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Each day, there are about 249,000 more people at the world’s dinner tables and many of them will have little or no food on their plates. By 2050, there will likely be at least 2.3 billion more people to feed. Most of these newcomers will be born in the major cities of less-developed countries. A critical question is how will we feed the projected 9.9 billion people in 2050 without causing serious harm to the environment? We explore possible answers to this question throughout this chapter.

12.1bChronic Hunger and Malnutrition

To maintain good health and resist disease, individuals need large amounts of macronutrients (such as carbohydrates, proteins, and fats) and smaller amounts of micronutrients—vitamins, such as A, B, C, and E, and minerals, such as iron, iodine, and calcium.

In order, the countries with the most overweight and obese people are the United States, China, India, Russia, and Brazil. According to a study by the McKinsey Global Institute, the resulting healthcare and lost-productivity costs are about $2 trillion a year—more than the combined annual global costs of war, terrorism, and armed violence.

72%

Percentage of U.S. adults over age 20 who are obese (38%) or overweight (34%)

These three systems depend on a small number of plant and animal species. Of the estimated 50,000 plant species that people can eat, about 90% of the world’s food calories come from only 14 of them. At least half the world’s people survive primarily by eating rice, wheat, and corn because they cannot afford meat. Only a few species of mammals and fish provide most of the world’s meat and seafood.

Such food specialization puts us in a vulnerable position. If any of the small number of crop strains, livestock breeds, and fish and shellfish species that we depend on were to become depleted, the consequences would be dire. Plant or livestock diseases, environmental degradation, and climate change could cause such depletion. This food specialization violates the biodiversity principle of sustainability, which calls for depending on a variety of food sources as an ecological insurance policy against changing environmental conditions.

Despite such genetic vulnerability, since 1960, there has been a staggering increase in global food production from all three of the major food production systems. Three major technological advances have been especially important:

Polyculture is an application of the biodiversity principle of sustainability. Crop diversity helps protect and replenish the soil and reduces the chance of losing most or all of the year’s food supply to pests, bad weather, and other misfortunes. Research shows that, on average, low-input polyculture produces higher average yields than high-input industrialized monoculture, while using less energy and fewer resources, and provides more food security for small landowners. For example, ecologists Peter Reich and David Tilman found that carefully controlled polyculture plots with 16 different species of plants consistently out-produced plots with 9, 4, or only 1 type of plant species.

Learning from Nature

Scientists are studying natural biodiversity to learn how to grow crops using polyculture. The idea is to grow stable crop systems, less vulnerable to environmental threats than monoculture crops are, and to increase yields.

10.

11. 12.2dOrganic Agriculture

12.2eGreen Revolutions Have Increased Crop Yields

Farmers have two ways to produce more food: farm more land or increase yields from existing cropland. Since 1950, most of the dramatic increase in global grain production has been the result of increasing crop yields through industrialized agriculture.

Because of the efficiency of U.S. agriculture, Americans spend the lowest percentage of disposable income in the world—an average of 10% on food. By contrast, low-income people in less-developed countries typically spend 50–70% of their income on food, according to the USDA and FAO.

However, because of a number of hidden costs related to food production and consumption, most American consumers are unaware that their actual food costs are much higher than the market prices they pay. Such hidden costs include the costs of pollution and environmental degradation, higher health insurance bills related to the harmful health effects of industrialized agriculture, and government farm subsidies.

12.2fGenetic Revolutions: Crossbreeding and Genetic Engineering

12.3a

Energy Use in Industrialized Food Production

The industrialization of food production and increased crop yields have been made possible by use of fossil fuels—mostly oil and natural gas—to run farm machinery and fishing vessels, to pump irrigation water for crops, and to produce synthetic pesticides and synthetic inorganic fertilizers. Fossil fuels are also used to process food and transport it long distances within and between countries. Altogether, food production accounts for about 17% of all of the energy used in the United States, more than any other industry. Burning such large quantities of fossil fuels pollutes the air and water and contributes to climate change.

When we consider the energy used to grow, store, process, package, transport, refrigerate, and cook all plant and animal food, it takes about 10 units of fossil fuel energy to put 1 unit of food energy on the table in the United States. In addition, according to a study led by ecological economist Peter Tyedmers, the world’s fishing fleets use about 12.5 units of energy to put 1 unit of food energy from seafood on the table. In other words, today’s food production systems operate with a large net energy loss.

On the other hand, the amount of energy per calorie used to produce crops in the United States has declined by about 50% since the 1970s. One factor in this decline is that the amount of energy used to produce synthetic nitrogen fertilizer has dropped sharply. Another reason for the decline is the rising use of conservation tillage or no-till farming (see Core Case Study), which sharply reduces energy use and the harmful environmental effects of plowing.

12.3b

Environmental Impact of Industrialized Agriculture

Industrialized food production has allowed farmers to use less land to produce more food. This has reduced the need to convert forests and grasslands to cropland and thereby destroying the wildlife habitats provided by these ecosystems.

However, many analysts point out that industrialized agriculture has greater overall harmful environmental impacts (Figure 12.16) than any other human activity. These impacts may limit future food production.

Figure 12.16

Food production has a number of harmful environmental effects.

Critical Thinking:

Which item in each of these categories do you think is the most harmful? Why?

An illustration shows information about Food Production within a box which is labeled as, “Natural Capital Degradation.” Five photos are shown, namely, the first photo shows a heavy equipment which is used for harvesting a land where crops are ready for harvesting and labeled as Biodiversity Loss, the second photo shows an unfertile land labeled as soil, the third photo shows a river flowing and vegetation around and labeled as water, the fourth photo shows several cattle being fed and labeled as Air Pollution, and the fifth photo shows jet flying water and labeled as human health. The text below the first photo reads, “Conversion of grasslands, forests, and wetlands to crops or rangeland, fish kills from pesticide runoff, killing of wild predators to protect livestock, and loss of agrobiodiversity replaced by monoculture strains.” The text below the second photo reads, “Erosion, loss of fertility, Salinization, waterlogging, and Desertification.” The text below the third photo reads, “Aquifer depletion, increased runoff, sediment pollution, and flooding from cleared land, pollution from pesticides, Algal blooms and fish kills caused by runoff of fertilizers and farm wastes.” The text below the fourth photo reads, “Emissions of greenhouse gases CO2 from fossil fuel use, N2O from inorganic fertilizer use, and methane (CH4) from cattle, and other air pollutants from fossil fuel use and pesticide sprays.” The text below the fifth photo reads, “Nitrates in drinking water (blue baby), pesticide residues in water, food, and air, livestock waste in drinking and swimming water, and bacterial contamination of meat”Enlarge Image

Left: Orientaly/ Shutterstock.com. Left center: pacopi/ Shutterstock.com. Center: Tim McCabe/USDA Natural Resources Conservation Service. Right center: Mikhail Malyshev/ Shutterstock.com. Right: B Brown/ Shutterstock.com.

