GCSE Geography | Causes of Desertification (Hot Deserts 8)
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Last updated 19 Jul 2023
Desertification is the process of semi-arid grassland becoming degraded and drier and turning into desert. Most of the areas at risk from desertification are on the borders of existing deserts, for example the Sahara Desert in northern Africa. Desertification is a risk across most continents but the biggest area of risk is the Sahel, which is a strip of land south of the Sahara Desert, An estimated one billion people live in areas at risk from desertification.
As populations across semi-arid areas grow, there is more pressure on food and water resources which can lead to desertification. Population in areas of the Sahel has grown for two reasons. Firstly, through natural increase, this is when the birth rate exceeds the death rate - this tends to happen as countries develop their economies and the standard of living improves, which means the life expectancy is higher. Secondly, through migration, for example armed conflict has driven many people to desert fringe areas. Conflict also results in many people becoming homeless, which has happened to approximately 3 million people in the Darfur region of Sudan - these people will need many trees to rebuild homes and fences.
The climate of the Sahel has become much drier over the last 50 years. Less rainfall means poorer grazing and lower crop production, and prevents underground water reserves from recharging, which affects crop production further. The lack of precipitation causes the semi-arid desert fringe areas to slowly turn to desert.
In semi-arid areas such as the Sahel around 80% of domestic energy comes from burning firewood, and with population growth the demand for this increases. People use any trees that they find - either cutting down whole trees or stripping leaves and branches and leaving trees bare.
If trees are felled then there are fewer leaves to provide shade, so the soil dries out, and roots no longer bind the soil together, so soil erosion occurs and the loose top layer can blow away, or be washed away if it rains, leaving the soil exposed and vulnerable to desertification. The lack of leaf canopy also means that there is less leaf litter to return nutrients back into the soil, so it loses fertility further.
Poor farming practices
Poor farming practices cause the land to get stripped of all nutrients, leading to soil degradation which takes a long time to recover from. There are many reasons for this...
- Overgrazing - Many farmers in semi-arid regions are pastoral farmers and graze livestock. They either do this nomadically, meaning that they let their livestock graze in one area before moving on once the soil quality becomes poor, or they farm one site permanently. Overgrazing occurs when animals (in particular cattle and goats) are allowed to graze on one site for too long - they strip the vegetation so that there is nothing left to bind the soil together, so the soil blows away without the protective cover of vegetation, and they also trample the land, which leads to soil erosion.
- Overcultivation - population growth has out pressure on agricultural land to produce more and more food. This more intensive use of the land exhausts the soil of its nutrients so crops can no longer grow. This is a particular problem as many developing countries are dependant on growing water hungry cash-crops for export, which has led to aquifers and surface stores of water being drained.
- Monoculture - planting just one crop leads to a lack of nutrients in the soil, which results in soil infertility.
- Poor irrigation systems - these lead to an unsustainable use of water with lots lost through evaporation, which then leads to a build up of salt crusts. Irrigation often leads to over-abstraction of local water sources, which can lead to rivers and lakes drying up.