.g. Rudnicky and Hunter 1993),

but most only report the number of

species in each fragment.

Third, small fragments will, on

average, have smaller populations

of any given species than large

islands, and a small population is

more susceptible to becoming

extinct than a large population

(Henle et al. 2004). This idea was a

key point in the preceding chapter.

Fragments that are isolated from

other, similar patches by great distances

or by terrain that is especially

inhospitable are likely to

have fewer species than less isolated

fragments for two reasons.

First, relatively few individuals of a

given species will immigrate into

an isolated fragment. Immigrating

individuals are important both

because they can “rescue” a small

population from extinction and

because they can replace a population

that has already disappeared

(Brown and Kodric-Brown 1977).

Second, species that are mobile

enough to use an “archipelago” of small habitat patches to collectively comprise a

home range are less likely to use an isolated fragment simply because it is inefficient to

visit it. For example, the copperbelly water snake travels among ephemeral wetlands

foraging for frogs and it seems to fare badly when wetlands are lost and the average

distance among the remaining wetlands increases (Roe et al. 2004).

Causes of Fragmentation

The fundamental cause of fragmentation is expanding human populations converting

natural ecosystems into human-dominated ecosystems. Fragmentation typically

Figure 8.13 The number of species in a sample plot or on an island

increases as area increases, but the steepness or slope of the curve

varies considerably among taxa. Note that in these graphs for taxa on

islands in the Baltic Sea some of the y axes are linear and some are logarithmic.

All of the x axes are logarithmic. Recall from Chapter 6 that

these lines are described by the formula S = CAz, where S is number of

species, A is area, and C and z are constants. (Redrawn from Järvinen

and Ranta 1987.)

Ecosystem Degradation and Loss 177

begins when people dissect a natural landscape with roads and then perforate it by

converting some natural ecosystems into human-dominated ones (Fig. 8.14). It culminates

with natural ecosystems reduced to tiny, isolated parcels. Thus fragmentation

almost always involves both reducing the area of natural ecosystems and increasing

their isolation, although some authors have advocated reserving the term for isolation

(Fahrig 2003). As the single largest user of land, agriculture is the proximate cause of

most fragmentation. Certainly, for many terrestrial species, a large expanse of cropland

is a barrier nearly as effective as a stretch of water. Urban and suburban sprawl

may be a more effective barrier to movement, but their total area is much more limited

than that of agriculture. Some writers use “fragmentation” to describe any

process that breaks up extensive ecosystems, including natural events such as fires,

whereas other writers restrict the term to human-induced changes. In any case,

human activities are the major cause of fragmentation in most landscapes.

Sometimes, it is unclear whether human land uses cause fragmentation. Consider

clearcutting forests; if this leads to the forest’s being converted to farmland, then

clearcutting obviously contributes to fragmentation. However, if the clearcut site is

allowed to undergo succession and return to forest, this may or may not constitute

fragmentation, depending on whether the clearcut is extensive enough to constitute a

significant barrier to the movement of plants and animals (Haila 1999, 2002). Of

course, this will vary from species to species. A slow-moving, moisture-loving slug is

far more likely to be deterred by a clearcut than most birds that can fly across a

clearcut in a few seconds. Similarly, at what point on the continuum of desertification

does fragmentation occur? A plant whose seeds are dispersed long distances by wind

may cross a desertified barrier easily, whereas a short-dispersal plant may be incapable

of crossing the barrier in one trip and unable to establish a population halfway

across in the degraded habitat.

Consequences of Fragmentation

Ecosystem destruction is the driving force behind fragmentation, and thus it is

inevitable that fragmentation is associated with negative effects on biodiversity. The

reason why fragmentation elicits so much special concern from conservationists is that

its consequences are greater than we would anticipate based solely on the area of

ecosystems destroyed. Notably, remnant ecosystems that seem to have escaped destruction

may no longer be available for area-sensitive species that cannot use small patches

of habitat. Most prominent among these are large predators that need extensive home

ranges to find enough prey (Crooks 2002). Some small species with limited home

ranges also avoid small habitat patches: for example, birds (Davis 2004) and beetles

(Laurance et al. 2002). This may occur because they require the microclimate characteristic

of the interior of large habitat patches, or because they select habitat patches

large enough to support other members of their species (a type of loose coloniality)

(Stamps 1991), or because of their interactions with other biota as predators, prey, or

competitors (Gibbs and Stanton 2001).

In highly fragmented landscapes, it is difficult for individuals (usually juvenile animals,

seeds, or spores) to disperse to another suitable patch of habitat. If immigration

and emigration are very limited, then the individuals occupying a fragment may effectively

constitute a small independent population and, as we saw in Chapter 7, small

178 Part II Threats to Biodiversity

Figure 8.14

People usually initiate

fragmentation

by building a road

into a natural landscape,

thereby dissecting

it. Next,

they perforate the

landscape by converting

some natural

ecosystems into

agricultural lands.

As more and more

lands are converted

to agriculture,

these patches coalesce

and the natural

ecosystems are

isolated from one

another; at this

stage fragmentation

has occurred.

Finally, as more of

the natural patches

are converted,

becoming smaller

and farther apart,

attrition is occurring.

(Terminology

from R. Forman,

personal communication,

and 1995;

also see Collinge

and Forman 1998.)

populations are more likely to disappear. Furthermore, if a population

does disappear, a low immigration rate will mean it takes much

longer to establish a new population. Even if fragmentation only

leads to partial isolation, this may change one large population into a

metapopulation, which may also affect population viability and persistence.

The dispersal of fire is also an issue; fragmentation has

greatly disrupted natural fire regimes in regions where fires once

swept across the landscape (Van Lear et al. 2005).

The migration of animal species that travel between habitats seasonally

could be impeded by fragmentation (Hunter 1997). In practice, this

is likely to be a problem mainly for species that walk, such as large

mammals that travel up and down mountains in spring and autumn, or

amphibians that migrate to and from spring breeding pools. Similarly,

the climate changes described in Chapter 6 require species to shift their

entire geographic ranges over long periods. In a fragmented landscape

this may be difficult for species with limited dispersal abilities, such as

many plants (Pearson and Dawson 2005).

Finally, one consequence of fragmentation is based on a simple rule

of geometry: the perimeter length of a patch changes as a linear

function, whereas its area changes as a square function. To take a

simple example, a 4 4 km patch has a perimeter of 16 km and an

area of 16 km2, and if we decrease it to 2 2 km, its perimeter halves

to 8 km, but its area decreases fourfold to 4 km2. This means that as

fragmentation makes patches smaller and smaller, their ratio of edge

to interior increases disproportionately (Fig. 8.15). Similarly, if we

define a zone in the patch that is within a certain distance of the

patch’s edge, the relative area of this edge zone will also increase

disproportionately as the patch gets smaller. Finally, although fragmentation

does not necessarily affect the shape of a patch, it should

be noted that another rule of geometry (a circle is the shape with the

shortest perimeter) means that the further a patch’s shape departs

from circular, the longer its edge will be.

Why is it important that small patches have relatively more edge

or ecotone habitat and less interior habitat? This is a complex topic (Ries et al.

2004), but one basic issue is that the physical environment near an edge is different.

For example, in a forest fragment bounded by fields, the edge zone will often be

windier, drier, and warmer than the forest interior, and this may increase tree mortality

and prevent some species, especially certain plants, from inhabiting this zone

(Laurance et al. 2002; Harper et al. 2005). Edge zones are also different because

early-successional species associated with the surrounding disturbed environment

often penetrate the edge. These are likely to include exotic species (e.g. competitors

such as weeds, and predators such as cats, rats, and people) that we will discuss in

Chapter 10, “Invasive Exotics.” One of the most extensively studied aspects of edges

concerns the reproductive success of birds nesting near forest–farmland edges.

Many studies have reported unusually high levels of nest predation near the edges

of forest fragments, although it is difficult to distinguish the specific effects of edges

from the overall effects of fragmented landscapes (Stephens et al. 2003). In general,

Ecosystem Degradation and Loss 179

Figure 8.15 Three principles of

geometry that affect the edge-toarea

ratios of patches. (a) Small

patches have relatively longer edges

than large patches. (b) Patches that

are less circular in shape have longer

edges than circular patches. (c) The

interior zone of a small or noncircular

patch is relatively small compared

with that of a large, circular

patch. (In these patches the shaded

edge zone is 100 meters wide.)

180 Part II Threats to Biodiversity

Figure 8.16 Penetration distances of different edge effects into forest remnants of the

Biological Dynamics of Forest Fragments Project in the Brazilian Amazon. (From Laurance

et al. 2002.)

it seems clear that whenever we have a natural ecosystem surrounded by a disturbed

ecosystem, the natural ecosystem is going to experience some disturbing

effects, what Dan Janzen (1986) has called “the eternal external threat.” The width

of these “impact zones” will vary greatly, from tens of meters in the case of microclimate

issues to kilometers in the case of poachers invading a protected reserve

(Laurance et al. 2002) (Fig. 8.16).

Ecosystem Degradation and Loss 181

CASE STUDY

Madagascar1

The island of Madagascar lies only 400 km from the cradle of human evolution in Africa, yet for thousands of years

after Homo sapiens had spread throughout most of the world, Madagascar remained undiscovered by people.

Madagascar was not, however, isolated from all primates. At least 50 million years ago some primitive primates colonized

the island, perhaps floating to the island on a tree swept to sea in a flood. Eventually, they evolved into

dozens of species represented in modern times by five families: lemurs, dwarf lemurs, sportive lemurs, indris/sifakas,

and the aye-aye (Fig. 8.17). Having split away from Africa and then India about 160 million and 80 million years

ago, respectively, Madagascar has been an isolated haven for evolution in many life forms besides primates. Seven

families of plants, five of birds, and six of mammals are restricted to Madagascar and nearby isles; overall roughly

80–90% of all the non-marine native plant and animal species are endemic to the island. The biota is rich, as well

as unique. For example, Madagascar has about 12,000 plant species compared with Europe’s 12,500, even though

Madagascar is only about the size of France. Frogs provide a more impressive comparison; only 25 frog species

inhabit all of Europe, while Madagascar has 230 described species (all but two species are endemic; and 45 more

potential species await formal description). Madagascar’s great climatic and geologic diversity is probably the main

reason for its biotic diversity. The island is subdivided into many regions with profoundly different topography, geology,

soils, and weather patterns. Collectively, these provide a diverse array of environments, from rain forests to

semiarid lands dominated by didiereas, an endemic group of spine-covered plants vaguely reminiscent of cacti.

Madagascar’s isolation came to a rather abrupt end roughly 2000 years ago when human colonists arrived,

probably from both Africa and Southeast Asia, and began shaping the land to their needs. The Malagasy people set

fires to produce fodder for large herds of cattle and cleared the forest for “slash and burn” agriculture. It is unclear

how extensively forested Madagascar was when people arrived. Some ecologists have assumed that some type of forest

or woodland covered the whole island; others believe that some parts of central Madagascar were grasslands. In

Figure 8.17

Madagascar is

home to many

unique species

such as the indri,

the largest species

of lemur. (Photo by

M. Hunter.)

182 Part II Threats to Biodiversity

Summary

Ecosystems and habitats (the physical and biological environment used by a particular species)

are routinely degraded, and sometimes destroyed, by human activities. These activities are the

most critical threat to biodiversity. Contamination of air, water, soil, and organisms by pollutants

is a major form of degradation. Pollution can range from relatively innocuous materials

such as sediment that smothers the bottom of a stream to extraordinarily toxic chemicals that

are lethal at small doses. Sometimes, populations are eliminated outright by pollution, especially

by pesticides; more often, pollution represents a stress that reduces population fitness.

People also construct many physical structures that may degrade habitat quality for certain

species. Roads are the best known examples; they impede the movement of some organisms,

and, worse still, some organisms are run down by vehicles. Moreover, dams and fences are likely

to be absolute barriers to the movements of some species. Ecosystems can also be degraded by

altering physical processes. For example, people commonly: (1) accelerate soil erosion, which

causes silt pollution and decreases site productivity; (2) decrease the frequency of fire in ecosystems

where it is a natural event, or increase the frequency of fire where it is uncommon; and

(3) remove too much water from ecosystems where it is needed.

Deforestation is a major form of ecosystem destruction that has profound consequences for

biodiversity because forests cover less than 6% of the earth’s total surface area yet are habitat

for a majority of the earth’s known species. Deforestation has slowed in many temperate

regions, but tropical deforestation continues at an alarming pace and threatens an incredibly

diverse biota. Many arid and semiarid ecosystems are being degraded and even destroyed by a

process called desertification, primarily the product of overgrazing by livestock and unsound

cultivation. Myriad species occur in these environments and are at risk because of desertification.

Many aquatic ecosystems have been destroyed by profound changes in their hydrologic

either case, virtually all types of ecosystems are highly degraded today, and less than 25% of the island remains in

forests and woodlands (Dufils 2003). Presumably, the loss of forests and resulting siltation has also affected freshwater

and coastal ecosystems (which include many mangrove swamps and coral reefs), but this has been little studied.

We do know that Madagascar’s unique freshwater fish fauna is severely threatened by deforestation, overfishing, and

exotic species (Benstead et al. 2000). One port, Mahajanga, was lost after 100 million m3 of sediment was deposited

in 25 years. Many of Madagascar’s most striking species – elephant birds, giant lemurs, and giant tortoises – disappeared

after humans inhabited much of the island (Burney et al. 2004). The fact that many of the species were relatively

large suggests that overhunting played a role in their demise too, and we will return to this issue in the next

chapter. The bottom line in all of this is that the growing numbers of Malagasy people and cattle have made ecosystem

degradation and loss almost inevitable. (There were about 2.5 million people in 1900, 4 million in 1950, and 18

million in 2005; it is generally estimated that the Malagasys keep about one head of cattle per person.)

