Explain the physical and human causes of land degradation and desertification, analyse their uneven impacts, and evaluate strategies for prevention and rehabilitation.

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.

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.

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.