The resulting systems were in a state of dynamic balance, maintaining both extensive diversity and balanced inter-relationships between the species represented. Extremely rapid change, of the type experienced in Australia since non-Aboriginal humans arrived, has markedly different effects. Land use practices and the introduction of new species of plant and animal have dramatically changed the face of much of Australia. Many of the introduced plants and animals, lacking any natural biological controls, have spread like the wildfires that have raged periodically since Aboriginal fire management practices were abandoned, wiping out indigenous species and leading to a dramatic reduction in diversity. In response, on occasion, we have attempted to introduce biological controls fom other places.
Nobody needs to be reminded about the problems posed by introduction of the cane toad.
But by far the most potent impact of non-Aboriginal society derives from the sheer number of people and the vast areas of land involved. In south eastern and south western Australia particularly, but in many parts of the country as well, few areas remain in which little change has occured. For a large country with a small population our record is deplorable in areas such as land degradation, deforestation, and species extinction. Per head of population we are also one of the top five producers of greenhouse gasses. Land clearing is a major contributor to this.