According to a study by 27 experts assembled by the United Nations Environment Programme (UNEP), agriculture uses massive amounts of the world’s resources and pollutes the air and water. It uses about 70% of the world’s freshwater removed from aquifers and surface waters, worldwide. It also produces about 60% of all water pollution, degrades and erodes topsoil, emits about 25% of the world’s greenhouse gas emissions, and uses about 38% of the world’s ice-free land.

As a result, many analysts view today’s industrialized agriculture as environmentally and economically unsustainable. However, proponents of industrialized agriculture argue that its benefits outweigh its harmful effects. Figure 12.17 lists the major advantages and disadvantages of industrialized agriculture.

Figure 12.17

Industrialized agriculture has advantages and disadvantages.

Critical Thinking:

Do you think that the advantages outweigh the disadvantages? Why or why not?

The advantages and disadvantages of industrialized agriculture are as follows. Advantages. Greatly increases yields. Efficiency helps preserve wildlife habitat. Can support local economies. Spurs improvements in agricultural technology. Disadvantages. Pollutes air. Pollutes water. Erodes topsoil. Plays large role in climate change.

Top: Orientaly/ Shutterstock.com; Bottom: B. Brown/ Shutterstock.com12.3c

Topsoil Erosion

Topsoil, is the fertile top layer of many soils (Figure 3.10). It is one of the most important components of the earth’s natural capital because all terrestrial life depends directly or indirectly on this potentially renewable resource. Topsoil stores and purifies water and supplies most of the nutrients needed for plant growth. It recycles these nutrients endlessly as long as they are not removed faster than natural processes replenish them. Organisms living in topsoil remove and store carbon dioxide from the atmosphere, thereby helping to control the earth’s climate as part of the carbon cycle. Thus, sustainable agriculture begins with sustaining topsoil.

A major environmental problem related to agriculture is soil erosion—the movement of soil components, especially surface litter and topsoil from one place to another by the actions of wind and water. Some topsoil erosion is natural, but much of it is caused by clearing forests and grasslands for agriculture, plowing the soil to plant new crops each year, and leaving the soil exposed during part of the year.

Flowing water, the largest cause of erosion, carries away particles of exposed topsoil that have been loosened by rainfall (Figure 12.18, left). Severe erosion of this type leads to the formation of gullies (Figure 12.18, right). Wind also loosens and blows particles of topsoil away, especially in areas with a dry climate and relatively flat and exposed land (Figure 12.19).

Figure 12.18

Natural capital degradation: Flowing water from rainfall is the leading cause of topsoil erosion as seen on this farm in the U.S. state of Tennessee (left). Severe water erosion can become gully erosion, which has damaged this cropland in western Iowa (right).

A figure shows two photos, one in the left and the other in the right. A photo on the left side shows vegetation which is slightly damaged due to the topsoil erosion caused due to the flow of running water. A photo on the right side shows vegetation and buildings at the back and a gully erosion is caused due to the water erosion and the entire cropland is damaged making a big pit in that area.Enlarge Image

Left: Tim McCabe/USDA Natural Resources Conservation Service. Right: © USDA Natural Resources Conservation Service.

Figure 12.19

Wind is an important cause of topsoil erosion in dry areas that are not covered by vegetation such as this bare crop field in the U.S. state of Iowa.

A photo shows a dry land or a bare land without any vegetation and a few houses behind it which are not clearly seen, due to top soil wind erosion.

Lynn Betts/USDA Natural Resources Conservation Service

In undisturbed, vegetated ecosystems, the roots of plants help anchor topsoil and prevent some erosion. However, topsoil can erode when soil-holding grasses, trees, and other vegetation are removed through activities such as farming, clear-cut logging (see Figure 10.7), and overgrazing (see Figure 10.11). A joint survey by the UNEP and the World Resources Institute indicated that topsoil is eroding faster than it forms on about one-third of the world’s cropland (Figure 12.20). Soil in the United States is eroding ten times faster than it is being replenished by natural processes. In India and China it is eroding 30 to 40 times faster.

Figure 12.20

Natural capital degradation: Topsoil erosion is a serious problem in some parts of the world.

Critical Thinking:

Can you see any geographical pattern associated with this problem?

An illustration shows the world map to describe serious concern, some concern, and stable or nonvegetative concern for topsoil erosion. Serious concern is shown by shading a few parts of southern North America, almost all parts of Central America, few parts of South America, Africa, southern and western Asia, Europe, and a small portion in Australia in one shade. Some concern is shown by shading a few parts of southern North America, few parts of South America, Africa, southern and western Asia, Europe, and a larger portion in Australia in another shade. The stable or nonvegetative concern is shown by leaving the northern portion of North America and eastern portion of Asia without shading. Few portions of South America, Africa, Asia, Europe, and Australia are also left without shading. The entire Greenland is left without shading.Enlarge Image

(Compiled by the authors using data from the U.N. Environment Programme and the World Resources Institute.)

Erosion of topsoil has three major harmful effects:

Loss of soil fertility through depletion of plant nutrients in topsoil (see Figure 3.12).

Water pollution in surface waters where eroded topsoil ends up as sediment, which can kill fish and shellfish and clog irrigation ditches, boat channels, reservoirs, and lakes. Pesticides in eroded sediment can be ingested by aquatic organisms and in some cases biomagnified in food webs (see Figure 9.14).

Release to the atmosphere of carbon stored in the soil as , which contributes to atmospheric warming and climate change.

Soil pollution is also a problem in some parts of the world. Some of the chemicals emitted into the atmosphere by industrial and power plants and by motor vehicles can pollute soil and irrigation water. Some pesticides can also contaminate soil. A recent study by China’s environment ministry estimated that 2.5% of the country’s cropland is too contaminated to grow food safely. China, with 18% of the world’s people and only 7% of the world’s arable land, cannot afford to lose 2.5% of its cropland.

12.3d

The Phosphate Crisis

The amount of food we produce through modern industrialized agriculture is heavily dependent on the use of phosphate-based fertilizers. However, the amount of phosphate available from mines is limited, which could at some point limit food production and affect the world’s economies. In addition, phosphate mining can disrupt the land and overload nearby water systems with excess phosphates.