Conservationists throughout the world have set their sights on Madagascar because the stakes are so high (we

have so many unique taxa to lose) and the threats so enormous. Here lies some ground for optimism. Ambitious

projects to protect key examples of various ecosystems by more than tripling the size of the protected area system

(1.7 million km2 to 6 million km2), to foster ecotourism and other forms of sustainable development, and to improve

land-use practices throughout the island are under way with sponsorship from a diverse array of national and

international organizations.

1 This case study is primarily based on Jolly (1980), Jolly et al. (1984), Groombridge (1992), Quammen (1996), Goodman

and Patterson (1997), Goodman and Benstead (2003, 2005), and personal communication with Eleanor Sterling.

Ecosystem Degradation and Loss 183

regime imposed by filling, draining, dredging, damming, channelizing, and diking. Rivers and

wetlands have been especially vulnerable to these alterations. For this reason, and because they

represent a small portion of the earth’s area, the species tied to these ecosystems are in considerable

jeopardy.

Fragmentation is the process by which a natural landscape is broken up into small parcels of

natural ecosystems isolated from one another in a matrix of other ecosystems, usually dominated

by human activities. Fragmentation can diminish biodiversity because small, isolated

patches of habitat have fewer species than larger, less-isolated patches. This is true because: (1)

small patches have less environmental heterogeneity than large patches; (2) some area-sensitive

species and uncommon species are unlikely to be found in small patches; (3) small patches

have small populations that are more vulnerable to local extinction; (4) immigration into populations

occupying isolated patches is limited; and (5) isolated patches are less likely to be used

by species that routinely travel among patches. Besides affecting biodiversity by reducing patch

size and increasing isolation, fragmentation also creates more edges between different types of

ecosystems. These edge zones represent degraded habitat for many species.

FURTHER READING

Many books review the various ways the earth has been degraded by pollution; one of the popular textbooks is

Miller (2005a). For statistics and an overview, see the periodic reviews published by the World Resources Institute

and its collaborators and their web-based service, Earthtrends (accessible at www.wri.org), a United Nations assessment

of the state of the planet (www.millenniumassessment.org), and the Atlas of the Human Footprint

(www.wcs.org/Footprint). For books on the degradation and destruction of various types of ecosystems, see

Mainguet (1994) on desertification, Williams (2003) on deforestation, Mitsch and Gosselink (2000) on wetlands,

Boon et al. (2000) on rivers, and Norse and Crowder (2005) on marine ecosystems. Forman et al. (2003) reviews

road impacts; for the effects of fragmentation see Rochelle et al. (1999). Quammen (1996) is a very readable

account of island biogeography and fragmentation.

TOPICS FOR DISCUSSION

1 Do you think that, whenever people significantly change an ecosystem from its natural state, this constitutes

ecosystem degradation? Recall one example of ecosystem degradation: a power plant warming a river, causing

temperature-sensitive species to disappear. Would you consider this ecosystem degradation if all the species that

disappeared were common and they were replaced by a larger number of species, all of them native, including

one that is an endangered species?

2 Habitat loss for one species often leads to habitat gain for another species; for example, removing a dam may

increase habitat for riverine species while decreasing habitat for lake species. How do you balance these out, especially

if you are comparing two species that are of equal concern to conservationists and neither habitat is particularly

natural?

3 Describe some reasonable thresholds at which habitat degradation can be considered habitat destruction, or

ecosystem degradation can be considered ecosystem destruction.

4 Why are some species more sensitive to contamination than others?

5 Discuss the fundamental similarities and dissimilarities between deforestation and desertification.

6 Why are lakes less vulnerable to ecosystem destruction than rivers?

e eBook Collection Chapter 16

Both a date palm and a tiny mite living in a crack in the palm’s bark may stand equal

in the eyes of people who believe that every life-form has intrinsic value, value that is

independent of the special, self-centered interests of humanity. However, intrinsic values

do not eliminate or invalidate instrumental values. Instrumental values are still

there, profoundly influencing the way most people view date palms and mites. Why?

Instrumental values are readily translated into economic values that people can relate

to in their daily lives. The phrase “money makes the world go round,” may seem trite

given the realities of astronomy, but it does hint at the central role of economics in

human endeavors, including conservation. Consider the World Conservation Union’s

definition of conservation: “the management of human use of the biosphere so that it

may yield the greatest sustainable benefit to present generations while maintaining its

potential to meet the needs and aspirations of future generations” (IUCN et al. 1980).

These certainly sound more like the words of an economist than the words of a biologist,

and they remind us of the need to have a solid grounding in economics if one is

to participate meaningfully in the societal dimensions of conservation biology.

In this chapter we will first address a two-pronged question: what are the costs and

benefits of maintaining biodiversity? Then we will examine how these costs and benefits

are distributed among people. Perhaps you can already anticipate the take-home

message of this chapter: people will be compelled to overexploit species and degrade

ecosystems if the costs and benefits of maintaining biodiversity are not distributed in

a fair and sensible manner (Fig. 16.1). Moreover, there is a fundamental, though often

unappreciated, conflict between economic growth to improve the lives of humans

versus the welfare of wild life. To put it directly, as the human economy grows and

appropriates increasing amounts of matter and energy it degrades or eliminates

ecosystems (Czech 2000; Czech et al. 2000). Addressing discrepancies between those

who bear the costs and those who enjoy the benefits is the clearest path to a solution.

The Benefits

Coal, copper, and gold are fundamentally different from cod, ducks, and oak in the

eyes of an economist who sees the world as a collection of resources to be exploited

for the benefit of people. The first three are nonrenewable resources, supplies of which

are finite and exhaustible. The latter three are renewable resources; they will last

indefinitely if used wisely. Most renewable resources are living, biological resources,

but some nonliving resources are also renewable. Clean air and water are examples.

CHAPTER 16

Economics

To exclude domestic species, which are also a

renewable resource, the term renewable natural

resource is often used. Quantifying the values of

renewable resources is often more difficult than

quantifying the values of nonrenewable

resources. A cod is not just an inert commodity

waiting to be extracted and sold at market. It is

a living thing – dynamic, mobile, and interacting,

often unpredictably, with many other

species.

In this section we will describe benefits as

economists do – goods and services. Briefly,

goods are physical objects that you can purchase,

own, and use, while services are labor

that is performed for your benefit (e.g. by a professor

teaching you). We will also discuss two

types of benefits that are less concrete: potential

values and existence values. We will continue

to focus on wild species, but we will not

overlook domestic species entirely. Domestic

species may be a small component of biodiversity,

a few hundred species among millions, but

they are a significant portion of the overall

economy.

Goods

Plants and animals harvested from the earth’s farmlands, rangelands, forests, and

waters and sold at market every year account for nearly $2 trillion (United Nations

Development Programme et al. 2003), roughly 6% of the global domestic product. (All

monetary figures used here will be in United States dollars.) In many less-industrialized

countries such as Albania, Burundi, Guyana, and Nepal the percentage is much

higher, 30–50% or more. The commercial value of wild species is a significant portion

of this total because two major enterprises, forestry (Fig. 16.2) and fisheries, rely far

more heavily on wild stocks than on plantations and aquaculture. Global values for

wood and fishery products have been estimated at $418 billion and $70 billion, respectively

(Freese 1998). (Note: the annual production of fisheries is about $20 billion less

than the cost because of government subsidies that we will discuss further below.)

A significant portion of the goods derived from biota are not bought and sold commercially.

They are used for direct subsistence by the people who collect them. For

example, modern supermarkets with thousands of food products – sardines from

Norway, grapes from Chile, tea from Sri Lanka – are amazing things, but far more

people grow or gather much of their own food than use supermarkets (Fig. 16.3).

Similarly, wild species gathered from nearby ecosystems are often very important to

subsistence lifestyles, especially for fuel and building materials.

Estimating the total volume and value of wild and agricultural products that are

consumed directly by the people who grow and harvest them is not easy for two

Economics 347

Figure 16.1 Strong tensions arise when those asked to

bear the costs of protecting biodiversity do not perceive that

they receive any benefits for doing so. Here anger is being

expressed at restrictions to logging in government-owned

forests in the US Pacific Northwest designed to

protect the spotted owl under the Endangered Species Act.

(Photo from Steven Holt/stockpix.com.)

reasons. First, because items move from ecosystem to home quickly, not changing

hands except within a family, it is difficult for government data collectors to record

these uses except by doing a house-by-house survey. Second, many wild products are

seldom sold at market, making it difficult to estimate their true value. Despite these

difficulties, several assessments have been made. For example, on the Kizilirmak Delta,

a wetland of international importance on Turkey’s Black Sea coast, villagers sell

about $500,000/year of sharp-pointed rush for making flower arrangements, baskets,

and spikes for frying mussels, shish kebabs, and drying pasta. Villagers make five

to seven times as much money in this activity as in farm labor (and fear being

excluded from the delta if it is protected as a nature park) (Ozesmi 2003).

In some areas, simply determining the variety of wild species being used is a substantial

exercise. For example, Phillips et al. (1994) documented uses of 57 families of

woody plants in one small area of the Peruvian Amazon. Similarly, Borana pastoralists

of southern Ethiopia use 248 rangeland plant species and can identify many more

(Gemedo-Dalle et al. 2005).

Services

The distinction between goods and services is readily applied to the benefits we receive

from other living things. If you eat the dates of a date palm, it has provided you with

goods; if you rest in its shade, it has provided you with a service. Of course, estimating

the value of the shade provided by a date palm can be difficult unless the person who

owns the date palm charges a fee for this service, and, in practice, most of the services

provided by genes, species, and ecosystems are not sold.

348 Part IV The Human Factors

Figure 16.2

Harvesting trees

from natural

forests for fuel,

fiber, and construction

materials is a

major source of

goods derived

from wild species.

(Photo from

J. Gibbs.)

This has not stopped creative people from devising ways to estimate the value of

biological services (Daily 1997; Pimentel et al. 1997; Cullen et al. 2005). For example,

horticulturalists routinely estimate the value of the aesthetic services provided by

ornamental trees, usually to settle insurance claims, and values often reach thousands

of dollars for a tree too large to be directly replaced (Council of Tree and

Landscape Appraisers 1992). One ambitious project attempted to estimate the total

value of global ecological services in two steps (Costanza et al. 1997a). First, they

summed value estimates (dollars per hectare per year) for 17 types of service across

16 major types of ecosystem in a huge matrix. (Some goods were included too, but

they were dwarfed by services.) For example, the value of coral reefs was estimated

at $6075 per hectare per year by summing up $3008 for recreational value, $1 for

cultural value, $2750 for disturbance regulation (blocking storm waves), $58 for

waste treatment, and so on for eight types of service provided by coral reefs. For

tropical forests, estimates for 14 different types of service totaled $2007 per hectare

per year. Open oceans totaled $252 per hectare per year. After they had summed

estimates for each ecosystem type these were multiplied by the global area of that

type. For example, although the per-hectare figure for open ocean was small, $252,

when multiplied by 33 billion hectares, it yielded a total value over $8 trillion.

Summed across all the ecosystem types, the grand estimate for global ecosystem

services was $33 trillion per year, with a reasonable range of $16 trillion to $54

trillion. As a point of reference, the gross national products of all the world’s

nations total about $18 trillion. Because of various uncertainties, notably missing

estimates for many services of many ecosystem types, the estimate was considered a

minimum. A similar accounting by Pimentel et al. (1997) is given in Table 16.1.

Economics 349

Figure 16.3 In

many parts of the

world, wild meat is

an important

source of protein

for people, such as

these subsistence

hunters with

recently captured

tortoises in northern

Amazonia.

(Photo from Joel

Strong.)

350 Part IV The Human Factors

Table 16.1 A biotic

invoice, that is,

estimated annual

economic benefits

of biodiversity in

the United States

and worldwide

(figures are in

billion US dollars).

Activity United States World

Waste disposal 62 760

Soil formation 5 25

Nitrogen fixation 8 90

Bioremediation of chemicals 22.5 121

Crop breeding (genetics) 20 115

Livestock breeding (genetics) 20 40

Biotechnology 2.5 6

Biocontrol of pests (crops) 12 100

Biocontrol of pests (forests) 5 60

Host plant resistance (crops) 8 80

Host plant resistance (forest) 0.8 6

Perennial grains (potential) 17 170

Pollination 40 200

Fishing 29 60

Hunting 12 25

Seafood 2.5 82

Other wild foods 0.5 180

Wood products 8 84

Ecotourism 18 500

Pharmaceuticals from plants 20 84

CO2 sequestration 6 135

Total 319 2928

Source: from Pimentel et al. 1997.

Because people do not actually pay, for example, $6075 per hectare per year

for the services of a coral reef, these numbers are arguably too speculative to

be useful. Nevertheless, these numbers do clearly illustrate the importance of

ecosystems to human welfare, especially to those who view the world in

economic terms. (See Box 16.1 for a more detailed example of estimating

value; see Wilson and Carpenter [1999] for a comparison of three common

methods.)

Economics 351

BOX 16.1

Using contingent valuation to value elements

of biodiversity1

Kevin J. Boyle2

About one-half of all land in the contiguous United States is used for cropland or pasture. Biologists have expressed

concern about the declining populations of grassland bird species, and loss of habitat is generally cited as the major

reason for their decline. The major historical grassland area of the United States is in the plains states, where agriculture

dominates the landscape. Over time, farms have been established and consolidated, leaving less undisturbed

habitat for grassland birds.

Beginning in 1985 the US Department of Agriculture’s (USDA) Conservation Reserve Program (CRP) converted

about 7% of the cropland in the 48 contiguous states to grassland. Over four-fifths of this area is concentrated in

one-fifth of the counties, which are predominantly in the plains states. The Wildlife Management Institute (1994)

reports that CRP grasslands cover at least twice the area of grasslands in all of the national and state wildlife

refuges within the continental United States. Anecdotal evidence by wildlife experts (e.g. National Audubon Society)

and empirical analyses suggest that the CRP has helped to reduce, stop, or reverse the declines in the populations of

some grassland bird species.

