Desertification, as defined in Chapter 12 of "Agenda 21" and in the International Convention on Desertification, is the degradation of the land in arid, semi-arid and sub-humid dry areas caused by climatic changes and human activities.
It is accompanied by a reduction in the natural potential of the land and depletion in surface and ground water resources. But above all it has negative repercussions on the living conditions and the economic development of the people affected by it. Desertification not only occurs in natural deserts, but can also take place on land that is prone to desertification processes.
Desertification reduces the ability of land to support life, affecting wild species, domestic animals, agricultural crops and people. The reduction in plant cover that accompanies desertification leads to accelerated soil erosion by wind and water. For example, South Africa loses approximately 300-400 million tonnes of topsoil every year. As vegetation cover and soil layer are reduced, rain drop impact and run-off increases. Water is lost off the land instead of soaking into the soil to provide moisture for plants. Even long-lived plants that would normally survive droughts die. A reduction in plant cover also results in a reduction in the quantity of humus and plant nutrients in the soil, and plant production drops further. As protective plant cover disappears, floods become more frequent and more severe. Desertification is self-reinforcing - once the process has started, conditions are set for continual deterioration.
By impoverishing the natural potential of the ecosystems, desertification also reduces agricultural yields, making them more unpredictable. It therefore affects the food security of the people living in the affected areas. These consequences, in turn, weaken the economies of the developing countries affected by desertification, particularly when they have no other resources than their agriculture. This is particularly true in the African countries in the dry zones: their economy is unable to offset the increasingly serious effects of desertification, and they have to deal with emergency situations created by drought and desertification despite the increasing debt burden that is reducing their possibility of making productive investment in order to break the spiral of underdevelopment.
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