Ways to deal with this problem include

Watering crops with wastewater that contains phosphates.

Reducing soil erosion so that more phosphorus is available for crops.

Applying fertilizer so that less of it is lost to water and wind erosion.

12.3e

Desertification

Drylands in regions with arid and semiarid climates occupy about 40% of the world’s land area and are home to some 2.5 billion people. A major threat to food security in some of these areas is desertification—the process in which the productive potential of topsoil falls by 10% or more because of a combination of prolonged drought and human activities that expose topsoil to erosion.

Desertification can be moderate (with a 10–25% drop in productivity), severe (with a drop of 25–50%), or very severe (with a drop of more than 50%, usually resulting in large gullies and sand dunes). Desertification decreases soil productivity but only in extreme cases does it lead to what we call a desert.

Over thousands of years, the earth’s deserts have expanded and contracted, primarily because of climate change. However, human uses of the land, especially for agricultural purposes, have increased desertification in some parts of the world. Such uses can involve clearing trees, plowing excessively, and overgrazing (Figure 10.11), which have left much topsoil bare and unprotected.

In the 1930s, much of the topsoil in several dry and windy regions of the Midwestern United States was lost because of a combination of poor cultivation practices and prolonged drought. The resulting severe wind erosion led to crop failures and to the formation of a barren dust bowl. Thousands of farmers had to abandon their degraded land and move to other parts of the United States.

Researchers at the Earth Policy Institute have warned that overgrazing, overplowing, and deforestation are creating two new dust bowls. One is in the central African Sahel, a vast savanna-like area south of the Sahara Desert. The other straddles northern China and southern Mongolia. The researchers reported that about 90% of China’s grasslands are degraded and suffering from desertification. Since 1950, more than 24,000 Chinese villages have been abandoned to spreading sands. Moreover, according to the Indian Space Research Organization, 24% of India’s land is threatened by desertification.

12.3f

Excessive Irrigation, Soil Salinization, and Waterlogging

Irrigation accounts for about 70% of the water that humanity uses. Currently, the 16% of the world’s cropland that is irrigated produces about 36% of the world’s food.

However, irrigation has a downside. Most irrigation water is a dilute solution of various salts, such as sodium chloride, that are picked up as the water flows over or through soil and rocks. Irrigation water that is not absorbed into the topsoil evaporates and leaves behind a thin crust of dissolved mineral salts in the topsoil. Repeated applications of irrigation water in dry climates can lead to an accumulation of salts in the upper soil layers—a soil degradation process called soil salinization. It stunts crop growth, lowers crop yields, and can eventually kill plants and ruin the land.

The FAO estimates that severe soil salinization has reduced yields on at least 10% of the world’s irrigated cropland, and that by 2020, 30% of the world’s arable (farmable) land will be salty. The most severe salinization occurs in China, India, Egypt, Pakistan, Mexico, Australia, and Iraq. According to the USDA, salinization reduces yields on about 30% of irrigated cropland in the United States, especially in western states (Figure 12.21).

Figure 12.21

Natural capital degradation: White alkaline salts have displaced crops that once grew on this heavily irrigated land in the U.S. state of Colorado.

A photo shows a fence to the left of which is a green vegetation and to the right is a dry land without any vegetation with white alkaline salt deposition.

USDA Natural Resources Conservation Service

Another problem with irrigation is waterlogging, in which water accumulates underground and gradually raises the water table. This can occur when farmers apply large amounts of irrigation water in an effort to reduce salinization by leaching salts deeper into the soil. Waterlogging lowers the productivity of crop plants and kills them after prolonged exposure because it deprives plants of the oxygen they need to survive. At least 10% of the world’s irrigated land suffers from this worsening problem, according to the FAO.

12.3g

Pollution, Climate Change, and Industrialized Agriculture

Some farmers contribute to pollution by over-fertilizing their fields. Globally, the use of fertilizers has grown 45-fold since 1940. Nitrates in fertilizer can also percolate down through the soil into aquifers where they can contaminate groundwater used for drinking. According to the FAO, fully one-third of all water pollution from the runoff of nitrogen and phosphorus is due to excessive use of synthetic fertilizers.

Agricultural activities also pollute the air. Clearing and burning forests to raise crops or livestock adds dust and smoke to the air. By applying fertilizer and pesticides, farmers emit particles and various chemicals into the air. Agriculture also accounts for about a third of all human-generated emissions of greenhouse gases—more than all of the greenhouse gases emitted by the world’s cars, trucks, ships, airplanes, and trains combined. These emissions warm the atmosphere and contribute to climate change, which can reduce crop productivity and food security.

12.3h

Food Production and Biodiversity Loss

Biodiversity and some ecosystem services are threatened when forests are cleared and when grasslands are plowed up and replaced with croplands. For example, one of the fastest-growing threats to world’s biodiversity is happening in Brazil. Large areas of tropical forest in its Amazon Basin and in cerrado—a huge tropical grassland region south of the Amazon Basin—are being burned or cleared for cattle ranches and for large plantations of soybeans grown for cattle feed. Biodiversity is threatened in these and many other areas because tropical forests and grasslands have much greater biodiversity than does agricultural land.

A related problem is the increasing loss of agrobiodiversity—the genetic variety of animal and plant species used on farms to produce food. Scientists estimate that since 1900, we have lost around 75% of the genetic diversity of agricultural crops. For example, India once planted 30,000 varieties of rice. Now more than 75% of its rice production comes in only 10 varieties. Soon most of its production might come from just one or two varieties. In the United States, about 97% of the food plant varieties available to farmers in the 1940s no longer exist, except perhaps in small amounts in seed banks and occasional home gardens.

Traditionally, farmers have saved seeds from year to year to save money and to have the ability to grow food in times of famine. Families in India and most other less-developed countries still do this, but in the United States, this tradition is disappearing as more farmers plant seeds for genetically engineered crops. Companies that sell these seeds have patents on them, forbid users to save them, and have successfully sued a number of farmers who saved and used such seeds.

Ecologists warn that farming practices that reduce biodiversity are rapidly shrinking the world’s genetic “library” of plant varieties, which are critical for increasing food yields through crossbreeding and genetic engineering. This failure to preserve agrobiodiversity is a serious violation of the biodiversity principle of sustainability that could reduce the sustainability of food production.

Efforts are being made to save individual plants and seed from endangered varieties of crops and wild plant species important to the world’s food supply. About 1,750 refrigerated seed banks store individual plants and seeds. They are also stored in agricultural research centers and botanical gardens scattered around the world.

