water issues
annyzyl123
stateoftheworldsfreshwaterecosystems.pdf
EG36CH04-Carpenter ARI 19 September 2011 7:22
State of the World’s Freshwater Ecosystems: Physical, Chemical, and Biological Changes Stephen R. Carpenter, Emily H. Stanley, and M. Jake Vander Zanden Center for Limnology, University of Wisconsin, Madison, Wisconsin 53706; email: [email protected], [email protected], [email protected]
Annu. Rev. Environ. Resour. 2011. 36:75–99
First published online as a Review in Advance on July 29, 2011
The Annual Review of Environment and Resources is online at environ.annualreviews.org
This article’s doi: 10.1146/annurev-environ-021810-094524
Copyright c© 2011 by Annual Reviews. All rights reserved
1543-5938/11/1121-0075$20.00
Keywords
aquatic invasive species, climate change, ecosystem services, freshwater biogeochemistry, land-use change, natural capital
Abstract
Surface freshwaters—lakes, reservoirs, and rivers—are among the most extensively altered ecosystems on Earth. Transformations include changes in the morphology of rivers and lakes, hydrology, biogeo- chemistry of nutrients and toxic substances, ecosystem metabolism and the storage of carbon (C), loss of native species, expansion of invasive species, and disease emergence. Drivers are climate change, hydrologic flow modification, land-use change, chemical inputs, aquatic invasive species, and harvest. Drivers and responses interact, and their relation- ships must be disentangled to understand the causes and consequences of change as well as the correctives for adverse change in any given wa- tershed. Beyond its importance in terms of drinking water, freshwater supports human well-being in many ways related to food and fiber pro- duction, hydration of other ecosystems used by humans, dilution and degradation of pollutants, and cultural values. A natural capital frame- work can be used to assess freshwater ecosystem services, competing uses for freshwaters, and the processes that underpin the long-term maintenance of freshwaters. Upper limits for human consumption of freshwaters have been proposed, and consumptive use may approach these limits by the mid-century.
75
A nn
u. R
ev . E
nv ir
on . R
es ou
r. 2
01 1.
36 :7
5- 99
. D ow
nl oa
de d
fr om
w w
w .a
nn ua
lr ev
ie w
s. or
g A
cc es
s pr
ov id
ed b
y U
ni ve
rs it
y of
C al
if or
ni a
- S
an D
ie go
o n
06 /2
9/ 17
. F or
p er
so na
l us
e on
ly .
EG36CH04-Carpenter ARI 19 September 2011 7:22
Contents
INTRODUCTION . . . . . . . . . . . . . . . . . . 76 EARTH’S SURFACE
FRESHWATERS . . . . . . . . . . . . . . . . . 76 WHY ARE FRESHWATERS
CHANGING? . . . . . . . . . . . . . . . . . . . . 77 Climate Change . . . . . . . . . . . . . . . . . . . 77 Hydrologic Change . . . . . . . . . . . . . . . . 79 Land-Use Change . . . . . . . . . . . . . . . . . 79 Changing Chemical Inputs . . . . . . . . . 80 Aquatic Invasive Species . . . . . . . . . . . . 81 Harvest . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
HOW ARE FRESHWATERS CHANGING? . . . . . . . . . . . . . . . . . . . . 83 Physical Transformations . . . . . . . . . . 83 Biogeochemistry and Nutrients . . . . . 85 Ecosystem Metabolism
and Carbon Balance . . . . . . . . . . . . . 86 Biotic Transformations . . . . . . . . . . . . . 87 Disease Emergence and
Transmission . . . . . . . . . . . . . . . . . . . 89 FRESHWATER CHANGE
AND HUMAN WELL-BEING . . . 89 ARE THERE LIMITS? . . . . . . . . . . . . . . 90
INTRODUCTION
An essential resource for human life, freshwater has no substitutes. Freshwater is also essential for many natural systems that support human well-being. Expanding human activity has extensively altered the planet’s freshwaters, with modifications impacting the physical, chemical, and biological features of aquatic systems. In this review, we first describe freshwaters with a focus on lakes, reservoirs, and rivers. We then address the major drivers of change and the responses in terms of fresh- waters to these drivers. These changes have many implications for human well-being that we discuss in a natural capital framework. We also consider the idea that human well-being can be maintained only if human uses of freshwater stay within certain boundaries. Most freshwaters have been altered in multiple
ways, and changes in any particular freshwater system usually have multiple causes. These interactions are noted throughout the paper.
This review emphasizes large-scale physical, chemical, and biological changes in freshwaters and their associated drivers, including human factors that affect freshwaters, but does not address institutional aspects of water man- agement. Water management is a vast subject embracing such diverse topics as water markets (1), political conflict over water (2), connections between water and social development (3), and social aspects of drought (4). This review focuses on the natural science aspects of fresh- water resources while recognizing that a com- prehensive approach to sustaining freshwater resources will go beyond this scope to address aspects of engineering and policy as well (5).
EARTH’S SURFACE FRESHWATERS
All freely available water (liquid, solid, or gas) in the atmosphere, on Earth’s surface, and in Earth’s crust to a depth of 2 km, a water vol- ume of approximately 1.386 × 106 km3, com- pose the hydrosphere (6). Only 2.5% of this water is freshwater, of which 68.7% is peren- nially frozen and 29.9% is groundwater. Only 0.26% of liquid freshwater on Earth is in lakes, reservoirs, and rivers, which are the focus of this article. We do not consider freshwater wetland habitats and consider groundwater only with respect to its interactions with surface fresh- water. For recent reviews on groundwater and wetlands, see References 7 and 8, respectively.
Surface freshwaters are in rapid flux com- pared with other pools of liquid water on Earth. The turnover time is approximately 160 years for lake and reservoir water and 16 days for rivers (9), compared with 1,500 years for groundwater and 2,500 years for the oceans (6). Globally, lakes cover approximately 2.7 × 106 km2 with a volume of approximately 175 × 103 km3. The role of small lakes and impound- ments has been poorly recognized and could add to these area and volume estimates (10, 11).
76 Carpenter · Stanley · Vander Zanden
A nn
u. R
ev . E
nv ir
on . R
es ou
r. 2
01 1.
36 :7
5- 99
. D ow
nl oa
de d
fr om
w w
w .a
nn ua
lr ev
ie w
s. or
g A
cc es
s pr
ov id
ed b
y U
ni ve
rs it
y of
C al
if or
ni a
- S
an D
ie go
o n
06 /2
9/ 17
. F or
p er
so na
l us
e on
ly .
EG36CH04-Carpenter ARI 19 September 2011 7:22
Forest Dryland Cultivated Polar Urban
Renewable or accessible water
Ecosystem
P ro
p o
rt io
n o
f p
re ci
p ita
tio n
0 .0
0 .1
0 .2
0 .3
0 .4
0 .5
Renewable Accessible
Figure 1 Renewable and accessible freshwater as a proportion of precipitation for selected ecosystem types (Reference 16, chapter 7, table 7.2).
Water withdrawals by humans are used for agriculture (76% or 3.81 × 103 km3 year−1), in various industries (15% or 0.77 × 103 km3 year−1), and within domestic households (9% or 0.38 × 103 km3 year−1) (9). However, most of the water withdrawn for agriculture is con- sumed (transferred to the atmosphere as water vapor), whereas most of the water withdrawn for industrial and domestic use is returned to surface flows.
Surface freshwaters supply approximately three-quarters of the water withdrawn for hu- man use. Ecosystems differ in their capacities to generate renewable water [i.e., water that is not lost immediately to evapotranspiration (ET)] and accessible water that is available for human use (Figure 1). Forests receive roughly half of the global precipitation over land and contribute approximately half of the global re- newable freshwater. Drylands are larger in area than are forests and receive appoximately the same annual volume of precipitation, but they generate far less runoff.
WHY ARE FRESHWATERS CHANGING?
Freshwaters are always in flux, but current changes are novel and exceptionally large. Major drivers of change are climate, human alteration of water flows, land-use and cover alterations, chemical inputs, aquatic inva- sive species, and human harvest including aquaculture (Figure 2).
Climate Change
Climate change directly affects freshwaters as a result of increased temperatures, greater vari- ability of precipitation among locations and over time, and rising sea levels. Several observed climate trends are significant for freshwaters: increased precipitation over land north of 30◦N since 1901, decreased precipitation over land between 10◦S and 30◦N after the 1970s, and increasing intensity of precipitation in some regions and droughts in others (12). In turn,
www.annualreviews.org • State of the World’s Freshwater Ecosystems 77
A nn
u. R
ev . E
nv ir
on . R
es ou
r. 2
01 1.
36 :7
5- 99
. D ow
nl oa
de d
fr om
w w
w .a
nn ua
lr ev
ie w
s. or
g A
cc es
s pr
ov id
ed b
y U
ni ve
rs it
y of
C al
if or
ni a
- S
an D
ie go
o n
06 /2
9/ 17
. F or
p er
so na
l us
e on
ly .
EG36CH04-Carpenter ARI 19 September 2011 7:22
Figure 2 Many interacting drivers, and interacting responses, affect the condition of freshwaters on any particular landscape. Reprinted from Carpenter & Biggs (5) and used by kind permission from Springer Science+Business Media B.V.
changing precipitation and temperature are as- sociated with decreased extent of glaciers and duration of ice cover and snowpack; increased thawing of permafrost; and regional changes in ET, lake levels, and streamflow (12). Modeled future trends relevant to freshwaters are warm- ing temperatures, more variable precipitation, and rising sea level (12).
Warmer water temperatures decrease the amount of oxygen that can be dissolved in sur- face waters and thereby decrease the availabil- ity of oxygen for respiration by organisms and processing of organic matter and pollutants.
Warming also decreases thermal niche and habitat availability for aquatic organisms that require cold water, such as galaxid or salmonid fishes (13, 14). At higher latitudes and eleva- tions, warming decreases the duration of the ice season and melts glaciers and permafrost, thereby changing the seasonality, magnitude, and sources of hydrologic flows. Greater vari- ability of precipitation, over time and among locations, adds to the variability of hydrologic inputs to lakes and streams.
Rising sea levels increase the extent of salt- water penetration into tidal rivers. The effects
78 Carpenter · Stanley · Vander Zanden
A nn
u. R
ev . E
nv ir
on . R
es ou
r. 2
01 1.
36 :7
5- 99
. D ow
nl oa
de d
fr om
w w
w .a
nn ua
lr ev
ie w
s. or
g A
cc es
s pr
ov id
ed b
y U
ni ve
rs it
y of
C al
if or
ni a
- S
an D
ie go
o n
06 /2
9/ 17
. F or
p er
so na
l us
e on
ly .
EG36CH04-Carpenter ARI 19 September 2011 7:22
of rising sea levels on lowland rivers are exac- erbated by decreased buildup of sediment due to siltation in impoundments upstream and de- creased runoff due to irrigation (15).
Hydrologic Change
Freshwater is distributed unevenly in space and time. To counter this heterogeneity, wa- ter resource development and management ac- tivities attempt to make water accessible for all human needs at all times. The tendency to store or divert water when it is present in excess or procure it when it is lacking is global in scope and is accomplished by irri- gation, drainage, groundwater pumping, im- poundment, levee construction, and interbasin transfer. Because of these manipulations and climate change, the world’s hydrologic cycle is changing with notable, widespread alterations in the hydrologic regimes of the world’s fresh- water ecosystems (16).
Water scarcity is the single largest global challenge facing water resource management. Over large continental areas, human demand for freshwater approaches or exceeds current supply, and approximately 2.4 billion people live in water-stressed environments (9). Provi- sioning of water to water-stressed regions for human needs is routinely done at the expense of ecosystems, both aquatic and terrestrial (16– 18). Conventional responses to water scarcity are withdrawals of deep groundwater and sur- face water storage. In many regions in North Africa, the Middle East, South and Central Asia, western North America, and Australia, ground- water withdrawals exceed recharge, so ground- water pools are declining (7) and groundwater- dependent ecosystems are threatened (19).
Surface water storage in ponds and reser- voirs is the most common strategy for ensuring a reliable water supply, especially because dam building can also provide other economic benefits such as electricity generation and flood control (20). Although reservoirs may provide a reliable source of water to meet human demand, they have transformative effects on rivers, including fragmentation, flow regime
modification, enhanced evaporative loss, and increased water residence times, in addition to wide-ranging consequences impacting aquatic communities. Dam construction has shifted from developed to developing regions, espe- cially China, India, and South America in the past 20 years (21). Thus hydrologic changes to rivers are continuing to increase both in spatial extent and degree of alteration. Our current understanding of the effects of dams on fresh- water environments is strongly biased toward the impacts of large structures, yet small dams (less than 15 m) outnumber large dams by per- haps tenfold. The number of small ponds and impoundments has increased over the past two decades, particularly in arid regions. Over the past 50 years, increases have been 60% in India (10) and 900% in some areas of Africa (22). This trend will likely continue, and the poorly appre- ciated but significant roles of these diminutive but numerous systems will also expand (10).
