ENVIRONMENT. People farm Earth's biosphere to produce food for the sustenance of the human species. Thus, human food systems are part of Earth's complex ecological systems. All of these systems begin with interactions with the sun, which is the ultimate energy source. Sunlight enables plants to manufacture carbohydrates through the process of photosynthesis, in which chlorophyll converts sunlight into chemical energy, synthesizing organic compounds from inorganic compounds. Plants take carbon dioxide, water, and inorganic elements for this conversion process from the air and soil. Humans obtain their nourishment directly from plants, or from animals nourished directly or indirectly by plants. Thus humans ultimately rely on air, soil, water, and sunlight for sustenance.

Humankind has a strong interest in not fouling the environment, as contaminants in the air, water, or soil can end up in the plants that people or their food animals eat. An extreme example of such contamination was the 1986 Chernobyl nuclear power plant explosion in the Ukraine. Although hundreds of thousands of people fled the area that was immediately affected by the explosion, as many as three million people still live in contaminated areas in this farming region. As a result of the ecological devastation from this disaster, enormous amounts of money have been and continue to be spent in an effort to relocate communities and decontaminate the rich farmland.

Environmental Progress and Challenges for Agriculture

Agriculture and food systems play a major role in the ecological health of Earth, including the number and diversity of life forms that inhabit it. Half of the land mass of the United States, excluding Alaska, is privately owned crop, pasture, and range land. As noted in America's Private Lands: A Geography of Hope, the farmers and ranchers who manage these 907 million acres play a key role in maintaining the abundance of these natural resources for present and future generations.

Driven by changing economic and demographic trends, agriculture has become more consolidated, intensified, and specialized. At the same time, there has been increased scientific and public awareness of the detrimental environmental impacts of some agricultural activities, such as the problem of soil erosion. However, by adopting new practices and working with government conservation cost-share and technical-assistance programs, farmers are significantly reducing many of those detrimental impacts. Although soil erosion threatens the future productivity of 29 percent of cultivated acres in the United States, farmers reduced soil erosion on U.S. farmland by 38 percent from 1982 to 1997. Much of this reduction was accomplished by changing from traditional plowing to no-till or minimum-tillage systems that disturb the soil less and leave a protective layer of crop residue. The United States Department of Agriculture (USDA) programs, such as the Conservation Reserve Program and Wetland Reserve Program, take marginal or fragile croplands out of production and assist landowners with plantings or practices to buffer stream banks and enhance wildlife habitat. Wetlands, including productive yet fragile ecosystems like prairie potholes, have been restored, and the nesting success of ducks has increased.

Many livestock farmers and ranchers have improved grazing management to benefit livestock productivity as well as soil, water, and wildlife resources. For example, the United States and several western European nations are addressing the problem of excess manure in areas with high concentrations of livestock. Farmers are developing nutrient-management plans to make the best use of fertility-building resources in manure and to prevent excessive field applications or run-off into waterways.

Problems with water quality and water supply due to agricultural practices persist in some areas and have recently emerged in others, such as in the northeastern United States, where the water supply has not been a problem historically. Water quality also affects both freshwater and saltwater fisheries (discussed in more detail below). Careful management of agricultural production is critical in maintaining the ecological health of many estuaries (nurseries for fish and shellfish stocks and food webs). Efforts to improve nutrient management and agricultural conservation practices in the extensive watershed of the U.S. Chesapeake Bay are evidence of the growing awareness of the ecological links between farming and fishing.

Developed countries in North America and western Europe use a combination of technical assistance, incentives, and regulatory approaches to address environmental problems associated with agriculture. However, a lack of human and economic resources limits the ability of developing countries to address environmental problems associated with agriculture or other human activities. The clearing of forests in Brazil continues to accelerate in an effort to develop agricultural production for export. Land is cleared for crops and cultivated pasture, much of it to expand livestock and crop production for export markets. The USDA's Agricultural Baseline Projections February 2002 report (Westcott) predicted that the conversion of undeveloped land into arable land in Brazil's interior will gain momentum over the next decade. Brazil's share of the world soybean market is projected to grow from 28 to 35 percent by 2011.

In his 2000 Nobel anniversary lecture, agricultural researcher Norman Borlaug noted that irrigated agriculture uses 70 percent of global water withdrawals, covers 17 percent of cultivated land (about 679 million acres), and accounts for 40 percent of world food production.

Loss of genetic diversity in crop plants and livestock—driven by market rewards for high yield, cost-efficiency, and product uniformity—is increasingly recognized as an environmental concern for agriculture. Other concerns include agriculture's effects on biodiversity and health of critical habitats. Working agriculture can be a positive or negative factor in all these areas of environmental concern, depending on local site conditions and management practices.