However, power failures, fires, storms, and wars can cause irreversible losses of these stored plants and seeds. The world’s most secure seed bank is the underground Svalbard Global Seed Vault, also called “the doomsday seed vault,” carved into the Arctic permafrost on a frozen Norwegian arctic island near the North Pole (Figure 12.22). It is being stocked with duplicates of much of the world’s seed collections. By 2018, it stored more than a million seeds from all around the world and has a capacity for 2.5 billion seeds.

Figure 12.22

Svalbard Global Seed Vault.

A photo shows a room which has got a shelf with partitions comprising of sealed containers with seeds, which acts as a seed bank. A man carries a sealed container in his hand and is trying to find out a place for the container in the shelf.Enlarge Image

JIM RICHARDSON/National Geographic Image Colllection

However, a 2018 report by the Norwegian government warned that the entire seed collection is threatened by projected global warming that would increase the air temperature above the facility by about

‍

by 2075. This increase in heat will thaw the protective surrounding permafrost and destroy the seeds. Rainfall will be more common and intense along with landslides and avalanches. During the last 4 to 5 decades, the air temperature above the vault has increased by 3 to , the permafrost has warmed, and avalanches in the area have increased. In 2017, water from partial melting of the surrounding permafrost penetrated into the vault, which was designed to be impenetrable. No seeds were damaged and the leaks have been repaired.

Another problem is that the seeds of many plants cannot be stored successfully in seed banks. In addition, stored seeds must be planted and germinated periodically and new seeds must be collected. Unless this is done, seed banks become seed morgues.

Connections

GM Crops and Organic Food Prices

The spread of GM crop genes by wind carrying pollen from field to field threatens the production of certified organic crops, which must be grown without such genes to be classified as organic. Organic farmers have to perform expensive tests to detect GMOs or take costly planting measures to prevent the spread of GMOs to their fields from nearby crop fields. This has forced some organic producers to raise their prices.

12.3i

Limits to Expanding Green Revolutions

So far, several factors have limited the success of the green revolutions and may limit them more in the future. For example, without large inputs of water and synthetic inorganic fertilizers and pesticides, most green revolution and genetically engineered crop varieties produce yields that are no higher (and are sometimes lower) than those from traditional strains. Climate change and the growing world population also limit the success of green revolutions. The high inputs required to sustain green revolutions also cost too much for most subsistence farmers in less-developed countries.

Scientists point out that at some point yields stop increasing because of the inability of crop plants to take up nutrients from additional fertilizer and irrigation water. This helps to explain the slowdown in the rate of growth in global yields for most major crops since 1990.

Can we expand the green revolutions by irrigating more cropland? Since 1978, the amount of irrigated land per person has been declining, and it is projected to fall much more by 2050. One reason for this is population growth, which is projected to add 2.2 billion more people between 2018 and 2050. Other factors are limited availability of irrigation water, soil salinization, and the fact that most of the world’s farmers cannot afford to irrigate their crops.

Climate change is expected to reduce yields of crops such as wheat, rice, and corn during this century. Mountain glaciers that provide irrigation for many millions of people in China, India, and South America are melting and this will lessen the area of crops that can be irrigated. During this century, fertile croplands in coastal areas, including many of the major rice-growing floodplains and river deltas in Asia, are likely to be flooded by rising sea levels resulting from climate change. Food production could also drop sharply in some major food-producing areas because of longer and more intense droughts and heat waves, also likely resulting from climate change.

Learning from Nature

Scientists are searching for wild relatives of common food crops such as wheat, rice, and corn to produce new climate-smart varieties that can help reduce the harmful effects of climate change. This includes drought-tolerant varieties and varieties of rice that can grow in flooded areas and in salty water that intrudes because of rising sea levels.

Can we expand or extend green revolutions with the use of genetic engineering? Many scientists and engineers argue that we can, but this is a controversial topic. See Science Focus 12.1.

Science Focus 12.1

Controversy over Genetically Engineered Foods

Bioengineers have talked about developing new GM varieties of crops that are resistant to heat, cold, drought, insect pests, parasites, viral diseases, herbicides, and other environmental threats. They also hope to develop crop plants that can grow faster and survive with little or no irrigation and with less use of fertilizer and pesticides. Accomplishing these goals can reduce hunger and increase food security.

However, critics have raised some concerns about the widespread and growing use of GM crops and foods. One concern is that while many people are consuming GM foods daily, we know too little about their long-term health effects. For example, one type of GMO makes use of bacillus thuringiensis, a natural soil bacterium with a gene, known as Bt, that produces a chemical toxic to some insects. This gene has been inserted into corn plants, which then incorporate the Bt toxin in their leaves, making them resistant to damage by certain insects. This has reduced the use of pesticides by 37%. However, the Global Citizens’ Report on the State of GMOs summarized findings indicating that GM crops with Bt toxins could threaten human health by triggering an inflammatory response leading to diseases such as diabetes and heart disease. Proponents of GMOs dispute this finding.

Another problem is that promised yield increases from the use of GM crops have not materialized. Studies have shown small increases during the first years of such use with generally plateauing or falling yields thereafter.

GM crops could also threaten biodiversity. Some GM crops are designed to enable increased use of herbicides, which could be part of the reason for declining populations of Monarch butterflies (see Chapter 4 Case Study) and other pollinators. Declines in pollinators can cause declines in the plant communities that depend on them and the animals that depend on those plants. The end effect could be a cascade of biodiversity losses.

Critics also point out that if GM crops or seeds released into the environment were to cause some harmful genetic or ecological effects those organisms could not be recalled. In addition, genes in plant pollen from genetically engineered crops have been known to spread to non–genetically engineered species. This could result in hybrids with wild crop varieties, which could reduce the natural genetic biodiversity of the wild strains. This could in turn reduce the gene pool from which new species can evolve or be engineered—a violation of the biodiversity principle of sustainability.

Some GM crops require increased use herbicides, which can put farmers on a costly treadmill because they might have to use larger amounts or more toxic herbicides as weeds become resistant to them. One study by scientists at the University of Minnesota found that farmers who cultivated GM crop varieties earned less money over a 14-year period than those who continued to grow non-GM crops.