Initial enrollments in the CRP were prioritized according to the erodibility of the soil. As priorities of

the CRP are expanded to recognize other environmental benefits such as improved habitat for grassland birds,

information is needed on the values the public places on such benefits. Revisions of the CRP in 1990

introduced the Environmental Benefits Index (EBI) as a tool to prioritize and rank landowners’ offers of land for

enrollment in the CRP. Contingent-valuation estimates of the values the public places on changes in the populations

of grassland birds can be used to help to justify changes in grassland bird populations as a component of

the EBI.

Two samples were used, one national and one of Iowa residents, and the survey was administered by mail.

Individuals in the national sample were asked about changes in populations of grassland birds in the plains states,

which included all of Iowa and parts of the border areas of each state that is adjacent to Iowa. Iowa is one of three

areas of high concentrations of CRP lands.

Empirical analyses of grassland bird populations suggested that CRP lands may benefit populations of grassland

birds whose populations have been decreasing over the past 30 years (grasshopper sparrow, Henslow’s sparrow,

mourning dove, eastern kingbird, northern bobwhite quail, horned lark, dickcissel, and ring-necked pheasant) and

may also benefit species whose populations have been constant or increased over the past 30 years (lark sparrow,

upland sandpiper, gray partridge, field sparrow, indigo bunting, killdeer, barn swallow, and house wren). We asked

respondents to reveal their monetary values, through a contingent-valuation question, for restoring populations

352 Part IV The Human Factors

of grassland birds to their population of 30 years ago (for the species whose populations had declined), or for

increasing the populations (for species whose populations had been constant or increased over the same period).

For declining populations the proposed increases ranged from 14% for ring-necked pheasants to 136% for

grasshopper sparrows. The proposed increases for the second group of species ranged from 20% for house wrens to

84% for lark sparrows.

The survey described a proposal where changing agricultural lands to native grasses would result in the

populations of each of the species specified above being increased by a certain amount. For each species,

respondents were told: (1) whether it was native or introduced; (2) whether it was a permanent resident or

migratory with breeding habitat in the study area; (3) the population 30 years ago; (4) the current population;

and (5) the population with the habitat enhancement. Study participants were asked two questions. The Iowa

sample was first asked:

Those who answered “yes” were asked a second question:

The amounts ranged from $1 to $100. Participants in the national sample received similar questions where

they were asked about increases in their federal income tax. Responses from the first question allowed us to find out

if respondents held a value for changes in the populations of the specified grassland birds, and the second question

allowed us to statistically estimate the value for people who hold values for the population changes.

For the national sample, 71% of respondents answered yes to the first question, and the comparable figure for

the Iowa sample was 72%. The average values were $12 for the national sample and $13 for the Iowa sample.

The values for the national sample are primarily composed of existence values because these people are not

expected to have any direct use of these grassland birds for viewing or hunting, while the Iowa values contain a use

component. Quail, pheasant, and partridge can all be hunted in Iowa, and other species in the lists are popular for

viewing.

These results indicate substantial public values for improving grassland bird habitats in the greater Iowa

area from both a national and local perspective. When the averages of $12 or $13 are multiplied by the

respective populations of households, the aggregate economics benefits are substantial: over $500 million at the

national level. While increased populations of grassland birds are only one of the environmental benefits of the

CRP, these valuation results indicate that providing habitat for grassland bird populations should be a component

of USDA’s EBI for prioritizing land to take out of agricultural production.

Would you vote for the proposal if passage of the proposal would increase your household’s 1998 Iowa income tax?

How would you vote on the proposal if passage of the proposal would increase your household’s 1998 Iowa income

tax by the following amounts?

1 This box is distilled from Ahearn et al. (2004).

2 Department of Resource Economics and Policy, University of Maine, Orono, Maine.

There are some important exceptions to the generalization that ecological services are not bought and

sold. In particular, ecological services that are chiefly based on aesthetics and recreation are widely purchased.

This happens whenever people pay for the privilege of visiting a natural ecosystem or encountering

wild life by paying for transportation, food, lodging, equipment, guide services, licenses, entrance fees, and

so on. The total value of nature-based recreational activities or ecotourism is enormous. In the United

States alone, people pay about $108 billion per year just for recreation centered on

wild animals: hunting, fishing, and wild animal viewing (US Fish and Wildlife Service

2002). When the actual expenditures people make for recreational services are compared

with the amounts they are willing to pay, people tend to be willing to pay more

than they actually have to pay. In other words, the potential value of recreational

services probably greatly exceeds the current market value, at least in wealthier

nations. Even in South Africa, where the gross domestic product per capita is only

about $11,100 per year, citizens are willing to pay about $3.3 million per year to

maintain the endemic-rich fynbos region, and $58 million for biodiversity nationally,

values about comparable to the government budgets for conserving these areas

(Turpie 2003).

Potential Values

Most economists are reasonably comfortable with the idea of predicting the future,

but they are quite conservative about predicting the future value of all the species

that are not currently of direct use. Their reticence is understandable. Who is to say

which species of plant or microbe, if any, will be discovered to contain a cure for AIDS

or malaria?

Given that we cannot predict where science will take us, the one thing that we can say

with confidence is that all life-forms have potential value. Perhaps we can say that some

life-forms have more potential value than others: for example, plants in families that are

well known to have high levels of bioactive compounds, or wild species that are close

relatives to important domesticates and that might serve as a source of genetic material.

Again, however, we can never definitively say of any form of life that it has no potential

value. Who would guess, for example, that “slime” collected from a hotspring in

Yellowstone National Park would contain an organism, Thermus aquaticus, that would

give rise to a revolution in biotechnology that would change our lives irrevocably?

Biodiversity advocates usually think of potential values, also called option values,

with respect to species and genes not known to be of direct value currently. However,

in a broad sense, the term could be used for populations or ecosystems that are known

to be of value if someone wished to initiate exploitation. For example, forests in currently

protected nature reserves or in parts of Siberia and Canada that are too remote

to be logged have potential value because we can cut them in the future if we choose

to. It is not a matter of determining their potential usefulness, only of deciding

whether it makes sense to use them at a particular time.

Existence Values

Your chances of ever seeing a wild snow leopard, slinking down a slope of snow and

scree, are exceedingly small. Snow leopards are so rare and elusive, and their habitat

in the mountain fastness of central Asia is so inaccessible, that only a handful of

outsiders (or even local residents) have ever seen one. Nevertheless, you probably

derive some pleasure simply from knowing that snow leopards exist in the wild.

Many people feel this way about species that they will never encounter and ecosystems

that they will never visit. Whether this phenomenon is based on spiritual values,

ethical values, respect for intrinsic value, or other factors can be argued, but the

key point is that it is not tied to tangible goods or services. Economists prefer to speak

Economics 353

of existence values (Fig. 16.4), the value of simply knowing that something exists

(Krutilla 1967).

Sometimes, people like to know that something exists simply because it might be of use

to future generations, even though it is not used now. This is called bequest value, and one

could consider it to be a special type of existence value or a special type of potential

value. Many wild species lurking in obscure locations whose commercial value is as yet

unrealized qualify for having significant bequest value. They have historic precedents in

species such as the rosy periwinkle, with its anti-cancer compounds upon which we are

now so dependent.

Economists have estimated existence values by asking people questions such as “How

much would you pay to save blue whales from extinction, even though you will never

see one?” The average amounts mentioned in response are usually rather small, typically

a few dollars, although they may reach tens of dollars for well known species such

as bald eagles (Bishop and Welsh 1992). Nevertheless, if you multiply these figures by

millions of people and across whole ecosystems, then the total values can be quite

impressive. Existence values are quite controversial because some economists object to

attempts to quantify something so intangible, especially by asking people hypothetical

questions about how they would spend money (see, for example, Attfield 1998; White

et al. 2001).

Consumptive versus Nonconsumptive Uses

Natural resource managers often use particular terminology in discussing benefits.

Using something in such a manner that it is

no longer available for someone else to use

(e.g. we harvest an oak tree or codfish) is called

consumptive use. On the other hand, if our use

does not eliminate or substantially reduce its

value (e.g. children joyously climbing in the oak

tree or bird watchers ogling a rare warbler in

the oak’s crown), this is nonconsumptive use.

Generally, goods used for commerce and subsistence

involve consumption, whereas services

and existence values are nonconsumptive.

Sometimes, using ecological services can involve

a form of consumption: for example, when so

many people visit an ecosystem that they degrade

it simply by compacting soil, trampling vegetation,

and frightening animals. Some economists

also distinguish a third style of use, indirect use. In

this sense, people who know and value the

Serengeti, Amazonia, Great Barrier Reef, mountain

gorillas, and blue whales through books and

films, but will never encounter them directly, are

making indirect use of these ecosystems and

species.

354 Part IV The Human Factors

Figure 16.4 Gorillas are an excellent example of a

species with significant existence value. Despite the

remote possibility that the average person will ever get

to see an actual gorilla many people still derive great

satisfaction out of knowing that gorillas exist in the wild

and are willing to contribute financially to support

gorilla conservation. (Photo from M. Hunter.)

The Costs

“There is no such thing as a free lunch.” This truism is a favorite among environmentalists,

who frequently use it when pointing out the hidden costs of environmental

degradation. Consider a simple example: historically, when a business person weighed

the costs and benefits of building a coal-fired power plant, the costs in terms of respiratory

disease of people living downwind were not included in the calculations. These

were external costs (externalities, in the language of economics) that did not affect

business profits and losses.

One consequence of the environmental movement is that some costs that were formerly

external have been internalized. Today, in many countries environmental regulations

mean that business people must include the costs of pollution control in

their calculations. This is often called the “polluter-pays” principle. The extent to

which a country requires polluters to internalize these costs has major consequences

for biodiversity (Stone 2001). Of course, many environmental costs, beyond the

more blatant effects of pollution on human health, still exist but remain hidden;

however, at least a precedent for internalizing them has been set. We will return to

this issue below, but in the balance of this section we will turn the “no free lunch”

truism upside down by asking: what are the costs of maintaining biodiversity – of

maintaining a healthy environment? There are basically two; we will call them

explicit and implicit costs.

Explicit Costs

Human beings are doers, actors, manipulators. If we encounter a problem, we try to

solve it. As it became apparent that loss of biodiversity was a problem, we began to

attack the problem by using a host of technological approaches outlined in the chapters

of Part III, “Maintaining Biodiversity.” We restore wetlands, grasslands, and other

ecosystems; we translocate endangered species and provide them with food and other

required resources; we redesign our existing technology to reduce environmental pollution

and energy use; and so on. Collectively, we could refer to these explicit costs as

the cost of environmental technology.

Our response may be grossly inadequate, but this work still requires money. Some

projects have substantial budgets, such as bringing California condors back from the

brink of extinction (well over $1,000,000 per year) (Cohn 1993; Alagona 2004) or

restoring the Everglades wetland complex of southern Florida (estimated at $7.8

billion over 30 years) (Perry 2004). Others get by on a shoestring. For example, the

entire world population of the Chittenango ovate amber snail is located on a small

ledge at the base of a 30 meter high waterfall in central New York state. The species

has been rescued from near extinction largely due to the efforts of a group of dedicated

volunteers who pluck out members of an invasive snail species that competes

with the endangered snail. In between these extremes we have estimates that $32

million to $42 million per year would pay for habitat management for 681 endangered

species in the United States (chiefly through the control of exotic species and

the management of natural fire regimes) (Wilcove and Chen 1998).

Turning to the big picture, in terrestrial parts of developing countries where

much biodiversity resides some $1–1.7 billion per year is needed to manage all

Economics 355

existing protected areas and some $4 billion more per year over the next decade to

establish and manage an adequate protected area system (Bruner et al. 2004). For

marine protected areas globally, conserving 20–30% of the world’s seas would cost

$5–19 billion annually (Balmford et al. 2004). Developing subsidies designed to

make farming, logging, fishing, etc. ecologically friendly would bring the total global

bill for conservation to $300 billion (James et al. 1999) or only about $50 per person

per year. This is an extraordinary bargain when you consider how many individuals

spend much more than this each month on junk food alone. Moreover, it is

not a great deal of money when compared with the subsidies governments currently

give to farmers, fishers, etc., usually to do things that are rather detrimental

to the environment. These negative subsidies have been estimated at roughly $1.5

trillion dollars per year, about five times the amount needed for conservation (Myers

1998). Notably, where to invest geographically is also a significant consideration.

More specifically, the returns on investment in conservation are highly skewed

around the world, with benefits-to-costs ratios being far greater in less developed,

tropical regions than in the industrialized nations where land is so expensive

(Balmford et al. 2003).

Implicit Costs

From an economist’s perspective, whenever a logger is prevented from cutting a tree, a

whaler from harpooning a whale, or a farmer from draining a wetland, they have suffered

an implicit cost because they have lost an opportunity to use a resource to make

money. These losses of opportunity will seem most acute if a specific investment has

been made: for example, if the wetlands, forest land, whaling ship, logging equipment,

and so on were purchased on the assumption that the trees, whales, or wetlands were

available for use. If the farmer has owned the wetland for many years and only recently

considered draining it, or if the whaler purchased the ship 20 years ago and long ago

repaid the initial investment, then the loss may seem less severe. Similarly, the loss will

seem less acute if the investment can be easily redirected somewhere else – if the logging

equipment can be used to cut a different stand of trees, for example. However, if

the investment is in land, it can be difficult to sell the land if it has special ecological

values that restrict how it can be used.

The implicit costs imposed by environmental regulations can be significant. The

timber in a single hectare of old-growth Douglas fir in the Pacific Northwest can

have a stumpage value (the price paid by the logger to the landowner) of about

$75,000 per hectare (Lippke and Bishop 1999). This translates into $75 million for a

thousand hectares of old-growth forest. This is approximately the area needed by a

single pair of spotted owls. The value is even greater loss if you assume that the land

is protected into perpetuity and will not be available for growing lumber in the

future.

