Analyse the impacts of land cover change on biodiversity and ecosystem services, including habitat loss, fragmentation and degradation

What this dot point is asking

QCAA wants you to analyse how changing the land surface damages biodiversity and the services ecosystems provide. Biodiversity is the variety of life at three levels: genetic, species and ecosystem. Ecosystem services are the benefits people gain from ecosystems (clean water, pollination, climate regulation, coastal protection). "Analyse" means breaking the impact into mechanisms (habitat loss, fragmentation, degradation) and showing how they affect both biodiversity and human wellbeing. Strong answers use named Australian and global cases and connect ecological change to human consequences.

The answer

Biodiversity and ecosystem services

Biodiversity operates at three levels: genetic diversity (variation within a species), species diversity (the number and balance of species), and ecosystem diversity (the variety of habitats). Ecosystem services are grouped as provisioning (food, timber, water), regulating (climate, flood, disease control), supporting (soil formation, nutrient cycling) and cultural (recreation, spiritual, Indigenous connection to Country). Land cover change threatens both biodiversity and the services that depend on it.

Mechanism 1: habitat loss

Habitat loss is the outright removal of the cover a species needs. Clearing brigalow scrub removes the home of species adapted to it; draining a wetland removes habitat for water birds. Habitat loss is the leading cause of species decline in Australia. The brigalow belt's near-complete clearing left remnant species, including the bridled nailtail wallaby, restricted to tiny pockets of surviving vegetation.

Mechanism 2: fragmentation

Fragmentation breaks continuous habitat into isolated patches separated by cleared land, roads or farmland. Even where total habitat area is similar, fragmentation harms biodiversity by:

• Reducing patch size below what large or wide-ranging species need.
• Increasing edge effects (wind, weeds, predators and altered microclimate penetrate patch edges).
• Isolating populations, reducing gene flow and increasing local extinction risk.

Koalas in South East Queensland illustrate this. Urban growth corridors fragment eucalypt habitat, forcing koalas to cross roads and exposing them to vehicle strike and dog attack. Wildlife corridors are a planned response to reconnect fragments.

Mechanism 3: degradation

Degradation reduces the quality of remaining habitat without removing it entirely. Causes include weed invasion, altered fire regimes, grazing pressure, pollution, salinity and sediment runoff. The Great Barrier Reef catchment shows degradation at a continental scale: clearing and agriculture increase sediment, nutrient and pesticide runoff into reef waters, degrading water quality, smothering coral and feeding crown-of-thorns starfish outbreaks. The reef habitat persists but its quality and resilience decline.

From biodiversity loss to lost services

The analytical step QCAA rewards is linking ecological change to human consequences. When mangroves are cleared, coastal communities lose storm protection and nursery habitat for fisheries. When forests are cleared, water catchments lose filtration and local rainfall regulation. When pollinator habitat is fragmented, crop yields can fall. Biodiversity loss is not only an ecological problem; it removes services people depend on, which is why it appears in land management decisions.

Compounding with climate change

Climate change compounds these mechanisms. Warming oceans bleach the already-degraded Great Barrier Reef; shifting rainfall stresses fragmented populations that cannot migrate across cleared land. The combination of habitat fragmentation and climate change is especially damaging because species need to move to track suitable conditions but cannot cross hostile cleared land.

Examples in context

Example 1. Brigalow belt. Near-complete clearing caused habitat loss that pushed species like the bridled nailtail wallaby to the edge of extinction, surviving only in remnant reserves.

Example 2. South East Queensland koalas. Urban expansion fragments eucalypt habitat, isolating populations and increasing vehicle strike and dog attack; wildlife corridors are a planned response.

Example 3. Great Barrier Reef catchment. Clearing and agriculture degrade reef water quality through sediment, nutrient and pesticide runoff, reducing coral cover and resilience, with knock-on losses to tourism and fisheries services.