prolific, most often seen at waterholes at dawn and dusk. Huge flocks of budgerigars, cockatoos, corellas and galahs are often sighted. On bare ground or roads during the winter, various species of snakes and lizards bask in the sun, but they are rarely seen during the summer months. Feral animals such as camels thrive in central Australia, brought to Australia by pastoralists and explorers, along with the early Afghan drivers. Feral horses known as 'brumbies' are station horses that have run wild. Feral pigs, foxes, cats, goats and rabbits and other imported animals are also degrading the environment, so time and money is spent eradicating them in an attempt to help protect fragile rangelands. The Outback is home to a diverse set of animal species, such as the kangaroo, emu and dingo. The Dingo Fence was built to restrict movements of dingoes and wild dogs into agricultural areas towards the south east of the continent. The marginally fertile parts are primarily utilised as rangelands and have been traditionally used for sheep or cattle grazing, on cattle stations which are leased from the Federal Government. While small areas of the outback consist of clay soils the majority has exceedingly infertile palaeosols. Riversleigh, in Queensland, is one of Australia's most renowned fossil sites and was recorded as a World Heritage site in 1994. The 100 km2 (39 sq mi) area contains fossil remains of ancient mammals, birds and reptiles of Oligocene and Miocene age. Industry Pastoralism The largest industry across the Outback, in terms of the area occupied, is pastoralism, in which cattle, sheep, and sometimes goats are grazed in mostly intact, natural ecosystems. Widespread use of bore water, obtained from underground aquifers, including the Great Artesian Basin, has enabled livestock to be grazed across vast areas in which no permanent surface water exists naturally. Capitalising on the lack of pasture improvement and absence of fertiliser and pesticide use, many Outback pastoral properties are certified as organic livestock producers. In 2014, , most of which is in Outback Australia, was fully certified as organic farm production, making Australia the largest certified organic production area in the world. Tourism Tourism is a major industry across the Outback, and commonwealth and state tourism agencies explicitly target Outback Australia as a desirable destination for domestic and international travellers. There is no breakdown of tourism revenues for the "Outback" per se. However, regional tourism is a