Environment. Although most of Australia is semi-arid or desert, it includes a diverse range of habitats from alpine heaths to tropical rainforests

Although most of Australia is semi-arid or desert, it includes a diverse range of habitats from alpine heaths to tropical rainforests, and is recognised as a megadiverse country. Because of the continent's great age, extremely variable weather patterns, and long-term geographic isolation, much of Australia's biota is unique and diverse. About 85 per cent of flowering plants, 84 per cent of mammals, more than 45 per cent of birds, and 89 per cent of in-shore, temperate-zone fish are endemic.^[171] Australia has the greatest number of reptiles of any country, with 755 species.^[172]

Australian forests are mostly made up of evergreen species, particularly eucalyptus trees in the less arid regions, wattles replace them in drier regions and deserts as the most dominant species.^[173] Among well-known Australian fauna are the monotremes (the platypus and echidna); a host of marsupials, including the kangaroo, koala, and wombat, and birds such as the emu and the kookaburra.^[173] Australia is home to many dangerous animals including some of the most venomous snakes in the world.^[174] The dingo was introduced by Austronesian people who traded with Indigenous Australians around 3000 BCE.^[175] Many plant and animal species became extinct soon after first human settlement, ^[176] including the Australian megafauna; others have disappeared since European settlement, among them the thylacine.^[177][178]

Many of Australia's ecoregions, and the species within those regions, are threatened by human activities and introduced plant and animal species.^[179] The federal Environment Protection and Biodiversity Conservation Act 1999 is the legal framework for the protection of threatened species.^[180] Numerous protected areas have been created under the National Strategy for the Conservation of Australia's Biological Diversity to protect and preserve unique ecosystems; ^[181][182] 65 wetlands are listed under the Ramsar Convention, ^[183] and 16 natural World Heritage Sites have been established.^[184] Australia was ranked 51st of 163 countries in the world on the 2010 Environmental Performance Index.^[185]

Climate change has become an increasing concern in Australia in recent years, and protection of the environment is a major political issue.^[186][187] In 2007, the Rudd Government signed the instrument of ratification of the Kyoto Protocol. Nevertheless, Australia's carbon dioxide emissions per capita are among the highest in the world, lower than those of only a few other industrialised nations.^[188] Rainfall in Australia has slightly increased over the past century, both nationwide and for two quadrants of the nation, ^[189] According to the Bureau of Meteorology's 2011 Australian Climate Statement, Australia had lower than average temperatures in 2011 as a consequence of a La Nina weather pattern, however, " the country's 10-year average continues to demonstrate the rising trend in temperatures, with 2002-2011 likely to rank in the top two warmest 10-year periods on record for Australia, at 0.52 °C above the long-term average".^[190] Water restrictions are frequently in place in many regions and cities of Australia in response to chronic shortages due to urban population increases and localised drought.^[191][192] Throughout much of the continent, major flooding regularly follows extended periods of drought, flushing out inland river systems, overflowing dams and inundating large inland flood plains, as occurred throughout Eastern Australia in 2010, 2011 and 2012 after the 2000s Australian drought.