Transfer of water among different drainage basins is often expensive, yet it is common in places where water can be moved from snowy mountainous areas to low-lying arid regions (23). Large metropolitan areas in the western United States (e.g., Los Angeles, California, and Phoenix, Arizona) rely on such transfers, delivering water from the Sierra Nevada and Rocky Mountains via an extensive series of canals and aqueducts. More elaborate plans have been proposed, ranging from towing icebergs to large-scale desalinization oper- ations (24). Such unconventional strategies will likely continue and expand over the next several decades, and they will affect freshwater environments in ways that are only beginning to be recognized and quantified.
Land-Use Change
Land-use change, the conversion of natural lands to human use or the alteration of manage- ment practices on human-dominated lands, is a major driver of ecosystem change (25). Land- use change affects freshwater flows by changing the fates of precipitation among ET, runoff, and groundwater recharge. Conversion of natural
www.annualreviews.org • State of the World’s Freshwater Ecosystems 79
A nn
u. R
ev . E
nv ir
on . R
es ou
r. 2
01 1.
36 :7
5- 99
. D ow
nl oa
de d
fr om
w w
w .a
nn ua
lr ev
ie w
s. or
g A
cc es
s pr
ov id
ed b
y U
ni ve
rs it
y of
C al
if or
ni a
- S
an D
ie go
o n
06 /2
9/ 17
. F or
p er
so na
l us
e on
ly .
EG36CH04-Carpenter ARI 19 September 2011 7:22
ecosystems to cropland or urban uses generally increases runoff as well as flood frequency and intensity, and it decreases ET and groundwater recharge (16). Invasion by terrestrial plant species (such as Tamarix in the western United States) with high ET rates has the opposite effect of decreasing runoff to surface waters (26).
Agricultural land use for pasture or crop- land occupies 37% of terrestrial land area (27). Among human activities, agriculture uses the greatest amount of freshwater (28), emits the highest levels of greenhouse gases into the at- mosphere (29–31), and contributes the most to soil erosion and runoff of nutrients to freshwa- ters (32, 33). Agriculture accounts for 52% and 84% of global human emissions of the green- house gases CH4 and N2O, respectively (31). Intensive agriculture employs high fossil fuel inputs and reduces soil storage of carbon (C), although the C balance of agriculture varies considerably among tillage practices (30, 31, 34). Croplands, high-density livestock opera- tions, and urban lands add silt, nutrients, and toxic pollutants to surface waters (32).
Substantial expansion of agricultural pro- duction and water use will be needed in com- ing decades to meet the demand for food and perhaps biofuels (28, 35). Alternative agricul- tural practices have different implications for intensification or extensification of land use, magnitude of water use, nutrient emission, and greenhouse gas emission (31, 34, 36, 37). Future trends in agricultural production will affect freshwater sources directly through wa- ter withdrawals, nutrient emissions, and effects on riparian ecosystems as well as indirectly through climate change.
Although much smaller in extent than agriculture, Earth’s urban areas are growing rapidly. Food and fiber production that sup- ports urban populations requires substantial flows of water (38). Although groundwater ac- counts for only one-quarter of the world’s wa- ter withdrawals, it makes up approximately half the world’s potable water and provides drinking water for many of the world’s cities (7).
Changing Chemical Inputs
The history of pollution of freshwater is perhaps as long as that of water resource development. Both are consequences of human population expansion. Hydrology and biogeo- chemistry interact in many ways (39), and water management and water quality impacts show strong spatial correlation (40). The increase in chemical inputs to freshwaters is a result of diffuse inputs from landscapes dominated by human use (agricultural and urban areas) and atmospheric sources as well as from direct discharges of waste waters from sources such as mining, industry, or municipal sewage. The diverse array of anthropogenic chemicals added to freshwaters includes organic compounds, heavy metals, acids, and alkalis, some of which are toxic to aquatic organisms or humans.
The role of agriculture in providing diffuse (nonpoint-source) inputs of nutrients (nitro- gen, N, and phosphorus, P) and other chem- icals to aquatic systems is well established (32). Urban areas are also becoming signifi- cant sources of chemicals to freshwater envi- ronments. Limited investment in water supply and treatment infrastructure and rapid urban population growth—particularly in developing countries—interact to create water-quantity and -quality problems (41). When present, wastewater treatment mitigates nutrient- and organic-matter loading to freshwaters. Treat- ment of point-source effluents is far more com- mon in economically developed nations, as less than 20% of the population was connected to sewer systems in Africa and southern Asia in 2000 (16). Even in Europe, estimates of the per- cent of the population connected to wastewa- ter treatment facilities range from 35% to 80% among different countries (42). Furthermore, much of the water infrastructure in developed countries such as the United States is now aged and prone to leakage and failure (43). Urban areas also contribute surface runoff enriched in metals or organic compounds as well as at- mospheric inputs of automobile and industrial emissions that can eventually move into aquatic systems. Southeast Asia, a region of rapid
80 Carpenter · Stanley · Vander Zanden
A nn
u. R
ev . E
nv ir
on . R
es ou
r. 2
01 1.
36 :7
5- 99
. D ow
nl oa
de d
fr om
w w
w .a
nn ua
lr ev
ie w
s. or
g A
cc es
s pr
ov id
ed b
y U
ni ve
rs it
y of
C al
if or
ni a
- S
an D
ie go
o n
06 /2
9/ 17
. F or
p er
so na
l us
e on
ly .
EG36CH04-Carpenter ARI 19 September 2011 7:22
economic development with limited environ- mental regulations, is now a major source of these pollutants.
Aquatic Invasive Species
Humans intentionally and accidentally trans- port vast numbers of live organisms outside of their native range. Only a fraction of intro- duced species establish self-sustaining popula- tions, and a fraction of those become a nui- sance, spread, and cause harm (44). Never- theless, species invasion is now recognized as an important driver of global environmental change (45, 46), and freshwater ecosystems are especially vulnerable to species invasion and its effects (47).
The scope of biological invasions in fresh- water ecosystems is enormous. Biomass and species diversity of many freshwater ecosys- tems (e.g., the Laurentian Great Lakes) and even entire faunas (Mediterranean fishes) are currently dominated by nonnative species (48, 49). There are >180 nonnative species in the Laurentian Great Lakes, and the rate of new invasions is accelerating (48). The Non- indigenous Aquatic Species Database (Bio- logical Resources Division, U.S. Geological Survey, http://nas.er.usgs.gov/) reports 1,147 freshwater-introduced species (and 77 addi- tional species inhabiting brackish water) in the United States. Approximately 40% of these are native to the United States but now occur be- yond their native range. Although many aquatic invasive species were accidentally introduced, others have been introduced deliberately— stocked for aquaculture, pest control, aesthetic reasons, and recreational fisheries.
Aquatic invasive species have altered the physical, chemical, and ecological conditions of freshwater ecosystems, and they are one of the two most important factors threatening aquatic ecosystems and biodiversity (50). Ross (51) re- ported that in 77% of cases the introduction of nonnative fish corresponded with the reduction or elimination of native fishes. Introductions of predatory sport fishes are the major threat to endemic fishes in the western United States
(52). Introducing the Nile perch to Lake Vic- toria caused the extinction of perhaps hundreds of native haplochromine cichlids (53). Invasive species were a central factor in the food-web disruption of the Laurentian Great Lakes (see The Laurentian Great Lakes, sidebar below). Introduction of opossum shrimp (Mysis relicta) to Flathead Lake, Montana, disrupted the food web and affected the plankton, fish, bear, and eagle communities (54). Invasion by zebra mussels is accelerating extinction rates of native Unionid mussels (55). The spread of nonnative freshwater species is a key contributor to the ongoing biotic homogenization of freshwater ecosystems occurring at the global level (56).
The implications of aquatic invasive species for ecosystem services are not well known.
THE LAURENTIAN GREAT LAKES
The history of the Laurentian Great Lakes is that of a progression of successive anthropogenic impacts spanning nearly two cen- turies. The nineteenth century saw the wholesale loss of forests, lake-shoreline alteration, wetland destruction, and dam building on tributaries. It was also a period of intense fishery exploitation. By the mid-1800s, fisheries had already overexploited the fish populations, and declines and collapses of fish stocks continued into the mid-twentieth century. Invasive sea lamprey invasion fur- ther decimated fisheries from the 1940s onward. Concern over cultural eutrophication as well as the bioaccumulation of toxic substances peaked in the 1960s and 1970s. Zebra mussel invasion in the 1980s focused attention on the multitude of nonnative species (>180 species) in the Laurentian Great Lakes, both in- tentional and accidental in origin. More recent concerns include changing lake levels and the system-wide effects of climate change (158).
Over this period, some impacts have abated. Nutrient loading and levels of some contaminants have declined, and sea lamprey populations have been successfully controlled. Nevertheless, the ecosystems have been fundamentally transformed. Much of the native biota has been lost, including a suite of endemic deep- water coregonids. These have been replaced by a suite of non- native fishes such as rainbow smelt, alewife, and stocked Pacific salmonids. Food webs composed of nonnative species now sup- port valuable recreational fisheries and pose some management challenges owing to competing human goals for these ecosystems.
www.annualreviews.org • State of the World’s Freshwater Ecosystems 81
A nn
u. R
ev . E
nv ir
on . R
es ou
r. 2
01 1.
36 :7
5- 99
. D ow
nl oa
de d
fr om
w w
w .a
nn ua
lr ev
ie w
s. or
g A
cc es
s pr
ov id
ed b
y U
ni ve
rs it
y of
C al
if or
ni a
- S
an D
ie go
o n
06 /2
9/ 17
. F or
p er
so na
l us
e on
ly .
EG36CH04-Carpenter ARI 19 September 2011 7:22
Awareness of the need for valuation studies is growing (57). Examples of economic impacts include water hyacinth effects on navigation in Lake Victoria and other tropical African lakes (58), zebra mussel fouling of water systems (59), and Tamarix reduction of riparian water availability in the southwestern United States (26). Annual economic damages from each of the above examples are in the US$107 to 108
range. Perhaps the most troubling feature of
aquatic invasive species is their irreversibility once established. In contrast with chemical pol- lutants, which can diminish over time, invasive species often exhibit accelerated rates of spread following initial establishment. Preventing the introduction of new species and containing ex- isting species are central to managing their im- pacts, and some progress has been made in reg- ulating key vectors such as ballast water and recreational boaters (60). Quantifying the eco- nomic impacts and consequences for ecosystem services is a critical step to improve manage- ment (57).
Harvest
Fish production is a valuable provisioning ecosystem service generated by freshwater ecosystems. Aquatic resources, particularly fish and invertebrates, but also birds, reptiles, and amphibians, are harvested for local subsistence, commercial use, recreational use, or pet trade. Recent concern about the “global fisheries crisis” has focused almost exclusively on marine ecosystems, although the impacts of recre- ational fishing and overfishing of inland waters have garnered increased attention (61, 62).
Declining fish stocks and increasing de- mand for fish have led to sharp increases in aquaculture production in recent decades (63). Freshwater ecosystems constitute nearly half of the global aquaculture production, estimated at 68 million metric tons (64). This inland aquaculture boom has led to increases in the harvesting of wild fish for feed, water pollution, altered hydrologic flows, and the accidental release of nonnative species (63).
The annual commercial and subsistence fish harvest from inland waters, excluding aquacul- ture and recreational fishing, has increased ap- proximately fourfold since 1950 and is currently estimated at 10 million metric tons (64), with Asia (65%) and Africa (24%) dominating (62). In contrast, annual harvests from marine fish- eries are approximately 80 million metric tons (64). Fisheries that target high-value species provide many examples of harvesting that have caused sharp reductions in catch, abun- dance, and body size [e.g., Nile perch in Lake Victoria, lake trout in the Laurentian Great Lakes (62)]. For multispecies fisheries, more common in tropical waters, the limited data suggest that intensive harvesting has often led to depletion of large body-sized fishes, causing a shift toward the harvesting of smaller species and younger fish (62, 65).
In contrast with commercial fisheries, inland recreational fisheries are poorly tracked, although there is growing interest in their po- tential effects on aquatic resources (66). Recre- ational fishing is a multibillion-dollar industry, with diverse subsectors and rapid growth driven by affluent anglers in rich countries. Post et al. (61) documented the widespread decline of recreational fisheries adjacent to popula- tion centers in Canada, demonstrating that recreational fisheries often show depensatory dynamics and that recreational fishing can collapse freshwater fisheries. Fishery declines are often masked and exacerbated by fish stock- ing (67). These recent findings challenge the conventional belief that recreational fisheries tend to be self-regulating and less vulnerable to collapse than commercial fisheries.
