Desert

Article By:

Owen, Denis F. Department of Biology, Oxford Polytechnic, Oxford, United Kingdom.

Last reviewed:November 2019

DOI:https://doi.org/10.1036/1097-8542.187700

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• Desert, published June 2014:Download PDF Get Adobe Acrobat Reader

A wide, open, comparatively barren tract of land with little rainfall and, consequently, few forms of life. Deserts (Fig. 1) comprise about one-fifth of the land surface on Earth. From an ecological viewpoint, the scarcity of rainfall in deserts is all important because it directly affects plant productivity, which in turn affects the abundance, diversity, and activity of animals. It has become customary to describe deserts as extremely arid where the mean precipitation is less than 60–100 mm (2.4–4 in.), arid where it is 60–100 to 150–250 mm (2.4–4 to 6–10 in.), and semiarid where it is 150–250 to 250–500 mm (6–10 to 10–20 in.). However, mean figures tend to distort the true state of affairs because precipitation in deserts is unreliable and variable. In some areas, such as the Atacama in Chile and the Arabian Desert, there may be no rainfall for several years. It is the biological effectiveness of rainfall that matters, and this may vary with wind and temperature, which affect evaporation rates. The vegetation cover also alters the evaporation rate and increases the effectiveness of rainfall. Rainfall, then, is the chief limiting factor to biological processes, but intense solar radiation, high temperatures, and a paucity of nutrients (especially of nitrogen) may also limit plant productivity, and hence animal abundance. See also: Desertification; Ecology; Precipitation (meteorology)

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