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. This spread of arid areas is caused by a variety of factors, such as overexploitation of soil as a result of human activity and the effects of climate change.^[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]