An assessment of inland fisheries by the Food and Agriculture Organization (68) concluded that many inland fisheries were overfished and degraded by pollution and habitat loss. Fisheries often target large and high-value apex predators that have life-history traits that make them especially vulnerable to overexploitation. Following overexploitation, target species are often replaced by smaller, faster-growing, or less desirable species, which subsequently become the new target
82 Carpenter · Stanley · Vander Zanden
A nn
u. R
ev . E
nv ir
on . R
es ou
r. 2
01 1.
36 :7
5- 99
. D ow
nl oa
de d
fr om
w w
w .a
nn ua
lr ev
ie w
s. or
g A
cc es
s pr
ov id
ed b
y U
ni ve
rs it
y of
C al
if or
ni a
- S
an D
ie go
o n
06 /2
9/ 17
. F or
p er
so na
l us
e on
ly .
EG36CH04-Carpenter ARI 19 September 2011 7:22
of fisheries. In addition to impacting target species directly, fishery overharvest can pro- duce ecosystem-level effects. Fishes can play an important role in regulating ecosystem processes via nutrient excretion, bioturbation, and mass migration (69). The decline of apex predators produces trophic cascades that can extend to the base of the food web (70).
The harvest of wild freshwater fishes and aquaculture make up an essential and rapidly growing source of protein for the world’s populations (63). This situation necessitates balancing current demand with the protection of freshwater ecosystems to preserve future harvest potential and other ecosystem services. Degraded fisheries are often difficult to rebuild, and the available management tools (stocking of hatchery fish) can exacerbate the problem. Recreational and subsistence harvests are widely distributed on the landscape, not well quantified, and difficult to regulate. Perhaps most importantly, overharvest often acts synergistically with other human impacts.
HOW ARE FRESHWATERS CHANGING?
Multiple aspects of freshwaters are affected by the drivers described above, and frequently, there are complex interactions among the re- sulting responses. We focus here on changes in physical features, biogeochemistry, ecosys- tem metabolism, biotic transformations, and disease.
Physical Transformations
Dam construction is perhaps the most conspic- uous anthropogenic modifier of riverine sys- tems and their hydrology. Natural flow regimes and hydrologic connectivity of approximately 60% of the world’s large river basins are now affected by dams (20). Dams often stabilize dis- charge patterns by reducing the magnitude and duration of high flows and by supplementing low flows (71). The net global effect of im- poundments has been to reduce the average an- nual discharge to the ocean as a result of storage,
evaporation, and withdrawal, leading in some cases to complete desiccation of the aquatic ecosystem (72). Other water management prac- tices such as levee building and ditching gener- ally increase baseflow and flood magnitudes by rapidly routing water to channels and confining flow to these conduits (73, 74), whereas inter- basin transfers increase flows in one region at the expense of discharge in another.
The hydrology of many freshwater sys- tems is profoundly affected by agriculture. Over the past three centuries, the expansion of pasture and nonirrigated croplands has in- creased streamflow approximately tenfold by reducing ET. Conversely, the expansion of irrigation-based farming is associated with de- clining streamflow (75). At the global scale, the combined effects of agricultural water with- drawals and reservoirs have been estimated at a modest 3.5% reduction in the long-term aver- age riverine discharge to the ocean. However, among regions, this decline varies substantially, from no measurable change (e.g., in parts of Southeast Asia) to an average annual discharge decrease of 35% or more (representing 16% of the global land area excluding Greenland and Antarctica) (76).
Finally, the hydrologic consequences of land use and reservoir construction manifest within the context of changing climate conditions. Analyses of long-term discharge records have linked regional climate dynamics to a variety of river-flow trends, including both increased and decreased annual discharge and shifts in seasonal flow magnitudes (12). Climate-driven hydrologic changes have also been accompa- nied by temperature warming and decreased ice duration (77). Warming is most rapid in the mid- and high latitudes of the Northern Hemisphere, and surface temperatures in sev- eral lakes are increasing faster than regional air temperatures (78). Surprisingly, some of the best examples of lake warming are provided by the world’s largest lakes—Superior (79), Tanganyika (80), and Baikal (81)—a puzzling trend because these very large masses of wa- ter would be expected to warm slowly. Warm- ing trends and previous ice-out dates (and in
www.annualreviews.org • State of the World’s Freshwater Ecosystems 83
A nn
u. R
ev . E
nv ir
on . R
es ou
r. 2
01 1.
36 :7
5- 99
. D ow
nl oa
de d
fr om
w w
w .a
nn ua
lr ev
ie w
s. or
g A
cc es
s pr
ov id
ed b
y U
ni ve
rs it
y of
C al
if or
ni a
- S
an D
ie go
o n
06 /2
9/ 17
. F or
p er
so na
l us
e on
ly .
EG36CH04-Carpenter ARI 19 September 2011 7:22
some cases, ice-free winters) increase the sta- bility of thermal stratification, thus limiting the upwelling of nutrient-rich waters and primary productivity (80) and modifying planktonic population and community dynamics (81, 82).
FRESHWATER CONSERVATION PRIORITIES
Certain species groups and ecosystem types are particularly sen- sitive or vulnerable to anthropogenic impacts and, thus, are par- ticularly threatened. Below we highlight several examples:
Diadromous fishes: Diadromous fishes migrate between freshwater and marine systems to complete their life cycle. A recent assessment described dramatic and widespread declines in the diadromous fish stocks of the North Atlantic (159). Thirty- two of the 35 stocks showed overall declines, and 68% (24/35) of the stocks showed abundance declines of 90% or more. All species underwent population extirpations. A suite of threats— dams, alteration of flow regimes, overfishing, invasives, pollution, and climate change—are responsible for the declines (159).
Megafishes: A large number of the world’s largest fresh- water fishes, the megafishes, are threatened with extinction (http://megafishes.org/). These species often inhabit large river ecosystems, are highly migratory, and inhabit large geographic ranges—characteristics that make them particularly vulnerable to overharvest, habitat destruction, pollution, dams, and altered flow regimes. These impacts all threaten the extinction of these species. Accordingly, the plight of the megafishes also serves as an indicator of the threats faced by many of the world’s large river ecosystems.
Floodplains: Floodplains are among the most dynamic, pro- ductive, and diverse ecosystems on Earth. In developed regions, most rivers have been channeled and leveed, floodplains have been converted for agricultural and urban use, and natural flow regimes have been altered through river regulation. This combi- nation has led to widespread elimination of floodplain function and the associated floodplain aquatic ecosystems, both of which are defined by lateral connectivity with the river. Though flood- plains cover ∼1.5% of land surface, they provide >25% of all ter- restrial ecosystem services including nutrient removal, flood reg- ulation, water supply, and fishery production. The tremendous value of these ecosystem services highlights the need to protect and restore floodplain ecosystems. Yet, floodplains ecosystems are being lost at a rapid rate, particularly in Asia and parts of the developing world (86).
Changes to the physical structure and geo- morphic processes of freshwater environments are closely linked to hydrologic modifications, and they similarly vary within and among regions. For example, riverine transport of sediment has both increased (owing to human land use, particularly agriculture) and de- creased (owing to retention by reservoirs) (83). Changes in flow and sediment regimes cause a variety of channel form adjustments (e.g., incision, bed armoring, siltation, bank failures), which, in turn, often trigger management responses intended to stabilize channels (e.g., hardening of stream banks by addition of large boulders). Anthropogenic modifications can occur in lakes as well: Littoral habitats are modified by shoreline structures; armoring of banks; and removal of riparian vegetation, coarse woody habitat, and aquatic plants. Such alterations generally decrease fish abundance, biomass, and diversity (84).
Other manipulations of river channels in- clude dredging and installation of hydraulic de- vices to maintain navigation channels and boat access, channel redesigns (e.g., ditching, chan- nel relocation), and wood removal associated with deforestation and/or human development (85). The most extreme form of modification involves elimination of specific habitats (e.g., disconnection of floodplains via levee construc- tion) or of the entire ecosystem, and such al- terations are common. Floodplains, which are heavily used by humans because of abundant ecosystem services (see the Freshwater Conser- vation Priorities sidebar), are frequently mod- ified. Floodplain loss can be extensive; for ex- ample, as much as 90% of floodplain habitats have been eliminated from European rivers (86).
Expansion of urban areas is associated with engineered adjustments in channel form, fol- lowed by conversion to canals or ditches (87), and ultimately burial (88). Headwater streams in the United States have been buried under overburden materials from mountaintop min- ing (89). Such physical changes have substantial consequences for structure and, more broadly, biodiversity of aquatic communities.
84 Carpenter · Stanley · Vander Zanden
A nn
u. R
ev . E
nv ir
on . R
es ou
r. 2
01 1.
36 :7
5- 99
. D ow
nl oa
de d
fr om
w w
w .a
nn ua
lr ev
ie w
s. or
g A
cc es
s pr
ov id
ed b
y U
ni ve
rs it
y of
C al
if or
ni a
- S
an D
ie go
o n
06 /2
9/ 17
. F or
p er
so na
l us
e on
ly .
EG36CH04-Carpenter ARI 19 September 2011 7:22
Biogeochemistry and Nutrients
The capacity of freshwater ecosystems to trans- form or retain added solutes is a function of in- puts, hydrology, and biogeochemical process- ing. As noted above, inputs and hydrology are changing. Biogeochemical processing rates are also subject to change as a result of altered tem- perature regimes, chemical composition, and biota. A shift in any one driver is unlikely to affect just one chemical constituent alone, and similarly, a change in one individual chemical typically reflects multiple and often interacting causes that vary geographically. Modification of any one chemical can trigger a cascade of responses in other chemicals. Here we provide select examples of ongoing, large-scale changes in the biogeochemistry of freshwater systems.
Freshwaters exhibit geographically ex- tensive changes in concentrations of key nutrients (N and P), inorganic and organic C, sulfate (SO4), total dissolved salts, and micropollutants. Nutrient-enriched runoff from agriculture and urban land is a major cause of eutrophication, i.e., the overenrich- ment of aquatic ecosystems with nutrients or organic matter, leading to harmful blooms of algae, deoxygenation, loss of economically valuable species, and human health problems (32, 90). Seitzinger et al. (91) estimated that global riverine loads of N and P increased by approximately 30% between 1970 and 2000. Although riverine loads increased on all continents, the greatest increases and largest total loads occured in southern Asia. Whereas riverine fluxes of inorganic P declined in North America and Europe over this 30-year period, they increased in Africa, South America, Oceania, and South Asia (91). Organic C pools and fluxes are also changing, as soil disruption, altered plant cover, use of organic fertilizers, and effluent discharges are influencing organic C quantity and quality in aquatic systems (92).
Chemicals transferred to aquatic environ- ments via the atmosphere affect large regions and include SO4, nitrate (NO3), and contam- inants such as mercury. SO4 emissions from coal burning and industrial activities date from
Large lakes: The 189 largest lakes (>500 km2 each) contain ∼68% of the planet’s liquid surface freshwater (158). Large lakes are of tremendous importance to humans. They are mag- nets for human settlements and provide a wide range of ser- vices: transportation, fishing, power generation, waste disposal, irrigation, and domestic and industrial water supplies. Conse- quently, the world’s large lakes have been disproportionately al- tered by human activity. Many are ancient and support large num- bers of endemic species. The Great African Rift lakes (Victoria, Tanganyika, Malawi) are heavily impacted by rapid human pop- ulation growth, deforestation, soil erosion, and overfishing. Inva- sion of water hyacinth and Nile perch in Lake Victoria have had major effects including the widespread decline of native fishes. In contrast, the world’s oldest lake (25 million years old), Lake Baikal is remote, and although it has been affected by industrial and domestic pollution and overfishing, its water quality remains high, and none of the 1,500–2,000 endemic species have been lost (158).
the start of the Industrial Revolution, and aquatic consequences became apparent during the 1960s and 1970s (93). Policies that cur- tailed emissions in Europe and North America prompted a decline in SO4 concentrations and the recovery of pH in many lakes and rivers (94, 95). However, both biotic and chemical recov- ery has been delayed or incomplete in some af- fected regions (96, 97). Three additional chap- ters to the acid rain story are now emerging. First, long-term inputs of acid and SO4-rich precipitation has triggered a cascade of other chemical trends in many acid-sensitive fresh- waters that are now becoming apparent. These include declines in base cations (98) and in- creases in dissolved organic carbon (DOC) (99). Second, rather than diminishing as a global problem, acid rain and acidification have moved from North America and Europe to other con- tinents. Acid rain is now a notable environmen- tal issue in China (100) and will likely emerge in other developing industrial areas. Third, even though SO4 emissions have decreased in some parts of the world, emissions of oxidized nitro- gen (NOx), mercury, and other pollutants from fossil fuel combustion have not. Inputs of these constituents are increasing globally, especially
www.annualreviews.org • State of the World’s Freshwater Ecosystems 85
A nn
u. R
ev . E
nv ir
on . R
es ou
r. 2
01 1.
