In recent years, the full range of ecological functions and economic benefits associated with wetlands has become much better understood; these include critical wildlife habitat, temporary stormwater storage, groundwater recharging, pollution control, sport hunting and fishing opportunities, wildlife viewing, and breeding grounds and nurseries for many commercially important fish, fur, and game species. As a result, Federal wetlands policy has increasingly emphasized conservation, and much of this policy shift has been directed at agriculture. Swampbuster provisions of the Food, Agriculture, Conservation, and Trade Act of 1990, for example, denied crop subsidy payments to farmers who converted wetlands to boost commodity program acreage-even if the converted wetlands were not directly used to produce program crops (U.S. Congress, OTA, 1993). Violation of Swampbuster regulations can mean the loss of eligibility for all farm program benefits—including commodity program participation, crop insurance, and disaster payments-until the violation is remedied. The Wetlands Reserve Program and the Emergency Wetlands Reserve Program pay farmers to preserve their wetlands and offer cost shares to encourage wetlands restoration.

Agriculture's role in converting wetlands to other uses has been declining. Between 1954 and 1974, agriculture accounted for 81 percent of all gross wetlands losses; between 1982 and 1992, it accounted for only 20 percent (see table 6.5.2 in chapter 6.5, Wetlands Programs). Furthermore, this percentage change reflects a decrease in conversions of land to agriculture rather than an increase in wetlands losses due to other activities.

About 90 percent of the 124 million acres of wetlands remaining in 1992 in the 48 States was on rural nonfederal lands. Given its ownership of these land resources, the farm sector will likely remain a primary target of wetlands conservation efforts. (See chapter 6.5, Wetlands Programs, for more detail.)

Water Quality. Agriculture threatens many wetland and aquatic ecosystems via the discharge of runoff laden with sediments and chemical residues. Nationally, runoff from agricultural land accounts for 60 percent of the sediment and about half of the phosphorus and nitrogen reaching freshwater systems (Crutchfield and others, 1993). This can create a variety of environmental problems in aquatic ecosystems. Nutrients from fertilizer applications can increase algae and plant growth, which in extreme cases can promote eutrophication of streams, lakes, and estuaries. Residues from pesticide applications can have toxic effects on freshwater and marine

species as well as their predators. Soil sediments can decrease sunlight penetration in water bodies, deteriorate spawning grounds, and reduce supplies of dissolved oxygen.

Because of the widespread nature of environmental problems associated with agricultural runoff, water quality will continue to be an important source of conflicts between the farm sector and the environment. (For more detail, see chapter 2.2, Water Quality, and chapter 6.2, Water Quality Programs).

Air Quality. Onfarm air pollution has recently received increased attention. Principal concerns include crop damage, noxious odors, particulate matter or dust, and wildfires. Crop damages occur due to off-farm pollution, such as ozone and other airborne pollutants, drifting into agricultural areas reducing growth and seed formation of field crops. These yield reductions of 5-10 percent are concentrated in areas near large population centers (Westenbarger and Frisvold, 1995). While airborne pollutants do not directly cause a severe reduction in yields, they can weaken plants and make them more susceptible to disease or insect damage.

Onfarm odors have brought about legal action by nearby property owners, who have seen their quality of life and property values suffer. These odors are generally a problem around large-scale livestock facilities, as well as near farms that fertilize with stored manure sludge. Anticipated odor problems have delayed or prevented construction of some livestock or poultry operations. The backlash against noxious odors has prompted some farmers to band together to create "right-to-farm" zones that protect farm operators against lawsuits by newcomers who were aware of the farms' existence before purchasing their property.

Using Agricultural Lands for Biomass and Fuel
Production

New uses for existing crops have helped to stabilize
demand for agricultural commodities. Corn, primarily
considered a feedgrain, is increasingly being used in
food and industrial products. Food uses-including
high-fructose corn syrup, glucose and dextrose,
cereals and other products, food starch, and beverage
alcohol-will account for a forecasted 975 million
bushels of corn in the 1996/97 (September 1-August
31) marketing year (Glaser, 1996). Corn used for
industrial uses and fuel alcohol production is forecast
to require an additional 661 million bushels (of the
9.3 billion bushels of corn expected to be produced in
1996/97) (USDA, NASS, 1997a).

As the nonfeed demand for corn has increased, a greater share of harvested corn acres has been devoted to food and industrial uses. Based on average yields, food and industrial uses of corn will account for 13 million of the 73 million acres of corn harvested in 1996/97 (USDA, NASS, 1997a). The share of total harvested corn devoted to all food and industrial uses is expected to be the same in 1996/97 as in 1990/91-nearly 18 percent. It has been as high as 25 percent in intervening years (fig. 1.1.7). Much of the increase in nonfeed uses of corn is a result of fuel alcohol production, which increased from about 900 million gallons in 1990/91 to an expected 1.4 billion gallons in 1995/96.

