British naturalist A.R. Wallace (1823-1913) postulated an imaginary line (named after him Walace's Line) as the dividing line between Asiatic and Australian fauna. It passes between Bali and Lombok islands and between Kalimantan and Sulawesi, then continues south of the Philippines and north of Hawaii. This theory explains the presence of species of fauna familiar to both Asia and Australia in Indonesia. However, there are spices indigenous to Indonesia, like the "orang utan" apes of Sumatra and Kalimantan, the giant "komodo" lizards, the one-horned rhinoceros of Java, the wild "banteng" oxen, tigers and many other species which are now protected in wildlife reserves. The flora Indonesia ranges from the tiny orchid the giant "Rafflesia" plant which has a bloom almost a metre (3.2 feet) in diameter, the largest flower in the world.

Agricultural products include rubber, coconut, coffee, tea, cocoa, corn, spices, kapok, tobacco, rice, etc. and an abundance of vegetable and fruit. Indonesia has some of the richest timber resources in the world and the largest concentration of tropical hardwoods. The total area of state-controlled forests is approximately 12,9 million hectares. Meranti constitutes about 56% of the entire timber export. Other varieties include ramin, agathis, teak, pinewood, rattan and bamboo.