Desertification

• Desertification refers to the degradation of land resources in arid and semi arid regions.
• Desertification is often referred to as the spread of the deserts. It is a major problem in the Sahel region of Africa.
• The Sahel is a region in Africa that lies to the south of the Sahara desert.
• The Sahel stretches from the Atlantic Ocean in the west to the Red Sea in the east. Eleven countries have territory in the Sahel.
• The Sahel was originally a grassland savanna biome and it is now being converted into a hot desert biome.
• The Sahel supports a nomadic pastoral population. 
• Desertification results from a combination of climatic change and human activities.
• The climate of the Sahel has changed in a number of ways in recent decades. There has been a decrease in the amount of total rainfall. The amount of rainfall has declined by more than 30% in the last ten years.
• Also there have been 2 major periods of drought in 1968 – 1973 and 1983 – 1985
• Global warming is also having a negative effect on the region. Higher temperatures have meant increased evaporation.
• As a result of the above factors wells, rivers and watering holes have dried up affecting the water content of the soil and causing a reduction in the amount of vegetation cover. This has left the soil exposed to wind erosion and desertification.
• Desertification can also be caused by human activities such as over cropping, overgrazing and deforestation.
• Overgrazing removes the surface vegetation and leaves the soil exposed to erosion.
• Over cropping often involves monoculture and strips the soil of its nutrients leaving it infertile. 
• Deforestation is the cutting down of trees
• As a result of high birth rates and immigration population levels rose in the Sahel region. This led to an increased demand for wood as a fuel.
• In the Sahel up to 90 % of energy requirements are supplied by wood.
• Trees are also cut down in the Sahel for building materials and to make more land available for farming.
• In Mali alone half a million acres of trees have been cleared.
• Trees are being cut down 30 times faster than they are being replaced. This is because most people in the Sahel do not have the resources to replant the trees.
• Even young trees, small bushes and scrub vegetation are cleared.
• Trees are invaluable to this region as they act as barriers to prevent wind erosion. Their roots help to bind the soil. This improves the structure of the soil.
• Structure is a characteristic of soil.
• When trees die they add valuable nutrients to the soil forming humus. Humus content is a characteristic of soil.
• Deforestation also impacts on the water content of the soil
• Trees absorb rainfall. If trees are cut down the soils can become waterlogged and unsuitable for cultivation. Water content is a characteristic of soil. 
• As a result of a combination of these activities the Sahara Desert is spreading at a rate of 5 to 10 km per year into this vulnerable area.
• It has been proposed to create a Great Green Wall which would stretch across the Sahel region. This will involve planting a green belt of vegetation which will be 15 km wide and 7,775 km long in an attempt to halt the spread of the Sahara.
• In June 2010 the Global Environmental Forum announced the Great Green Wall project will be financed by a $119 million grant