The living world · GCSE Geography
Desertification in the Sahel
GCSE Geography revision on Sahel desertification: climate variability, overgrazing and population pressure as causes, and management through magic stones, zaï pits, afforestation and grazing control.
Desertification is land wearing out at the desert’s edge — drought loads the gun, overgrazing and fuelwood collection pull the trigger.
The important bits
What you need to know
- 1
The Sahel is the semi-arid belt south of the Sahara, from Senegal toward Sudan and the Horn. Rainfall is low, seasonal and unreliable. Desertification here means soil and vegetation degradation that reduces the land’s carrying capacity — not a cartoon of sand dunes marching south in a straight line.
- 2
Climate causes: multi-year droughts (famously the 1970s–80s), high variability from year to year, intense storms that crust bare soil, and a hotter climate that raises evapotranspiration. Natural variability and climate change both belong in the answer.
- 3
Overgrazing: herd sizes rise after good rains or as a store of wealth; animals strip cover around wells; hooves compact soil; infiltration falls; runoff rises; grass cannot recover. The well becomes a sacrifice zone.
- 4
Population pressure: more people means more fuelwood, more short-fallow cultivation on marginal plots, and ploughing of drought-prone land. Poverty reduces the option to leave land resting. This is social, not a blame-the-poor slogan — people farm the margin because the better land is taken or dry.
- 5
Other human causes: cash-crop pressure, insecure tenure that discourages long-term trees, and conflict that concentrates refugees and herds. Keep physical and human causes in separate sentences so the 6-marker is easy to mark.
- 6
Magic stones (diguettes): lines of stones along contours, widely taught from Burkina Faso. They slow runoff, trap soil and water, lift yields, and are buildable with local labour. Zaï pits (Yacouba Sawadogo and neighbours in Burkina) are the planting-hole cousin.
- 7
Afforestation and the Great Green Wall idea: trees as windbreaks, fodder, fuel and nitrogen-fixers (e.g. acacia). Success is patchy — survival rates, grazing of seedlings, and funding gaps. Agroforestry beats a single ceremonial tree-planting photo.
- 8
Management also includes rotational grazing, improved wells that do not create new sacrifice zones, drought-resistant crops, and early-warning for food security. Intermediate technology that farmers maintain beats imported kit that rusts.
Quotations worth analysing
Short evidence. Real method.
“Desertification is the degradation of land in arid, semi-arid and dry sub-humid areas, not simply the Sahara sliding south.”
Use this to kill the “sand dune invasion” myth. Examiners want soil, vegetation and productivity, not a Hollywood wall of sand.
“Lines of stones along the contour hold the rain where the crop can drink it.”
Name the place, the method, and the hydrological job: slow runoff, increase infiltration, trap silt. Then mention labour and maintenance.
“Drought stresses the Sahel; overgrazing and fuelwood collection decide whether the soil recovers.”
A 6-mark causes question should split climate from land use. One without the other is half an answer.
Go deeper
Causes without a blame cartoon
Start with rain that fails or arrives as a violent burst on bare ground. High temperatures lift evaporation. That is the physical load. Then add land use: more animals around a borehole strip the last grass; more households cut shrubs for cooking; farmers shorten fallow because they need this year’s grain. Compacted, crusted soil sheds the next storm, so even a wet year helps less. Population growth and poverty are linked, but writing “too many people” as a complete cause is lazy and often unfair: colonial cash crops, conflict and global food prices also squeeze the margin. In the exam, give one climate mechanism, one grazing mechanism, one fuelwood or cultivation mechanism. Three named processes beat a paragraph of adjectives such as “bad farming”.
Go deeper
Magic stones and zaï are hydrology you can build
A diguette is a contour bund of stones. Water that would have sheet-washed now ponds, drops sediment, and soaks. Yields of sorghum or millet can rise on the same rainfall because more of it becomes soil moisture. Zaï pits concentrate compost and water on each planting hole, a farmer-scale answer to crusted soils in Burkina Faso. These are intermediate technologies: local materials, labour-intensive, repairable. Limits: stones are heavy; badly aligned lines can concentrate flow and gully; they do not create rain in a decadal drought; and they need collective agreement along a slope. For 6 marks, describe the method, locate it, explain infiltration versus runoff, then add a limitation. That last clause is evaluation, which is where living-world answers often stall.
Go deeper
Trees are not a magic wall
The Great Green Wall is taught as a belt of trees across the Sahel. The working version is patchier and smarter: farmer-managed natural regeneration, acacia and other useful species, windbreaks, and fodder, not a continuous hedge from Dakar to Djibouti. Trees cut wind erosion, lift soil organic matter, and can fix nitrogen. Seedlings die if goats get there first, if the well is too far, or if a project ends when the photographer leaves. Afforestation without grazing rules is a temporary green headline. Pair trees with stone lines, compost pits and rights to the land, and you have a system. In 9-mark “assess management” answers, praise what farmers already proved (regreening in parts of Niger and Burkina) and refuse the idea that one megaproject will switch off desertification like a tap.
See the idea in action
Question: explain two causes of desertification and one management strategy in a named region. Region: Sahel (Burkina Faso). Cause 1: multi-year drought plus intense rain on bare soil. Cause 2: overgrazing around wells and fuelwood cutting that remove cover. Strategy: contour stone lines (magic stones) that slow runoff, trap silt and raise infiltration, plus zaï pits with compost. Limitation: stones do not replace rainfall in a severe drought; seedlings still need protection from goats. Judgement: climate stresses the system; land-use change decides recovery; intermediate tech helps where communities maintain it.
Exam technique
Turn knowledge into marks
Define desertification as land degradation, not “the desert moving”. Split causes into climate and human. Learn magic stones and one tree strategy with a named Sahel country. Add a limitation or you cap at mid-level.
Common mistakes
Do not give these marks away
- 01
Describing desertification as a wall of Sahara sand advancing on a map.
- 02
Giving only “overgrazing” with no climate variability, or only drought with no land use.
- 03
Naming the Great Green Wall as if a single row of trees has already solved the Sahel.
What are “magic stones” (diguettes) designed to do in the Sahel?
ACreate rainfall by cooling the air above the Sahara
BLie along contours to slow runoff, trap soil and increase infiltration so crops can use scarce rain
CFence the Sahara so dunes cannot physically cross
DReplace the need for any trees, grazing rules or compost
Show the answer
Lie along contours to slow runoff, trap soil and increase infiltration so crops can use scarce rain. They are a hydrological tool built from local stone. They improve the use of existing rainfall; they do not switch off drought or replace wider land management.
Quick questions
If this is the bit you searched
What is desertification?
The degradation of dryland soils and vegetation so the land produces less. It is not simply desert dunes moving into farmland.
Where is the Sahel?
A semi-arid belt along the southern edge of the Sahara, across West and north-central Africa, including countries such as Burkina Faso, Niger and Mali.
How does overgrazing cause desertification?
Animals remove plant cover and compact soil, especially around wells. Infiltration falls, erosion rises, and grass cannot recover between droughts.
What is the Great Green Wall?
A Sahel-wide restoration idea: trees, agroforestry and land management to restore degraded land. Progress is real in places and oversold as a single forest belt.