Some 64 countries require that food labels identify genetically modified food content. Polls consistently indicate that around 90% of U.S. consumers want to have such information clearly listed on food labels. In 2016, Congress passed a law requiring GMO content labels. However, it allows food manufacturers three choices: a symbol, a label, or a digital bar code enabling buyers to read the labels on their smart phones. Many consumers are opposed to having to use a smartphone to scan a bar code to get this information, arguing that it puts the burden on the consumer to find information that should be readily available to all consumers with or without cell phones.

In 2016, an advisory panel of experts for the U.S. National Academies of Science and Engineering concluded that genetically engineered food does not appear to pose serious risks to human health or the environment based on analysis of more than 1,000 studies, testimonies from 80 witnesses in a series of public meetings, and 700 comments submitted by the public. However, the report noted that GM crops have not increased the ability to feed the world because the crops have not substantially increased crop yields, as proponents promised.

The report also pointed that while GM crops have decreased the use of insecticides, some herbicide-resistant GM crops have led to increased herbicide use and to herbicide-resistant superweeds. This has forced farmers to spend more money increasing their use of herbicides or switching to stronger herbicides.

About 90% of scientists and organizations such as the American Medical Association (AMA), the U.S. National Academy of Sciences, the World Health Organization,(WHO), and the American Association for the Advancement of Science (AAAS) have concluded that GM crops are safe to use and that their advantages outweigh their disadvantages (Figure 12.A). However, almost two-thirds of consumers disagree with this conclusion and call for stricter regulation to ensure the safety of this rapidly growing technology.

Figure 12.A

Use of genetically modified crops and foods has advantages and disadvantages.

Critical Thinking:

Do the advantages outweigh the disadvantages? Why or why not?

An illustration provides information about Genetically Modified Crops and Foods in three columns. The first column comprises of information of potential benefits that reads, “May need less fertilizer, pesticides, and water, can be resistant to insects, disease, frost, and drought, can grow faster and could raise yields, may tolerate higher levels of herbicides, and could have longer shelf life.” The second column shows the photo of tomatoes and the photo of two corns placed in a plate. The third column provides information about possible drawbacks that reads, “have unpredictable genetic and ecological effects, may put toxins in food, could repel or harm pollinators, can promote pesticide-resistant insects, herbicide-resistant weeds, and plant diseases, and could disrupt seed market and reduce biodiversity.” The entire information is encapsulated in a box and the heading reads, “Trade-offs.”

Top: Lenar Musin/ Shutterstock.com. Bottom: Oksana Shufrych/ Shutterstock.com

Can we increase the food supply by cultivating more land? Clearing more tropical forests and irrigating arid land could more than double the area of the world’s cropland. However, massive clearing of forests and irrigation of arid land would decrease biodiversity, speed up climate change and its harmful effects, and increase soil erosion. In addition, much of this land has poor soil fertility, steep slopes, or both, and cultivating such land would be expensive and probably not ecologically sustainable.

Commercial fertilizers have played a role in green revolutions, but their use in more-developed countries has reached a level of diminishing returns in terms of increased crop yields. However, there are parts of the world, especially in Africa, where additional fertilizer could boost crop production.

12.3j

Environmental Impact of Industrialized Meat Production

Industrialized meat production has increased meat supplies, reduced overgrazing, and kept food prices down. However, feedlots (Figure 12.12) and CAFOs (Figure 12.13) have widespread harmful health and environmental effects. Analysts point out that meat produced by industrialized agriculture is artificially cheap because most of its harmful environmental and health costs are not included in the market prices of meat and meat products, a violation of the full-cost pricing principle of sustainability.

A major problem with feedlots and CAFOs is that huge amounts of water are used to irrigate the grain crops that feed the livestock. According to waterfootprint.org, producing a quarter-pound hamburger requires 1,752 liters (63 gallons) of water. This is four to six times what the average American uses every day for all household water needs, the largest of which is flushing toilets.

Large volumes of water are also used to wash away livestock wastes. Much of this wastewater flows into streams and other waterways and pollutes those aquatic ecosystems.

Another problem is what to do with the wastes (mostly manure) produced by feedlots and CAFOs. According to the USDA, animal waste produced by the American meat industry amounts to about 67 times the amount of waste produced by the country’s human population. Ideally, manure from CAFOs should be returned to the soil as a nutrient-rich fertilizer in keeping with the chemical cycling principle of sustainability. However, it is often so contaminated with residues of antibiotics and pesticides that it is unfit for use as a fertilizer.

Despite potential contamination, up to half of the manure slurry from CAFOs in the United States is applied to crop fields and creates severe odor problems for people living nearby. Much of the other half of CAFO animal waste is pumped into large lagoons, which can leak and pollute nearby surface and groundwater, overflow when exposed to excessive rain, produce foul odors, and emit large quantities of climate-changing greenhouse gases into the atmosphere.

Industrialized meat production uses large amounts of energy (mostly from oil), which make it a major source of air and water pollution and greenhouse gas emissions. For example, producing a pound of beef emits an amount of climate-changing into the atmosphere that is equivalent to driving an average American car 113 kilometers (70 miles). In addition, as part of their digestion process, cattle and dairy cows release methane , a greenhouse gas with about 25 times the warming potential of per molecule. According to the FAO study, Livestock’s Long Shadow, industrialized livestock production generates about 18% of the world’s greenhouse gases—more than all of the world’s cars, trucks, airplanes, and ships combined.

Beef and lamb have the highest climate-change footprints per gram of protein. In addition, the stomachs of cows and sheep contain bacteria that help them digest grass and other foods. These bacteria produce the potent greenhouse gas methane, which is released in burps and flatulence. Scientists are trying to find ways to reduce methane emissions from cows by introducing seaweed or other additives in their feed. Cheese and farmed shrimp also have high climate-change footprints. According to a number of studies, chicken and other poultry have a lower climate-change impact than other livestock. Plants have the lowest climate-change impacts.

Another growing problem is the use of antibiotics in industrialized livestock production facilities. The U.S. Food and Drug Administration (FDA) and the Union of Concerned Scientists estimate that 70% to 80% of all antibiotics used in the United States (and 50% of those in the world) are added to animal feed. This is done to help prevent the spread of diseases in feedlots and CAFOs and to promote the growth of the animals before they are slaughtered. According to FDA data and several studies, this heavy use of antibiotics plays a role in the rise of genetic resistance among many disease-causing bacteria (see Figure 4.14). Such resistance can reduce the effectiveness of some antibiotics used to treat humans for bacterial infections, and it can promote the development of new, more genetically resistant infectious disease organisms, some of which can infect humans.

Figure 12.23 summarizes key advantages and disadvantages of using animal feedlots and CAFOs.