36 :7
5- 99
. D ow
nl oa
de d
fr om
w w
w .a
nn ua
lr ev
ie w
s. or
g A
cc es
s pr
ov id
ed b
y U
ni ve
rs it
y of
C al
if or
ni a
- S
an D
ie go
o n
06 /2
9/ 17
. F or
p er
so na
l us
e on
ly .
EG36CH04-Carpenter ARI 19 September 2011 7:22
in southeast Asia, and are producing a range of ecological and, in the case of mercury, human health effects (101).
Mercury is just one example of a growing number of micropollutants that are becom- ing more concentrated and more widely dis- tributed in freshwater environments. Products from industrial, farming, and mining activities entering surface waters range from heavy met- als to organic compounds such as polychlori- nated biphenyls and polycyclic aromatic hydro- carbons, and they can contribute to biological consequences such as direct toxicity, mutage- nesis, developmental disruption, and reduced primary production in aquatic environments (102, 103). A few toxins, such as hydrocar- bons and methyl mercury, are magnified in con- centration as they move through food chains and therefore are most harmful to top preda- tors including humans. Pesticides from agricul- ture, including genetically engineered insecti- cides (104), can change freshwater invertebrate communities. Pharmaceuticals and personal- care products are found in surface waters at con- centrations that may affect freshwater organ- isms (105, 106), whereas health risks to humans are plausible but poorly understood (107).
Many freshwaters are becoming increas- ingly saline, particularly in urban and dry- land settings. Multiple processes are involved in salinization of freshwaters, including point- source discharge of treated effluents, irrigation, marine saltwater intrusion due to overpumping of coastal aquifers, sea-level rise, and, in some cold climate regions, road salting (108), but ir- rigation and water abstraction in water-stressed environments is the most widespread cause (72). Chloride and sodium can interact with other chemical constituents, and salinization has been associated with increased base cation concen- trations in lakes (109), altered DOC flushing from soils, and interactions with other metal contaminants (110). Chloride concentrations often surpass chronic and acute toxicity levels (108); thus, they represent a major stressor of resident biota.
Rates of biogeochemical processes are often modeled as a function of temperature and
concentrations of substrates. The total amount of chemical processing is, in turn, dictated by the time available for these processes to occur. As discussed in sections above, all these factors are undergoing anthropogenic modification. Residence times have been alter- natively expedited or delayed, temperatures are often increasing, and concentrations of some reactants are declining while those of many more are increasing.
Examples of shifting biogeochemical rates in freshwaters are accruing in the literature. Because they increase residence time, reser- voirs substantially influence sediment as well as C, N, P, and silicon (Si) fluxes from continents to oceans (83, 91). Increased nutrient inputs promote primary production and ecosystem respiration, and they reduce the efficiency of nutrient uptake because biological demand is saturated (111). Shifting ratios of C, N, and P favor different biogeochemical transformations as well as the species composition of aquatic communities (112).
Ecosystem Metabolism and Carbon Balance
Although freshwaters cover only a small percentage of Earth’s land surface, they play a disproportionately large role in the C cycle because net C fluxes per unit area are greater for freshwater systems than for the surround- ing land (113). Freshwater systems tend to have high rates of carbon dioxide (CO2) and methane (CH4) emissions to the atmosphere. Whereas freshwater CH4 emissions offset approximately 25% of the continental sink for organic C (114), lakes and reservoirs contribute to the C sink through C storage in stable, long-lasting sediments.
Current land storage of organic C is esti- mated to be approximately 1,500 Pg in soils and 560 Pg in biomass (115, 116). Over the Holocene, lake sediments accumulated approx- imately 420–820 Pg C (113). The current stor- age rate in freshwater ecosystems is at least 0.23 Pg C year−1 (113). By comparison, during the 1980s–1990s, land-use change is thought to
86 Carpenter · Stanley · Vander Zanden
A nn
u. R
ev . E
nv ir
on . R
es ou
r. 2
01 1.
36 :7
5- 99
. D ow
nl oa
de d
fr om
w w
w .a
nn ua
lr ev
ie w
s. or
g A
cc es
s pr
ov id
ed b
y U
ni ve
rs it
y of
C al
if or
ni a
- S
an D
ie go
o n
06 /2
9/ 17
. F or
p er
so na
l us
e on
ly .
EG36CH04-Carpenter ARI 19 September 2011 7:22
have released 0.3–3 Pg C year−1 to the atmo- sphere, whereas terrestrial ecosystems stored between 0 and 5 Pg C year−1 (16). Organic C in lake sediments is preserved for a consider- ably longer duration (tens of thousands or more years) than organic C in terrestrial ecosystems (decades to centuries).
Intensive metabolism or storage of organic C in freshwaters may also be significant for regional C budgets. In the Northern High- land Lake District of Wisconsin, a region of ∼7,000 km2, freshwater wetlands and lakes cover only 20% and 13% of the land area, re- spectively, but account for >90% of the stored organic C (117). In Amazonia, upland forests appear to be accreting organic C, but for the region as a whole, the C budget is roughly bal- anced owing to large CO2 emissions from wet- lands and rivers (118).
Changing climate and land use are likely to affect processing and storage of organic C in freshwaters. Building of reservoirs for irriga- tion, flood control, or hydropower increases sedimentation and C storage while produc- ing energy, thereby offseting greenhouse gas emissions (119). However, reservoirs also emit greenhouse gases to the atmosphere at rates that can offset the benefits of reservoirs (120). Sedi- ment organic C burial rates by reservoirs range from 150 to 17,000 g C m−2 year−1, far greater than sedimentation rates in natural lakes and oceans (121). Globally, impoundments bury ap- proximately four times as much organic C as the world’s oceans (121). Warming temper- atures increase aquatic ecosystem respiration (122, 123) and are likely to decrease rates of or- ganic C storage while increasing rates of CO2 and CH4 emission to the atmosphere.
Biotic Transformations
Although freshwater composes less than 1% of the planet’s surface, the 126,000 known freshwater animal species make up approxi- mately 10% of described animal species and one-third of global vertebrate diversity (124). Freshwaters support ∼15,000 fish species (45%
of the global total)—a disproportionate con- centration of global fish diversity (http://www. iucn.org/what/tpas/biodiversity/). A number of other measures indicate that freshwater ecosystems support a disproportionately high level of species diversity relative to their area. Rates of endemism can be high for fresh- waters, especially for ancient and physically isolated ecosystems (125). High levels of en- demism increase species vulnerability to extinc- tion. Aquatic biodiversity remains poorly de- scribed, even for better-known groups such as vertebrates. For example, each year, approxi- mately 200 new fish species are described (126).
Aquatic biota are subject to a wide range of interacting threats. Direct alteration of aquatic ecosystems as well as their low-lying and in- tegrative position within catchments makes aquatic biota sensitive to altered land-use prac- tices. Sediment and nutrient loading from nonpoint-source pollution, invasive species, and altered flow regimes due to impoundment operations were the leading threats to imperiled freshwater taxa in North America (127).
Some of the most detailed data regarding species imperilment is for North America and the United States. Freshwater taxa have a higher rate of imperilment than do terrestrial or ma- rine taxa (128), and the taxonomic groups with the greatest proportion of at-risk species are all freshwater. The list is topped by fresh- water mussels (69% at risk or extinct), cray- fishes (51%), stoneflies (43%), freshwater fishes (37%), and amphibians (36%). High-profile terrestrial taxonomic groups have lower rates of imperilment (birds 14%, mammals 16%) (129). High rates of imperilment for North Ameri- can freshwater fishes have been recently cor- roborated by an American Fisheries Society as- sessment (39% imperiled: 230 vulnerable, 190 threatened, 280 endangered, and 61 extinct or extirpated) (130).
The Red Lists for freshwater species by the Internation Union for Conservation of Nature (IUCN) parallel imperilment trends for the United States, although the IUCN assesses fewer taxa. The 2009 IUCN Red List notes 1,147 freshwater fishes (37% of species
www.annualreviews.org • State of the World’s Freshwater Ecosystems 87
A nn
u. R
ev . E
nv ir
on . R
es ou
r. 2
01 1.
36 :7
5- 99
. D ow
nl oa
de d
fr om
w w
w .a
nn ua
lr ev
ie w
s. or
g A
cc es
s pr
ov id
ed b
y U
ni ve
rs it
y of
C al
if or
ni a
- S
an D
ie go
o n
06 /2
9/ 17
. F or
p er
so na
l us
e on
ly .
EG36CH04-Carpenter ARI 19 September 2011 7:22
assessed) and 1,369 species of freshwater invertebrates (131). Listed invertebrates are dominated by the handful of assessed and rela- tively well-studied invertebrate taxa: mollusks, crayfishes, and odonates. For these groups, approximately 8% of species are classified as imperiled, and 73% of listed invertebrate species are from North America, Europe, Australia, and New Zealand, reflecting the greater amount of recorded biological data in these countries. The majority of groups have not been assessed, but if overall rates are com- parable with those for assessed groups, then 12,000 freshwater invertebrate species may be extinct or imperiled (131). High rates of im- perilment are documented for other freshwater taxa such as amphibians, freshwater-reliant reptiles, and waterbirds (16). The Living Planet Index developed by the World Wildlife Fund (http://www.wwf.panda.org) provides a com- posite measure of trends in biota. The Fresh- water Living Planet Index, based on trends for 1,463 freshwater vertebrate populations (458 species), declined by 35% since 1970—more rapidly than either terrestrial or marine indices.
Human activities have caused species extinction rates that far exceed background rates. Current and projected extinction rates for freshwater faunal groups in North America are five times those of terrestrial taxa and are on par with species extinction rates for tropical rainforests. Freshwater extinction rates were estimated to be 1,000 times greater than background rates (128). Researchers have documented 123 North American freshwater taxa as extinct (128), including approximately 60 mussel species (131). Global extinctions are difficult to tally, but range from 95 to 290 fish species (132).
A species-by-species view of the status of freshwater biological resources may not be optimal for considering freshwater biota, particularly for invertebrates, which are highly diverse and not well-known (131). There has been growing interest in classifying and assess- ing freshwater communities and ecoregions at broad geographic scales. Efforts to assess the status of wetland plant communities or associa-
tions (classification based on the U.S. National Vegetation Classification System) in North America indicated high rates of imperilment: Of the 1,560 wetland plant communities, 60% are considered at risk, 12% critically imperiled, 24% imperiled, and 25% vulner- able (http://www.natureserve.org/servlet/ NatureServe?init = Ecol). Freshwater ecore- gions provide a starting point for assessing and prioritizing conservation efforts (132a). Rather than focus on the status of individual species, conservation efforts may be more effectively focused on unique community and ecosystem types as well as on hot spots of species diversity and endemism such as ancient rivers, floodplains, groundwater ecosystems, and large or ancient lakes (see Freshwater Conservation Priorities, sidebar above).
Species extinctions are generally due to the extirpation of many individual populations (133). Rates of population extirpation of fresh- water taxa are not well-known. Using histor- ical data for rivers in Mexico, Mercado-Silva et al. (134) reported native-species loss rates of 10%–30% per decade and a concomitant 10%– 20% increase per decade in nonnative species. Numerous other studies report similar trends of extirpation of native species and increas- ing incidence of nonnative species (135). This is a classic example of biotic homogenization, whereby many species are declining as a result of human activity and are being replaced by a small number of tolerant and expanding species. The consequence is that biotic communities be- come increasingly similar over time. Three key processes—habitat alternation, invasions, and extinctions—interact in ways that tend to fur- ther biotic homogenization (56).
Species replacement can alter ecosystem processes (136). A variety of mechanisms are involved, including alterations in habitat struc- ture and in species abundances resulting from changes in predation and competition. There are numerous examples of how loss or gain of species impacts ecosystems. For example, de- clines of a migratory tropical fish decreased downstream transport of organic C and in- creased primary production and respiration
88 Carpenter · Stanley · Vander Zanden
A nn
u. R
ev . E
nv ir
on . R
es ou
r. 2
01 1.
36 :7
5- 99
. D ow
nl oa
de d
fr om
w w
w .a
nn ua
lr ev
ie w
s. or
g A
cc es
s pr
ov id
ed b
y U
ni ve
rs it
y of
C al
if or
ni a
- S
an D
ie go
o n
06 /2
9/ 17
. F or
p er
so na
l us
e on
ly .
EG36CH04-Carpenter ARI 19 September 2011 7:22
(137). McIntyre et al. (138) found that nutri- ent cycling rates and N:P ratios were highly sensitive to changes in the fish community. Consumer-driven changes in nutrient availabil- ity and N:P can have strong impacts on au- totrophic productivity and species composition (69). Changes to the top predators in lakes have altered primary production, ecosystem respira- tion, the direction and magnitude of CO2 ex- change with the atmosphere, and sedimentation rates (139).
