This causation covers Desertification: A Seven-Step Cascade within Hot Deserts for GCSE Geography. Revise Hot Deserts in The Living World for GCSE Geography with 0 exam-style questions and 22 flashcards. This topic shows up very often in GCSE exams, so students should be able to explain it clearly, not just recognise the term. It is section 7 of 14 in this topic. Use this causation to connect the idea to the wider topic before moving on to questions and flashcards.
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⛓️ Desertification: A Seven-Step Cascade
Desertification is not the desert naturally spreading outward. It is the process by which fertile or semi-fertile land on the margins of deserts becomes permanently degraded through a combination of human pressure and climate change. It currently affects approximately 2 billion people globally and causes the loss of 12 million hectares of productive land per year — equivalent to losing an area the size of England every 18 months.
The Sahel region of sub-Saharan Africa (the semi-arid zone south of the Sahara, running from Senegal to Ethiopia) is the world's most severely affected area. The following cause-chain explains how desertification unfolds there — and the same logic applies wherever population pressure meets semi-arid conditions:
The Sahel's population has grown rapidly since the 1960s. More people need more food, more fuel, and more water. The land is pushed to — and beyond — its ecological limits. Niger's population grew from 3 million in 1960 to over 25 million in 2023; the land has not expanded with it.
More people means more livestock — but when animal numbers exceed the land's carrying capacity, vegetation is removed faster than it can regrow. In the Sahel, cattle, goat and camel numbers doubled between 1970 and 2000. Without vegetation, plant roots no longer bind the soil particles together.
Farmers in food-insecure areas cannot afford to leave land fallow for soil recovery. Continuous cropping removes nutrients and destroys soil structure. Sandy, nutrient-poor soils become dust.
Over 90% of sub-Saharan Africa's energy comes from biomass (firewood and charcoal). Trees are removed for fuel, leaving the ground bare. Tree roots that previously bound the soil are gone. Without leaf litter, soil organisms die and humus levels collapse — the soil loses its ability to hold water or support plant growth.
The Sahel has experienced severe droughts (most devastatingly, 1968–1973 and 1983–1985) that caused widespread famine. The IPCC projects a 5–10% decrease in mean Sahel rainfall by 2100, with increasing variability — more intense droughts followed by intense floods, neither of which benefits agriculture.
Bare, dry, loose soil is taken by wind. The Sahara's dust plume regularly reaches the Caribbean — satellite imagery shows African dust clouds thousands of kilometres out into the Atlantic. Once the thin topsoil layer (sometimes only 3–5cm) is removed, only bare rock or sterile subsoil remains.
At this point, the process becomes self-reinforcing. Less vegetation means less water retained means fewer plants can establish means more soil erosion means less vegetation. The land cannot recover without direct human intervention. Communities that depended on the land are forced to migrate — creating environmental refugees and placing pressure on already-stressed urban areas and neighbouring countries.