Indonesia is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Sulawesi, Java, and parts of Borneo and New Guinea. Indonesia is the world's largest island country and the 14th-largest country by area, at 1,904,569 square kilometres, With about 270 million people, Indonesia is the world's fourth-most populous country.
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 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.
Indonesia is second only to Australia in terms of total endemic species, with 36% of its 1,531 species of bird and 39% of its 515 species of mammal being endemic. Tropical seas surround Indonesia's 80,000 kilometres of coastline. The country has a range of sea and coastal ecosystems, including beaches, dunes, estuaries, mangroves, coral reefs, seagrass beds, coastal mudflats, tidal flats, algal beds, and small island ecosystems. Indonesia is one of Coral Triangle countries with the world's most enormous diversity of coral reef fish, with more than 1,650 species in eastern Indonesia only.
British naturalist Alfred Russel Wallace described a dividing line between the distribution of Indonesia's Asian and Australasian species. It runs roughly north–south along the edge of the Sunda Shelf, between Kalimantan and Sulawesi, and along the deep Lombok Strait, between Lombok and Bali. Flora and fauna on the west of the line are generally Asian, while east from Lombok, they are increasingly Australian until the tipping point at the Weber Line. In his 1869 book, The Malay Archipelago, Wallace described numerous species unique to the area. The region of islands between his line and New Guinea is now termed Wallacea.
Indonesia's large and growing population and rapid industrialisation present serious environmental issues. They are often given a lower priority due to high poverty levels and weak, under-resourced governance. Problems include the destruction of peatlands, large-scale illegal deforestation, over-exploitation of marine resources, air pollution, garbage management, and reliable water and wastewater services. These issues contribute to Indonesia's low ranking in the 2020 Environmental Performance Index. The report also indicates that Indonesia's performance is generally below average in both regional and global context.
Indonesia reportedly has one of the fastest deforestation rates in the world. In 2018, forests cover approximately 49.7% of the country's land area, down from 87% in 1950. Starting in 1970s, and continuing up to the present day, log production, various plantations and agriculture have been responsible for much of the deforestation in Indonesia. Most recently, it has been driven by the palm oil industry. Such industries have been criticised for their environmental impact and displacement of local communities. The situation has made Indonesia the world's largest forest-based emitter of greenhouse gases. It also threatens the survival of indigenous and endemic species. The International Union for Conservation of Nature identified 140 species of mammals as threatened and 15 as critically endangered, including the Bali myna, Sumatran orangutan, and Javan rhinoceros.