Desertification and Soil Erosion: KS3 Geography Guide

Every minute, an area of fertile land the size of around 30 football pitches is lost to desertification worldwide. Across the Sahel in Africa, in northern China, and in parts of Central Asia, land that once fed communities is turning to dust. Understanding why this happens — and what can be done — is essential KS3 geography.

What is desertification?

Desertification is the process by which fertile land in semi-arid regions gradually becomes desert or semi-desert, losing its ability to support vegetation, agriculture, and human life. It is important to be precise: desertification does not mean the spread of natural deserts. It means land degradation — a human-driven and climate-driven deterioration of previously productive drylands on the margins of existing deserts.

Closely linked is soil erosion: the removal of the topsoil layer — the thin, nutrient-rich upper layer of earth — by wind or water. Topsoil takes hundreds of years to form naturally but can be stripped in a single storm. Once gone, the land beneath is far less fertile, more prone to compaction, and far more susceptible to further degradation.

Together, desertification and soil erosion affect roughly 40% of Earth's land surface — the world's drylands — and threaten the livelihoods of over two billion people.

Where does desertification occur?

Desertification is not confined to a single region. It affects semi-arid zones across multiple continents — places already marginal for agriculture, where any additional stress can push land over the edge into irreversible decline.

The most intensively studied example is the Sahel — a broad belt of semi-arid savannah running 5,400 km across Africa from Senegal and Mauritania in the west to Sudan and Ethiopia in the east, lying between the Sahara Desert to the north and the wetter tropical savannah to the south. Countries across the Sahel — Mali, Niger, Burkina Faso, Chad, Sudan — are among the world's poorest and most food-insecure, partly as a direct result of land degradation.

Other major affected regions include:

Northern China: The Gobi Desert is expanding southwards, threatening farmland in Inner Mongolia and Gansu Province, and generating devastating dust storms that periodically blanket Beijing.

Central Asia: The near-total drying-up of the Aral Sea — once the world's fourth-largest lake, now largely a salt desert — stands as one of the worst environmental disasters in human history, caused by unsustainable irrigation of cotton crops during the Soviet era.

The Mediterranean region: Spain, Greece, and Portugal face serious desertification risk, accelerated by hotter and drier summers linked to climate change.

Parts of sub-Saharan Africa, the Indian subcontinent, and central Australia are all significantly affected.

Causes of desertification and soil erosion

Desertification is almost always caused by a combination of climate pressures and human activities acting simultaneously on already-fragile dryland ecosystems.

Cause | Mechanism | Affected region example
Climate change | Reduced and more erratic rainfall; higher temperatures increase evaporation; longer and more frequent droughts | Sahel — rainfall patterns have become markedly less predictable since the 1970s
Overgrazing | Too many livestock strip vegetation; bare ground hardens and compacts; roots no longer hold soil | Sahel; Inner Mongolia (China)
Deforestation | Removing trees exposes soil to rain impact and wind erosion; tree roots no longer bind soil or draw up moisture | Sahel; Mediterranean coast
Over-cultivation | Growing the same crops repeatedly without rest depletes soil nutrients; removing hedgerows increases wind erosion | Parts of India; Sahel margin
Unsustainable irrigation | Waterlogging and salinisation (salt accumulation as irrigation water evaporates) render soil infertile | Aral Sea basin (Central Asia); Indus Valley
Population pressure | Growing populations on fragile dryland ecosystems exceed the land's carrying capacity | Niger and Mali — among the world's highest population growth rates

A critical concept here is the positive feedback loop: less vegetation means less moisture is retained in the soil and released into the atmosphere, leading to less rainfall, which in turn kills more vegetation. Desertification can become self-reinforcing once it passes a threshold, making recovery without deliberate intervention extremely difficult.

SEEP consequences of desertification

Social: Food insecurity and famine risk are the most immediate social consequences. The Sahel famines of 1972–73 and 1984–85 killed hundreds of thousands and were closely linked to accelerating land degradation. When farmland fails, communities face stark choices — adapt in place or leave. Many become environmental refugees, forced to migrate to cities or across borders. Competition for remaining fertile land and shrinking water resources has driven inter-communal violence across the Sahel. Lake Chad — once shared by Niger, Nigeria, Chad, and Cameroon — has shrunk by approximately 90% since the 1960s, triggering conflict among communities that depended on it.