The Distribution of Benefits and Costs

Life can be unfair, and so can biodiversity conservation. Some people derive more benefits

from the maintenance of biodiversity than do some other people; some people

bear relatively more costs. Before going on to some ideas about how to make costs and

356 Part IV The Human Factors

benefits more equitable, in this section we will briefly examine how the benefits and

costs described are distributed among people.

Goods. The commercial and subsistence benefits of biodiversity flow most directly

to the producers who grow domestic species or harvest wild life; to the manufacturers

who generate secondary products such as paper and medicines from biotic materials;

and to the merchants who distribute these items to consumers. Of course, the ultimate

beneficiaries of commercial use are consumers, and we all consume other

species.

Services. Everyone benefits from the ecological services of the earth’s biota, even

urbanites who never leave cities, but still need clean air to breathe and water to drink.

New York City is a case in point – an agglomeration of some 13 million people drinking

water derived from well managed ecosystems in nearby mountains that is so clean

that it requires only minimal treatment. Most people also enjoy ecological services

based on aesthetics, especially if you include watching nature films on television and

walking in a city park.

Potential values. Potential values simply reflect the possible future value of goods

and services, and thus one could describe their principal beneficiaries as our children

and grandchildren.

Existence values. Many people have heard of at least a few of the better known

species (e.g. ostriches, giraffes, koalas) and have a generally positive impression

toward them that can be construed as an existence value. Of course, on the other

hand, most people have not heard of very similar creatures such as rheas, okapis, and

wombats, to say nothing of the myriad species of invertebrates and microorganisms.

In other words, most people hold existence values for biota, but they are focused on a

tiny subset of biodiversity.

Explicit costs. Understanding how the costs of environmental technology are

distributed is a bit complex because there are four widely overlapping groups

involved: taxpayers, consumers, business owners, and volunteers. Taxpayers fund all

the government agencies that undertake conservation work, such as establishing and

maintaining reserves, restoring ecosystems, protecting endangered species, and so

forth. Consumers usually pay for environmental technology through higher prices

whenever regulations mandate that businesses internalize the costs of maintaining a

healthy environment. On the other hand, there are at least two circumstances under

which the owners of a business will bear the cost of internalizing environmental

technology through a reduction in their profits. First, this can happen if competing

businesses are not subject to the same regulations. For example, imagine that government

regulations require Argentinean farmers to use an expensive, low-toxicity pesticide,

whereas Chilean farmers can use a cheaper but more dangerous pesticide. If

farmers in both countries are competing for the same international market, the

Argentinean farmers may have to lower their profits so that they can still sell their

produce at the same price as the Chilean farmers. Second, some businesses (e.g. utilities

companies) have their profits regulated by the government, and the government

can decree that internalization of environmental costs should be borne by the company

owners rather than consumers. The fourth group of people who pay the explicit

cost of environmental technology are the millions of individuals who make donations

to private conservation groups, thereby supporting conservation work with voluntary

contributions of money and sometimes labor.

Economics 357

Implicit costs.When protection of biodiversity takes precedence over someone’s

opportunity to use a species or ecosystem for personal gain, the costs are borne most

directly by people who make their living by farming, logging, fishing, hunting, trapping,

mining, developing land, and so on. Most of these people are commercial entrepreneurs,

ranging from huge corporations that own millions of hectares of forest to

loggers who may own little more than an axe. A few are subsistence users who sell little,

if any, of their harvest. Merchants and manufacturers who might have used the

species or ecosystem later (e.g. converting a tree to paper and then selling it) will also

experience an implicit cost through losing an opportunity to use a resource.

Problems and Solutions

Superficially, there seems to be a fairly good balance in the distribution of biodiversity

maintenance costs and benefits. Everyone to varying extent sits on both sides of the

equation. We all use ecological services and consume biota-based products on the one

hand; we all support biodiversity maintenance through taxes and higher prices on the

other hand. On closer inspection there are many fundamental imbalances. In this section

we will examine four problems and outline some possible solutions. Note that

while it is easy to suggest solutions, this does not mean that it is easy to implement

them. As you will see, many of them require fundamental changes to how society

operates.

Problem 1

Many biological resources are communally owned, and thus the costs of overexploitation and

degradation are shared by many people, whereas the benefits of overexploitation are taken

largely by the people who are doing the overexploiting. If you are familiar with Garrett

Hardin’s classic essay “The Tragedy of the Commons,” you will realize that this situation

tends to compel overexploitation. (See Box 16.2 if you are not familiar with the

“tragedy of the commons,” formally known in economic circles by terms like “openaccess

resource management” [Costanza et al. 1997b]) This phenomenon is particularly

pervasive in aquatic ecosystems, especially the oceans, where private ownership

is rare. Indeed, in most parts of the oceans and in Antarctica, ownership is not even

claimed by nations, let alone by individuals or corporations. Ownership is also a very

tenuous thing in many tropical forests where local people have only a tradition of

access, not legally binding deeds, as a basis of “ownership.” As a result they are frequently

at risk of being displaced by programs concocted by the government and large

businesses (see Oldfield and Alcorn 1991).

The “tragedy of the commons” dilemma is also applicable to biodiversity in general

if you think of genes and species as communally owned assets. From this perspective,

you may own the individual sequoia trees growing on your land at this time, but

the sequoia as a species is owned by everyone on earth as part of a global biological

heritage. (Note that this requires an anthropocentric perspective; it would not be

accepted by a biocentrist; recall Chapter 15.) If sequoias were to become extinct, we

would all lose something; however, the people who drove the species into extinction

might gain more than they lost and thus would be acting consistently with their

self-interest.

358 Part IV The Human Factors

Economics 359

BOX 16.2

Tragedy of the commons

In a classic essay entitled “Tragedy of the Commons,” Garrett Hardin (1968) explained how communally owned

natural resources are highly vulnerable

to degradation through overuse.

This is easy to understand

using the metaphor of an English

village commons, a tract of pasture

land used by all the farmers of a village

to graze their cattle. Imagine

that the commons can support 100

cattle without being degraded and

that currently there are 20 farmers

using the commons, each of whom

owns five cows. Each of these cows

can produce an average of 10kg of

milk per day, so the total milk production

of the commons averages

1000kg/day, and the production for

each farmer averages 50kg/day.

Now, imagine that one day one of

the farmers considers buying

another cow, thus increasing her

herd to six cows and the commons

herd to 101. She knows that, if she

does this, she will push the herd

above the carrying capacity of the

commons and average milk production

per cow will fall; let us assume

it will fall 1% to 9.9kg/day. Should

she buy the extra cow? If she is acting

in terms of her own immediate

economic interest, she should

because her cows’ daily milk production

will increase from 50 to

59.4kg (6 cows 9.9kg/cow).

Unfortunately, average milk production

for the other 19 farmers will

fall to 49.5kg/day (5 9.9). Now,

imagine that one of these farmers

decides that he needs more than

49.5kg/day, so he buys another cow

too, even though average production

per cow will fall again, to

Figure 16.5 Fisheries such as this for tuna are recurring examples of the

“tragedy of commons” dilemma. (Photo from U.S. National Oceanic and

Atmospheric Administration.)

360 Part IV The Human Factors

9.8kg/day. This will make economic sense for him because his production will be 58.8kg/day (6 9.8), far better

than 49.5kg/day. This pattern can continue to snowball until all 20 farmers have six cows, total production is

960kg/day for 120 cows, and each farmer is producing 48kg/day. This is 2kg less than when the cycle began, and

now each farmer has to care for six cows instead of five. (This assumes that production per cow continues to drop

by 0.1kg for each cow over the carrying capacity; in reality the drop per cow may get larger as the carrying capacity

is exceeded by a greater and greater number of cows.)

Although the numbers used here were contrived to make a simplified, hypothetical example, the tragedy of the

commons is real. It is well illustrated in many fisheries (Fig. 16.5) where each fisher buys more equipment and

works longer hours to catch a larger share of a fish population that is constantly dwindling because it is being overexploited

(Wilson 1977, Butler et al. 1993, Cinner et al. 2005). It remains a problem on communal grazing land in

many countries (Yonzon and Hunter 1991; Yeh 2003). It also underlies one problem with ecotourism: tour guides

will take their clients closer and closer to wild animals, thus assuring a good tip, until they end up molesting

the animals. Although the classic image of a commons is a communal resource that everyone consumes, we can

also think of the commons as a communal place where everyone deposits his or her wastes, such as the earth’s

atmosphere and waters. In both cases, each individual, acting in accord with his or her own short-term economic

interest, degrades the long-term economic well-being of everyone. For a collection of writings about the tragedy of

the commons, see Hardin and Baden (1977); also see Ciriacy-Wantrup and Bishop (1975), Uphoff and Langholz

(1998), and Baird and Dearden (2003).

Solutions

Passing and enforcing laws are the standard ways of ensuring that people do not harm

society as a whole while acting in their own self-interest, and laws designed to protect

biodiversity are widespread. Nevertheless, new laws and better enforcement of existing

laws are needed. For example, in many countries wild animals are owned and protected

by society as a whole because they can move from property to property, but wild

plants are owned by whoever owns the land where they are rooted (Bean 1983). This

can make it very difficult to prevent landowners from destroying plants, even if they

are a highly endangered species, and thus new laws to protect endangered plants are

sorely needed. Laws to protect biodiversity may simply prohibit certain actions

(e.g. banning the killing of endangered species), or they may impose significant financial

costs (e.g. by requiring mining companies to establish a fund that will be used to

restore a mined ecosystem after the mine is closed). In small, local communities formal

laws are often unnecessary because simple rules of conduct regulate sharing common

property as a public trust (Ciriacy-Wantrup and Bishop 1975). Sometimes, the benefits

of smaller groups can be achieved while retaining some central government control.

For example, the lobster fishery along the coast of Maine is now managed in large part

by seven local councils of elected lobster fishers (Acheson et al. 2000). Sharing authority,

so-called comanagement (see Chapter 17), between these councils and the state

government has produced one of the most successful examples of sustainable fisheries

management on earth. Australian lobster fisheries are a further example of successful,

co-managed fisheries (Phillips and Melville-Smith 2005).

The regulatory approach to protecting our global biotic heritage becomes quite

complex when the species concerned are mobile and cross political boundaries.

In such cases international laws or treaties are required. International treaties designed

to protect migratory birds have been moderately successful in terms of curbing

overhunting, although they have done little to stem habitat loss. Attempts to restrict

overfishing the oceans through the Law of the Sea conferences have been much less

successful. A major advantage of international coordination is that it can make the

regulatory approach to maintaining biodiversity fairer by compelling all the businesses

that are competing for the same market to internalize the environmental costs

of doing business. To return to our earlier hypothetical example, international coordination

of environmental regulations can force both Chilean and Argentinean farmers

to use less dangerous, but more expensive, pesticides and thus can avoid giving either

group an unfair advantage. Furthermore, if collaboration fails, a government could

act unilaterally by imposing “ecological tariffs” to increase the cost of goods imported

from any country where environmental costs are not internalized (Costanza et al.

1997b). However, this approach runs headlong against the World Trade

Organization’s (WTO) General Agreement of Tariffs and Trade (GATT), which

requires international agreements on any environmental constraints to free trade

(Abboud 2000). Arguably GATT could work for biodiversity conservation by eliminating

the “perverse” subsidies governments pay to prop up unsustainable economic

activity. Such subsidies typically lead to overharvest of natural resources because

they sustain the harvest long after the market would make it unprofitable to

continue. This said, in practice powerful nations often succeed in protecting their use

of subsidies despite agreeing to the principles of trade agreements and treaties

(Polasky et al. 2004).

It is often argued that the solution to the “tragedy of the commons” dilemma is to

privatize resources that are usually communal. Some governments have done this by

giving or selling permanent ownership or long-term leases on government-controlled

resources; leases of coastal waters to private aquaculture operations or restricting the

numbers of individuals who can use the commons through licensing are common

examples. Privatization of genetic information derived from natural populations of

plants and animals has, to date, been resisted. In particular, germplasm of wild relatives

of crop plants is traditionally considered a global heritage and is widely shared

among agricultural researchers as communal property. However, the advent of

biotechnology has complicated the application of international laws protecting intellectual

property rights (Gepts 2004). If plant breeders use genetic engineering to

develop a new breed of rice, should they have exclusive rights to sell this breed with its

unique genetic information? Should pharmaceutical researchers who develop a new

medicine based on a chemical they identified in a plant have to share their profits with

the people who live where the plant grows?

Considerable dissension has arisen over genetic resources, especially between developed

countries, which tend to be rich in technology but relatively poor in terms of

genetic diversity, and tropical developing countries, which tend to be technology poor

and gene rich. The issue was particularly prominent at the 1992 Earth Summit (formally

UNCED, the United Nations Conference on Environment and Development),

where the Convention on Biodiversity called for a “fair and equitable” sharing of

the profits obtained by biotechnological development based on biological resources.

In other words, if a United States pharmaceutical company developed a new medicine

from a plant obtained in Ecuador, the company would have to share a “fair and

Economics 361

equitable” portion of its profits with the government of Ecuador. Without this provision

there might be little economic incentive for Ecuador to protect biota that have

potential value to biotechnology companies elsewhere. The United States has refused

to sign the Convention because of ambiguity over what was “fair and equitable.”

See Kowalski et al. (2002) and Tsioumanis et al. (2003) for further insights on the

issue of who owns genetic information.

Problem 2

When biodiversity maintenance generates an implicit cost by reducing opportunities to use

resources, this cost often falls on relatively few people, especially poor people in rural areas.

The richest parts of our planet in terms of biodiversity are often the poorest economically.

