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Land and food
North America's land base is more than 19.3 million km2, or approximately 14 per cent of the world's land area (FAO 1997a). Currently, about 27 per cent of the land is devoted to agriculture, with 2.3 million km2 in crops and 2.7 million km2 in permanent pasture (OECD 1997). Most of North America's agricultural land is in the United States: approximately 82 per cent of all cropland and 90 per cent of all permanent pastures is found south of the US/Canadian border.
At the turn of the century, land could be easily acquired in North America, and waves of new settlers were drawn to the region's productive agricultural lands. As settlements spread across the continent, forests and grasslands were converted to agricultural uses. The vast natural grasslands of North America's Great Plains were gradually transformed into agricultural lands to cultivate grain or support livestock. With the advent of the tractor and the market forces created by World War I, the largest expansion of tilled areas for wheat occurred in the Great Plains. The area planted to wheat increased by 69 000 km2. Between 1924 and 1929 another 61 000 km2 of grassland in the southern plains were converted to wheat. However, overgrazing, poor farming techniques and drought conditions led to massive soil erosion on the Plains during the Dust Bowl years of the 1930s (Southwick 1996). Huge dust storms extending from Canada to Mexico affected nearly 4 million km2, until they were eventually brought under control by soil conservation and farm rehabilitation programmes (MacNeill 1989, Mannion 1991).
After World War II, intensified and modernized agricultural practices led to a large rural-to-urban migration and a decline in traditional, small-scale family farming practices. Fewer and larger farming enterprises came to manage the production of large fields of monocultures or intensively-rotated crops. Several factors led to the intensification and modernization of agriculture including the movement of people away from agricultural pursuits; replacement of human labour with mechanization; temporarily improved pest control technologies; and specialization within the production sector. Canada and the United States eventually became the world's leading sources of surplus foodgrain, exporting 132 million tonnes yearly during the 1980s, compared to about 5.5 million tonnes before World War II (World Commission on Environment and Development 1987).
The intensification of agricultural production in the United States and Canada has increased productivity by a factor of three or four since the 1950s (Lipske 1993) but these gains have also increased environmental stresses. The heavy use of pesticides and fertilizers (see bar chart below) resulted in run-off that became and remains a major source of water pollution. Approximately 950 000 km2 of land in the United States and Canada are affected by soil degradation, primarily water and wind erosion (UNEP/ISRIC 1991). Farmers have responded by applying increasing amounts of fertilizers but studies have shown continued declines in the average rates of change in productivity (Batie 1993). In 1997 the United States used 20 million tonnes of fertilizer, a figure slightly less than the all-time high of 21.5 million tonnes in 1981 (FAO 1997c). Despite efforts to reduce negative environmental impacts, agricultural production accounts for a significant use and release of toxic material (International Joint Commission 1997), and OECD studies list nitrate pollution as one of the most serious water quality problems in North America (OECD 1994). As the amount of fertilizer used approaches the physiological capacity of crops to absorb nutrients, the excess nitrogen poses a threat to ecosystem health. Along with phosphorus, another key fertilizer ingredient, nitrogen promotes overgrowth of algae in rivers, lakes and bays. As the algae die and decay, they use up large amounts of the water's oxygen, depriving other species of the oxygen they need to survive. In the case of the US Gulf Coast, the oxygen-depleted 'dead zone' (see box on page 151) that now appears each summer - at the peak of fertilizer run-off from the Corn Belt - is nearly the size of El Salvador (Tolman 1995).
The United States and Canada are involved in an issue of emerging international concern - the impact of certain chemical pesticides that are classed as persistent organic pollutants (POPs). POPs are toxic substances composed of organic chemical compounds and are of particular concern because they are toxic to humans and animals; do not degrade readily in the environment; tend to bioaccumulate; and often change from solid to gaseous phase, travelling long distances in the air before being redeposited in the environment (US EPA 1997a). Research on POPs has focused on 12 chemicals - the 'dirty dozen' - nine of which are pesticides and include DDT, chlordane and heptachlor (WWF 1998). Scientific evidence continues to show that some POPs cause genetic, reproductive and behavioural abnormalities in wildlife and humans, and may be associated with increased incidence in humans of cancer and neurological deficits (US EPA 1997a). The pesticides are used on crops such as cotton, vegetables, fruits and nuts. Although specific data on the location and amount used worldwide are difficult to obtain, most of the nine pesticides are still in use or exist in many countries (WWF 1998). All of the 12 POPs are either banned from use or regulated in North America (FASE 1996). Recent efforts to find and promote alternatives to POPs include newer and pest-specific pesticides and biological control methods (US Congress 1995a, National Research Council 1996). An international agreement on POPs is expected to be adopted in the year 2000.
A further source of concern in North America is the long-range transport of airborne emissions from other countries or regions, such as Eastern Europe, the Russian Federation and Asia, that may lead to deposition in North America. These pollutants bioaccumulate in wildlife and humans that consume the wildlife, particularly affecting the health of aboriginal and northern Canadian communities.
The expansion of farmland, especially into wetlands, destroyed habitats and contributed to the loss of biodiversity. Since the 1950s, however, the conversion of wetlands to agricultural land has declined. In the mid-1950s, agriculture, with government encouragement, was responsible for approximately 87 per cent of wetland conversions. In contrast, during 1982-92 about 57 per cent of total wetland losses were attributed to urban development and only 20 per cent to agriculture. Since 1992, approximately 4 000 km2 of wetlands have been placed into the US Department of Agriculture's Wetland Reserve programme. These lands are mostly under permanent easement and are not available for conversion to farmland. A shift toward organic farming and other low-impact agricultural techniques, including conservation tillage and integrated pest management, also helps to moderate some environmental stresses.
With mounting concern over the health and environmental effects of agricultural chemical use, organic agriculture is expanding. According to the Organic Farming Research Foundation (Organic Farming Research Foundation 1996), 49 per cent of US organic farmers intended to increase their organic areas over the next two to three years, and only 4 per cent were planning to decrease them. In recognition of this trend, in 1998 the US Department of Agriculture's Agricultural Marketing Service launched a proposal to establish a National Organic Program which would establish national standards for the organic production and handling of agricultural products, and would include a National List of synthetic substances approved for use in the production and handling of organically-produced products. It would also establish an accreditation programme for State officials and private entities that wish to be accredited to certify farm, wild-crop harvesting and handling operations that comply with the programme's requirements. The programme would also include labelling requirements for organic products and products containing organic ingredients, and enforcement provisions (US Department of Agriculture 1998).
Hazardous waste management has received attention in both Canada and the United States, at least in part from public pressure about sites posing threats to public health, as well as from concerns about potential liability for damage caused by hazardous waste (OECD 1995 and 1996). By September 1995, the US EPA had identified 1 374 National Priority List sites - sites where contamination presents the most serious threat to human health and the environment (Council on Environmental Quality 1997). Work was being conducted at 93 per cent of these sites, with permanent clean-up in progress at 60 per cent of the sites. An additional 15 622 sites remained which were classified as potentially hazardous or low priority. In Canada, in 1993, provinces reported on close to 4 800 contaminated sites that posed a threat to the environment (OECD 1995).
Over the next 10 years, changing trade patterns may intensify environmental impacts on agricultural land. Recent reductions in agricultural subsidies and tariff protection may increase US and Canadian production. As global trade barriers are reduced, there may be increasing pressure on export agriculture to satisfy a growing demand for food. For instance, a greater demand for meat by Asian countries could lead to an expansion in livestock production (Government of Canada 1996). If agricultural production increases, water and land use pressures may increase.
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