Desertification reduces land's ability to support life and leads to accelerated soil erosion and loss of topsoil. As vegetation cover and soil layers reduce, water runs off instead of soaking into the soil. Reclamation techniques to control desertification include controlling sand dunes, afforestation, and irrigation methods. However, once desertification starts, conditions reinforce continual deterioration and rehabilitation becomes increasingly difficult and expensive.

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4. The term desert usually refers to areas that, in addition to being extremely dry, have high daytime temperatures, particularly in the summer. Many scientists also consider polar regions to be deserts, since they are arid and sustain little or no vegetation. Deserts occupy between 15 and 20 per cent of the earth's land area. They usually receive less than 10 inches (250 mm) of precipitation yearly. Precipitation, usually rain, tends to come in a few heavy storms of short duration. Deserts are often bordered by semiarid areas.

5. Kinds of Deserts Though most scientists who study deserts agree that there are several types of deserts, they do not agree on how to classify these types

8. What are the effects of desertification 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. South Africa losing 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.

9. 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, i.e. once the process has started, conditions are set for continual deterioration.

10. Control of sand dunes is a traditional technology originating from the Ming Dynasty (1368-1644). Flood water is used to reclaim deserted land, flattening sand dunes, thus controlling wind sand erosion and creating farmland.Oil in areas of water shortage. Afforestation is an effective method used to enhance areas that are affected by drifting sand. Air-seeding allows the distribution of seeds into regions that would otherwise be ecologically unreachable. Reclamation techniques

11. Irrigation techniques are inexpensive, the equipment is user-friedly, plants are guaranteed to grow in all seasons and the permantly wet roots deter termite infestations.

12. Examples : The Mongolian tradition of combating desertification : Involves tree planting which reduces sand movement and provides. Algeria Green Wall : The "Green Wall" was to halt the advancing desert to the north, creating a barrier of greenery, that protects the steppe from the Moroccan border to that of Tunisia. A total of 3 million hectares were to be afforested. 160 000 hectares have been only. 160 000 hectares which are most often the appearance of large fields withered the colors more than gray green

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