The image of poor peasant farmers trying to scratch out a living by clearing garden

patches in tropical forests is a dramatic example of a widespread discrepancy

between biotic and economic wealth. These situations are rife with unfairness. If the

government of Gabon establishes a new national park to protect gorilla habitat from

encroachment by local farmers, it will cost the affluent fans of gorillas in Boston and

Bern virtually nothing, perhaps a few cents each if they pay an annual membership

fee to an international conservation group that is supporting the project. For a young

Gabon couple, living in a village on the border of the proposed park and looking for

land where they can start a farm and a family, establishment of the park might

severely constrain their opportunities (Colchester 2004). Inequities often occur

within a single country too. If the people of Belgium decide that there is not enough

forest remaining in the country and pass a law prohibiting the conversion of forest to

farmland or housing developments, the loss of opportunity falls on the small number

of Belgians who own forests.

Solutions

Simply put, maintaining biodiversity is everyone’s responsibility, and therefore

everyone must share part of the burden. Sometimes, this will require a net flow of

funds from society as a whole to those people who experience the costs of maintaining

the earth’s biota most directly (Shogren et al. 1999). This is particularly

important because in many parts of the world relatively poor people bear much of

the cost.

Within a single government this redistribution of funds is relatively easy because

governments have many mechanisms for subsidizing activities deemed to be in the

public interest. For example, property taxes on lands that are managed to maintain

their ecological values can be reduced or waived, or subsidized prices can be paid for

carefully harvested commodities. Conservation groups and governments often purchase

conservation easements from private landowners, a legal mechanism by which

landowners give up certain property rights for conservation purposes (typically, they

sell, in perpetuity, the right to develop the property). Permanent conservation

easements often cost over 80% of the regular purchase price of a tract of land.

Sometimes, specific ecological services are purchased on an annual basis (Ferraro and

Kiss 2002). For example, Main et al. (1999) described resource conservation agreements

designed to give private landowners a financial incentive to maintain habitat

362 Part IV The Human Factors

Economics 363

for the Florida panther: $74–82 per hectare per year. Conservation easements are

rapidly proliferating as a means of extending limited conservation funding to protect

ever larger amounts of land, although the approach is not without its complexities

(see Merenlender et al. 2004).

Sharing the burden internationally is more difficult. Monies collected by international

conservation groups in wealthy countries and spent in poor countries are one

mechanism. Formerly, these monies were used almost exclusively for the cost of environmental

technology, especially as salaries for foreign biologists who would travel to

developing countries to try to conserve the local wild life. Now, much of this money

goes to building capacity “in country” by focusing on local conservationists, whose

activities often include developing economic alternatives, schools, medical aid, and

other forms of assistance for the people whose ability to make a living is compromised

by biodiversity projects. One innovative way of generating funds used by international

conservation groups is debt-for-nature swaps (Webb 1994), which are explained

in Box 16.3. There is also growing interest in allowing industries that produce

greenhouse gases to compensate for this activity by paying to maintain forests

where carbon can be sequestered, especially tropical forests in developing countries

(Schulze et al. 2002).

BOX 16.3

Debt-for-nature swaps

Many nations have borrowed large sums of money, well over two trillion dollars in total, to invest in their economy

by building roads, dams, irrigation systems, factories, and the like (United Nations Development Programme et al.

2003). Some of this debt is being steadily repaid, and it contributes to a net flow of money from the world’s poorer

countries to the world’s richer countries of many billions of dollars per year. However, even this rate of repayment is

slow compared with what is owed, and, consequently, the commercial banks that made these loans often sell the

debts on the secondary market for much less than their face value, commonly at about 10–20%. This means, to

take a hypothetical example, that if the government of a Latin American nation owes $10 million to a bank in New

York City, the bank would be willing to sell the debt bond to another institution between $1 million and $2 million.

Beginning in 1987 conservation groups and some wealthier nations have bought these discounted debt bonds to

generate funds for conservation in what are called debt-for-nature swaps (Hansen 1989).

For example, in 1990 a coalition of the government of Sweden, the World Wide Fund for Nature, and the

Nature Conservancy banded together to purchase $10,753,631 worth of Costa Rica’s debt bonds, which, because

they were discounted, only cost $1,953,473 (WRI 1992). They gave these bonds to Costa Rica, and in exchange the

Costa Rican government agreed to spend $9,602,904 on a series of conservation projects in Costa Rica, mutually

agreed on by Costa Rica and the donors.

The advantage to the Costa Ricans is that they can repay their debt through projects that will benefit their own

country, and they can pay for these projects in colones (their own national currency) rather than in a foreign currency

such as United States dollars or German marks. (International banks would not accept payment in Costa

Rican colones, only in so-called hard currencies, which are scarce in Costa Rica because they have to be earned

through international trade.) The advantage to the donors is that they can multiply the impact of their donation

dramatically, 4.9-fold in this example. Retiring international debt has another benefit because many debtor nations

364 Part IV The Human Factors

Another mechanism for sharing the financial burden internationally is the transferring

of funds from wealthy governments to poor governments as bilateral aid, either

directly or channeled through an intermediary organization such as the World Bank

or the United Nations. Historically, international aid has done far more harm to the

environment than good, particularly through construction of dams and roads and

the initiation of badly designed agricultural, fishing, and logging schemes. In recent

years, most international-development agencies have at least been trying to

ameliorate the environmental impact of their projects, and in some cases they are

undertaking projects such as establishing new national parks or protecting endangered

species that have a primary goal of conservation (e.g. Mukherjee and Borad

2004). It would be easy to digress into a long critique of large-scale projects that

completely overwhelm the people or ecosystems they are meant to help – whether

they be building a dam or a park – but that lies beyond our purview here. See Ayittey

(1998) or Wieczkowski (2005) for examples.

Probably the best way to offset the losses experienced by people who share their

land with wild life is to find ways to increase the benefits they receive from the local

biota. This idea is the basis for what is often called “community-based conservation”

or an “integrated conservation and development project” (Jones and Horwich 2005).

Conservationists often promote ecotourism to this end (Fig. 16.6) because the Gabon

couple may not need a farm if they can get jobs as guides for tourists who come to see

the gorillas (Paaby et al. 1991). Ecotourism has some problems. For example, it can

lead to significant environmental degradation; some people do not relish working for

demanding tourists; and much of the money it generates goes to foreign-owned airlines,

hotels chains, tour companies, etc. rather than to local people (Bookbinder et al.

1998). However, if done properly with careful planning, significant local involvement,

and control measures, ecotourism can produce significant benefits for local people

(Kruger 2005). Improving markets for local products based on sustainable use of wild

life is another way to offset costs. For example, several organizations encourage consumers

to purchase tropical hardwoods that have been sustainably harvested by local

people so that these people will have an incentive to use their forests judiciously

(Shanley 1999).

Problem 2 has a corollary: Environmental technology costs are often experienced by

people and governments who are least able to afford them. Why should Gabonese taxpayers

pay for wardens to protect gorillas when gorillas are more highly valued by

people in Boston and Bern and when the average Ugandan is far poorer than the

average person in the United States or Switzerland? (One crude measure of this is

have tried to repay their debts through mining, logging, and ranching enterprises that are designed to generate foreign

revenues quickly, even if it is at the expense of the environment and long-term, sustainable, natural resource

use. To date this mechanism has been used in many contexts; despite its complexities it can help alleviate debt

while securing habitat (Resor 1997). There are many countries with attributes that make them good candidates for

debt-for-nature swaps: heavily indebted, experiencing ongoing environmental degradation, and possessing an

inability to provide adequate resources for environmental conservation from internal sources, all coupled with a

demonstrated commitment toward environmental conservation. Nepal is an example (Thapa and Thapa 2002).

Economics 365

the gross domestic product [sum of all economic activity] divided by the population

size. In 2004 it was $5900 in Gabon, $40,100 for United States residents,

and $33,800 for the Swiss [CIA World Factbook: www.cia.gov/cia/publications/

factbook]). Again, the solution involves transfer of wealth from rich nations to poor;

but technical know-how needs to be shared as well (see Watkins and Donnelly

2005). This can involve sending conservation biologists, environmental engineers,

and other specialists to parts of the world where their expertise is in short supply.

Addressing the need for technical know-how must be done collaboratively. For

example, an assessment of why Africa lacks sufficient professionals to manage its

wetland ecosystems argued that it is critical both for scientists from the “North” to

foster development of a self-sustaining research community in Africa and for

African institutions to build research momentum and invest in their own scientific

enterprise (Denny 2001).

Problem 3

Resource exploitation that yields a quick profit is more attractive than harvesting programs

that produce moderate profits, but are sustainable over a longer period. The shortsightedness

of “get-rich-quick” schemes has been decried since at least the days of

the Brothers Grimm and their tale of killing the goose that laid golden eggs, and

criticism of this folly formed one of the historical roots of conservation in Europe

Figure 16.6 If

carefully structured,

ecotourism

is one mechanism

for allowing local

people to obtain

economic benefit

from sharing their

environment with

tourists. (Photo

from Thane Joyal.)

and North America. In recent years, sustainable development has become the

catchphrase for natural resource exploitation programs designed to produce goods

and services in perpetuity with little or no environmental degradation. Treating

future generations equitably (i.e. leaving them a healthy, diverse planet) is the key

ethical concern here. Unfortunately, “A bird in the hand is worth two in the bush,”

and people have a clear tendency to devalue something that they will not use until

the future (Marsh 1994).

Economists account for our tendency to devalue use by employing discount rates to

calculate net present value. A simple formula for calculating net present value is

NPV V/r; where V is the current annual value for production of some commodity

and r is the rate at which we discount its future value. For example, if your date palm

produces a crop worth $100 per year and your discount rate is 5%, then the net present

value of the date palm is 100/0.05 or $2000. This is roughly equivalent to saying

that the palm tree is worth $100 for this year’s crop, plus $95 for next year’s crop,

plus $90.25 for the following year’s crop, and so on in perpetuity, for a grand total of

$2000. To put it another way – if your discount rate is 5%, receiving $2000 now is

equivalent to the promise of receiving $100 per year forever.

Peters et al. (1989) used net present values to argue that sustainable production

of nontimber plant products from a tract of tropical rainforest was more valuable

than if the forest were cut and converted to another purpose. They measured

annual production of fruits and natural rubber from one hectare of riparian forest

in Peru and estimated that it could be sold for $422 profit, after deducting the costs

of collecting and transporting the products 30km to the city of Iquitos. They used

a figure of $316.50 for current annual value (having deducted 25% from $422 on

the assumption that some fruit and latex should be left unharvested) and a discount

rate of 5% to arrive at a net present value estimate of $6330 per hectare.

They estimated that clearcutting all the commercially valuable timber on the

hectare would generate an immediate net profit of $1000 on delivery to a sawmill.

If the site were then converted to another use, potential NPVs might include

$3184 for a tree plantation or $2960 for a cattle pasture. Either figure, when

added to the $1000 for selling the timber, is still far less than $6330.

(See Rosenberg and Marcotte [2005] for a similar analysis based on various

land use options for protecting forest in Belize.)

Are people acting irrationally when they cut down tropical forests rather than

slowly harvest its fruits? Not necessarily. Cutting down the forest may not be wise

from the perspective of the biosphere, of humanity as a whole, or of their own

descendants, but it still may make sense in terms of their personal economics.

Phillips (1993) argued that the 5% discount rate used by Peters et al. (1989) was

far too low. Many Amazonian villagers discount future value much more than

this because they have little confidence that they will be able to use the forest into

the future. For example, if they discount future value at 20% because they

fear they will lose their access to the forest to powerful political and commercial

interests, then the estimated NPV would decline from $6330 to $1582.50. Many

people in less-developed countries are so impoverished – they lead lives so close to

the margin of survival – that discount rates are practically 100%. Future values

mean virtually nothing because, if they do not use a resource now, they will

probably die.

366 Part IV The Human Factors

Finally, uncertainty may not be the major reason why people devalue future uses.

Some individuals and corporations are always ready to reap a quick profit and

reinvest their gains somewhere else for more quick profits, despite the long-term

consequences for the biota or the people who continue to live in the degraded areas

remaining. If you are a beneficiary of this practice you might commend it as an

aggressive business strategy, but if you are one of the many who suffer the consequences

of this approach you would call it simple greed.

Solutions

Trying to mitigate uncertainty and greed is a tall order. Let us consider greed first.

Regulations can curb some of the environmental consequences of greed, but some of

the most promising approaches are based on environmentally based tax reform.

“Polluter-pays” taxes are the best known of these; “natural capital depletion”

taxes that act as a brake on exploitation of natural resources are another idea

(Costanza et al. 1997b). Unfortunately, governments routinely find themselves

caught between two goals: a desire to encourage economic activity and a desire to

protect their citizens, including future generations, from the undesirable spinoffs of

economic development. The paradox is that liquidation of natural capital is clearly

associated with economic expansion (e.g. Naidoo 2004). In practice most environmentalists

feel that too often the economic well-being of a relatively few people takes

precedence over the environmental well-being of everyone (Smith and Walpole

2005).

Dealing with uncertainty or risk is also complex. If the problem is poor people

whose land tenure is insecure, then the solution is to give them land and legal protection

from those who might take the land away. For people whose immediate survival

is in jeopardy, economic assistance is needed to allow them to envision a future

beyond finding food and fuel for tomorrow. Uncertainty is also a significant problem

for large corporations. Not knowing how markets, supplies, government regulations,

and other factors will affect profitability is a major catalyst for reaping short-term

profits. Governments can mitigate this tendency by trying to create a stable business

climate, but ironically this can conflict with the need for new environmental regulations

that arises when scientists discover new problems. Addressing these uncertainties

is at the heart of novel conservation approaches that involve regulation of

businesses, such as conservation banking and “safe harbor” agreements (Wilcove

and Lee 2004).

Problem 4

Not everyone agrees that the benefits of biodiversity far outweigh the costs of maintaining it.

