Although most of Australia is semi-arid or desert, it covers a diverse range of habitats, from alpine heaths to tropical rainforests. Because of the great age and consequent low levels of fertility of the continent, its extremely variable weather patterns, and its long-term geographic isolation, much of Australia’s biota is unique and diverse.
About 85% of flowering plants, 84% of mammals, more than 45% of birds, and 89% of in-shore, temperate-zone fish are endemic. Many of Australia’s ecoregions, and the species within those regions, are threatened by human activities and introduced plant and animal species.
The federal Environment Protection and Biodiversity Conservation Act 1999 is a legal framework used for the protection of threatened species. Numerous protected areas have been created to protect and preserve Australia’s unique ecosystems, 64 wetlands are registered under the Ramsar Convention, and 16 World Heritage Sites have been established. Australia was ranked 13th in the World on the 2005 Environmental Sustainability Index.
Most Australian plant species are evergreen and many are adapted to fire and drought, including the eucalypts and acacias. Australia has a rich variety of endemic legume species that thrive in nutrient-poor soils because of their symbiosis with Rhizobia bacteria and mycorrhizal fungi.
Well-known Australian fauna include monotremes (the platypus and echidna), and a host of marsupials, including the koala, kangaroo, wombat, and birds such as the emu, cockatoo, and kookaburra. The dingo was introduced by Austronesian people that traded with Indigenous Australians around 4000 BCE.
Many plant and animal species became extinct soon after human settlement, including the Australian megafauna; many more have become extinct since European settlement, among them the Thylacine (Tasmanian Tiger).