Figure 12.23

Use of animal feedlots and confined animal feeding operations has advantages and disadvantages.

Critical Thinking:

Do the advantages outweigh the disadvantages? Why or why not?

An illustration shows information about Feedlots and CAFOs in three columns. The first column provides information about the Advantages that reads, “Increased meat production, higher profits, less land use, reduced overgrazing, reduced soil erosion, and protection of biodiversity.” The second column shows the photo of cattle feeding and another photo shows chickens being fed through confined animal feeding operations. The third column provides information about disadvantages that reads, “Animals unnaturally confined and crowded, large inputs of grain, fishmeal, water, and fossil fuels, greenhouse gases such carbon-di-oxide and methane emissions, concentration of animal wastes that can pollute water, and use of antibiotics can increase genetic resistance to microbes in humans.” The entire information is encapsulated in a box and the heading reads, “Trade-offs.”

Top: Mikhail Malyshev/ Shutterstock.com. Bottom: Maria Dryfhout/ Shutterstock.com.

When livestock are grass-fed, environmental impacts can still be high, especially when forests are cut down or burned to make way for grazing land, as is done in Brazil’s Amazon forests. According to an FAO report, overgrazing and erosion by livestock has degraded about 20% of the world’s grasslands and pastures. The same report estimated that rangeland grazing and industrialized livestock production has caused about 55% of all topsoil erosion and sediment pollution.

In addition, grass-fed cows emit more of the powerful greenhouse gas methane than do grain-fed cows. Thus, expanding grass-fed production could increase the agricultural contributions to deforestation and climate change.

Connections

Meat Production and Aquatic Biodiversity

Synthetic fertilizers are used in the Midwestern United States to produce corn for animal feed and ethanol fuel for cars. Much of this fertilizer washes from cropland and into the Mississippi River, which empties into the Gulf of Mexico. The added nitrate and phosphate nutrients overfertilize the gulf’s coastal waters. Each year this leads to oxygen depletion in the gulf’s waters, which threatens one-fifth of the nation’s seafood yield. In other words, growing corn in the Midwest, largely to feed cattle and fuel cars, degrades aquatic biodiversity and seafood production in the Gulf of Mexico.

12.3k

Environmental Impact of Aquaculture

Aquaculture produces about 47% of the world’s seafood, according to the FAO, and is growing rapidly. In 2017, China accounted for 60% of the world’s aquaculture production. The World Bank projects that by 2030, aquaculture could produce 62% of all seafood. Figure 12.24 lists key advantages and disadvantages of aquaculture. Some analysts warn that the harmful environmental effects of aquaculture could limit its future production potential unless efforts are made to make it more sustainable.

Figure 12.24

Aquaculture has advantages and disadvantages.

Critical Thinking:

Do the advantages outweigh the disadvantages? Why or why not?

An illustration provides information about Aquaculture in three columns. The first column provides information about the Advantages and the text below reads, “High efficiency, high yield, reduces overharvesting of fisheries, and jobs and profits.” The second column shows aquaculture farms and a photo of two dead fishes caught while fishing. The third column provides information about the disadvantages and reads, “large inputs of land, grain, and fishmeal, large waste output, loss of mangrove forests and estuaries, and dense population vulnerable to disease.” The entire information is encapsulated in a box and the heading reads, “Trade-offs.”

Top: Vladislav Gajic/ Shutterstock.com. Bottom: FeellFree/ Shutterstock.com.

In the 1990s, up to a third of the wild fish caught from the oceans was used to make the fishmeal and fish oil that were fed to farmed fish. This has contributed to the depletion of many populations of wild fish that are crucial to marine food webs—a serious threat to marine biodiversity and ecosystem services.

In 2016, aquaculture used 69% of all fishmeal and 75% of all fish oil. Some of the fishmeal and fish oil fed to farm-raised fish is contaminated with long-lived toxins such as PCBs and dioxins that are picked up from the ocean floor. This can contaminate farm-raised fish and people who eat such fish. Fish farms, especially those that that raise carnivorous fish such as salmon and tuna also produce large amounts of wastes that can contain pesticides and antibiotics used on fish farms. These chemicals can contaminate farm-raised fish and people who consume such fish. Aquaculture producers contend that the concentrations of these chemicals are not high enough to threaten human health, but some health scientists disagree.

Another problem is that farmed fish can escape their pens and mix with wild fish and possibly disrupt the gene pools of wild populations or become invasive species. Aquaculture can also destroy or degrade aquatic ecosystems, particularly mangrove forests (Figure 8.8) that are cleared for coastal fish farms. This loss of mangrove forests decreases biodiversity and valuable ecosystem services such as natural flood control in these sensitive coastal areas that are expected to experience severe flooding because of rises in sea level caused by climate change.

According to recent research, farmed mollusks (mussels, scallops, and oysters) have low climate-change footprints. On average, farmed salmon have a lower climate change footprint than pork or chicken. However, wild lobster and shrimp can have a larger climate change footprint than pork or chicken because of the fuel burned in fishing boats. On the other hand, wild fish such as sardines, anchovies, tuna, herring, cod, haddock, and pollack on average have lower climate-change footprints than pork or chicken. 12.4a

Nature Helps Control Many Pests

A pest is any species that interferes with human welfare by competing with us for food, invading our homes, lawns, or gardens, destroying building materials, spreading disease, invading ecosystems, or simply being a nuisance. Worldwide, only about 100 species of plants (weeds), animals (mostly insects), fungi, and microbes cause most of the damage to the crops we grow. However, insects consume up to 20% of the plants that we grow for food. That percentage will increase as global warming expands the populations of some insects and makes many insects hungrier by speeding up their metabolism and causing them to reproduce faster. This will decrease crop yields according to a 2018 article by Curtis Deutsch and his scientific colleagues at the University of Washington.

In natural ecosystems and in many polyculture crop fields, natural enemies (predators, parasites, and disease organisms) control the populations of most potential pest species. This free ecosystem service is an important part of the earth’s natural capital. For example, biologists estimate that the world’s 46,700 known species of spiders kill far more crop-eating insects every year than humans do by using insecticides. Most spiders, including the wolf spider (Figure 12.25), do not harm humans.

Figure 12.25

Natural capital: This ferocious-looking wolf spider is eating a grasshopper. It is not harmful to humans.

A photo shows a ferocious looking wolf spider which is eating a grasshopper.