To most biodiversity advocates the benefits of conservation are obvious and unassailable

and therefore should be automatically secured. This premise is easily challenged

by people who weigh only direct economic benefits against the explicit costs of environmental

technology and the implicit costs of opportunity losses. Such economic

rationalists would dismiss potential values as too speculative. They would say we

should not worry about some obscure plant in the highlands of Tanzania that might

have a cure for breast cancer because by the time we figure out that it has this

Economics 367

368 Part IV The Human Factors

property, biochemists will have already synthesized a cure. They would argue that

while the earth’s biota as a whole clearly has ecological value, it has not been proven

that each species has a unique role and that disaster will ensue if we lose some or

even many species. They would dismiss existence values as too abstract, too philosophical

to have meaning in the hard-headed world of business with its “bottom line”

of profitability.

Solutions

The solution to this problem begins with the rhetorical argument that the burden

of proof must lie with those who assert that a species lacks value. If some people

wish to dismiss a species as without commercial, subsistence, or ecological value,

let them demonstrate convincingly that it lacks value now and will probably have

no value in the future. This conservative approach is the only reasonable course in

the absence of deep knowledge and understanding. If the case for conserving a

species relies heavily on potential values or ill-defined ecological values, then this

suggests that taxpayers should pay most of the costs because one of the major

responsibilities of a government is to provide for the well-being of future generations.

It may be useful to weigh the costs of environmental technology against other

expensive undertakings such as medical and military endeavors. If human overpopulation

and environmental degradation continue to widen the gap between rich

nations and poor, spurring military conflict and diminishing human health

(Donohoe 2003), then it is also appropriate to think of efforts to maintain a healthy

environment as an alternative to increasing national security through military

expenditures and boosting health through investment in the medical industry. Some

conservationists, notably David Ehrenfeld (1988), have argued that this problem is

essentially insoluble. He believes that cost–benefit analyses will serve biodiversity

badly, particularly because the species that are rarest, and thus most vulnerable to

extinction, are least likely to have critical ecological roles. Disavowing cost–benefit

analyses would force conservationists to focus on solutions based on morality, particularly

a shift from anthropocentrism toward biocentrism. Others, however, have

made strong arguments that commercialization of wild life is a viable way to save it.

For example, based on a cost–benefit analysis, Lindsey et al. (2005) concluded that

reintroducing African wild dogs to private game ranches could play a key role in

conserving the species. The revenues derived from ecotourism to view the dogs can

fund compensation for harm the wild dogs may cause to livestock, which often is

the root of persecution of wild dogs. There are many additional ways to express the

basic problem of an imbalance in the costs and benefits of maintaining biodiversity.

We can summarize the solutions by characterizing them as either economic incentives

(e.g. subsidies, privatization of government-owned assets) or economic disincentives

(e.g. regulations, tax penalties, tariffs). The costs of economic incentives

will be borne largely by taxpayers; the costs of economic disincentives will be paid

largely by the owners of biological resources and their customers. On the whole,

incentives are generally preferable to disincentives because carrots work better than

sticks. Moreover, it is most fair to favor carrots when poor people are the resource

owners.

Economics 369

CASE STUDY

Butterfly Ranching1

When you think of ranches, images of cattle grazing on a dusty plain under the watchful eye of a cowboy are likely

to come to the fore. You probably would not envision butterflies fluttering about a small opening in a tropical forest,

yet in Papua New Guinea people have created hundreds of butterfly ranches. Most of these consist of a small patch

planted with some plant species that are preferred food for the caterpillars of certain butterfly species, especially the

elegant birdwing butterflies. Surrounding the patch, the rancher maintains a border of plants that produce nectar

and thus attract the adults. Pupae are collected from the food plants and protected from predators, chiefly ants, until

they hatch. Although butterfly ranches (which rely on a wild butterfly population that will use the ranch) are the

norm, there are some butterfly farms where captive butterfly populations are maintained in cages. Butterflies may

seem a strange form of livestock, but not to the Papua New Guineans. They understood the basic ecology of the butterflies

even before ranching was initiated and in contrast have virtually no familiarity with sheep and cattle.

There are three potential markets for ranched butterflies. First, decorative specimens are popular as tourist

souvenirs and are exported to curio shops. Serious butterfly collectors are a second market; they seek to own a

wide variety of butterflies, preferably of rare species. Collectors want perfect specimens, and these are provided

more readily by a

rancher than by

someone who

nets wild butterflies.

Finally, there

is a significant

market for live

specimens, which

are exported, usually

as pupae, to

be displayed in

butterfly houses,

often at zoos. In

1986 over four

million people visited

40 butterfly

houses in Great

Britain. Papua

New Guinea has

chosen not to

enter this live

market for fear

that, if they

export live specimens,

competitors

will start

breeding programs

with their

species.

Figure 16.7 Butterfly ranching involves cultivation of productive larval habitat to attract

members of wild butterfly populations to lay eggs in the cultivated areas. Ranchers can

then harvest a portion of the eggs deposited, hatch the eggs, rear the larvae to metamorphosis,

and sell the adults on the marker. The undertaking can be both sustainable and

lucrative. Many tropical butterflies such as this blue morpho have been used in ranching

schemes. (Photo from Dan Perlman/EcoLibrary.)

370 Part IV The Human Factors

Summary

Recognition of the true costs and benefits associated with wise natural resource management

has led to a paradigm shift in many circles. Many people are no longer asking,

“Can we afford to conserve?” but, rather, “Can we afford not to conserve?” The benefits of

biodiversity include the wide variety of organisms that we use as goods for commerce or

subsistence, plus many ecological services such as providing us with clean air and water

and recreational opportunities. Less tangible benefits include existence values (the value

in simply knowing that a species or ecosystem exists) and potential values (the future, possible

values of a gene, species, or ecosystem). The costs of maintaining biodiversity can be

divided into two major types: explicit costs for environmental technology, such as salaries for

people who undertake projects that maintain and restore biodiversity; and implicit costs, the

loss of potential benefits when conservation means giving up an opportunity to use a

resource.

From an economic perspective, the fundamental problem with maintaining biodiversity is

that there is often an imbalance between who pays for maintaining biodiversity and who

enjoys its benefits. We all enjoy the goods and services provided by biodiversity, but often the

costs of maintaining biodiversity fall disproportionately on rural people and developing

nations that have the richest biodiversity. Furthermore, when biological resources are open to

unrestricted access, the “tragedy of the commons” can prevail and an imbalance of costs and

benefits can drive overexploitation within a single community. Solutions can be characterized

as economic incentives or disincentives. Incentives can encourage people to maintain biodiversity

by giving them subsidies such as tax breaks. Disincentives can encourage sound stewardship

by imposing financial penalties such as fines and tariffs on activities that degrade or

overexploit natural resources.

People are not getting rich through butterfly ranching – annual incomes generally range from $100 to $3000

in Papua New Guinea – but in a country where the average annual income in rural areas is about $50, these are

significant amounts. More importantly, butterfly ranching is the kind of development that many conservationists

advocate for rural areas because it allows local people to participate in a cash economy through the sustainable use

of their renewable natural resources. Indeed, for many Papua New Guineans butterfly ranching has been their first

opportunity to earn cash. In other countries, such as Malaysia and Costa Rica (Fig. 16.7), butterfly ranching is

more likely to supplement existing cash income.

Butterfly ranching is not a complete solution to the problem of overcollecting butterflies. In particular, not all

marketable species lend themselves to ranching, and thus the collecting of wild specimens continues. This is

generally viewed as acceptable as long as overexploitation is avoided. The key to avoiding overexploitation, black

markets, and related problems is to have a reliable, well run agency that will serve as an honest broker for the

ranchers, buying their produce at fair prices and marketing it effectively overseas. When the system works, it can

provide a significant incentive for people to maintain butterflies and the entire ecosystems that support both the

butterflies and themselves.

1 Primary references for this section are National Research Council (1983) and New (1991, 1994, 1997). See

also Webb et al. (1987) and Thorbjarnarson (1999) for details on crocodile farming and Hoogesteijn and Chapman

(1997) about capybara and caiman farming.

Economics 371

FURTHER READING

For further information on ecological economics, we recommend Barbier et al. (1995), Rees (2003), Costanza et al.

(1997b) or Costanza (2001). Barbier et al. is strong for methods and Costanza for the development of ecological

economics. McNeely (1988) describes both general concepts and case studies. Elephants, Economics and Ivory by

Barbier et al. (1990) is an interesting case study. A compelling exploration of environmentally sound ways to use

land for human benefit under the umbrella of “reconciliation ecology” is provided by Rosensweig (2003). Ecological

Economics and Land Economics are key journals for this field. See www.ecologicaleconomics.org to learn more about

the International Society for Ecological Economics. Important resources on interactions among biological diversity,

human welfare, and economic activity are the various reports associated with the Millennium Ecosystem

Assessment, available at www.millenniumassessment.org.

TOPICS FOR DISCUSSION

1 Is conservation ultimately possible only if economic growth ceases?

2 Can you think of any creative mechanisms for sharing the benefits and costs of maintaining biodiversity more

equitably?

3 Why is the environmental record of countries with a communist economic system generally worse than that of

capitalist countries?

4 Some people think that we need to maximize economic growth to keep people satisfied with their lifestyle and to

pay for environmental technology. What do you think?

5 What are the relative advantages and disadvantages to using financial incentives versus disincentives to effect

conservation activities?

6 Many of our technological developments, notably the automobile, have had negative impacts on environmental

quality. Do you think that future technological advances will have a net effect on environmental quality that is

positive or negative?

e eBook Collection Chapter 15

The Human

Factors

Conservation biologists are constantly reminded of what our species has done to extirpate or

threaten other life-forms. As Aldo Leopold wrote in A Sand County Almanac: “one of the

penalties of an ecological education is that one lives alone in a world of wounds” (Leopold

1949). This awareness seems to make some conservation biologists a bit misanthropic.

Moreover, many conservation biologists purposefully select careers in which they can interact

with other species in preference to their own. Consequently they may not be very comfortable

in dealing with human institutions such as the social, economic, and political

systems that are the subjects of our last three chapters (Jacobson and McDuff 1998). Yet this

does not diminish the importance of human institutions to conservation biology. If people

are the primary force degrading biodiversity, then people must change their actions. If

we wish to facilitate these changes, we must understand social, economic, and political systems.

These three chapters are far too brief to provide a real foundation for understanding

sociology, economics, and politics, but they can give you an appreciation of how critical these

subjects are to conservation biology.

PART IV

Photo opposite: CAS copyright Venezuela – Glenn and Martha Vargas © Californian Academy of Sciences

This statement, ascribed to a Bedouin of Jordan by Guy Mountforth, says two important

things about the values held by individuals and societies. Values differ between

hungry people and well-fed people. Values change when a person who was hungry

has eaten. More generally put, values differ and values change. We will begin by

examining how different groups value biodiversity – focusing on different cultures,

rural and urban people, and women and men.

Values Differ

Cultures and Religions

The cultural diversity that characterizes humanity is one of our greatest assets. It is a

deep, rich lode of human potential that reflects our religious, ethnic, racial, and linguistic

diversity. At times, however, when universal cooperation and unanimity are needed,

this diversity seems like a significant liability, a source of frustration and bafflement.

Differences in cultural values are seen on the world stage most often when human

rights are being discussed, but cultural differences in attitudes about nonhuman

organisms are at least as profound. Consider the various rodents known as rats. In

most places they are loathed as the epitome of vermin, but in several parts of the world

they are relished as food; in Nigerian markets grasscutter rats sell for more than beef

and pork (Adu et al. 1999). In India, rats are fed and protected in temples of the Hindu

goddess Bhagwati Karniji (Canby 1977). Many people find insects generally disgusting

but an estimated 2000 species of insects serve as food for people around the world

(RamosElorduy 1997). In North America and Europe dogs are beloved companions; in

many East Asian countries they are prized as food; among the Zoroastrians of the

Middle East they are key participants in certain religious rites. Similar stories could be

told for many species: bats, snakes, whales, ravens, and more (Fig. 15.1).

We often explain such differences with the simplistic statement “It’s their culture.” For

example, Hindus consider cows to be sacred and do not eat them because that is their

culture. However, such a statement is not really an explanation. In his book, Cows, Pigs,

Wars, and Witches: The Riddles of Culture, anthropologist Marvin Harris (1974) argues

that usually a rational, ecologically based explanation can be found. For example, he

CHAPTER 15

Social Factors

When I am hungry, a date palm gives me food. When my belly is full, behold, the tree is beautiful.

Social Factors 331

Figure 15.1

Snakes epitomize

widely divergent

attitudes held by

humans toward

wild life. For example,

snakes are typically

vilified in

European cultures

owing to myths

such as that of

Medusa, punished

for her beauty by

Athena, who

turned her beautiful

tresses into

snakes, which gave

her the power to

turn to stone anyone

who looked at

her. (Peter Paul

Rubens/Art

Resource.) In contrast,

at religious

ceremonies in Asia

snakes are often

given offerings. In

this sculpture from

Thailand Buddha is

in repose upon

Naga, a serpentbeing

that can

both bestow

wealth and assure

crop fertility as well

as decline these

blessings. (Artist

unknown/Art

Resource.)

argues that the Jewish and Islamic strictures against pigs are based on the fact that these

religions originated in a desert environment where raising pigs (which require a highquality

diet compared with sheep, goats, and cattle) was a waste of limited resources.

Once an idea has been codified as part of a set of cultural values, it can persist, even if

the original reason for it disappears, because it becomes a mechanism for maintaining

group cohesion. In other words, Jews and Muslims who do not live in desert environments

also do not eat pork because it is a way to demonstrate their cultural identity.

Differences in the ways that various cultures perceive their relationship with nature

are sometimes linked to theology. For example, it has been argued that Verse 26 of the

first chapter of Genesis compels Christians, Jews, and Muslims to think that all other

species exist for the use of people (White 1967):

Other scholars have argued that this verse should be interpreted as a mandate to be

good stewards of nature (Van Dyke et al. 1996). Certainly, an environmental ethic in

the Old Testament can be found in passages such as Isaiah (5:8):

Nevertheless, it seems clear that these religions see humans as distinct from the rest of

creation in some way, and in this respect they contrast with some other religions,

such as Hinduism, Buddhism, and Taoism, that emphasize the sameness of humans

and nature (Callicott 1994). Consider this passage from the Ishopanashads, a holy

scripture of Hinduism:

Ultimately, the theological distinction between religions that emphasize “sameness”

versus “separation” may or may not mean a great deal in practical terms. For example,

recognition of the Ganges as a sacred river has not prevented Hindus from polluting

it. Religion is only part of what distinguishes cultures, and one must consider

other influences, such as history, politics, economics, and technology, to understand

cultural differences in the way people interact with nature. Yet religions evolve, and a

strong religious response to the biodiversity crisis may emerge as the effects of loss

begin to affect people more profoundly (McNeely 2001).

