Desertification

Desertification is the degradation of land in arid, semi arid and dry sub-humid areas into desert, resulting from various factors including climatic variations and human activities. Modern desertification often arises from the demands of increased populations that settle on the land in order to grow crops and graze animals.

Prehistoric patterns

Desertification is a historic phenomenon; the world's great deserts were formed by natural processes interacting over long intervals of time. During most of these times, deserts have grown and shrunk independent of human activities. Paleodeserts, large sand seas now inactive because they are stabilized by vegetation, extend well beyond the present margins of core deserts, such as the Sahara.

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Through dated fossil pollen, it has been found that today's Sahara desert has been changing between desert and fertile savanna. Studies also show that advance and retreat depend on yearly rainfall.

Related Topics:
Dated fossil - Pollen - Sahara - Desert - Savanna

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