Arid desert land occupies as much a

Arid desert land occupies as much as 33% of the global terrestrial surface, much of which surrounds the equator. The Sahara desert alone occupies the same square acreage as the United States. Arid climates are defined by the significant absence of rainfall. Within
this climate zone are three generally accepted subcategories: hyper-arid regions, which receive less than 100 mm annual rainfall, arid regions, which receive 100e300 mm annual rainfall and subarid regions, which can receive up to 800 mm annual rainfall. Of these three subcategories, arid is the most common, occupying 14.6% of the world’s land area (FOA Forest, 1989).