Disease Emergence and Transmission
Water availability is a major determinant of human health, particularly in regions of lim- ited economic development (9). Risk of water- borne diseases increases when encounters be- tween aquatic vectors and humans are high, as occur when water is scarce and people aggregate around limited water points or when water is abundant and aquatic vector populations (such as mosquitoes) are widespread (140). Water- borne diseases are closely associated with absent or compromised waste-management infras- tructure and water pollution (141). Contami- nation of domestic water supplies with human or animal feces increases the risk of cholera, other diarrheal diseases, and a range of para- sitic infections. Ironically, construction of im- poundments also increases the risk of diseases such as schistosomiasis (bilharzia) and malaria by creating or expanding the habitat for aquatic disease vectors such as snails and mosquitoes (142). Deforestation; land-use change; and the development of dams, canals, and irrigation sys- tems are associated with increases in the habitat available for parasites and vectors and with hu- man morbidity and mortality related to emer- gent parasitic diseases (143). Biodiversity loss frequently increases the incidence of human and wild-organism diseases (144).
Whereas relationships between water and human diseases are well studied, the dynamics and ecological significance of diseases of aquatic organisms have only recently begun to garner significant attention. Diseases play an impor- tant role in aquaculture and fish production and
are a factor in the global decline in amphibians. Vertebrate models dominate the literature, al- though examples are also known for disease im- pacts on aquatic invertebrates (145).
As with species invasions, disease spread involves transport, establishment, and expan- sion of pathogens and vectors in new habi- tats. In the case of fish, introduction of nonna- tive species has been a major pathway for dis- ease spread. For example, in European fresh- waters, aquaculture has been associated with the introduction and translocation of 94 known pathogens from 13 different taxonomic groups (146). Reports of antibiotic-resistant bacteria in and around aquaculture facilities are increasing (147). Pathogenicity, host susceptibility, and disease spread can be affected by the trophic status of an infected water body; although spe- cific mechanisms vary, nutrient enrichment is a common attribute of disease outbreaks across a range of freshwater systems and taxonomic groups (145). Eutrophication often increases infection risk by acting in concert with other environmental stressors such as agrochemicals (148) that weaken host resistance.
FRESHWATER CHANGE AND HUMAN WELL-BEING
Ecosystem services are the benefits that humans derive from nature (16). Ecosystem services from freshwater include flows that are withdrawn (e.g., for irrigation or municipal use) and in situ flows (e.g., for hydropower or transportation) (149). In addition to water flows, freshwaters also provide fish, waterfowl, edible plants such as wild rice, and other nat- ural products for human use. Freshwaters are associated with several processes that regulate the condition of ecosystems or the capacity of ecosystems to provide services (16). Floods can be moderated or intensified, depending on the physical configuration of landscapes and the capacity of the land to hold water. Nutrient flows can be regulated by the capacity of riparian ecosystems to retain sediment and nu- trients. Disease can be regulated by ecosystem processes, such as the association of cholera
www.annualreviews.org • State of the World’s Freshwater Ecosystems 89
A nn
u. R
ev . E
nv ir
on . R
es ou
r. 2
01 1.
36 :7
5- 99
. D ow
nl oa
de d
fr om
w w
w .a
nn ua
lr ev
ie w
s. or
g A
cc es
s pr
ov id
ed b
y U
ni ve
rs it
y of
C al
if or
ni a
- S
an D
ie go
o n
06 /2
9/ 17
. F or
p er
so na
l us
e on
ly .
EG36CH04-Carpenter ARI 19 September 2011 7:22
Natural capital Soil Vegetation Freshwater Habitat Biotic interactions
Human use and management Institutions, incentives, regulations Markets Operators Equipment
Human-driven changes: land cover; ecosystem heterogeneity; water infiltration, runoff, and quality;
carbon storage; nutrient flows; soil fertility; biota
Ecosystem services: food and fiber production, freshwater, flood regulation,
nutrient regulation, carbon sequestration, recreation, aesthetics
Figure 3 Freshwater ecosystem services are derived from natural capital as well as the human-use and management practices of a region.
outbreaks with phytoplankton blooms (150). Finally, freshwater ecosystems provide cultural benefits in terms of education, enjoyment of nature, recreation, or spiritual values.
Freshwater ecosystem services interact with other ecosystem services through the dynamics of natural capital (Figure 3). Natural capital is the capacity of a particular place or region to provide ecosystem services in both the present and the future. Natural capital includes, e.g., the region’s soils, vegetation, freshwater, habitat, as well as biota and their interactions. The dynamics of natural capital depend on external factors such as climate, in- ternal physical and biotic processes, and human actions. Human use and management affect not only the current status and future trends of natural capital, but also the ecosystem services derived from it. Depending on human use and management, a region’s natural capital can be configured quite differently and yield distinct sets of ecosystem services. Efforts to maximize
food and fiber production often degrade water quality, groundwater recharge, and the capacity of landscapes to moderate floods (16).
Up to one-third of Earth’s human pop- ulation is affected by water scarcity and the attendant problems associated with food production, human health, and diversion of labor simply to meet water needs (16). Nations affected by water shortage may choose to purchase water-intensive commodities on the global market. The resulting trade in virtual water may lead to significant efficiencies in water use (Figure 4). However, dependency on the virtual water trade may decrease global flexibility to respond to severe famines caused by drought or crop failures (151).
ARE THERE LIMITS?
Access to adequate water is recognized by the United Nations as a basic human right (152). South Africa has legalized water priorities for
90 Carpenter · Stanley · Vander Zanden
A nn
u. R
ev . E
nv ir
on . R
es ou
r. 2
01 1.
36 :7
5- 99
. D ow
nl oa
de d
fr om
w w
w .a
nn ua
lr ev
ie w
s. or
g A
cc es
s pr
ov id
ed b
y U
ni ve
rs it
y of
C al
if or
ni a
- S
an D
ie go
o n
06 /2
9/ 17
. F or
p er
so na
l us
e on
ly .
EG36CH04-Carpenter ARI 19 September 2011 7:22
Maize Wheat Rice Barley Beef Pork Chicken
Global trade in virtual water in 2000
Commodity
A n
n u
a l w
a te
r tr
a d
e , km
3
0 1
0 0
2 0
0 3
0 0
4 0
0
Virtual water Real water
Figure 4 Global trade in virtual water in 2000 (Reference 16, chapter 7, table 7.8). Virtual water is the water that would have been used by the importing country to produce the commodity. Real water is the water that was in fact used by the exporting country to produce the commodity.
human and ecosystem needs by establishing a “reserve” that provides an allocation of 25 liters per person per day to meet basic human needs (5). The ecological reserve is defined as the water necessary to maintain ecosystems needed to ensure sustainable development. Concepts of peak renewable water (flow constraints limit water availability), peak nonrenewable water (extraction rates exceed recharge rates of groundwater systems), and peak ecological water (aggregate loss of natural capital from water extraction exceeds the total value from human use of water) clarify trade-offs in water-allocation decisions (153).
Pollution and water flows are closely cou- pled given that concentrations of a pollutant equal its mass divided by the water volume. In economic terms, pollution decreases the supply of clean water and adds to the costs of water use. Thus many countries have established up- per limits for pollution of freshwater by N, P, or toxic materials. These upper limits are based on
expectations of water flows sufficient to dilute pollutants to acceptable concentrations. Policy instruments for the management of water sup- ply must also take account of changing climate, land use, and chemical inputs to freshwaters.
Are there natural upper limits for human use of freshwater resources? Between 5% and 25% of global freshwater extraction exceeds the re- newable supply, although there is great variabil- ity among regions (16). Sustainable water with- drawals computed for the driest 10% of years are substantially lower than those computed for the average year (25). Thus planning for aver- age conditions is of little use in drought-prone regions.
Because freshwater is heterogeneously dis- tributed and expensive to transport, it is difficult to establish an upper limit for human con- sumptive use of freshwater at the global scale. If overconsumption of water is widespread, however, it will be difficult to meet needs by moving water from place to place. Thus a
www.annualreviews.org • State of the World’s Freshwater Ecosystems 91
A nn
u. R
ev . E
nv ir
on . R
es ou
r. 2
01 1.
36 :7
5- 99
. D ow
nl oa
de d
fr om
w w
w .a
nn ua
lr ev
ie w
s. or
g A
cc es
s pr
ov id
ed b
y U
ni ve
rs it
y of
C al
if or
ni a
- S
an D
ie go
o n
06 /2
9/ 17
. F or
p er
so na
l us
e on
ly .
EG36CH04-Carpenter ARI 19 September 2011 7:22
global pattern of overconsumption would raise concern about exceeding global limits. Any upper limit for water consumption, regional or global, must allow for environmental flows to maintain natural capital that supports essential ecosystem services. A safe upper limit for hu- man consumptive use of freshwater worldwide
was suggested to be 4,000–6,000 km3 year−1
(154). Current consumptive water use of approximately 2,600 km3 year−1 is within this boundary. However, global requirements for water to meet food and biofuel demand may bring consumptive use close to the proposed upper limits by mid-century (155, 156).
SUMMARY POINTS
1. Freshwaters, along with land transformed for agriculture use, are the most extensively and rapidly altered ecosystems on the planet. Responses by freshwater systems are also broad in scope, encompassing changes in physical structure, chemistry, ecosystem processes, biotic characteristics, and diseases.
2. Major drivers of change include climate, hydrologic modification, land use, chemical inputs, invasive species, and harvest. All drivers play a role, but some have already had substantial effects on freshwaters (e.g., changing hydrology, channel form, land use, chemical inputs, species introductions, harvest), whereas the impacts of others have not yet reached their peak impact.
3. The projections of long-term directional climate change suggest massive effects on fresh- waters within a few decades. Because temperature and precipitation patterns affect fresh- water flows, rates of nutrient cycling and toxin breakdown, as well as thermal niches of organisms, the effects of future climate change could impact all aspects of freshwaters.
4. The drivers of change and the responses of freshwaters interact. For example, variation in storm intensity affects stream channel form, inputs of nonpoint pollutants, habitat, and transport of invasive species and diseases. Deforestation, urbanization, and infrastructure development often lead to increases in the host vectors of human parasites, resulting in increased disease rates. Reservoirs, in addition to their hydrologic and biogeochemical effects, facilitate the spread of nonnative species and are associated with spread of diseases such as schistosomiasis (bilharzia).
5. Human impacts on freshwater ecosystems sometimes follow a predictable sequence. Overharvest often precedes other anthropogenic effects on aquatic ecosystems, produc- ing declines in populations of the most valuable fishes. These changes have often been followed by increases in pollution, invasive species, and habitat destruction. This suite of stressors inhibits the future recovery of many degraded fisheries, such that in the absence of harvest, many major fisheries may never return to their previous abundance.
FUTURE ISSUES
1. Substantial uncertainties remain about the effects changing climate and land use have on surface and groundwater flows, water quality, and aquatic biota.
2. Agricultural policies and practices will have powerful effects on surface and groundwa- ter flows, flood frequency and spatial pattern, water quality, human and wild-organism diseases, and living aquatic resources.
92 Carpenter · Stanley · Vander Zanden
A nn
u. R
ev . E
nv ir
on . R
es ou
r. 2
01 1.
36 :7
5- 99
. D ow
nl oa
de d
fr om
w w
w .a
nn ua
lr ev
ie w
s. or
g A
cc es
s pr
ov id
ed b
y U
ni ve
rs it
y of
C al
if or
ni a
- S
an D
ie go
o n
06 /2
9/ 17
. F or
p er
so na
l us
e on
ly .
EG36CH04-Carpenter ARI 19 September 2011 7:22
3. Basic research is needed to determine the factors that control transport, the establish- ment and expansion of invasive species, and aquatic diseases related to humans and wild organisms.
4. Effective policies, practices, and technologies must be invented and implemented to contain the spread of, or extirpate, harmful freshwater diseases and invasive species.
5. There is a critical need for research to develop a basic understanding, technologies, policy instruments, and institutions that can maintain the flow of freshwater ecosystem services without degrading the natural capital that creates these services. This research will go beyond the natural science disciplines we draw from here and embrace engineering and policy sciences as well.
6. Appropriate policy instruments, economic incentives, and technologies are needed to constrain pollution by N, P, and other chemicals within boundaries for acceptable water quality.
DISCLOSURE STATEMENT
The authors are not aware of any biases or conflicts of interest that might be perceived as affecting the objectivity of this review.
ACKNOWLEDGMENTS
We thank Mimi Chapin for her work on Figure 2 and Helen Sarakinos for helpful comments on drafts. Financial support was provided by the National Science Foundation through North Temperate Lakes Long-Term Ecological Research program and other research grants to the authors.
