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.

Countering desertification

A number of schemes have been tried to reduce the rate of desertification and regain lost land. Leguminous plants, which use nitrogen they extract from the air, can be planted. Stones placed around the base of trees increase the shade available for plants and insects. Artificial grooves in the ground can be dug to retain moisture and trap wind-pollinated seeds. In Iran petroleum is being sprayed over semi-arid land with crops. This coats seedlings to prevent moisture loss and stop them being blown away. Windbreaks made from trees and bushes to reduce soil erosion and evapotranspiration was widely encouraged by development agencies from the middle of the 1980s in the Sahel area of Africa.

Related Topics:
Leguminous plants - Nitrogen - Iran - Petroleum - Erosion - Evapotranspiration - 1980 - Sahel - Africa

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With many of the local people using trees for firewood and cooking the problem has become acute. In order to gain further supplies of fuel the local population add more pressure to the depleted forests; thus adding to the desertification process. Solar ovens are being advocated as a means to relieving some of this pressure upon the environment.

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While desertification has received tremendous publicity by the political and news media, there are still many things that we don't know about the degradation of productive lands and the expansion of deserts. In 1988 Ridley Nelson pointed out in an important scientific paper that the desertification problem and processes are not clearly defined. There is no consensus among researchers as to the specific causes, extent, or degree of desertification. Contrary to many popular reports, desertification is actually a subtle and complex process of deterioration that may often be reversible.

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At the local level, individuals and governments can help to reclaim and protect their lands. In areas of sand dunes, covering the dunes with large boulders or petroleum will interrupt the wind regime near the face of the dunes and prevent the sand from moving. Sand fences are used throughout the Middle East and the United States, in the same way snow fences are used in the north. Placement of straw grids, each up to a square meter in area, will also decrease the surface wind velocity. Shrubs and trees planted within the grids are protected by the straw until they take root. In areas where some water is available for irrigation, shrubs planted on the lower one-third of a dune's windward side will stabilize the dune. This vegetation decreases the wind velocity near the base of the dune and prevents much of the sand from moving. Higher velocity winds at the top of the dune level it off and trees can be planted atop these flattened surfaces.

Related Topics:
Dune - Petroleum - Sand fence - Middle East - Snow fence - Irrigation

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Oases and farmlands in windy regions can be protected by planting tree fences or grass belts. Sand that manages to pass through the grass belts can be caught in strips of trees planted as wind breaks 50 to 100 meters apart adjacent to the belts. Small plots of trees may also be scattered inside oases to stabilize the area. On a much larger scale, a "Green Wall," which will eventually stretch more than 5,700 kilometers in length, nearly as long as the Great Wall of China, is being planted in northeastern China to protect "sandy lands"--deserts believed to have been created by human activity.

Related Topics:
Green Wall - Great Wall of China

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More efficient use of existing water resources and control of salinization are other effective tools for improving arid lands. New ways are being sought to use surface-water resources such as rain water harvesting or irrigating with seasonal runoff from adjacent highlands. New ways also being sought to find and tap groundwater resources and to develop more effective ways of irrigating arid and semiarid lands. Research on the reclamation of deserts also is focusing on discovering proper crop rotation to protect the fragile soil, on understanding how sand-fixing plants can be adapted to local environments, and on how grazing lands and water resources can be developed effectively without being overused.

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Off-road vehicles significantly increase soil loss in the delicate desert environment of the western United States, which can be controlled by restrictions on such vehicles.

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