World Fisheries and Food Security

Fisheries contribute to world food security, especially since fish are a major source of protein for some of the world's poorest populations. Per capita fish consumption varies among countries, depending on economic wealth, cultural traditions, and fisheries resource base. According to the United Nations Food and Agriculture Organization (FAO), world per capita fish consumption has been increasing since the 1960s, a trend that has been accompanied by increasing incomes. Global trade in fish and shellfish continues to grow and gain importance in developing countries. However, a practice of over-fishing now threatens fisheries around the world. Consumption of fish has been increasing quite dramatically for at least half a century, and stocks have been severely depleted. Too many fish have been harvested with too little thought or provision for protecting the resource base so that it can continue to produce sustainably. U.S. efforts to protect fisheries from over-fishing are showing some results. For example, some long-threatened resources, such as cod and haddock stocks in New England, have begun to recover after decades of decline. However, achieving international cooperation to protect coastal and estuarine environments and to manage and sustain world fisheries remains a challenge.

Toward a More Sustainable Aquaculture

Aquaculture, often promoted as a solution to over-fishing, has expanded dramatically in Asia for domestic and export markets. As with agriculture, the environmental impacts of aquaculture can vary greatly over the range of management systems and practices. The article "Effect of Aquaculture on World Fish Supplies," by Naylor et al., describes the paradox of aquaculture as both a possible solution and a contributing factor to the collapse of fisheries stocks worldwide.

In the late twentieth and early twenty-first centuries, capture fisheries provided a decreasing share of world food fish, while the share that aquaculture provided surged—nearly tripling from 10 million metric tons in 1987 to 29 million metric tons in 1997. World capture fish harvests leveled off at around 85–95 million metric tons per year, with the catch shifting from larger, higher value carnivorous species of fish to smaller, lower value fish used to make feed for farmed fish. Four of the top five capture fish species were used in feed production for the aquaculture and livestock industries.

Alteration of habitat—especially the large-scale transformation of mangroves and coastal wetlands in Asia into fish-and shrimp-farming ponds—also harms wild fish nurseries and the ecological health of coastal wetlands, coral reefs, and related marine habitat. Other factors that diminish wild fisheries are the collection of wild seed stock, food-web interactions (e.g., over-fishing of small fish species that form the food supply for marine predators, including valuable fish species consumed by humans), introduction of exotic species and pathogens, and nutrient pollution from fish farms.

Aquaculturists farm more than 220 species of finfish, shellfish, and crustaceans. Raising carnivorous species such as salmon, which consume wild fish for feed (producing one pound of farm-raised salmon takes eight pounds of wild fish), can create problems such as inter-breeding of wild fish with escaped farmed fish. But some aquaculture benefits estuarine and marine ecosystems, such as filter-feeding oysters, mussels, clams, and some carp, all of which help purify water. A range of fish and shellfish farming systems are being developed for different species, locations, and conditions. Naylor et al. (pp. 1021–1023) offered four primary goals for the sustainability and continued growth of the aquaculture industry: (1) expand farming of smaller, lower feeding-level fish; (2) reduce use of fish meal and fish oils in feed; (3) develop integrated farming systems; (4) promote environmentally sound aquaculture practices and resource management.

Food and Ecosystems: Linked since the Rise of Civilization

Humans have always interacted with their environment in order to obtain food. Local ecosystem characteristics, such as the types and quantities of edible plants and plants eaten by food-producing animals, have significantly affected the evolution and development of human societies and cultures. In his Pulitzer-Prize-winning book Guns, Germs, and Steel: The Fates of Human Societies, Jared Diamond traced many of the outcomes of human history, including the comparative advantages of different societies and the availability and relative abundance of different types of plants and animals. For example, a hospitable growing environment with deep, fertile soil, adequate rainfall, and moderate temperatures provides people with a food-producing advantage. (Examples are the traditional "breadbasket" regions of the world: the midwestern United States, the pampas of South America, the plains of central Europe and the Ukraine, and China's river valleys.) However, through ingenuity, skill, and careful stewardship of resources, humans have produced ample food supplies in challenging environments such as the mountains of Switzerland, the Nile Valley, and arid parts of Australia.

In his book, Diamond also links the development of civilizations to people's ability to produce abundant food supplies in an environment. For example, settlements could become permanent only when people no longer had to wander in search of food, and when they learned to protect and replenish the soil so that they did not have to abandon exhausted farming sites. A sustained and ample food supply enabled societies to develop technology, writing, and political systems, all of which advanced agriculture even further. Highly developed farming systems were the cornerstone of the rise of the Roman Empire and the unification of China. The ancient Romans understood, and wrote extensively about, the practice of sustainable agriculture. They improved plants and animals through selective breeding, and they emphasized the use of manure and composts to replenish and enrich the life-giving capacity of farmed soils.

Lessons from Famines and Ecological Disasters of the Middle Ages

Cycles of disaster and famine in medieval Europe offer an instructive study in the interplay of agriculture and the environment. A series of extreme natural disasters including floods, crop failures, and epidemics among humans and livestock culminated in the Great European Famine of the early 1300s. In the mid-fourteenth century, another wave of natural disasters, which included the spread of bubonic plague, resulted in the loss of about one-third of the population of Europe, with death rates as high as 60 percent in some communities. These famines and ecological disasters most likely resulted from a complex combination of causes. Bruce M. S. Campbell discussed several theories about the famines in "Ecology Versus Economics in Late Thirteenth-and Early Fourteenth-Century English Agriculture," in Agriculture in the Middle Ages (pp. 76–97). The floods were most likely part of a period of climate change to cooler, wetter weather, accompanied by storm surges in the North Sea.

