Land degradation: An assessment of the human impact on global land resources.
Hari Eswaran1, Paul Reich1, and Friedrich Beinroth2. (1) USDA Natural Resources Conservation Service, 1400 Independence AVenue, Room South 4836, Washington, DC 20250, (2) University of Puerto Rico, Dept. of Agronomy & Soils, University of Puerto Rico, Mayaguez, PR 00681-9030
The conversion of natural ecosystems to agroecosystems causes changes that require tradeoffs between environmental concerns and agricultural practices if the integrity of the land resource base is to be preserved. In the absence of protective policies and practices land degradation ensues, threatening the sustained development of humankind and even life on earth. This paper portrays different manifestations of anthropic impacts on land and evaluates land degradation and desertification in this context. Global maps of population density and land quality underpinned our assessment. About 33% of global land resources in the susceptible drylands are vulnerable to desertification; there are about two billion persons (46% of the 1994 global population) who are partially responsible, who would be impacted, or both. An analysis by continent shows that Africa has the largest extent (46%) of vulnerable land and also has a proportionately greater number of persons who are affected. Human impact on land has been widespread and in some cases has impaired the agricultural productivity of the land and the functions of ecosystems. Although it is difficult to establish the actual extent of impaired land, the present study shows that large land areas (33.5%) are threatened by human activity and in some parts of the world, this has resulted in the extinction of plant and animal species. The better quality lands are not greatly damaged although the lands that appear to have been most impacted are Classes IV, V, and VI, which are dominant in the tropics. The countries where maximum human impact and land degradation occur are largely low-income countries and countries with high population densities. Poverty, population increases, and land degradation are thus interlinked and land quality is at the mercy of land use. A better understanding of degradation processes and the resilience characteristics of the resource base coupled to improved soil, water, and nutrient management is necessary to meet the global challenges of sustained crop production in harmony with good environmental management, thereby mitigating the processes of land degradation.