Little of the production from the estimated 23 million corn acres required for the food and industrial uses has come at the expense of other commodities. Since 1990/91, the total amount of acres planted to corn plus the acres set aside under annual programs has declined from 85 million acres to 79 million acres in 1996/97. For the most part, the added food and industrial demand for corn has been met through higher yields and stocks. Since 1990/91, ending corn stocks have averaged about 1.3 billion bushels per year while the food and industrial demand for corn has averaged 1.5 billion bushels per year. However, ending stocks for corn have fallen during the 1990's and added demand could soon have more noticeable impacts on acreage allocation and prices.

Work on new commercial and industrial uses for crops, crop byproducts, and other renewable resources is continuous. Considerable applications are technically possible, but not economical compared with existing alternatives. For example, there is great interest in energy from biomass, which includes liquid and gaseous fuels as well as direct combustion of

The use of cropland to produce biomass as a primary product will depend on returns to biomass crops exceeding the return to crops currently produced. This may occur through increases in prices, including scarcity of alternative energy sources, the need for the use of biofuels to meet environmental quality standards, or as a result of economic incentives. Cropland idled in the Conservation Reserve Program (CRP) might be used to produce herbaceous or tree crops as biomass energy sources through subsidies that would keep the land out of crop production yet protect and maintain the land resource. However, in early 1996, there was increasing concern with commodity scarcity, not excess stocks, and there was a call for releasing the CRP land for crop production. Thus, estimates of how much land might be used for biomass production require assumptions regarding the demands and supplies of agricultural commodities, types of energy needed, and environmental quality programs (including taxes and incentives). One recent analysis of biomass production in the United States in 2000, 2005, and 2020 concluded that, with the current estimates of the future price and yield `relationships, "biomass-based electricity generation is likely to be more of a niche than a mass market where electricity is expensive and biomass fuel is cheap or incurs a disposal cost, e.g. waste wood, sawdust, etc." (Roningen and others, 1995). (For more discussion of energy from agricultural biomass, see chapter 3.3, Energy.)

Potential Impacts of Global Climate Change

The potential for emissions of greenhouse gases to change Earth's climate has been the subject of concerted Federal research since the late 1970's. The United Nations Framework Convention on Climate Change was signed by representatives from 155 countries, including the United States, at the United Nations Conference on Environment and Development (the Rio Earth Summit) in 1992. Ratification of the Convention by more than 50 nations occurred in late 1994, putting the agreement into force. The United States was among the early nations to ratify the Convention. The key provision for land use is Article 2: "The ultimate objective of this Convention ... is to achieve stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system. Such a level should be achieved within a time-frame sufficient to allow ecosystems to adapt naturally to climate change, to ensure that food production is not threatened and to enable economic development to proceed in a sustainable manner."

Recent research conducted at ERS links world land and water resources with climate conditions and economic activity to analyze how four climate change scenarios might affect world agriculture and land use (Darwin and others, 1995). Under the scenarios, reduced productivity on Earth's existing agricultural lands, because of new temperature and precipitation patterns, would be more than offset by expanding agricultural production in new areas. Global food production would increase. However, if climate change were relatively severe, increased food production might not counter losses in other sectors and global economic activity could decrease. Only the effects of changes in atmospheric concentrations of CO2 on climate were considered. The beneficial effects of greater atmospheric concentrations of CO2 on plant growth and the effects of changes in the atmospheric concentrations of other gases like ozone and sulphur dioxide on both the climate and plant growth are still under study.

In the United States, all climate change scenarios result in land use changes on at least 48 percent of existing cropland. In two scenarios, more than half of all U.S. cropland ends up with a shorter growing season and 8-19 percent is abandoned (40-90 million acres). Some farm communities would be severely disrupted, particularly in areas where the only economically viable adaptation would be to abandon agriculture. Forest losses in some areas would be offset by gains in others. Likewise, net change in

pasture could be negative or positive (from -0.1 to 7.4 percent). The environmental effects of such land use changes have yet to be determined, but will depend on the rate of change in the climate and the speed at which ecosystems migrate.

Author: Arthur Daugherty, (202) 219-0424 [arthurd@econ.ag.gov]

Contributors: Jan Lewandrowski, Marlow Vesterby, David Schimmelpfennig, Roger Claassen, Ralph Heimlich, Jim Hrubovcak, David Westenbarger, Kevin Ingram.

References

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