 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 . Fungi typify that diversity ; an estimated 250 @,@ 000 species — of which only 5 % have been described — occur in Australia . Because of the continent 's great age , extremely variable weather patterns , and long @-@ term geographic isolation , much of Australia 's biota is unique . 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 . 
