Desertification

Geographic Occurrence

Arid, semi-arid, and dry subhumid regions receiving less than 800 millimeters of rainfall annually are susceptible to desertification. With their variable rainfall, skeletal soils and scant vegetation, these drylands are more susceptible than are other areas to wind and water erosion. More than one-third of Earth's surface is considered dryland, including the Sahel, stretching across Africa south of the Sahara; parts of Southern and Northern Africa; much of Australia; Central Asia and parts of China; much of the Middle East and the Mediterranean; Southern South America, including the Patagonia region; and the North American West. Many of these areas are on the edges of deserts, such as the Sahara, the Gobi, and the Negev. It is important to keep in mind that desertification does not mean that the desert is expanding and eating up arable land, as the name implies, but that land has been (permanently) degraded and can no longer support productive vegetation. This degradation occurs in patches at the local level.

Although international bodies such as the United Nations wholly accept the reality of desertification and are committed to mitigating its effects, many researchers are not convinced that there is evidence of this widespread degradation. Desertification is difficult to measure, and it is hard to determine whether degradation is due to climate change, [Page 716]human action, or a combination of the two. Furthermore, many scientists caution that geographical and temporal scale must be taken into account. Degradation thus may occur in some locations, but in other locations land that is considered degraded actually is recovering. These differing assumptions about the extent and severity of desertification worldwide inherently lead to very different ideas about how to combat it.

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