Quick questions on Ecosystem vulnerability and resilience: HSC Geography

High biodiversity provides redundancy. If one species is lost, another can fill its functional role. Tropical rainforests with thousands of tree species lose less function from one species' decline than monocultures lose from the same pathogen.

Large ecosystems sustain larger populations, which are less vulnerable to extinction by chance events. Connectivity allows movement: species can shift range in response to climate change, recolonise after disturbance, and maintain gene flow.

Ecosystems near the edge of their climatic, hydrological, or geological envelope are vulnerable to small environmental shifts. Examples:

Ecosystems are adapted to historical patterns of disturbance. Slow change allows adaptation through migration, behavioural shift, or evolutionary change. Fast change exceeds adaptive capacity.

Some species have disproportionate roles in ecosystem function. Their removal triggers cascading change.

Ecosystems with longer histories of disturbance often have higher resilience because the species present have evolved to tolerate stress. Australian eucalypt forests are highly resilient to fire because they have co-evolved with fire over millions of years. Rainforests, which have not, are not resilient to fire and may not recover.

Ecosystems with high prior human pressure (clearing, pollution, fishing) have reduced resilience to additional stress. The Murray-Darling Basin is more vulnerable to drought now than pre-1788 because river regulation, wetland clearing, and invasive species have reduced resilience.