Land Degradation and Desertification (SACE Stage 2 Geography Environmental Change)
“Explain the physical and human causes of land degradation and desertification, analyse their uneven impacts, and evaluate strategies for prevention and rehabilitation.”
Land degradation is the long-term decline in the productive capacity of land, and desertification is land degradation in dryland regions. Both come from a mix of physical conditions and human pressure: overgrazing, overcultivation, deforestation, salinity and drought. SACE answers must explain these causes, analyse why degradation concentrates in particular places and harms particular communities, and evaluate prevention and rehabilitation strategies, using real Australian and global cases.
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What this dot point is asking
This dot point belongs in Topic 1, Environmental Change, and is distinct from land cover change because it focuses on the loss of land quality rather than simply a switch in cover type. The key geographical idea is that degradation is driven by the interaction of natural vulnerability and human land use, which is why it clusters in fragile dryland margins.
What degradation and desertification are
Land degradation reduces the land's ability to support plants, animals and people. It includes soil erosion, salinity, acidification, loss of nutrients and compaction. Desertification is the specific case where dryland soils lose productivity until the land takes on desert-like conditions. Importantly, desertification does not mean deserts physically advancing; it means previously productive dryland becoming unproductive.
Physical and human causes
Degradation usually results from human pressure on land that is naturally vulnerable.
- Overgrazing strips vegetation that holds soil together, exposing it to wind and water erosion.
- Overcultivation and continuous cropping exhaust soil nutrients and structure.
- Deforestation and clearing remove roots and canopy, accelerating erosion and runoff.
- Irrigation without drainage raises water tables and brings salt to the surface, causing dryland and irrigation salinity.
- Drought and climate variability reduce vegetation cover and increase pressure on remaining land.
In Australia, salinity is a major form of degradation. Clearing deep-rooted native vegetation for shallow-rooted crops and pasture allowed water tables to rise and mobilise stored salt, damaging soils and waterways in regions such as the Murray-Darling Basin and the WA wheatbelt.
About two-fifths of the world's land is drylands, and these margins, where rainfall is low and variable, are the most vulnerable to desertification. Regions such as the African Sahel, parts of central Asia and much of inland Australia carry the highest risk. Recognising that degradation concentrates where natural vulnerability meets human pressure is the core spatial insight examiners reward.
Uneven spatial and social impacts
The Sahel, a semi-arid belt south of the Sahara, is the classic case: population growth, overgrazing and recurrent drought have degraded vast areas, reducing food production and contributing to migration and conflict. In Australia, degradation reduces farm productivity, damages infrastructure through salinity, and silts rivers. The communities least able to absorb these losses, including subsistence farmers and pastoralists, are hit hardest, while wealthier producers can invest in remediation or move on.
Consequences across the three systems
Environmentally, degradation reduces soil fertility, biodiversity and water quality, and can become self-reinforcing as bare soil resists revegetation. Socially, it threatens food security and can displace rural populations, creating environmental migrants. Economically, it cuts agricultural output, raises remediation costs and lowers land values.
Evaluating prevention and rehabilitation strategies
Strategies work at the farm, catchment and national scale.
- Sustainable grazing and rotational cropping reduce pressure but require changes in farmer behaviour.
- Revegetation and replanting deep-rooted natives lower water tables and bind soil, though benefits take years.
- Contour banks, windbreaks and conservation tillage limit erosion at relatively low cost.
- Large-scale projects, such as Africa's Great Green Wall, aim to restore degraded land across the Sahel, but progress has been uneven and depends on funding and local participation.
- Improved irrigation and drainage management tackles salinity but is expensive.
Do not describe desertification as deserts physically expanding or treat it as a purely natural process. The dot point asks you to explain the interaction of physical vulnerability and human land use, show why degradation concentrates on dryland margins, and evaluate management strategies with evidence. Ignoring the human drivers, or listing strategies without judging them, will limit your marks.
Degradation questions reward separating physical from human causes, then tracing impacts and judging management. Work it in steps.
Step 1: define and locate
State that degradation is a long-term decline in productive capacity and desertification is its dryland form, then name a region such as the Sahel or the Murray-Darling Basin.
Step 2: separate physical and human causes
List natural vulnerability (low, variable rainfall, fragile soils) and the human pressure that triggers degradation (overgrazing, overcultivation, clearing, irrigation salinity). The interaction is the key insight.
Step 3: trace impacts across the three systems
Move through environmental (erosion, lost fertility), social (food insecurity, migration) and economic (lower output, remediation cost) consequences.
Step 4: evaluate at least one strategy
Judge a response such as revegetation or the Great Green Wall, weighing benefit against cost and time. A clear verdict, not a list, is what the top band rewards.
Linking it together
A complete response defines degradation and desertification precisely, explains the physical and human causes, shows why the problem concentrates on vulnerable dryland margins such as the Sahel and inland Australia, traces consequences through the three systems, and evaluates prevention and rehabilitation strategies. That structure matches the geographical skills and applications criteria the SACE Board assesses.
Exam-style questions
Questions in the style of SACE Board exam questions on this dot point, each with a worked answer. They are written by ExamExplained unless tagged "Past paper"; the year shows the paper a question is modelled on.
SACE 2021-style5 marksExplain the physical and human causes of desertification in a dryland region you have studied.Show worked answer →
A 5 mark explain response needs a named dryland region and clear cause chains separating physical from human factors.
Name the region. Use a specific case such as the African Sahel or inland Australia rather than "drylands" generally.
Physical causes. Explain natural vulnerability: low and variable rainfall, recurrent drought and fragile soils that lose vegetation cover easily.
Human causes. Explain pressure that tips vulnerable land into degradation: overgrazing strips protective vegetation, overcultivation exhausts soils, and firewood collection or clearing removes roots and canopy.
Markers reward a named region, the interaction of physical vulnerability with human land use, and clear cause-and-effect rather than a list of terms.
Practice8 marksUsing data you have studied on land degradation trends and rehabilitation efforts in a region over time, analyse the impacts of degradation and evaluate the effectiveness of the rehabilitation strategies.Show worked answer →
An 8 mark source-and-evaluate response needs data reading, analysed impacts across the three systems, then a judgement.
Analyse impacts. Read the trend from the data and trace consequences environmentally (lost fertility, biodiversity, water quality), socially (food insecurity, displacement) and economically (lower output, remediation cost).
Evaluate strategies. Weigh the rehabilitation shown (for example revegetation, the Great Green Wall, contour banks or improved drainage) against the data: did degradation slow or reverse after they began? Concede limits such as cost, slow benefits and the need for local participation.
Judgement. Conclude how effective the response has been on the evidence. Markers reward exact use of the supplied data, impacts across all three systems and a weighed verdict.
Practise this
Sources & how we know this
- Stage 2 Geography subject outline (2025 onwards) — SACE Board
- Stage 2 Geography: external assessment — SACE Board