Cathy Keifer/ Shutterstock.com

When we clear forests and grasslands, plant monoculture crops, and douse fields with chemicals that kill pests, we upset many of these natural population checks and balances that are in keeping with the biodiversity principle of sustainability. Then we must devise and pay for ways to protect our monoculture crops, tree plantations, lawns, and golf courses from pests that nature has helped to control at no charge. 12.4bSynthetic Pesticides

Scientists and engineers have developed a variety of synthetic pesticides—chemicals used to kill or control pest organisms. Common types of synthetic pesticides include insecticides (insect killers), herbicides (weed killers), fungicides (fungus killers), and rodenticides (rat and mouse killers).

We did not invent the use of chemicals to repel or kill other species. For nearly 225 million years, plants have been producing chemicals to ward off, deceive, or poison the insects and herbivores that feed on them. Scientists have used such chemicals to create biopesticides to kill some pests.

Learning from Nature

In the 1600s, farmers used nicotine sulfate, extracted from tobacco leaves, as an insecticide. Eventually, other first-generation pesticides—mainly natural chemicals taken from plants—were developed. Farmers were copying nature’s solutions to deal with their pest problems.

A major pest control revolution began in 1939, when entomologist Paul Müller discovered DDT (dichlorodiphenyl-trichloroethane)—the first of the so-called second-generation pesticides produced in the laboratory. It soon became the world’s most-used pesticide, and since then, chemists have created hundreds of other synthetic pesticides.

· They can increase food supplies by reducing food losses due to pests, for some crops.

12.4d

Problems with Synthetic Pesticides

Opponents of widespread use of synthetic pesticides contend that the harmful effects of these chemicals (Figure 12.26, right) outweigh their benefits (Figure 12.26, left). They cite several problems.

They accelerate the development of genetic resistance to pesticides in pest organisms (Figure 12.27). Insects breed rapidly, and within 5 to 10 years (much sooner in tropical areas), they can develop immunity to widely used pesticides through natural selection. In the same way, weeds develop genetic resistance to herbicides. Since 1945, about 1,000 species of insects and rodents (mostly rats) have developed genetic resistance to one or more pesticides.

They can put farmers on a financial treadmill. Farmers typically find themselves having to pay more and more for a chemical pest control program that can become less and less effective as pests develop genetic resistance to the pesticides.

Some insecticides kill natural predators and parasites that help to control the pest populations. About 100 of the 300 most destructive insect pests in the United States were minor pests until widespread use of insecticides wiped out many of their natural predators. (See the Case Study that follows.)

Some pesticides harm wildlife. According to the USDA and the U.S. Fish and Wildlife Service, each year, some of the pesticides applied to crops poison honeybee colonies on which we depend for pollination of many food crops (see Chapter 9 Core Case Study and Science Focus 9.2). According to a study by the Center for Biological Diversity, pesticides menace about a third of all endangered and threatened species in the United States.

Pesticides are usually applied inefficiently and can pollute the environment. According to the USDA, about 98–99.9% of the insecticides and more than 95% of the herbicides applied by aerial spraying or ground spraying do not reach the target pests. They end up in the air, surface water, groundwater, bottom sediments, food, and nontarget organisms, including humans.

Some pesticides threaten human health. The WHO and UNEP have estimated that pesticides annually poison at least 3 million agricultural workers worldwide. According to a 2017 UN report, pesticides cause about 200,000 deaths per year worldwide. Household pesticides such as ant and roach sprays sicken another 2.5 million people per year. According to studies by the National Academy of Sciences, pesticide residues in food cause an estimated 4,000–20,000 cases of cancer per year in the United States. The pesticide industry disputes these claims, arguing that if used as directed, pesticides do not remain in the environment at levels high enough to cause serious environmental or health problems.

Figure 12.27

When a pesticide is sprayed on a crop (a), a few pest insects resist it and survive (b). The survivors reproduce and pass on their trait for resistance to the pesticide (c). When the crop is sprayed again (d), more insects resist and survive it and continue reproducing (e). The pesticide has now become ineffective and the farmer must look for a stronger pesticide.

An illustration shows five photos of a corn namely a, b, c, d, and e. The photo a shows pesticide being sprayed on a corn and a few pest insects that survive are shown over the corn. The photo b shows a few pest insects lying dead on the floor and one of the pest insect is shown moving live over the corn. The photo c shows many pest insects spread over the corn. The photo d shows pesticide being sprayed again over the pest insects spread over the corn. The photo e shows only a few pest insects lying dead on the floor and the others spread over the corn.Enlarge Image

Figure 12.28 lists some ways to reduce your exposure to synthetic pesticides.

Figure 12.28

Individuals matter: You can reduce your exposure to pesticides.

Critical Thinking:

Which three of these steps do you think are the most important ones to take? Why?

An illustration provides information about Reducing Exposure to Pesticides in bulleted points that read the text, “Grow some of your food using organic methods, buy certified organic food, wash and scrub all fresh fruits and vegetables, eat less meat, no meat, or certified organically produced meat, and before cooking trim the fat from meat.”

Connections

Pesticides and Food Choices

The Environmental Working Group (EWG) produces an annual list of fruits and vegetables that tend to have the highest and lowest pesticide residues. In 2019, these foods with the highest pesticide residues (EWG’s “dirty dozen”) were strawberries, spinach, kale, nectarines, apples, grapes, peaches, cherries, pears, tomatoes, celery, and potatoes unless they were USDA certified organically grown. In 2019, the “clean 15” with the lowest pesticide residues were avocadoes, sweet corn, pineapples, sweet peas, onions, papayas, eggplants, asparagus, kiwi, cabbage, cauliflower, cantaloupes, broccoli, mushrooms, and honeydew melons.

Case Study

Ecological Surprises: Unintended Consequences

Malaria once infected 9 of every 10 people in North Borneo, now known as the eastern Malaysian state of Sabah. In 1955, the WHO sprayed the island with dieldrin (a DDT relative) to kill malaria-carrying mosquitoes. The program was so successful that the dreaded disease was nearly eliminated.

Then unexpected things began to happen. The dieldrin also killed other insects, including flies and cockroaches living in houses, which made the islanders happy. Next, small insect-eating lizards living in the houses died after gorging themselves on dieldrin-contaminated insects. Then cats began dying after feeding on the lizards. In the absence of cats, rats flourished in and around the villages. When the residents became threatened by sylvatic plague carried by rat fleas, the WHO parachuted healthy cats onto the island to help control the rats. Operation Cat Drop worked.

Then the villagers’ roofs began to fall in. The dieldrin had killed wasps and other insects that fed on a type of caterpillar that was not affected by the insecticide. With most of its predators eliminated, the caterpillar population exploded, munching its way through its favorite food: the leaves used in thatch roofs.

