Deserts: defining traits, formation, life, and humans

Definition of deserts and aridity concept

A desert is a landscape where little precipitation occurs, creating harsh living conditions and leading to distinctive biomes and ecosystems. Because vegetation is sparse, the ground surface is exposed to denudation and erosion, while occasional heavy rain can produce flash floods. Deserts cover about one-third of Earth’s land area and include both hot and cold environments; polar regions with low precipitation are sometimes called “polar deserts” or “cold deserts.” Aridity is central to desert definition and can be described using precipitation amounts and water-balance concepts. Deserts generally receive less than about 250 mm of precipitation per year, while semi-deserts receive roughly 250–500 mm and are often called steppes when grass-covered. Even when potential evapotranspiration is high, actual evapotranspiration may be low if water is unavailable. Deserts can also be classified by temperature (hot vs. cold), precipitation patterns (including hyperarid conditions with very little or no rainfall for long periods), and factors related to desertification and geographic setting (such as rain shadows).

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Etymology and meaning changes of “desert”

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