What causes desertification and what are its impacts on people and the environment?
the processes and human activities causing desertification as a form of land cover change, and the impacts of and responses to desertification
A VCE Geography Unit 3 answer on desertification: the natural and human processes degrading drylands, the impacts on people and environment, and responses, using the African Sahel and inland Australia as case studies.
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What this dot point is asking
VCAA wants you to explain desertification as a land cover change, distinguish the natural and human processes that cause it, evaluate its impacts on people and the environment, and assess responses. Use a precisely located case study with data.
What desertification is
Desertification is land degradation in arid, semi-arid and dry sub-humid areas, where vegetation cover is lost and fertile land takes on the characteristics of desert. It is not the natural expansion of existing deserts but the creation of desert-like conditions on once-productive land, usually at the margins of drylands where rainfall is low and variable.
Causes: natural and human processes
- Drought and climate variability reduce rainfall and stress vegetation, the natural trigger.
- Overgrazing by too many livestock strips the protective plant cover, exposing bare soil.
- Overcultivation exhausts soil nutrients and structure when land is farmed too intensively.
- Deforestation and fuelwood collection remove trees that anchor soil and retain moisture.
- Poor irrigation can cause salinisation, where salts accumulate in the soil and poison plants.
- Population pressure intensifies all of these as more people demand food, fuel and grazing from fragile land.
Case study: the African Sahel
The Sahel is a semi-arid belt stretching across Africa just south of the Sahara, through countries including Mali, Niger, Chad and Sudan. It suffers from highly variable rainfall and recurrent drought, most severely in the 1970s and 1980s, when crops failed and famine killed many people. A rapidly growing population has expanded cropping and herding onto marginal land, while fuelwood collection has stripped tree cover. Together, drought and human pressure have degraded large areas of soil.
Impacts on the environment
Desertification removes vegetation, so soil is exposed to wind and water erosion and can be blown or washed away. Soil fertility, structure and moisture decline, making recovery slow or impossible. Biodiversity falls as habitat is lost. Dust storms increase, and loss of vegetation reduces the land's ability to store carbon, adding to climate change.
Impacts on people
Degraded land produces less food, so crop yields and livestock numbers fall, threatening food security and incomes for some of the world's poorest people. This can drive hunger and, in severe cases, famine. Loss of livelihoods pushes people to migrate to cities or across borders, and competition for shrinking productive land can fuel conflict. Communities lose the natural resource base on which their culture and survival depend.
Responses to desertification
- Sustainable land management, including rotational grazing, terracing and leaving land fallow, lets soil recover.
- The Great Green Wall initiative aims to restore a band of vegetation across the southern edge of the Sahara to hold back degradation.
- Reforestation and water harvesting, such as planting trees and building small stone barriers (zai pits and demi-lunes) in Niger and Burkina Faso, trap water and rebuild soil.
- The United Nations Convention to Combat Desertification (UNCCD) coordinates international funding and policy.