Ultimately, this story ended well. Both malaria and the unexpected effects of the spraying program were brought under control. Nevertheless, this chain of unintended and unforeseen consequences reminds us that whenever we intervene in nature and affect organisms that interact with one another, we need to ask, “Now what will happen?”

12.4eEffectiveness of Synthetic Pesticides in the United States

Largely because of genetic resistance and the loss of many natural predators, synthetic pesticides have not always succeeded in reducing U.S. crop losses. David Pimentel, an expert on insect ecology, evaluated data from more than 300 agricultural scientists and economists. He found that between 1942 and 1997, estimated crop losses from insects in the United States almost doubled from 7% to 13%, despite a 10-fold increase in the use of synthetic insecticides. He also estimated that alternative pest management practices could cut the use of synthetic pesticides by half on 40 major U.S. crops without reducing crop yields.

The pesticide industry disputes such findings. However, numerous studies and experience support them. For example, Sweden has cut its pesticide use in half with almost no decrease in crop yields.

12.4fRegulating Synthetic Pesticide Use

In the United States, three federal agencies, the EPA, the USDA, and the FDA, regulate the use of these pesticides under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), first passed in 1947 and amended in 1972. Critics argue that that FIFRA has not been well enforced, and the EPA says that the U.S. Congress has not provided them with enough funds to carry out the complex and lengthy process of evaluating pesticides for toxicity.

In 1996, Congress passed the Food Quality Protection Act, mostly because of growing scientific evidence and citizen pressure concerning the effects of small amounts of pesticides on children. This act requires the EPA to reduce the allowed levels of pesticide residues in food by a factor of 10 when there is inadequate information on the potentially harmful effects on children. Some scientists call for reducing the levels for children by a factor of 100.

Between 1972 and 2018, the EPA used FIFRA to ban or severely restrict the use of 64 active pesticide ingredients, including DDT and most other chlorinated hydrocarbon insecticides. However, according to studies by the National Academy of Sciences, federal laws regulating pesticide use generally are inadequate and poorly enforced. A 2015 study by the U.S. General Accounting Office found that the FDA tests less than one-tenth of 1% of all imported fruits and vegetables. The FDA also does not test foods for some pesticide residues that are strictly regulated by the EPA.

Although laws within countries protect citizens to some extent, banned or unregistered pesticides may be manufactured in one country and exported to other countries. For example, U.S. pesticide companies make and export to other countries pesticides that have been banned or severely restricted—or never evaluated—in the United States. Other industrial countries also export banned or unapproved pesticides.

In what environmental scientists call a circle of poison, or the boomerang effect, residues of synthetic pesticides that have been banned in one country but exported to other countries can return to the exporting countries on imported food. Winds can also carry persistent pesticides from one country to another.

An increase in the demand for locally grown food could result in more small, diversified farms that produce organic, minimally processed food from plants and animals. Such eco-farming could be one of this century’s new careers for many young people. GREEN CAREER: Small-scale sustainable agriculture

Many urban schools, colleges, and universities are benefitting from having gardens on school grounds. Not only do the students have a ready source of fresh produce, but they also learn about where their food comes from and how to grow food more sustainably.

Finally, we can sharply cut food waste. According to the FAO, about one-third of the food produced for human consumption is lost or wasted. This is enough food to feed all of the world’s 815 million hungry people. It is equivalent to the output of an area of cropland almost half as large as the continental United States.

33%

Percentage of the world’s food that is lost or wasted

Big Ideas

· About 815 million people have health problems because they do not get enough to eat and 2.1 billion people face health problems from eating too much.

· Modern industrialized agriculture has a greater harmful impact on the environment than any other human activity.

· More sustainable forms of food production could greatly reduce the harmful environmental and health impacts of industrialized food production systems.

Tying It All Together

No-Till Farming and Sustainability

A photo shows several vegetables such as carrots, tomatoes, cucumbers, bottle-guard, onions, capsicums, cabbages, green vegetables, etc. which are placed in separate trays and displayed in a pattern so-as-to ease shopping.

Baloncici/ Shutterstock.com

This chapter began with a look at the promises and tradeoffs of no-till farming. This method of farming preserves topsoil, the base of the food web for most of the earth’s people. It lessens the ecological footprint of farming by reducing the need for water and fossil fuels and it creates a beneficial environmental impact by adding to soil quality and storing carbon in the soil, thus keeping it out of the atmosphere and reducing climate change. In doing so, it applies the biodiversity and chemical cycling principles of sustainability. It is one of many possible ways to shift to more sustainable food production. Making that transition means relying more on solar and other forms of renewable energy and less on fossil fuels. It also means sustaining chemical cycling by conserving topsoil and returning crop residues and animal wastes to the soil. It involves working to sustain natural, agricultural, and aquatic biodiversity by relying on a greater variety of crop and animal strains and seafood, produced by certified organic methods and sold locally in grocery stores and farmers’ markets. Controlling pest populations through broader use of conventional and perennial polyculture and integrated pest management will also help to sustain biodiversity.

Such efforts will be enhanced if we slow the growth of the human population and sharply reduce our wasteful use of food and other resources. Governments could help these efforts by replacing environmentally harmful agricultural and fishing subsidies and tax breaks with more environmentally beneficial ones. Finally, the transition to more sustainable food production would be accelerated for the benefit of the environment as well as current and future generations if we could find ways to include the harmful environmental and health costs of food production in the market prices of food, in keeping with the economic, political, and ethical principles of sustainability.

Chapter Review

Doing Environmental Science

For 1 week, weigh the food that is purchased in your home and the food that is thrown out. Also, keep track of the types of food you eat, using categories such as fruits, vegetables, meats, dairy, and other more specific categories if you wish. Record and compare these numbers and other data from day to day. Develop a plan for cutting your household food waste in half. Consider making a similar study for your school cafeteria and reporting the results and your recommendations to school ofChapter Review

Ecological Footprint Analysis

The following table gives the world’s fish harvest and population data.

Compiled by the authors using data from UN Food and Agriculture Organization and Earth Policy Institute.

1. Use the world fish harvest and population data in the table to calculate the per capita fish consumption for 1990–2012 in kilograms per person. (Hints: 1 million metric tons equals 1 billion kilograms; the human population data are expressed in billions; and per capita consumption can be calculated directly by dividing the total amount consumed by a population figure for any year.)

2. Did per capita fish consumption generally increase or decrease between 1990 and 2012?

ficials.