Deserts

DESERTS ARE AN environmental extreme, characterized by low rainfall that is highly variable intra-annually and interannually, with a coverage of about 27.7 Mkm.2, equivalent to 35 percent of the earth's surface and, thus, representing one of the largest terrestrial biomes. They occur mainly within latitudes between 5–35 degrees north of the equator and are characterized by very high aridity, very little vegetation cover and large surfaces of exposed bare soil, and high adaptations of plants and animals for survival during long droughts. According to bio-ecological definitions, the world's deserts represent all ecoregions of the world that harbor desert vegetation, identified [Page 315]by the xerophilous life-forms and the general desert-adapted physiognomy of the dominant plants.

Desert climate is characterized by precipitation of less than 9.84 in. (250 ...