Urban–Rural

Living in a city and living in the country are profoundly different experiences. Many

urban people are quite isolated from the natural world that lies outside their cities,

332 Part IV The Human Factors

Then God said, “Let us make humankind in our image, according to our likeness; and let them have dominion over

the fish of the sea, and over the birds of the air, and over the cattle, and over all the wild animals of the earth, and

over every creeping thing that creeps upon the earth.”

Woe to you who add house to house and join field to field till no space is left and you live alone in the land.

This universe is the creation of the supreme power meant for the benefit of all His creations. Individual species must,

therefore, learn to enjoy its benefits by forming a part of the system in close relation with other species. Let not any

one species encroach upon the other’s rights.

Social Factors 333

and this can limit their understanding of it. Such isolation can also lead to apathy

that may be broken only by an event with a direct impact; for example, if water

rationing were imposed because deforestation had ruined the city’s watershed. Of

course, not all urbanites are apathetic or poorly informed about nature. Indeed, many

of the world’s most committed naturalists and conservationists have deep urban

roots. Notably, what little research has been conducted on the topic has indicated that

urban and rural residents show complex attitudes toward nature that are not easily

dichotomized (see Hunter and Brehm 2004).

It is tempting to speculate that for some people their day-to-day distance from

nature has given them a stronger appreciation for it, a sort of “distance makes the

heart grow fonder” effect. Nevertheless, in general, rural people are more likely to

understand their relationship with the natural world, in part because they will be

more directly affected by any problems that arise. This is particularly true for people

who depend on wild life for their well-being. The understanding such people develop,

known in some circles as traditional ecological knowledge or TEK, encompasses much

more than a set of information; it shapes value systems and world views (see Berkes

et al. 2000 and other articles in Ecological Applications 10[5]). TEK is also a productive

springboard for initiating conservation efforts in both forest (Becker et al. 2003) and

marine environments (Drew 2005).

Certainly, urban isolation from nature does not mean that urban people are the villains

and rural people are the heroes in the drama of conservation. Through farming,

fishing, logging, and similar activities many rural people interact daily with other

species and have a strong utilitarian attitude toward them. Utilitarian attitudes are

not a threat as long as the species in question can sustain the usage, but, sometimes,

these attitudes are extended to species that are too uncommon to be exploited. To put

it in more practical terms: when an endangered species is exploited, it is usually a

rural person holding the gun or the axe.

If conflict arises between the well-being of biota and the well-being of people, rural

people are usually the ones on the front line. Consider two brief examples. Millions of

city dwellers cherish the tiger as one of the most spectacular life-forms on earth.

However, tigers inspire mostly fear among the people living in the Sunderbans, a large

delta on the border of India and Bangladesh where tigers kill people each year

(Saberwal 1997; Kleiven et al. 2004). Similarly, urbanites around the world write to

politicians and give money to conservation groups to save the rain forests of

Amazonia; however, for the poor people who live there, establishing parks impedes

their ability to hunt for game or cut the forest to grow crops (Schwartzman et al.

2000). In these cases the isolation of urban people may make it easier for them to

advocate for biodiversity because it costs them little to do so.

To make a summary generalization: rural people’s attitudes toward wild life –

both positive and negative – are likely to be pragmatic attitudes based on regular

interactions. On the other hand, the attitudes of urban people – positive, negative,

and apathetic – are likely to be more conceptual and removed from direct experience.

Where these distinctions become important is in geopolitical regions where

urban voters outnumber rural voters in conservation matters affecting primarily

rural areas. Such was recently the case with proposed reintroductions of wolves to

wilderness areas of New York state’s Adirondack Park, an action favored by urban

and suburban dwellers but not embraced by residents of the reintroduction area

334 Part IV The Human Factors

(Enck and Brown 2002). Only by rural voters passing local ordinances specifically

blocking wolf reintroduction in their towns did rural residents prevail in the debate.

Curiously, extrapolating attitudes over time in the context of an increasingly urbanized

society suggests attitudes will improve steadily toward carnivore conservation

(Williams et al. 2002).

Women–Men

The concept of equal rights and opportunities for women is widely accepted, if not

always practiced, in many countries. Equality of rights and opportunities does

not mean that women and men are identical physically or psychologically,

however; such differences could lead to both divergent interactions with nature

and different attitudes toward nature (Fig. 15.2). Some writers – Rachel Carson and

Ariel Kay Salleh, for example – have suggested that because most women bear

and care for children, they are more nurturing than men, and that this quality

shapes their attitudes toward nature (Norwood 1993; Mellor 1997). Moreover,

because fertility, nativity, birth, and renewal have always been associated with

females, nature has generally been portrayed with female features. Consider Gaia,

Mother Earth for the early Greeks, Pachama, who personified the Earth to the Incas,

or Bharat Mata, the modern Hindu Mother of India. This said, many feminist writers

minimize or reject the idea that women are closer to nature than men. They

contend that the stereotype perpetuates a dualism that separates men from women

and men from nature (Warren 1993). From their perspective, language that makes

nature seem feminine (e.g. raping Mother Earth) or that makes women seem more

like a part of nature (e.g. slang terms for women such as chick, bunny, kitten, fox,

bitch, etc.) lumps women and nature together, and thereby makes them both inferior

to men.

Whatever the case, all agree that both nature and women have been subjected

to domination by men, and that we must work toward more harmony and

balance. This idea is the foundation for a growing area of philosophy called ecological

feminism, or ecofeminism (see Norwood 1993, Mellor 1997, or Wilson 2005 for

further details), and may partly explain why women play such a pivotal role in the

environmental movement, especially at the grassroots level. Beyond romantic or

mythological notions of the connection between women and nature, the fact

remains that women play a pivotal role in maintaining biological diversity and

developing knowledge of its uses through their reliance on wild resources (Deda

and Rubian 2004).

Beyond differences in attitudes toward nature in general, men and women may

also differ in how they value particular species because they interact with different

suites of species (Shiva 1988). In many rural parts of southern Africa men are primarily

hunters of large mammals, whereas women interact with a much broader

array of wild life: gathering wild plants for food, fuel, fiber, and medicine and catching

birds, reptiles, fish, insects, and small mammals for food (Hunter et al. 1990). It

is interesting to speculate that the tendency of conservationists to focus heavily on

large mammals may, in part, reflect what is still a male-dominated culture and a

relationship between men and large mammals that stretches back to our earliest

ancestors.

Social Factors 335

Figure 15.2

Women and men

often interact with

the natural world

in different ways

that may reflect or

shape their values.

(Georges Seurat/

Art Resource, top;

Claude Monet/Art

Resource, bottom).

Additional Perspectives

Differences among cultures, rural and urban people, and women and men are but

three axes along which to view social values. We could also discuss how attitudes

about nature are influenced by age, occupation, income, education, and other factors.

Given all this complexity, it is often difficult to sort out why people feel the way they

do. If a male banker in London does not share the same attitude toward tigers as a

female farmer in the Sunderbans, to what degree are the differences based on

their gender, culture, geography, wealth, education, and so on? Sorting out these

complexities is more feasible if one uses a systematic approach to describing values;

in the next section we will examine one well known example.

Describing Values

How do you feel about crocodiles? Do they frighten you? Do they fascinate you? Do

you love them? Do you love them more than your parents do? Discussions about

human values can be rather fuzzy because they are difficult to describe systematically.

Stephen Kellert, a sociologist who works on conservation issues, has spent many

years developing systematic techniques for describing how people feel about animals,

especially wild animals, and then using them to better understand how values differ

among people of different ages, education, employment, culture, race, gender, region,

and so on (Kellert and Berry 1981; Kellert 1996). The basic method is to read statements

to people and ask them to strongly agree, agree, slightly agree, slightly disagree,

disagree, or strongly disagree. By scoring responses to statements such as

“I have owned pets that were as dear to me as another person” or “If I were going

camping I would prefer staying in a modern campground than in an isolated spot

where there might be wild animals around,” Kellert has identified several basic types

of attitudes toward animals. See Table 15.1.

Survey data of this type bear out many of the generalizations made above about

how values differ among cultures, between rural and urban people, and between

women and men. For example, Czech et al. (2001) identified that women ascribe

greater preservation value to nonhuman species, express greater concern for

species conservation relative to property rights, and seek stronger support for

endangered species protection than men. Similarly, people of rural areas (defined

as towns with populations less than 500) tend to have high scores for utilitarian

and naturalistic attitudes, whereas urban people (from populations greater than

1,000,000) show higher scores for moralistic and humanistic attitudes (Kellert

and Berry 1981). Finally, Kellert (1991, 1993) has contrasted attitudes toward

wild animals among western cultures. In a cross-cultural comparison of the United

States, Japan, and Germany the most noticeable results were the higher scores for

moralistic and ecologistic attitudes in the United States and for dominionistic attitudes

in Japan. Data from Germany revealed extremely high scores for moralistic attitudes

and relatively low scores for dominionistic and utilitarian attitudes. As a

generalization, people in all three countries cared more about the welfare of individual

species of wild animals, typically species with strong aesthetic, cultural, and historic

associations, than about broader, more conceptual entities such as ecosystems

or biodiversity. These results may help to explain why the public often seems to prefer

336 Part IV The Human Factors

Social Factors 337

Table 15.1

Stephen Kellert has

described several

types of attitudes

that people have

toward animals.

The types are

described here using

definitions slightly

modified from Kellert

and Berry (1981).

Following each definition

is the percentage

of United States

residents (based on a

survey of 2455 people

over 18 years old)

who strongly exhibited

that type of attitude

(Kellert and

Berry 1981). Note

that most people

have more than one

type of attitude, but

usually only one type

is strongly held. The

percentages total 148

because of people

who hold more than

one attitude strongly.

Term Definition

Naturalistic Showing an interest in, and affection for, wild animals and

the outdoors. 10%

Ecologistic Concerned with ecosystems, particularly the interrelationships

between species and their habitats. 7%

Humanistic Showing a strong affection for individual animals such as pets

or large wild animals. Strong tendency for

anthropomorphism. 35%

Moralistic Concerned with ethical treatment of animals; strongly

opposed to cruelty toward animals or presumed

overexploitation. 20%

Scientific Intellectual interest in organisms as biological entities. 1%

Aesthetic Interested in the physical attractiveness and symbolic

characteristics of animals. 15%

Utilitarian Interested in the practical value of animals and their

habitats. 20%

Dominionistic Interested in the mastery and control of animals, typically in

sporting situations. 3%

Negativistic Preferring to actively avoid animals because of dislike or fear.

2%

Neutralistic Preferring to passively avoid animals because of a lack of

interest. 35%

concerted efforts to conserve a few high-profile species rather than the coarse-filter

approach to conservation, despite its obvious efficiency (Chapters 11 and 13).

These techniques can also be used to try to understand how people feel about biodiversity

in general. For example, Czech and Krausman (1997) compared people’s attitudes

toward different groups of endangered species in the United States. Respondents

rated their favorability toward various taxonomic groups on a scale of 0 (lowest) to

100 (highest) as follows: a first tier consisting of plants (72), birds (71), and mammals

(71), a second tier of fish (68), a third tier of reptiles (59), amphibians (59), and

invertebrates (57), and a fourth tier of microorganisms (52). In an extension of this

work, Czech et al. (1998) examined if these attitudes were consistent with how we

allocate funds for conservation. They found that they generally were, with the

exception that amphibians and plants were gravely underfunded relative to the positive

values most people extend to them.

Values Change

A paradoxical truism worth remembering is that the only thing that never changes

is the fact that everything changes. A few millennia ago, when daily life revolved

around being predators and grazers and avoiding becoming prey, ecologistic and

utilitarian attitudes toward wild life must have been very widespread and neutralistic

attitudes virtually unknown. Even looking back just a few decades can reveal

some remarkable changes in values. Not very long ago, attitudes toward whales

and wolves were shaped by Moby Dick and Little Red Riding Hood. At best, these

creatures were irrelevant to the lives of most people; at worst, they were the embodiment

of evil. Today, attitudes toward whales and wolves seem to be much more

positive (Williams et al. 2002). Dramatic photographs and evocative recordings of

songs and howls have transformed these creatures into powerful and popular

symbols to people who denounce the human assault on nature (Fig. 15.3). If you

belong to a conservation group you have seen countless advertisements for merchandise

– jewelry, mugs, T-shirts, etc. – with whale and wolf motifs. Whales

and wolves have seemingly become sacred totems for thousands of people.

Amphibians are another good example; after being viewed for centuries with

utter indifference they are now the focus of world-wide concern (Beebee and

Griffiths 2005).

Marked changes can also occur within a single individual. During his early career

Aldo Leopold never passed up the chance to kill a wolf. Later in life the wolf became a

potent symbol of wilderness for him. Reflecting on his youth, he described the death

of a wolf he had shot in Thinking Like a Mountain:

Changing People’s Values

If we are to maintain the earth’s biodiversity, values must change in the future even

more than they have during the past few decades. In Kellert’s terminology, attitudes

toward wild life that are naturalistic, ecologistic, aesthetic, and moralistic must wax

stronger; while negativistic, neutralistic, dominionistic, and utilitarian values must

wane. Trying to sensitize people to the value of nature is a routine exercise for environmentalists;

in particular, it is a central part of environmental education (Orr

1992). In the words of the Senegalese ecologist Baba Dioum: “For in the end we will

conserve only what we love. We will love only what we understand, and we will

understand only what we are taught.”

