Australia's landmass of 7,617,930 square kilometres (2,941,300 sq mi)is on the Indo-Australian Plate. Surrounded by the IndianN4 and Pacific oceans, it is separated from Asia by the Arafura and Timor seas. The world's smallest continentand sixth largest country by total area,Australia—owing to its size and isolation—is often dubbed the 'island continent'and variably considered the world's largest island.Australia has 34,218 kilometres (21,262 mi) of coastline (excluding all offshore islands)and claims an extensive Exclusive Economic Zone of 8,148,250 square kilometres (3,146,060 sq mi). This exclusive economic zone does not include the Australian Antarctic Territory. Australia, as seen from spaceThe Great Barrier Reef, the world's largest coral reef,lies a short distance off the north-east coast and extends for over 2,000 kilometres (1,240 mi). Mount Augustus, claimed to be the world's largest monolith,is located in Western Australia. At 2,228 metres (7,310 ft), Mount Kosciuszko on the Great Dividing Range is the highest mountain on the Australian mainland, although Mawson Peak on the remote Australian territory of Heard Island is taller at 2,745 metres (9,006 ft). Australia is the flattest continent,with the oldest and least fertile soils;desert or semi-arid land commonly known as the outback makes up by far the largest portion of land. The driest inhabited continent, only its south-east and south-west corners have a temperate climate.The population density, 2.8 inhabitants per square kilometre, is among the lowest in the world,although a large proportion of the population lives along the temperate south-eastern coastline. Eastern Australia is marked by the Great Dividing Range that runs parallel to the coast of Queensland, New South Wales and much of Victoria – although the name is not strictly accurate, as in parts the range consists of low hills and the highlands are typically no more that 1,600 metres (5,249 ft) in height.The coastal uplands and a belt of Brigalow grasslands lie between the coast and the mountains while inland of the dividing range are large areas of grassland.These include the western plains of New South Wales and the Einasleigh Uplands, Barkly Tableland and the Mulga Lands of inland Queensland. The northern point of the east coast is the tropical rainforested Cape York Peninsula.The landscapes of the northern part of the country, the Top End and the Gulf Country behind the Gulf of Carpentaria, with their tropical climate, consist of woodland, grassland and desert.At the northwest corner of the continent is the sandstone cliffs and gorges of The Kimberley and below that the Pilbara while south and inland of these lie more areas of grassland, the Ord Victoria Plain and the Western Australian Mulga shrublands.The heart of the country is the uplands of central Australia while prominent features of the centre and south include the inland Simpson, Tirari and Sturt Stony, Gibson, Great Sandy, Tanami and Great Victoria Deserts with the famous Nullarbor Plain on the southern coast. The climate of Australia is significantly influenced by ocean currents, including the Indian Ocean Dipole and the El Niño-Southern Oscillation, which is correlated with periodic drought, and the seasonal tropical low pressure system that produces cyclones in northern Australia.These factors induce rainfall to vary markedly from year to year. Much of the northern part of the country has a tropical predominantly summer rainfall (monsoon) climate.Just under three quarters of Australia lies within a desert or semi-arid zone.The southwest corner of the state has a Mediterranean climate.Much of the southeast (including Tasmania) is temperate. Environment The koala and the eucalyptus form an iconic Australian pairMain article: Environment of Australia 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% of flowering plants, 84% of mammals, more than 45% of birds, and 89% of in-shore, temperate-zone fish are endemic.Australia has the greatest number of reptiles of any country, with 755 species. Australian forests are mostly made up of evergreen species, particularly eucalyptus trees in the less arid regions, Wattles replace them in dryer regions and deserts as the most dominant species.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.Australia is home to many dangerous animals including some of the most venomous snakes in the world.The dingo was introduced by Austronesian people who traded with Indigenous Australians around 3000 BCE.Many plant and animal species became extinct soon after first human settlement,including the Australian megafauna; others have disappeared since European settlement, among them the thylacine. 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 the legal framework for the protection of threatened species. Numerous protected areas have been created under the National Strategy for the Conservation of Australia's Biological Diversity to protect and preserve unique ecosystems;65 wetlands are listed under the Ramsar Convention,and 15 natural World Heritage Sites have been established.Australia was ranked 46th of 149 countries in the world on the 2008 Environmental Performance Index