Indonesia’s vegetation is similar to that of the Philippines, Malaysia, and Papua New Guinea. There are some 40,000 species of flowering plants, including 5,000 species of orchids, as well as the monster flower (Rafflesia arnoldii [see Rafflesiaceae]), which is the world’s largest flower. There are more than 3,000 tree species, including durian, which bears large, armoured, odorous yet edible fruit; sandalwood; Shorea macrophylla, which yields illipe nuts, a fruit that contains a fat substance similar to cocoa butter; and valuable timber varieties such as teak and ironwood. Woody rattan (supplejack) vines are abundant in Indonesia’s forests. Thousands of plant species are exploited for economic purposes, either directly or indirectly.

The most important vegetation type is the mixed lowland and hill tropical rainforest, which occurs below 5,000 feet (1,500 metres). It is characterized by a large number of species, including high-canopied and buttressed trees and woody, thick-stemmed lianas (climbing plants). Epiphytes (plants that derive nourishment from the air and usually live on another plant) such as orchids and ferns, saprophytes (plants that live on dead or decaying matter), and parasites are well developed. Above 5,000 feet (1,500 metres) this forest gives way to temperate upland forest dominated by oak, laurel, tea, and magnolia species. Another typical feature of Indonesian vegetation is the mangrove forest, characterized by the formation of stilt- or prop-rooted trees, which grow only in salty or brackish water along muddy shores. Mangrove swamps are extensively developed along the shallow seas on eastern Sumatra, southern Kalimantan, and the southeastern segment of western New Guinea.

Indonesia is located in the transitional zone between two of the world’s major faunal regions: the Oriental of Asia in the west and the Australian of Australia and New Guinea in the east. The boundary of these realms, called Wallace’s Line, runs between Borneo and Celebes in the north and Bali and Lombok in the south. To the west, the Asian animal community includes such mammals as rhinoceroses, orangutans, tapirs, tigers, and elephants. Animals related to Australian fauna include birds such as cockatoos, bowerbirds, and birds of paradise, as well as marsupials such as bandicoots (small insectivorous, herbivorous marsupial mammals) and cuscuses (brightly coloured, woolly-haired arboreal marsupials).

Many of the islands contain endemic species. Among these are such birds as the Javanese peacock and the Sumatran drongo. A certain mountain goat, the Sumatran serow (Capricornis sumatraensis), lives on the rugged slopes of the Barisan Mountains of Sumatra. A unique species of proboscis monkey is endemic to Kalimantan, and the babirusa (a large wild pig) and the tamarau (a small wild ox with nearly straight horns) can be found only in Celebes. A giant lizard—the prehistoric Komodo dragon, which attains a length of 12 feet (3.7 metres)—lives on two small islands, Rinca and Komodo, between Sumbawa and Flores.

Some of these endemic species have become exceedingly rare. Most of the remaining single-horned Javan rhinoceroses, for example, are now restricted to the Ujung Kulon National Park on the western tip of Java. This nearly extinct species is one of the world’s most highly protected forms of wildlife. Another such endangered species is the orangutan, which is native to Borneo and Sumatra. Several orangutan rehabilitation centres and programs have been established in an effort to prevent the capture and slaughter of the animals and to train those that have been held captive to return to the wild.

Indonesia has an enormous and varied insect life that includes many unusual species. Examples include giant walkingsticks that can attain 8 inches (20 cm) in length, leaf insects (walking leaves), huge atlas beetles, elegant luna moths, and beautiful birdwing and swallowtail butterflies.

Thousands of species of fish are found in Indonesia’s inland waters, and hundreds of these are endemic to the region. Many freshwater and marine fish are used for food, while many others, such as small gouramis, barbs, and anemone fish (clown fish), are bred as ornamental aquarium fish. The unusual flying gurnard, with its oversized pectoral fins, is common off the coasts of Sulawesi.