338 Part IV The Human Factors

We reached the old wolf in time to watch a fierce green fire dying in her eyes. I realized then, and have known ever

since, that there was something new to me in those eyes – something known only to her and to the mountain. I was

young then, and full of trigger-itch; I thought that because fewer wolves meant more deer that no wolves would

mean hunters’ paradise. But after seeing the green fire die I sensed that neither the wolf nor the mountain agreed

with such a view. (Leopold 1949)

Figure 15.3 Wolves fit into the human psyche in various ways. Wolves may embody nurturance, as in the case of

the twin brothers Romulus and Remus abandoned on the banks of the River Tiber and found by a she-wolf who

fed them with her own milk. (Musei Capitolini, Rome, Italy. Scala/Art Resource, NY.) Wolves may also be villainous,

as in the tale of Little Red Riding Hood and the conniving and evil intentioned wolf that has profoundly

spooked generations of small children. (Broune, Tom (1872–1910). 1990. Private collection. Image Select/Art

Resource, NY.) Why do we ascribe such complex attributes to these highly social canines? (Photo from Don Getty,

www.DonGettyPhoto.com.)

Environmental education can shift people’s attitudes toward nature through two

basic modes: information and experience. If we give people information about the

instrumental value of biodiversity, about how important it is to the welfare of

humanity and the biosphere in general, then people will probably place a higher

value on it. Millions of people around the world now think of tropical rain forests as

storehouses of medicinal plants and pivotal components of global climatic

processes, rather than as bug-infested jungles, simply because they were given information.

Notably, taking a course in conservation biology makes people more concerned

about wild life conservation (Caro et al. 2003). That said, more education is

not the simple solution to changing attitudes that it is often assumed to be.

Social Factors 339

In fact, often individuals with the greatest factual knowledge (for example, rural

people with direct contact and deep familiarity with endangered wild carnivores)

may express the most negative attitudes toward them (e.g. Reading and Kellert

1993).

Experience can shape people’s values too, and environmental educators often

try to get people outdoors where they can interact with the local biota. Not surprisingly,

Kellert’s (1980) research found that people who participated in outdoor,

nature-related activities (ranging from bird-watching to fur trapping) had higher

naturalistic and ecologistic scores than those who did not. People who have encountered

organisms in their natural habitat may also find it easier to accept the idea that

they have intrinsic value. Even indirect exposure, through wolf and whale paraphernalia,

for example, may help to shape values. Kellert (1980) found that watching

nature shows on television was positively correlated with naturalistic and ecologistic

attitudes.

Which shapes values more, experience or information? This is probably one of those

head-versus-heart, emotional-versus-rational, questions. Whatever the case, basic

natural history study, which combines both themes via personal discovery of organisms,

their diversification, and their environmental relationships, seems to have a particular

role in promoting awareness and concern for biodiversity, but its status in

modern biology curricula is diminishing (Greene 2005).

The idea of changing people’s values can be rather controversial. Environmental

educators often refer to “clarifying” values rather than “changing” values to avoid the

idea that they are imposing their own set of values on other people, especially children.

They are confident that knowledge and experience will lead to caring without

forcing one person’s values onto someone else. This issue becomes even more controversial

when the boundaries between cultures are crossed. For example, people in

many parts of the world are flooded by a tidal wave of music, movies, television, fashion,

fast food, and so on that emanate from the United States and Europe. Some people

welcome this because it makes them feel modern and cosmopolitan; others resent it

because it drowns their traditional culture. These conflicts become more troubling

when political and economic power are used to impose foreign value systems.

Consider the fact that animal-rights groups in the United States have been able to

coerce some Asian nations into banning the use of dogs for food. What do you suppose

the reaction in the United States would be if a group of Hindus, for whom cows

are sacred animals, came to Washington, DC, to persuade Congress to ban the consumption

of beef? More to the point, consider the widespread notion that people do

not belong in areas managed for biodiversity and should therefore be removed from

them. This paradigm has been widely exported by international conservationists but

may make little sense in parts of the world with ancient human cultures long dependent

on natural resources (Locke and Dearden 2005). Worse, it has disrupted the lives

of many local peoples and often stoked resentment to conservation efforts (Saberwal

et al. 1994). In reality, protected areas networks in much of the world typically

require some combination of strictly protected areas along with extensive areas accessible

to local people to engage in traditional resource use.

On the other hand, simply providing information seems to be an innocuous way

to change values across cultural boundaries. Imagine a scenario in which a Finnish

340 Part IV The Human Factors

Social Factors 341

ecologist doing comparative research on circumboreal forests discovers that the fruits

of a particular shrub species are critical to the overwinter survival of many birds and

mammals. If sharing this information results in Canadians changing their logging

practices to minimize detrimental effects on that shrub species, it would be hard to

argue that the Finnish ecologist’s values were inappropriately imposed on the

Canadians. Next, consider a survey of Costa Ricans that found a poor understanding

of the relationship between overpopulation and environmental quality (Holl et al.

1995). In this case, an educational campaign on this theme might seem reasonable,

but it certainly could spark a controversy if it were initiated by foreigners rather than

Costa Ricans.

People living in remote areas often have no idea that a particular local species is

globally significant until an outsider tells them so. Moreover, if cultivated carefully, the

knowledge that a local species is unique can be the source of great pride and conservation

action. Throughout the Caribbean there are nine parrots of the genus Amazona,

most of which are endemic to single islands (Butler 1992a). In recent years, these parrots

have become national treasures, celebrated with songs and plays, stamps and

posters (see case study below). The initial impetus to this outpouring was often an outsider

saying, “You have a special parrot living on your island.”

Some conservationists would argue that all this sensitivity about the feelings of

local people is missing the point. They would argue that all the earth’s species belong

to everyone (in other words, they are a globally shared inheritance) or that they all

belong to no one (i.e. their intrinsic value is paramount). There is an attractive simplicity

to this point of view, but, as we will see in the next two chapters, it is naive

because it overlooks important economic and political realities about who carries the

burden of conservation.

The Biggest Change: Anthropocentrism

versus Biocentrism

Many environmental philosophers have argued that if we are to maintain the

earth’s biota, we need a major shift in human values (Naess 1989; Snyder 1990).

They believe that we need to move from being anthropocentric (i.e. believing that

people are the center of the universe) to being biocentric (i.e. believing that life, in all

its various forms, is the center of the universe). A biocentric view (sometimes called

ecocentric) recognizes that all species have intrinsic value and rejects the idea that

Homo sapiens is more important than other species (Kawall 2003). Without such a

change we may be left cataloging the instrumental value of different species and

saving only those that we find useful. Biocentrism forms the philosophical foundation

of what Naess has called the deep ecology movement (Devall and Sessions

1985).

A related concept is that of “biophilia” or love of the biota. The term was coined by

the biologist Edward O. Wilson (1993) on the basis of “the innately emotional affiliation

of human beings to other living organisms. Innate means hereditary and hence

part of ultimate human nature.” The roots of biophilia lie in our coevolution with the

natural world for many millennia and, indeed, the fact that our very survival

depended on an intimate knowledge of and connection to wild life. It is a compelling

hypothesis that predicts that human performance and health – even emotional states

– are strongly connected to biological diversity. Medical literature bears this out insofar

as patients recover more quickly if, for example, they are exposed to greenery

rather than a purely artificial environment (Frumkin 2001).

As with most things in life, when ideas about biocentrism, biophilia, and anthropocentrism

are applied to action, they are not black and white. Even the most

ardent preservationists are not likely to be purely biocentric; given a choice between

the survival of humanity and the survival of a small species of snail, very few people

would flip a coin. Conversely, very few people would opt to eliminate a life-form simply

because it is not apparently essential to human welfare. It is probably better to

think of anthropocentrism and biocentrism as two poles that define a continuum

and to recognize that we need to shift more toward the biocentric pole from where

we are now.

Another way to represent this issue is as a nested hierarchy of concern (Fig. 15.4)

(Noss 1992). In this hierarchy the lowest, narrowest level is concern for one’s

342 Part IV The Human Factors

Figure 15.4 This figure conceptualizes an ethical sequence as a nested hierarchy, with

concern for oneself at the lowest, narrowest level and concern for ecosystems and the

whole biosphere at the highest, broadest level. The success of conservation hinges on

people expanding their level of concern to fully encompass all species and ecosystems.

(Redrawn by permission from Noss 1992.)

Social Factors 343

CASE STUDY

The Bahama Parrot

On October 12, 1492, Lucayan Indians greeted Christopher

Columbus on his arrival on the island they called Guanahani.

They presented him with a variety of items, and Columbus

seemed particularly attracted by the parrots he was given;

for when he returned to Spain a few months later, he carried

40 parrots with him. Much has changed in 500 years.

Guanahani is now known as San Salvador, and it is part of an

island nation, the Bahamas, inhabited by 254,000 residents

and visited by three million tourists annually. The Lucayans

are gone and the parrots – so abundant that Columbus

described them darkening the sky – have disappeared from

Guanahani. Today, the Bahama parrot persists on only two

islands, Abaco and Great Inagua, and numbers fewer than

3000 individuals. The parrot’s demise can be traced to several

factors, the broadest being loss of habitat because of development,

agriculture, and logging. Hunting parrots for food was a

significant issue at one time, but today catching live parrots

for the pet trade is a greater threat. Lastly and perhaps of most

immediate importance, feral cats cause heavy losses on Abaco

Island, where the parrots nest in holes in the ground.

In 1990 a program to save the Bahama parrot was initiated

by four organizations: the Forestry Section of the Lands

and Surveys Department; the Ministry of Agriculture; the

Bahamas National Trust, a private group dedicated to protecting

the natural and cultural heritage of the Bahamas; and the

RARE Center for Tropical Conservation, a small United Statesbased

conservation group. A wide-reaching campaign to

engender public support for the Bahama parrot followed. Here

are some of the tactics employed, as described by Paul Butler

(1992b), RARE’s director of conservation education. The

visual image of the Bahama parrot and a simple conservation

message were dispersed far and wide through posters, buttons,

bumper stickers, billboards, puppets, grocery bags, a one

Figure 15.5 A key part of the success of the

early public relations campaign to promote support

for Bahama Parrot conservation has been

Quincy – a person wearing a parrot costume –

who taught children a song about the Bahama

parrot, led them in a parrot dance, and told

them about the plight of the bird. (Photo from

Lynn Gape, Bahamas National Trust.)

personal well-being; the highest, broadest concern is at the level of ecosystems or the

whole biosphere. Most people have some concern about the welfare of all other humans

and many people care about sentient animals (i.e. those species – chiefly, mammals and

birds – that they perceive to have feelings). Raising people’s level of concern to embrace

all species and ecosystems is an essential goal for conservation biologists. Some will

argue that this can be done only if people become biocentric; others will argue that you

can be anthropocentric – caring primarily about people – and still reach out to care

about life in all its forms. Both of these are easier to do after basic needs are met; in

other words, date trees are more beautiful to someone with a full stomach.

Summary

The attitudes people have toward other organisms and conservation vary enormously from person

to person. While each person’s values may be unique, there are patterns that can, to some

extent, be explained by culture, religion, gender, income, occupation, age, and other factors.

Understanding how these factors affect someone’s attitudes is easier if we use a systematic

means of describing attitudes toward nature. Values change through time, and promoting positive

attitudes toward the natural world is a fundamental part of environmental education. By

informing people about the importance of biodiversity and encouraging them to experience

nature, we can foster attitudes that move us away from an anthropocentric (human centered)

view of the world with its attendant indifference and destructiveness to wild life toward a more

biocentric (life centered) perspective that embraces the other life forms with which we share

the earth.

344 Part IV The Human Factors

FURTHER READING

See Wilshusen et al. (2003), Callicott (2002), Smith (1999), and Van De Veer and Pierce (1994) for anthologies of

papers about environmental philosophy that include work on ecofeminism, biocentrism, and other relevant topics,

and see Pojman (1999) for a textbook on the same topics. Aldo Leopold’s (1949) Sand County Almanac remains an

important source. For a summary of Stephen Kellert’s work, see his 1996 book. For some recent ideas about environmental

education and changing values, read Orr (1992, 1994) and Jacobson (1995). Jacobson and McDuff

(1998) make a strong argument for why conservation biologists need to understand the human dimension of

conservation.

dollar bill, postage stamps in five denominations, and a cancellation mark used by the post office. Over 26,000

school children were visited by Quincy (a person wearing a parrot costume) plus a counterpart who taught the

children a song about the Bahama parrot, led them in a parrot dance, and told them about the plight of the

Bahama parrot and other wildlife (Fig. 15.5). Fact sheets about the Bahama parrot were distributed widely; for

example, clergy were sent these sheets along with a selection of universal prayers with an environmental theme

and scriptural sources pertaining to caring for the earth. A rap song, a music video, and a stream of press

releases made sure the Bahama parrot program was very conspicuous in the mass media.

The campaign has worked. Questionnaires have ascertained that most Bahamians are now aware of the

Bahama parrot’s plight, and this has translated into direct action. In particular, a 10,700 ha national park was

created on Abaco Island. It protects habitat not only for the parrot, but for many other species, at least one of

which, the Kirtland’s warbler, is even rarer than the parrot. It is also likely that the campaign has sensitized

Bahamians to the ecological well-being and biological riches of their nation in general.

Social Factors 345

TOPICS FOR DISCUSSION

1 How would you encourage Chinese peasants to protect giant pandas and their habitat even though they could

earn many years’ wages by catching one?

2 What factors do you feel have the most profound influence on a person’s attitudes toward wild organisms? Has

this changed in recent years? Will it change in the future?

3 Is trying to change another person’s values generally acceptable? When is it not acceptable? When is it acceptable?

4 Do you feel that you are more anthropocentric or more biocentric? Why? Has taking a conservation biology class

and/or reading this text shifted your values? (See Caro et al. 1994.)