LITERATURE CITED
1. Chong H, Sunding D. 2006. Water markets and trading. Annu. Rev. Environ. Resour. 31:239–64 2. Wolf AT. 2007. Shared waters: conflict and cooperation. Annu. Rev. Environ. Resour. 32:241–69 3. Ray I. 2007. Women, water, and development. Annu. Rev. Environ. Resour. 32:421–49 4. Kallis G. 2008. Droughts. Annu. Rev. Environ. Resour. 33:85–118 5. Carpenter SR, Biggs R. 2009. Freshwaters: managing across scales in space and time. In Principles of
Ecosystem Stewardship, ed. FSI Chapin, GP Kofinas, C Folke, pp. 197–220. New York: Springer 6. Shiklomanov IA. 2000. Appraisal and assessment of world water resources. Water Int. 25:11–32 7. Giordano M. 2009. Global groundwater? Issues and solutions. Annu. Rev. Environ. Resour. 34:153–78 8. Zedler JB, Kercher S. 2005. Wetland resources: status, trends, ecosystem services, and restorability.
Annu. Rev. Environ. Resour. 30:39–74 9. Oki T, Kanae S. 2006. Global hydrological cycles and world water resources. Science 313:1068–72
10. Downing JA, Prairie YT, Cole JJ, Duarte CM, Tranvik LJ, et al. 2006. The global abundance and size distribution of lakes, ponds, and impoundments. Limnol. Oceanogr. 51:2388–97
11. Seekell DA, Pace ML. 2011. Does the Pareto distribution adequately describe the size distribution of lakes? Limnol. Oceanogr. 56:350–56
12. Kundzewicz ZW, Mata LJ, Arnell NW, Döll P, Kabat P, et al. 2007. Freshwater resources and their management. In Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, ed. ML Parry, OF Canziani, JP Palutikof, PJ van der Linden, CE Hanson, pp. 173–210. Cambridge, UK: Cambridge Univ. Press
www.annualreviews.org • State of the World’s Freshwater Ecosystems 93
A nn
u. R
ev . E
nv ir
on . R
es ou
r. 2
01 1.
36 :7
5- 99
. D ow
nl oa
de d
fr om
w w
w .a
nn ua
lr ev
ie w
s. or
g A
cc es
s pr
ov id
ed b
y U
ni ve
rs it
y of
C al
if or
ni a
- S
an D
ie go
o n
06 /2
9/ 17
. F or
p er
so na
l us
e on
ly .
EG36CH04-Carpenter ARI 19 September 2011 7:22
13. Mohseni O, Stefan HG, Eaton JG. 2003. Global warming and potential changes in fish habitat in U.S. streams. Clim. Change 59:389–409
14. Schindler DW. 2001. The cumulative effects of climate warming and other human stresses on Canadian freshwaters in the new millennium. Can. J. Fisheries Aquatic Sci. 58:18–29
15. Ericson JP, Vörösmarty CJ, Dingman SL, Ward LG, Meybeck M. 2006. Effective sea-level rise and deltas: causes of change and human dimension implications. Glob. Planet. Change 50:63–82
16. Millennium Ecosystem Assessment. 2005. Ecosystems and Human Well-Being: Conditions and Trends. Washington, DC: Island
17. Gleick PH, Palaniappean M. 2010. Peak water limits to freshwater withdrawal and use. Proc. Natl. Acad. Sci. USA 107:11155–62
18. Shiklomanov IA. 2000. Appraisal and assessment of world water resources. Water Int. 25:11–32 19. Boulton AJ, Hancock PJ. 2006. Rivers as groundwater-dependent ecosystems: a review of degrees of
dependency, riverine processes and management implications. Aust. J. Bot. 54:133–44 20. Nilsson C, Reidy CA, Dynesius M, Revenga C. 2005. Fragmentation and flow regulation of the world’s
large river systems. Science 308:405–8 21. Fujikura R, Nakayama M. 2009. Lessons learned from the world commission on dams. Int. Environ.
Agreements Polit. Law Econ. 9:173–90 22. Hughes DA, Mantel SK. 2010. Estimating the uncertainty in simulating the impacts of small farm dams
on streamflow regimes in South Africa. Hydrol. Sci. J. 55:578–92 23. Gupta J, van der Zaag P. 2008. Interbasin water transfers and integrated water resources management:
where engineering, science and politics interlock. Phys. Chem. Earth 33:28–40 24. Smakhtin V, Ashton P, Batchelor A, Meyer R, Murray E, et al. 2001. Unconventional water supply
options in South Africa—a review of possible solutions. Water Int. 26:314–34 25. Foley JA, DeFries R, Asner GP, Barford C, Bonan G, et al. 2005. Global consequences of land use.
Science 309:570–74 26. Zavaleta ES. 2000. The economic value of controlling an invasive shrub. AMBIO 29:462–67 27. Ramankutty N, Evan AT, Monfreda C, Foley JA. 2008. Farming the planet: 1. Geographic distribution
of global agricultural lands in the year 2000. Glob. Biogeochem. Cycles 22:GB1003 28. Rosegrant MW, Ringler C, Zhu T. 2009. Water for agriculture: maintaining food security under
growing scarcity. Annu. Rev. Environ. Resour. 34:205–22 29. Robertson GP, Paul EA, Harwood RR. 2000. Greenhouse gases in intensive agriculture: contributions
of individual gases to the radiative forcing of the atmosphere. Science 289:1922–25 30. West TO, Marland G. 2002. A synthesis of carbon sequestration, carbon emissions, and net carbon flux
in agriculture: comparing tillage practices in the United States. Agric. Ecosyst. Environ. 91:217–32 31. Smith P, Martino D, Cai Z, Gwary D, Janzen H, et al. 2008. Greenhouse gas mitigation in agriculture.
Philos. Trans. R. Soc. Lond. B 363:789–813 32. Carpenter SR, Caraco NF, Correll DL, Howarth RW, Sharpley AN, Smith VH. 1998. Nonpoint
pollution of surface waters with phosphorus and nitrogen. Ecol. Appl. 8:559–68 33. Quinton JN, Govers G, Van Oost K, Bardgett RD. 2010. The impact of agricultural soil erosion on
biogeochemical cycling. Nat. Geosci. 3:311–14 34. Gelfand I, Snapp SS, Robertson GP. 2010. Energy efficiency of conventional, organic, and alternative
cropping systems for food and fuel at a site in the U.S. Midwest. Environ. Sci. Technol. 44:4006–11 35. Millennium Ecosystem Assessment. 2005. Ecosystems and Human Well-Being: Scenarios. Washington,
DC: Island 36. Sauer T, Havlı́k P, Schneider UA, Schmid E, Kindermann G, Obersteiner M. 2010. Agriculture and
resource availability in a changing world: the role of irrigation. Water Resour. Res. 46:W06503 37. Sharpley A, Foy B, Withers P. 2000. Practical and innovative measures for the control of agricultural
phosphorus losses to water: an overview. J. Environ. Qual. 29:1–9 38. Rockstrom J, Gordon L, Folke C, Falkenmark M, Engwall M. 1999. Linkages among water vapor flows,
food production and terrestrial ecosystem services. Ecol. Soc. 3:article 5 39. Lohse KA, Brooks PD, McIntosh JC, Meixner T, Huxman TE. 2009. Interactions between biogeo-
chemistry and hydrologic systems. Annu. Rev. Environ. Resour. 34:65–96
94 Carpenter · Stanley · Vander Zanden
A nn
u. R
ev . E
nv ir
on . R
es ou
r. 2
01 1.
36 :7
5- 99
. D ow
nl oa
de d
fr om
w w
w .a
nn ua
lr ev
ie w
s. or
g A
cc es
s pr
ov id
ed b
y U
ni ve
rs it
y of
C al
if or
ni a
- S
an D
ie go
o n
06 /2
9/ 17
. F or
p er
so na
l us
e on
ly .
EG36CH04-Carpenter ARI 19 September 2011 7:22
40. Vorosmarty CJ, McIntyre PB, Gessner MO, Dudgeon D, Prusevich A, et al. 2010. Global threats to human water security and river biodiversity. Nature 467:555–61
41. Van der Bruggen B, Borghgraef K, Vinckier C. 2010. Causes of water supply problems in urbanised regions in developing countries. Water Resour. Manage. 24:1885–902
42. Martı́ E, Riera JL, Sabater F. 2010. Effects of wastewater treatment plants on stream nutrient dynamics under water scarcity conditions. In Water Scarcity in the Mediterranean: Perspectives under Global Change, The Handbook of Environmental Chemistry, ed. S Sabater, D Barceló, pp. 173–95. Berlin/Heidelberg: Springer-Verlag
43. Doyle MW, Stanley EH, Havlick DG, Kaiser MJ, Steinbach G, et al. 2008. Environmental science— aging infrastructure and ecosystem restoration. Science 319:286–87
44. Williamson M, Fitter A. 1996. The varying success of invaders. Ecology 77:1661–66 45. Mack RN, Simberloff D, Lonsdale WM, Evans H, Clout M, Bazzaz FA. 2000. Biotic invasions: causes,
epidemiology, global consequences, and control. Ecol. Appl. 10:689–710 46. Vitousek PM, D’Antonio CM, Loope LL, Westbrooks R. 1996. Biological invasions as global environ-
mental change. Am. Sci. 84:468–78 47. Sala OE, Chapin FS, Armesto JJ, Berlow E, Bloomfield J, et al. 2000. Biodiversity: global biodiversity
scenarios for the year 2100. Science 287:1770–74 48. Riccardi A. 2006. Patterns of invasion in the Laurentian Great Lakes in relation to changes in vector
activity. Divers. Distributions 12:425–33 49. Marr SM, Marchetti MP, Olden JD, Garcia-Berthou E, Morgan DL, et al. 2010. Freshwater fish
introductions in Mediterranean-climate regions: Are there commonalities in the conservation problem? Divers. Distributions 16:606–19
50. Wilcove DS, Rothstein D, Dubow J, Phillips A, Losos E. 1998. Quantifying threats to imperiled species in the United States. BioScience 48:607–15
51. Ross ST. 1991. Mechanisms structuring stream fish assemblages—Are there lessons from introduced species? Environ. Biol. Fishes 30:359–68
52. Minckley WL, Deacon JE, eds. 1991. Battle Against Extinction: Native Fish Management in the American West. Tuscon: Univ. Arizona Press
53. Witte F, Goldschmidt T, Goudswaard PC, Ligtvoet W, Vanoijen MJP, Wanink JH. 1992. Species extinction and concomitant ecological changes in Lake Victoria. Neth. J. Zmol. 42:214–32
54. Ellis BK, Stanford JA, Goodman D, Stafford CP, Gustafson DL, et al. 2011. Long-term effects of a trophic cascade in a large lake ecosystem. Proc. Natl. Acad. Sci. USA. 108:1070–75
55. Ricciardi A, Neves RJ, Rasmussen JB. 1998. Impending extinctions of North American freshwater mussels following the zebra mussel (Dressena polymorpha) invasion. J. Anim. Ecol. 67:613–19
56. Rahel FJ. 2002. Homogenization of freshwater faunas. Annu. Rev. Ecol. Syst. 33:291–315 57. Pejchar L, Mooney HA. 2009. Invasive species, ecosystem services and human well-being. Trends Ecol.
Evol. 24:497–504 58. Kasulo V. 2000. The impact of invasive species in African lakes. In The Economics of Biological Invasions,
ed. C Perrings, M Williamson, S Dalmazzone, pp. 262–97. Cheltenham, UK: Edward Elgar 59. Leung B, Lodge DM, Finnoff D, Shogren JF, Lewis MA, Lamberti G. 2002. An ounce of prevention
or a pound of cure: bioeconomic risk analysis of invasive species. Proc. R. Soc. Lond. Ser. B 269:2407–13 60. Lodge DM, Williams SL, MacIsaac H, Hayes K, Leung B, et al. 2006. Biological invasions: recom-
mendations for U.S. policy and management. Ecol. Appl. 16:2035–54 61. Post JR, Sullivan M, Cox S, Lester NP, Walters CJ, et al. 2002. Canada’s recreational fisheries: the
invisible collapse? Fisheries 27:6–17 62. Allan JD, Abell R, Hogan Z, Revenga C, Taylor BW, et al. 2005. Overfishing of inland waters. BioScience
55:1041–51 63. Naylor RL, Goldburg RJ, Primavera JH, Kautsky N, Beveridge MCM, et al. 2000. Effect of aquaculture
on world fish supplies. Nature 405:1017–24 64. Food Agriculture Organization. 2008. Yearbook of Fishery Statistics Summary Tables. Rome:
United Nations 65. Welcomme RL. 1979. Fisheries Ecology of Floodplain Rivers. London: Longman
www.annualreviews.org • State of the World’s Freshwater Ecosystems 95
A nn
u. R
ev . E
nv ir
on . R
es ou
r. 2
01 1.
36 :7
5- 99
. D ow
nl oa
de d
fr om
w w
w .a
nn ua
lr ev
ie w
s. or
g A
cc es
s pr
ov id
ed b
y U
ni ve
rs it
y of
C al
if or
ni a
- S
an D
ie go
o n
06 /2
9/ 17
. F or
p er
so na
l us
e on
ly .
