Desertification

Desertification is a type of gradual land degradation of fertile land into arid desert due to a combination of natural processes and human activities.

The immediate cause of desertification is the loss of most vegetation. This is driven by a number of factors, alone or in combination, such as drought, climatic shifts, tillage for agriculture, overgrazing and deforestation for fuel or construction materials. Though vegetation plays a major role in determining the biological composition of the soil, studies have shown that, in many environments, the rate of erosion and runoff decreases exponentially with increased vegetation cover.^[2] Unprotected, dry soil surfaces blow away with the wind or are washed away by flash floods, leaving infertile lower soil layers that bake in the sun and become an unproductive hardpan.^[3][4]

At least 90% of the inhabitants of drylands live in developing countries, where they also suffer from poor economic and social conditions.^[5] This situation is exacerbated by land degradation because of the reduction in productivity, the precariousness of living conditions and the difficulty of access to resources and opportunities.^[6]

Geographic areas most affected are located in Africa (Sahel region), Asia (Gobi Desert and Mongolia) and parts of South America. Drylands occupy approximately 40–41% of Earth's land area and are home to more than 2 billion people.^[7] Effects of desertification include sand and dust storms, food insecurity, and poverty.

Methods of mitigating or reversing desertification include improving soil quality, greening deserts, managing grazing, and tree-planting (reforestation and afforestation).

Throughout geological history, the development of deserts has occurred naturally over long intervals of time.^[8] The modern study of desertification emerged from the study of the 1980s drought in the Sahel.^[9]