Economic: Lost agricultural productivity reduces national income in already-poor countries. Niger — one of the world's poorest nations — has seen vast areas of farmland abandoned as yields have collapsed. Restoring degraded land is extremely expensive and slow. Countries must spend scarce foreign exchange importing food they once grew domestically, deepening economic vulnerability.

Environmental: The positive feedback loop described above means desertification can accelerate beyond any easy reversal point. Massive dust storms carry Saharan soil across the Atlantic to the Caribbean and occasionally reach the UK, periodically turning British skies orange. Soil contains vast quantities of stored carbon; when it degrades, this carbon is released as CO₂, amplifying the very climate change that is driving further desertification. Biodiversity is lost as dryland habitat disappears and species lose their range.

Political: The scale of the crisis has prompted major international responses. The Great Green Wall — an African Union initiative to restore 100 million hectares of degraded land across the Sahel by planting and restoring an 8,000 km belt of vegetation from Senegal to Djibouti — is one of the world's most ambitious environmental projects. The UNCCD (United Nations Convention to Combat Desertification) provides the international legal framework. However, debates about land tenure — who legally has the right to use and manage particular land — remain politically contentious in many affected countries, often slowing restoration efforts.

Responses and solutions

The Great Green Wall is the most ambitious current response. As of the mid-2020s, roughly 18% of the target area has been restored, with Ethiopia, Nigeria, and Senegal leading progress. The project has evolved from a literal wall of trees — which failed in some areas where non-native species were planted — to a broader mosaic of restored landscapes that incorporates traditional land management practices.

At the community scale, traditional techniques are proving remarkably effective. In Burkina Faso, farmers have revived an ancient Mossi technique called zaï pits — small planting holes dug by hand to collect rainwater and concentrate organic matter around seeds. Satellite imagery shows millions of hectares of land across the Sahel gradually re-greening in areas where this technique has spread. Contour farming — ploughing along hillside contours rather than straight down the slope — dramatically reduces surface runoff and soil loss.

Other effective responses include rotational grazing (moving livestock regularly to allow vegetation to recover), afforestation (planting trees to bind soil and restore moisture cycles), and water harvesting (small earth dams and channels to collect and distribute rainfall). The key geographical insight is that the most effective solutions tend to be rooted in local knowledge and adapted to specific places — there is no single universal template that works everywhere.

Frequently asked questions

What is the difference between a natural desert and desertification?

A natural desert — such as the Sahara or the Gobi — has always been arid; it is the product of long-term climatic patterns operating over millions of years. Desertification is different: it is the degradation of formerly productive land in semi-arid regions, caused by a combination of human activity and climate change. The Sahel, which borders the Sahara, was never a desert — it supported farming and grazing communities for centuries. It is being degraded into a desert-like state through overgrazing, deforestation, and changing rainfall patterns.

What are the main causes of desertification in the Sahel?

The Sahel's desertification results from multiple interacting causes. Climate change has made rainfall less reliable and temperatures higher. Overgrazing has stripped vegetation as herd sizes grew with rising populations. Deforestation has removed the trees that bound the soil and recycled moisture. Over-cultivation has exhausted soil nutrients. Population growth has increased pressure on already-fragile land beyond its carrying capacity. Crucially, poverty limits farmers' ability to invest in soil conservation measures. These causes reinforce each other — addressing one in isolation is rarely sufficient without tackling the others.

What is salinisation, and why does it cause soil degradation?

Salinisation is the build-up of salt in the soil, caused by poor irrigation management. When irrigation water evaporates from fields, it leaves behind dissolved salts. Over time, salt concentrations reach levels that are toxic to most food crops, and the land becomes effectively useless. The Aral Sea basin in Central Asia is the starkest example: Soviet-era irrigation of cotton fields caused such severe salinisation that vast areas of formerly productive farmland became white salt flats. Salinisation is effectively permanent on human timescales — there is no practical way to remove the accumulated salt once it has built up.

What is the Great Green Wall, and how successful has it been?

The Great Green Wall is an African Union initiative, launched in 2007, to restore 100 million hectares of degraded land across the Sahel by 2030 through an 8,000 km belt of restored vegetation stretching from Senegal to Djibouti. It aims to provide food security, jobs, and climate resilience for 100 million people. Progress has been uneven — Ethiopia and Senegal have led — and the project has matured from a literal wall of trees into a broader landscape-restoration programme that incorporates traditional practices like zaï pits. As of the mid-2020s, around 18% of the target area had been achieved, with funding and political commitment remaining the main constraints.

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