Indonesia's size, tropical climate, and archipelagic geography support one of the world's highest levels of biodiversity and is among the 17 megadiverse countries identified by Conservation International. Its flora and fauna is a mixture of Asian and Australasian species. The Sunda Shelf islands (Sumatra, Java, Borneo, and Bali) were once linked to mainland Asia and have a wealth of Asian fauna. Large species such as the Sumatran tiger, rhinoceros, orangutan, Asian elephant, and leopard were once abundant as far east as Bali, but numbers and distribution have dwindled drastically. Having been long separated from the continental landmasses, Sulawesi, Nusa Tenggara, and Maluku have developed their unique flora and fauna. Papua was part of the Australian landmass and is home to a unique fauna and flora closely related to that of Australia, including over 600 bird species.