The causes of desertification on the margins of hot deserts; the role of climate change and human activity; the impacts on ecosystems, landscapes and populations; and strategies to manage and reverse it.

What this dot point is asking

AQA section 3.1.2 wants you to explain the causes of desertification on the margins of hot deserts, weigh the roles of climate change and human activity, set out the impacts on ecosystems, landscapes and people, and evaluate management strategies. This is the human-physical interface of the desert topic and a strong source of synoptic links to population and resource security.

What desertification is

It matters because desert margins, like the Sahel south of the Sahara, support large, fast-growing, mainly subsistence populations on naturally fragile land.

The causes

Desertification arises from the interaction of physical and human factors.

Physical factors:

• Declining and variable rainfall, with recurrent drought, reduces vegetation cover.
• High evaporation and fragile, low-organic soils are easily eroded once exposed.
• Climate change is shifting rainfall belts and increasing drought frequency, raising long-term vulnerability.

Human factors:

• Population growth intensifies demand for food, fuel and grazing.
• Overcultivation exhausts soil fertility and removes protective vegetation.
• Overgrazing by too many livestock strips ground cover and compacts soil.
• Deforestation for fuelwood removes roots that bind the soil.
• Poorly managed irrigation raises the water table and causes salinisation, poisoning the soil.

The factors reinforce each other: drought plus overgrazing degrades land far faster than either alone.

The impacts

The environmental impacts are loss of vegetation and biodiversity, soil erosion and falling soil fertility. The economic and social impacts fall hardest on subsistence communities: falling crop yields and grazing threaten food security, deepen poverty, cause malnutrition and can force migration (environmental refugees), increasing pressure on neighbouring land and towns and sometimes triggering conflict over shrinking resources.

Managing and reversing desertification

Effective management tackles both the symptoms and the underlying pressure:

• Afforestation and shelterbelts, such as the Great Green Wall initiative across the Sahel, stabilise soil, cut wind erosion and provide fuelwood.
• Soil and water conservation: contour bunds, terracing, zaï pits and small dams capture rainfall and rebuild fertility.
• Sustainable grazing and cropping: rotational grazing, drought-resistant crops and intercropping protect ground cover.
• Appropriate technology and microfinance make sustainable methods affordable for poor farmers.
• Tackling poverty and population pressure, including education and alternative livelihoods, addresses the root drivers.

Try this

Q1. Define desertification. [2 marks]

• Cue. The persistent degradation of land in arid, semi-arid and dry sub-humid areas, driven by climatic variation and human activity.

Q2. Explain two human causes of desertification. [4 marks]

• Cue. Overgrazing (livestock strip and compact the soil) and overcultivation or deforestation for fuelwood (remove protective vegetation, exposing soil to erosion).

Q3. Outline one strategy to manage desertification and one limitation. [3 marks]

• Cue. Afforestation/shelterbelts (Great Green Wall) stabilise soil and cut wind erosion; limitation: they need water, maintenance and time, and do not remove the underlying population pressure.