Land degradation
Some of the direct pressures leading to degradation have been agricultural expansion, intensification and overgrazing in arid lands (Dregne 1986, Gold 1999). These practices can cause erosion by water and wind, and chemical and physical degradation (Eswaran, Lal and Reich 2001). Socio-economic drivers include large federal subsidies, increasing global demand for agricultural products and increased trade liberalization (MacGregor and McRae 2000).
| Conservation programmes |
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The US Conservation Reserve Program (CRP) was enacted in 1985 and expanded in 1990 to help farmers retire cropland that was environmentally sensitive or susceptible to erosion for 10 years in return for rental and cost-sharing payments and technical assistance. The aim was to reduce erosion and excess production. As of October 1999, 12.5 million ha of cropland were enrolled in the CRP (Zinn 1994, H. John Heinz III Center 1999). In Canada, the Permanent Cover Program (PCP), first delivered in 1989 by the federal Prairie Farm Rehabilitation Administration, aims to reduce soil deterioration on cropland at high risk of soil damage by maintaining permanent cover of grass and trees. Although the programme has limited funds, only applies for a short period and restricts the amount of land each farmer can retire, some C$2-5 million of soil productivity has been saved by permanent cover on 320 000 ha of land (Tyrchniewicz and Wilson 1994, Vaisey, Weins and Wettlaufer 1996). |
| Water and wind erosion vulnerability: North America |
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In spite of vulnerability, soil erosion in the United States declined by about one-third during 1987-97 and in Canada's agricultural regions the average number of days soil was left bare declined by 20 per cent during 1981-96 Source: USDA 2001a and 2001b |
Lessons learned from the Dust Bowl experiences of the 1930s led to the adoption of soil conservation strategies such as contour ploughing, no-till methods, reduced summer fallow and increased crop residues. In the late 1970s and early 1980s, both countries reported on the status of their nation's soil. These reports led to the US Soil and Water Resources Conservation Act of 1977 and Canada's 1989 National Soil Conservation Program (Vaisey, Weins and Wettlaufer 1996, USDA 1996). They also adopted strategies that took fragile lands out of agricultural production to protect them from erosion (see box).
Conservation measures have led to significant declines in erosion over the past 30 years. In the United States, 30 per cent of croplands had highly erosion-prone conditions in 1982 compared to 24 per cent in 1992 (H. John Heinz III Center 1999, Huffman 2000, Padbury and Stushnoff 2000).
Data for other indices of land degradation are scarce: consistent US data for the national level of organic matter, the degree of soil compaction and the amount of land affected by salt are lacking (H. John Heinz III Center 1999). Conservation practices in Canada appear to have led to a decline in the rate of organic carbon loss from 70 kg/ha in 1970 to 43 kg/ha in 1990 (Smith and others 2000).
Desertification has generally been stabilized over the past 30 years as plant cover on rangelands has improved, and erosion and waterlogging have been controlled (Dregne 1986, UNCCD 2001). In the mid- 1980s, salinization was estimated to affect about 25 per cent of the irrigated land in the United States, and conditions in heavily irrigated agricultural areas of the dry US southwest continue to worsen (de Villiers 2000). In Canada, only 2 per cent of agricultural land has more than 15 per cent of its area affected by salinity (Environment Canada 1996).
Historically, government agricultural policy focused on economic and production goals but sustainability has guided policy reforms in the recent past (MacGregor and McRae 2000). The Canadian Agri-Environmental Indicator project, completed in 2000, contributed to a more informed debate about agricultural sustainability, and the 1985 and 1990 US Farm Bills led to more sustainable stewardship by farmers and landowners (McRae, Smith and Gregorich 2000, NRCS 2000). In 1994, the US Task Force on Sustainable Agriculture set out recommendations to achieve environmentally and socially sound agricultural production and, two years later, the Federal Agriculture Improvement and Reform Act was signed expanding on earlier conservation themes (Gold 1999). The Canadian government set out its strategy for sustainable agriculture in 1997 (AAFC 1997).
