Biodiversity and threats to Australian ecosystems (SACE Stage 2 Outdoor Education)

What this dot point is asking

You must investigate the biodiversity of a chosen Australian natural environment and analyse the threats that degrade it. Examiners want you to move beyond listing species to explaining why an environment is biodiverse and how specific pressures break it down.

Measuring biodiversity

Biodiversity is studied at three levels. Genetic diversity is the variation within a species, which gives populations the capacity to adapt to change. Species diversity is the number and relative abundance of different species in a community. Ecosystem diversity is the range of habitats and ecological processes across a region. High biodiversity usually means greater resilience, because more species provide more pathways for energy and nutrients and more capacity to recover from disturbance such as fire, flood or drought.

Why Australian environments are fragile

Australia is an old, flat, dry continent with nutrient-poor soils. Many native species are highly specialised and slow to recover, so disturbances that a richer environment might absorb can cause lasting damage here. Long isolation also means native species often have no defences against introduced predators or competitors, which is why feral animals and weeds spread so destructively.

The major threats

Habitat loss and fragmentation from clearing, agriculture and urban growth is the single largest threat. When habitat is broken into small patches, populations become isolated, genetic diversity falls and local extinctions follow.

Introduced weeds such as bridal creeper, gorse and olive outcompete native plants, change soil chemistry and fuel hotter fires. Feral animals including foxes, cats, rabbits, goats and deer prey on native wildlife, strip vegetation and cause erosion.

Altered fire regimes are a distinctly Australian problem. Many native plants need fire to germinate, but fires that are too frequent, too rare, too hot or in the wrong season degrade the system. Traditional Aboriginal cool burning maintained a patchwork that many ecosystems still depend on.

Salinity, both dryland and irrigation-driven, has badly affected the River Murray and Coorong, raising water and soil salt levels and killing vegetation. Climate change adds rising temperatures, shifting rainfall, more extreme fire weather and sea level rise, compounding every other threat.

Reading threats in a real environment

For your investigation you gather evidence in the field. You might record weed cover along a transect, note feral animal signs such as diggings or scats, observe erosion on tracks and watercourses, or compare burnt and unburnt areas. Interpreting this evidence lets you judge which threats are most active in your chosen area and how they are changing it. You also consider historical and First Nations perspectives, since Country was actively managed for tens of thousands of years before recent threats arose.

Linking biodiversity to the rest of the course

Understanding biodiversity and its threats connects directly to conservation and land management, where you evaluate strategies to reduce these pressures, and to your journeys in Assessment Type 2, where minimal impact practices help protect the very biodiversity you have studied. It also grounds your reflection in Assessment Type 3, because connection to a place often grows from understanding what makes it special and vulnerable.