Medieval agriculture lacked the dynamism to keep pace with the demands of growing urban populations. In response to food shortages, marginal lands that had been used for livestock, hay, and pasture were now used to raise crops for human consumption. However, reducing livestock numbers not only reduced the quantity of foods produced from animals, but also the supply and use of manure on cropland, which ultimately lessened crop yields.

Lack of technical progress in agriculture, nearly continuous wars, and the extractive feudal economic system made the bad situation worse. Campbell explained (p. 94) that warfare wreaked ecological havoc on the food and agriculture system through physical destruction of crops, livestock, stock, equipment, and physical structures. Burdensome taxes levied to finance warring armies and the expropriation of stock, crops, equipment, and marketing and transportation systems also weakened the existing agricultural systems.

This pattern of famine during and after periods of war or civil strife, often coinciding with epidemics and disastrous droughts or floods, recurs in most modern famines, such as those afflicting Africa since the 1970s. Modern famines show how the ecological, economic, and social destruction of war disrupts the production and distribution of food and, subsequently, a society's ability to feed itself.

From Renaissance to Agricultural Revolution

Significant changes in farming systems that began in parts of Europe during the later medieval period brought about major changes in the ecological health and productivity of the land. Farmers began to combine and integrate crops and livestock in ways that promoted soil quality and fertility and that boosted production. They adopted more intensive and flexible crop rotations, as well as new crops such as oats, turnips grown for animal feed, and nitrogen-fixing legumes. These innovations eliminated the need for fallowing (idling) of land, adding further to sustainable production gains. Campbell found (p. 92) that farmers adopted these systems most readily in areas with natural resource advantages, access to markets, or fewer institutional constraints such as feudal servile tenure or common property rights.

The enclosure of common lands across England in the 1700s and early 1800s transformed agriculture and the English landscape. Well over six million acres, or one-fourth of the cultivated acres in England, were converted from communally held and farmed lands to lands that were privately owned and managed. This conversion enabled farmers to integrate livestock and crops, using manure and crop rotations to restore and improve depleted lands that were formerly pastured or cultivated continuously. The dramatic gains in productivity and prosperity reflect the key role of private property and free enterprise in resource management.

The large amount of available land in the midwestern and western United States lured families to seek new land when the soil became depleted. As a result of this, President Theodore Roosevelt called for a national sense of duty to the land during a 1908 White House Conservation Conference. However, it was not until the dust bowl disaster of the 1930s that major efforts to protect soil and water finally emerged.

The Agricultural Revolution of 1750–1880 improved yields and adaptation of crops and livestock to local conditions around the world. This period of innovation also set the stage for unprecedented scientific and technical progress in the latter half of the twentieth century. In his Nobel address, Borlaug also noted that in 1940 U.S. farmers produced 56 million tons of corn on 77 million acres of land. In 1999 U.S. farmers produced 240 million tons of corn on 71.7 million acres—a greater than fourfold increase in yield per acre, reaped from hybrid seed, fertilizer, and weed control. The Green Revolution of the 1960s and 1970s applied these techniques to rice, wheat, and other crops in the developing world.

Biotechnology and Questions for the Future

In a response to critics who questioned the environmental effects of advances in agricultural science and technology, Borlaug noted that without the dramatic gains in yields brought about by those advances, three times as much land of equal quality would have been required to match food production in the world at that time. Much of that additional 4.4 billion acres of land would have to come from more marginal and environmentally fragile lands.

By the late twentieth century, biotechnology was yielding new adaptations of crops and animals for food and medicine. U.S. farmers quickly adopted new genetically modified crops. According to the USDA National Agricultural Statistics Service 2002 report Crop Production—Prospective Plantings, U.S. farmers intended to plant genetically modified seed on 74 percent of soybean acreage, 71 percent of cotton, and 32 percent of corn grown for grain in 2002. Most first-generation genetically engineered varieties were designed to reduce pesticide use or to allow use of more benign chemicals.

Proponents maintain that through biotechnology people will find new ways to increase yields, nutritional and health values, and environmental sustainability of food production. Still, controversy persists about environmental impacts, consumer concerns, and access to the new technology for impoverished people and nations. Some people question the new methods of genetic manipulation on philosophical grounds. Despite his strong support of biotechnology, Borlaug said that national, regional, and world policymakers must resolve serious issues raised by the dominant role of proprietary companies in biotechnology investment and research. He questioned how resource-poor farmers in developing countries could obtain products of biotechnology research and what amount of time product patents should last. Thus, in policymaking processes, societies, governments, and international agencies need to make policy decisions based on credible information about how best to meet human food needs from the land and water while safeguarding valuable resources, ecological integrity, and future productivity.

See also Agriculture since the Industrial Revolution; Aquaculture; Biodiversity; Biotechnology; Crop Improvement; Ecology and Food; Genetic Engineering; Green Revolution; High-Technology Farming; Pesticides; Population and Demographics; Sustainable Agriculture; Toxins, Unnatural, and Food Safety.

Lorraine Stuart Merrill