Desertification

• Desertification is where land is turned into desert
• The UN definition = land degradation in arid, semi-arid and dry sub-humid areas resulting from various factors including climatic variations and human activities
• Refers to expansion of desert-like conditions to parts of the world where they should not occur according to the climatic belt
• Loss of biological potential of the land and desert-like landscapes and processes develop
• One of the most serious problems of today
• Affects more than a third of the land's surface and a fifth of the world population

Main causes of land degradation in arid areas: soil erosion, salination and deforestation.

• Increased frequency of fires (human too)
• Drought
• Climate change

• Overgrazing
• Increased frequency of fires
• Removal of crops and crop residues for food
• Population increase and more pressure on the land
• Climate change
• Soil erosion
• Over-cultivation resulting in loss of soil nutrients
• Deforestation for fuel wood or materials for construction
• Salinity caused by inappropriate irrigation

Population growth

Between 1968 - 1998, the population of the Sahel increased from 274 million to 628 million

- puts pressure on land for food

- leads to more overgrazing, over-cultivation, deforestation and irrigation

Overgrazing

If there are more people/nomadic pastoralists wandering over wide areas it means that vegetation is eaten, leading to soil erosion

Animals can trample the ground, compressing it and breaking down the structure of the soil so erosion is more likely.

Over-cultivation

Land use for agriculture has inc. by double in 40 years (1960-2000).

• People are trying to grow crops on less suitable land
• Means over-exploitation of the soil
• Nutrients are used up, making plant growth less likely
• Without plant roots, soil is easily eroded for deforestation

Deforestation

The cutting of trees means there's less leaf litter, humus. W/out humus, there's less moisture in the soil and less humus to bind the soil together. Less roots to hold the soil together so soil will be washed away or blown away. Demand for fuel has led some to switch to wood collection to earn a living, increasing deforestation.

• Depletes surface water
• Can involve unsustainable pumping of aquifers
• Water availability for plants decreases - leads to soil erosion
• Some surface irrigation where large amounts of water are added to the soil can increase salinity after evaporation and can wash top soil away

• Erosion of topsoil - reduced area of agricultural land
• As land area decreases, amount of food produced decreases - loss of livelihoods & causes famine
• Many have had to migrate from areas that can't support them any longer
• Tensions between settlement farmers and nomadic herders because fertile soil is scarce - leads to violence sometimes
• Changing conditions have led to animal migrations - e.g. rodents from the Sahara travelling further south, destroying crops and bringing new diseases

• Mauritania - only 200km wide ***** of agricultural land running across the country
• Niger - 2500km squared lost each year to desertification
• Niger - some areas produce less than a 20th of the food they could 40 years ago
• 2 million + people migrated from Mali and Burkina Faso as a result of desertification

• Planting hedges around food crops in Mali - Jatropha Curcas - grows in poor quality soil - isn't eaten by animals - roots help bind soil - protects soil from erosion - oil produced from plant sold - reduces poverty and erosion in area - plant also burnt as fuel, reducing need for deforestation
• Contour bunding - stones placed along contour lines across the slope - keeps rainfall there long enough for it to soak in - maximise water use - prevents soil erosion - increased some yields by 40% in Burkina Faso
• NGOs in Niger providing free seeds suitable for arid conditions to farmers - extensive root system - holds soil together - long roots absorb water deep in ground - less vulnerable form drought
• Efficient version of mogogo (traditional stove) introduced in Eritrea - 50% less wood needed - reduces need to cut down trees for fuel
• In Chad, introduced new stoves that run on manure - reducing deforestation - number of respiratory diseases decreased due to less smoke produced
• Educating villagers about importance of maintaining plenty of vegetation & helping grow seedlings - promote cooperation between villages - share techniques for good land management