EG36CH04-Carpenter ARI 19 September 2011 7:22
66. Cooke SJ, Cowx IG. 2004. The role of recreational fishing in global fish crises. BioScience 54:857–59 67. Hilborn R. 1992. Hatcheries and the future of salmon in the Northwest. Fisheries 17:5–8 68. Food Agriculture Organization. 1999. Review of the state of world fishery resources: inland fisheries.
Rep. FAO Fish. Circ. No. 942, Dep. Fish., Rome, Italy 69. Vanni MJ. 2002. Nutrient cycling by animals in freshwater ecosystems. Annu. Rev. Ecol. Syst. 33:341–70 70. Salomon AK, Gaichas SK, Shears NT, Smith JE, Madin EMP, Gaines SD. 2010. Key features and
context-dependence of fishery-induced trophic cascades. Conserv. Biol. 24:382–94 71. Poff NL, Olden JD, Merritt DM, Pepin DM. 2007. Homogenization of regional river dynamics by
dams and global biodiversity implications. Proc. Natl. Acad. Sci. USA 104:5732–37 72. Meybeck M. 2003. Global analysis of river systems: from Earth system controls to Anthropocene
syndromes. Philos. Trans. R. Soc. Lond. Ser. B 358:1935–55 73. Blann KL, Anderson JL, Sands GR, Vondracek B. 2009. Effects of agricultural drainage on aquatic
ecosystems: a review. Crit. Rev. Environ. Sci. Technol. 39:909–1001 74. Tobin GA. 1995. The levee love affair: a stormy relationship. Water Res. Bull. 31:359–67 75. Scanlon BR, Jolly I, Sophocleous M, Zhang L. 2007. Global impacts of conversions from natural to
agricultural ecosystems on water resources: quantity versus quality. Water Res. Res. 43:W03437 76. Döll P, Fiedler K, Zhang J. 2009. Global-scale analysis of river flow alterations due to water withdrawals
and reservoirs. Hydrol. Earth Syst. Sci. 13:2413–32 77. Magnuson JJ, Robertson DM, Benson BJ, Wynne RH, Livingstone DM, et al. 2000. Historical trends
in lake and river ice cover in the Northern Hemisphere. Science 289:1743–46 78. Schneider P, Hook SJ. 2010. Space observations of inland water bodies show rapid surface warming
since 1985. Geophys. Res. Lett. 37:L22405 79. Austin JA, Colman SM. 2007. Lake Superior summer water temperatures are increasing more rapidly
than regional air temperatures: a positive ice-albedo feedback. Geophys. Res. Lett. 34:L06604 80. O’Reilly CM, Alin SR, Plisnier PD, Cohen AS, McKee BA. 2003. Climate change decreases aquatic
ecosystem productivity of Lake Tanganyika, Africa. Nature 424:766–68 81. Hampton SE, Izmest’eva LR, Moore MV, Katz SL, Dennis B, Silow EA. 2008. Sixty years of en-
vironmental change in the world’s largest freshwater lake—Lake Baikal, Siberia. Glob. Change Biol. 14:1947–58
82. Weyhenmeyer GA, Westoo AK, Willen E. 2008. Increasingly ice-free winters and their effects on water quality in Sweden’s largest lakes. Hydrobiologia 599:111–18
83. Syvitski JPM, Vorosmarty CJ, Kettner AJ, Green P. 2005. Impact of humans on the flux of terrestrial sediment to the global coastal ocean. Science 308:376–80
84. Smokorowski KE, Pratt TC. 2007. Effect of a change in physical structure and cover on fish and fish habitat in freshwater ecosystems—a review and meta-analysis. Environ. Rev. 15:15–41
85. Gregory KJ. 2006. The human role in changing river channels. Geomorphology 79:172–91 86. Tockner K, Bunn SE, Gordon C, Naiman RJ, Quinn GP, Stanford JA. 2008. Flood plains: critically
threatened ecosystems. In Aquatic Ecosystems, ed. NVC Polunin, pp. 45–61. Cambridge, UK: Cambridge Univ. Press
87. Chin A. 2006. Urban transformation of river landscapes in a global context. Geomorphology 79:460–87 88. Elmore AJ, Kaushal SS. 2008. Disappearing headwaters: patterns of stream burial due to urbanization.
Front. Ecol. Environ. 6:308–12 89. Palmer MA, Bernhardt ES, Schlesinger WH, Eshleman KN, Foufoula-Georgiou E, et al. 2010. Moun-
taintop mining consequences. Science 327:148–49 90. Schindler DW. 2006. Recent advances in the understanding and management of eutrophication. Limnol.
Oceanogr. 51:356–63 91. Seitzinger SP, Mayorga E, Bouwman AF, Kroeze C, Beusen AHW, et al. 2010. Global river nutrient
export: a scenario analysis of past and future trends. Glob. Biogeochem. Cycles 24:GB0A08 92. Stanley EH, Powers SM, Lottig NR, Buffam I, Crawford JT. 2011. Contemporary changes in dissolved
organic carbon in human-dominated rivers: Is there a role for DOC management? Freshwater Biol. In press
93. Likens GE, Wright RF, Galloway JN, Butler TJ. 1979. Acid rain. Sci. Am. 241:43–51
96 Carpenter · Stanley · Vander Zanden
A nn
u. R
ev . E
nv ir
on . R
es ou
r. 2
01 1.
36 :7
5- 99
. D ow
nl oa
de d
fr om
w w
w .a
nn ua
lr ev
ie w
s. or
g A
cc es
s pr
ov id
ed b
y U
ni ve
rs it
y of
C al
if or
ni a
- S
an D
ie go
o n
06 /2
9/ 17
. F or
p er
so na
l us
e on
ly .
EG36CH04-Carpenter ARI 19 September 2011 7:22
94. Cheny YS, Lin LS. 2009. Responses of streams in central Appalachian Mountain region to reduced acidic deposition—comparisons with other regions in North America and Europe. Sci. Total Environ. 407:2285–95
95. Skjelkvale BL, Stoddard JL, Jeffries DS, Torseth K, Hogasen T, et al. 2005. Regional scale evidence for improvements in surface water chemistry 1990–2001. Environ. Pollut. 137:165–76
96. Jeffries DS, Clair TA, Couture S, Dillon PJ, Dupont J, et al. 2003. Assessing the recovery of lakes in southeastern Canada from the effects of acidic deposition. AMBIO 32:176–82
97. Gray DK, Arnott SE. 2009. Recovery of acid damaged zooplankton communities: measurement, extent, and limiting factors. Environ. Rev. 17:81–99
98. Jeziorski A, Yan ND, Paterson AM, DeSellas AM, Turner MA, et al. 2008. The widespread threat of calcium decline in fresh waters. Science 322:1374–77
99. Clark JM, Bottrell SH, Evans CD, Monteith DT, Bartlett R, et al. 2010. The importance of the relationship between scale and process in understanding long-term DOC dynamics. Sci. Total Environ. 408:2768–75
100. Larssen T, Lydersen E, Tang DG, He Y, Gao JX, et al. 2006. Acid rain in China. Environ. Sci. Technol. 40:418–25
101. Zhang L, Wong MH. 2007. Environmental mercury contamination in China: sources and impacts. Environ. Int. 33:108–21
102. Schwarzenbach RP, Escher BI, Fenner K, Hofstetter TB, Johnson CA, et al. 2006. The challenge of micropollutants in aquatic systems. Science 313:1072–77
103. Ohe T, Watanabe T, Wakabayashi K. 2004. Mutagens in surface waters: a review. Mutat. Res. 567:109– 49
104. Rosi-Marshall EJ, Tank JL, Royer TV, Whiles MR, Evans-White M, et al. 2007. Toxins in transgenic crop byproducts may affect headwater stream ecosystems. Proc. Natl. Acad. Sci. USA 104:16204–8
105. Snyder SA, Westerhoff P, Yoon Y, Sedlak DL. 2003. Pharmaceuticals, personal care products, and endocrine disruptors in water: implications for the water industry. Environ. Eng. Sci. 20:449–69
106. Loraine GA, Pettigrove ME. 2005. Seasonal variations in concentrations of pharmaceuticals and per- sonal care products in drinking water and reclaimed wastewater in Southern California. Environ. Sci. Technol. 40:687–95
107. Kümmerer K. 2010. Pharmaceuticals in the environment. Annu. Rev. Environ. Resour. 35:57–75 108. Kaushal SS, Groffman PM, Likens GE, Belt KT, Stack WP, et al. 2005. Increased salinization of fresh
water in the northeastern United States. Proc. Natl. Acad. Sci. USA 102:13517–20 109. Rosfjord CH, Webster KE, Kahl JS, Norton SA, Fernandez IJ, Herlihy AT. 2007. Anthropogenically
driven changes in chloride complicate interpretation of base cation trends in lakes recovering from acidic deposition. Environ. Sci. Technol. 41:7688–93
110. Green SM, Machin R, Cresser MS. 2008. Long-term road salting effects on dispersion of organic matter from roadside soils into drainage water. Chem. Ecol. 24:221–31
111. Mulholland PJ, Helton AM, Poole GC, Hall RO, Hamilton SK, et al. 2008. Stream denitrification across biomes and its response to anthropogenic nitrate loading. Nature 452:202–5
112. Taylor PG, Townsend AR. 2010. Stoichiometric control of organic carbon-nitrate relationships from soils to the sea. Nature 464:1178–81
113. Cole J, Prairie Y, Caraco N, McDowell W, Tranvik L, et al. 2007. Plumbing the global carbon cycle: integrating inland waters into the terrestrial carbon budget. Ecosystems 10:172–85
114. Bastviken D, Tranvik LJ, Downing JA, Crill PM, Enrich-Prast A. 2011. Freshwater methane emissions offset the continental carbon sink. Science 331:50
115. Post WM, Emanuel WR, Zinke PJ, Stangenberger AG. 1982. Soil carbon pools and world life zones. Nature 298:156–59
116. Schlesinger WH. 1997. Biogeochemistry. New York: Academic 117. Buffam I, Turner MG, Desai AR, Hanson PC, Rusak JA, et al. 2010. Integrating aquatic and terrestrial
components to construct a complete carbon budget for a north temperate lake district. Glob. Change Biol. 17:1193–211
118. Richey JE, Melack JM, Aufdenkampe AK, Ballester VM, Hess LL. 2002. Outgassing from Amazonian rivers and wetlands as a large tropical source of atmospheric CO2. Nature 416:617–20
www.annualreviews.org • State of the World’s Freshwater Ecosystems 97
A nn
u. R
ev . E
nv ir
on . R
es ou
r. 2
01 1.
36 :7
5- 99
. D ow
nl oa
de d
fr om
w w
w .a
nn ua
lr ev
ie w
s. or
g A
cc es
s pr
ov id
ed b
y U
ni ve
rs it
y of
C al
if or
ni a
- S
an D
ie go
o n
06 /2
9/ 17
. F or
p er
so na
l us
e on
ly .
EG36CH04-Carpenter ARI 19 September 2011 7:22
119. Smith SV, Renwick WH, Buddemeier RW, Crossland CJ. 2001. Budgets of soil erosion and deposition for sediments and sedimentary organic carbon across the conterminous United States. Glob. Biogeochem. Cycles 15:697–707
120. St. Louis VL, Kelly CA, Duchemin É, Rudd JWM, Rosenberg DM. 2000. Reservoir surfaces as sources of greenhouse gases to the atmosphere: a global estimate. BioScience 50:766–75
121. Downing JA, Cole JJ, Middelburg JJ, Striegl RG, Duarte CM, et al. 2008. Sediment organic carbon burial in agriculturally eutrophic impoundments over the last century. Glob. Biogeochem. Cycles 22:GB1018
122. Gudasz C, Bastviken D, Steger K, Premke K, Sobek S, Tranvik LJ. 2010. Temperature-controlled organic carbon mineralization in lake sediments. Nature 466:478–81
123. Kosten S, Roland F, Da Motta Marques DML, Van Nes EH, Mazzeo N, et al. 2010. Climate-dependent CO2 emissions from lakes. Glob. Biogeochem. Cycles 24:GB2007
124. Strayer DL, Dudgeon D. 2010. Freshwater biodiversity conservation: recent progress and future chal- lenges. J. N. Am. Benthol. Soc. 29:344–58
125. Dudgeon D, Arthington AH, Gessner MO, Kawabata Z, Knowler D, et al. 2006. Freshwater biodiver- sity: importance, threats, status and conservation challenges. Biol. Rev. 81:163–82
126. Lundberg JG, Kottelat M, Smith GR, Stiassny MLJ, Gill AC. 2000. So many fishes, so little time: an overview of recent ichthyological discovery in continental waters. Ann. Missouri Botanical Garden 87:26–62
127. Richter BD, Braun DP, Mendelson MA, Master LL. 1997. Threats to imperiled freshwater fauna. Conserv. Biol. 11:1081–93
128. Ricciardi A, Rasmussen JB. 1999. Extinction rates of North American freshwater fauna. Conserv. Biol. 13:1220–22
129. Stein BA, Kutner LS, Adams JS, eds. 2000. Precious Heritage: The Status of Biodiversity in the United States. Oxford: Oxford Univ. Press
130. Jelks HL, Walsh SJ, Burkhead NM, Contreras-Balderas S, Diaz-Pardo E, et al. 2008. Conservation status of imperiled North American freshwater and diadromous fishes. Fisheries 33:372–407
131. Strayer DL. 2006. Challenges for freshwater invertebrate conservation. J. N. Am. Benthol. Soc. 25:271–87 132. Helfman GS. 2007. Fish Conservation: A Guide to Understanding and Restoring Global Aquatic Biodiversity
and Fishery Resources. Washington, DC: Island 132a. Abell R, Thieme ML, Revenga C, Bryer M, Kottelat M, et al. 2008. Freshwater ecoregions of the world:
a new map of biogeographic units for freshwater biodiversity conservation. BioScience 58:403–14 133. Hughes JB, Daily GC, Ehrlich PR. 1997. Population diversity: its extent and extinction. Science 278:689–
92 134. Mercado-Silva N, Lyons J, Diaz-Pardo E, Gutiterrez-Hernandez A, Ornelas-Garcia CP, et al. 2006.
