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|by Laurie J. Schmidt
May 18, 2001
A severe drought combined with poor soil conservation practices can lead to extreme topsoil erosion, with devastating effects on the land. This is just what happened in the Great Plains region of the U.S. during the 1930s Dust Bowl years.
In May 1934, a cloud of topsoil from the Great Plains blanketed the eastern U.S. as far as 2,400 km (1,500 miles) away. In 1935, the U.S. established the Soil Conservation Service to promote good soil management practices. But according to some experts, this is not enough. Human-accelerated soil erosion continues to occur because much of the Great Plains is suited to moderate grazing rather than farming. And in 1975, the Council of Agricultural Science and Technology warned that severe drought in the Great Plains could trigger another Dust Bowl.
In semiarid grasslands, such as the Sahel region, dust storms are often generated where the ground has been stripped of vegetative cover by cultivation or grazing. The path of dust from a single desert storm can be traced as far as 4,000 km (2,500 miles).
Desertification occurs when land surfaces are transformed by human activities, including overgrazing, deforestation, surface land mining, and poor irrigation techniques, during a natural time of drought. Desertification in the Sahel can largely be attributed to greatly increased numbers of humans and their grazing cattle.
Most overgrazing is caused by excessive numbers of livestock feeding too long in a particular area. Extreme overgrazing compacts the soil and diminishes its capacity to hold water, and exposes the soil to erosion.
Although the relationship between drought and human influences is complex, desertification can be successfully mitigated if financial resources are available. But exploding population growth in developing African nations means that pressures on the land there will continue to intensify.