Long-term changes in the fish assemblage of the Laja River, Guanajuato, central Mexico. Aquatic Conserv. Mar. Freshw. Ecosyst. 16:533–46
135. Gido KB, Dodds WK, Eberle ME. 2010. Retrospective analysis of fish community change during a half-century of landuse and streamflow changes. J. N. Am. Benthol. Soc. 29:970–87
136. Jones CG, Lawton JH, eds. 1995. Linking Species and Ecosystems. New York: Chapman & Hall, Inc. 137. Taylor BW, Flecker AS, Hall RO. 2006. Loss of a harvested fish species disrupts carbon flow in a diverse
tropical river. Science 313:833–36 138. McIntyre PB, Jones LE, Flecker AS, Vanni MJ. 2007. Fish extinctions alter nutrient recycling in tropical
freshwaters. Proc. Natl. Acad. Sci. USA 104:4461–66 139. Carpenter SR, Cole JJ, Hodgson JR, Kitchell JF, Pace ML, et al. 2001. Trophic cascades, nutrients,
and lake productivity: whole-lake experiments. Ecol. Monogr. 71:163–86 140. Wilks CR, Turner AJ, Azuolas J. 2006. Effect of flooding on the occurrence of infectious disease. In
Advances in Ecological Research: Floods in an Arid Continent, ed. A Poiani, 39:107–24. New York: Academic 141. Schwarzenbach RP, Egli T, Hofstetter TB, von Gunten U, Wehrli B. 2010. Global water pollution
and human health. Annu. Rev. Environ. Resour. 35:109–36 142. Fenwick A. 2006. Waterborne infectious diseases—could they be consigned to history? Science 313:1077–
81 143. Patz JA, Graczyk TK, Geller N, Vittor AY. 2000. Effects of environmental change on emerging parasitic
diseases. Int. J. Parasitol. 30:1395–405
98 Carpenter · Stanley · Vander Zanden
A nn
u. R
ev . E
nv ir
on . R
es ou
r. 2
01 1.
36 :7
5- 99
. D ow
nl oa
de d
fr om
w w
w .a
nn ua
lr ev
ie w
s. or
g A
cc es
s pr
ov id
ed b
y U
ni ve
rs it
y of
C al
if or
ni a
- S
an D
ie go
o n
06 /2
9/ 17
. F or
p er
so na
l us
e on
ly .
EG36CH04-Carpenter ARI 19 September 2011 7:22
144. Keesing F, Belden LK, Daszak P, Dobson A, Harvell CD, et al. 2010. Impacts of biodiversity on the emergence and transmission of infectious diseases. Nature 468:647–52
145. Johnson PTJ, Townsend AR, Cleveland CC, Glibert PM, Howarth RW, et al. 2010. Linking environ- mental nutrient enrichment and disease emergence in humans and wildlife. Ecol. Appl. 20:16–29
146. Gozlan RE, Peeler EJ, Longshaw M, St-Hilaire S, Feist SW. 2006. Effect of microbial pathogens on the diversity of aquatic populations, notably in Europe. Microbes Infect. 8:1358–64
147. Sapkota A, Sapkota AR, Kucharski M, Burke J, McKenzie S, et al. 2008. Aquaculture practices and potential human health risks: current knowledge and future priorities. Environ. Int. 34:1215–26
148. Rohr JR, Schotthoefer AM, Raffel TR, Carrick HJ, Halstead N, et al. 2008. Agrochemicals increase trematode infections in a declining amphibian species. Nature 455:1235–39
149. Brauman KA, Daily GC, Duarte TK, Mooney HA. 2007. The nature and value of ecosystem services: an overview highlighting hydrologic services. Annu. Rev. Environ. Resour. 32:67–98
150. Colwell RR. 1996. Global climate and infectious disease: the cholera paradigm. Science 274:2025–31 151. D’Odorico P, Laio F, Ridolfi L. 2010. Does globalization of water reduce societal resilience to drought?
Geophys. Res. Lett. 37:L13403 152. World Health Organization. 2003. Right to Water. Geneva, Switzerland: WHO 153. Gleick PH, Palaniappan M. 2010. Peak water limits to freshwater withdrawal and use. Proc. Natl. Acad.
Sci. USA 107:11155–62 154. Rockstrom J, Steffen W, Noone K, Persson A, Chapin FS, et al. 2009. Planetary boundaries: exploring
the safe operating space for humanity. Ecol. Soc. 14: article 32 155. Falkenmark M. 2008. Water and sustainability: a reappraisal. Environment 50:4–16 156. Rosegrant MW, Ringler C, Zhu TJ. 2009. Water for agriculture: maintaining food security under
growing scarcity. Annu. Rev. Environ. Resour. 34:205–22 157. Johnson PT, Olden JD, Vander Zanden MJ. 2008. Dam invaders: impoundments facilitate biological
invasions in freshwaters. Front. Ecol. Environ. 6:357–63 158. Beeton AM. 2002. Large freshwater lakes: present state, trends, and future. Environ. Conservation 29:21–
38 159. Limburg KE, Waldman JR. 2009. Dramatic declines in North Atlantic diadromous fishes. BioScience
59:955–65
www.annualreviews.org • State of the World’s Freshwater Ecosystems 99
A nn
u. R
ev . E
nv ir
on . R
es ou
r. 2
01 1.
36 :7
5- 99
. D ow
nl oa
de d
fr om
w w
w .a
nn ua
lr ev
ie w
s. or
g A
cc es
s pr
ov id
ed b
y U
ni ve
rs it
y of
C al
if or
ni a
- S
an D
ie go
o n
06 /2
9/ 17
. F or
p er
so na
l us
e on
ly .
EG36-FrontMatter ARI 7 September 2011 14:34
Annual Review of Environment and Resources
Volume 36, 2011 Contents
Preface � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � �v
Who Should Read This Series? � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � �vii
I. Earth’s Life Support Systems
Improving Societal Outcomes of Extreme Weather in a Changing Climate: An Integrated Perspective Rebecca E. Morss, Olga V. Wilhelmi, Gerald A. Meehl, and Lisa Dilling � � � � � � � � � � � � � � � � � 1
Ocean Circulations, Heat Budgets, and Future Commitment to Climate Change David W. Pierce, Tim P. Barnett, and Peter J. Gleckler � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � �27
Aerosol Impacts on Climate and Biogeochemistry Natalie Mahowald, Daniel S. Ward, Silvia Kloster, Mark G. Flanner,
Colette L. Heald, Nicholas G. Heavens, Peter G. Hess, Jean-Francois Lamarque, and Patrick Y. Chuang � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � �45
State of the World’s Freshwater Ecosystems: Physical, Chemical, and Biological Changes Stephen R. Carpenter, Emily H. Stanley, and M. Jake Vander Zanden � � � � � � � � � � � � � � � � � �75
II. Human Use of Environment and Resources
Coal Power Impacts, Technology, and Policy: Connecting the Dots Ananth P. Chikkatur, Ankur Chaudhary, and Ambuj D. Sagar � � � � � � � � � � � � � � � � � � � � � � � 101
Energy Poverty Lakshman Guruswamy � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 139
Water and Energy Interactions James E. McMahon and Sarah K. Price � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 163
Agroecology: A Review from a Global-Change Perspective Thomas P. Tomich, Sonja Brodt, Howard Ferris, Ryan Galt, William R. Horwath,
Ermias Kebreab, Johan H.J. Leveau, Daniel Liptzin, Mark Lubell, Pierre Merel, Richard Michelmore, Todd Rosenstock, Kate Scow, Johan Six, Neal Williams, and Louie Yang � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 193
viii
A nn
u. R
ev . E
nv ir
on . R
es ou
r. 2
01 1.
36 :7
5- 99
. D ow
nl oa
de d
fr om
w w
w .a
nn ua
lr ev
ie w
s. or
g A
cc es
s pr
ov id
ed b
y U
ni ve
rs it
y of
C al
if or
ni a
- S
an D
ie go
o n
06 /2
9/ 17
. F or
p er
so na
l us
e on
ly .
EG36-FrontMatter ARI 7 September 2011 14:34
Energy Intensity of Agriculture and Food Systems Nathan Pelletier, Eric Audsley, Sonja Brodt, Tara Garnett, Patrik Henriksson,
Alissa Kendall, Klaas Jan Kramer, David Murphy, Thomas Nemecek, and Max Troell � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 223
Transportation and the Environment David Banister, Karen Anderton, David Bonilla, Moshe Givoni,
and Tim Schwanen � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 247
Green Chemistry and Green Engineering: A Framework for Sustainable Technology Development Martin J. Mulvihill, Evan S. Beach, Julie B. Zimmerman, and Paul T. Anastas � � � � � 271
The Political Ecology of Land Degradation Elina Andersson, Sara Brogaard, and Lennart Olsson � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 295
III. Management, Guidance, and Governance of Resources and Environment
Agency, Capacity, and Resilience to Environmental Change: Lessons from Human Development, Well-Being, and Disasters Katrina Brown and Elizabeth Westaway � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 321
Global Forest Transition: Prospects for an End to Deforestation Patrick Meyfroidt and Eric F. Lambin � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 343
Reducing Emissions from Deforestation and Forest Degradation Arun Agrawal, Daniel Nepstad, and Ashwini Chhatre � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 373
Tourism and Environment Ralf Buckley � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 397
Literature and Environment Lawrence Buell, Ursula K. Heise, and Karen Thornber � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 417
Religion and Environment Willis Jenkins and Christopher Key Chapple � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 441
Indexes
Cumulative Index of Contributing Authors, Volumes 27–36 � � � � � � � � � � � � � � � � � � � � � � � � � � � 465
Cumulative Index of Chapter Titles, Volumes 27–36 � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 469
Errata
An online log of corrections to Annual Review of Environment and Resources articles may be found at http://environ.annualreviews.org
Contents ix
A nn
u. R
ev . E
nv ir
on . R
es ou
r. 2
01 1.
36 :7
5- 99
. D ow
nl oa
de d
fr om
w w
w .a
nn ua
lr ev
ie w
s. or
g A
cc es
s pr
ov id
ed b
y U
ni ve
rs it
y of
C al
if or
ni a
- S
an D
ie go
o n
06 /2
9/ 17
. F or
p er
so na
l us
e on
ly .
- Annual Reviews Online
- Search Annual Reviews
- Annual Review of Environment and Resources Online
- Most Downloaded Environment and Resources Reviews
- Most Cited Environment and Resources Reviews
- Annual Review of Environment and Resources Errata
- View Current Editorial Committee
- All Articles in the Annual Review of Environment and Resources, Vol. 36
- Improving Societal Outcomes of Extreme Weather in a Changing Climate: An Integrated Perspective
- Ocean Circulations, Heat Budgets, and Future Commitment to Climate Change
- Aerosol Impacts on Climate and Biogeochemistry
- State of the World’s Freshwater Ecosystems: Physical, Chemical,and Biological Changes
- Coal Power Impacts, Technology, and Policy: Connecting the Dots
- Energy Poverty
- Water and Energy Interactions
- Agroecology: A Review from a Global-Change Perspective
- Energy Intensity of Agriculture and Food Systems
- Transportation and the Environment
- Green Chemistry and Green Engineering: A Framework for Sustainable Technology Development
- The Political Ecology of Land Degradation
- Agency, Capacity, and Resilience to Environmental Change: Lessons from Human Development, Well-Being, and Disasters
- Global Forest Transition: Prospects for an End to Deforestation
- Reducing Emissions from Deforestation and Forest Degradation
- Tourism and Environment
- Literature and Environment
- Religion and Environment
- ar:
- logo:
