The Borneo rainforest is 130 million years old, making it the oldest rainforest in the world. There are about 15,000 species of flowering plants with 3,000 species of trees (267 species are dipterocarps), 221 species of terrestrial mammals and 420 species of resident birds in Borneo. There are about 440 freshwater fish species in Borneo (about the same as Sumatra and Java combined). It is the centre of evolution and radiation of many endemic species of plants and animals. The Borneo rainforest is one of the only remaining natural habitats for the endangered Bornean Orangutan. It is an important refuge for many endemic forest species, including the Asian Elephant, the Sumatran Rhinoceros, the Bornean Clouded Leopard, the Hose’s Civet and the Dayak Fruit Bat. The World Wide Fund for Nature has stated that 361 animal and plant species have been discovered in Borneo since 1996.
There are about 15,000 species of flowering plants with 3,000 species of trees (267 species are dipterocarps), 221 species of terrestrial mammals and 420 species of resident birds in Borneo. It is also the center of evolution and radiation of many endemic species of plants and animals. Subject to mass deforestation, the remaining Borneo rainforest is one of the only remaining natural habitat for the endangered Bornean Orangutan. It is also an important refuge for the Asian Elephant, the Sumatran Rhinoceros, the and the Bornean Clouded Leopard.
There are seven distinct ecoregions in Borneo. The Borneo lowland rainforests cover most of the island, with an area of 427,500 square kilometres (165,100 sq mi). Other lowland ecoregions are peat swamp forests, freshwater swamp forests, and mangrove forests. The Borneo mountain rainforests lie in the central highlands of the island, above the 1,000 meters elevation. The highest elevations of Mount Kinabalu include the Kinabalu mountain alpine meadow, an alpine shrubland notable for its numerous endemic species, including many orchids.
The high complexity of the Bornean tropical rain forest has created many niches that accommodate a rich diversity of fauna. Some fauna are specialised and some coexisted by having niche separation to avoid inter- and intra-specific competition within the same habitat.
There are 639 species of ants, 81 genera and 8 subfamilies of the Formicidae in Poring Sabah. There are 394 species of freshwater fish and 149 are endemic to Borneo. There are 100 species of amphibians. 105 species of lizards, in 35 genera from nine families, are now known from Borneo. The reticulated python is the biggest python in the world, and the longest snake in the world. This reptile can have a size of 9 m or more. The longer snakes have a size of ten meters. There are about 600 species of birds and 37 are endemic to Borneo. There are 288 species of terrestrial mammals in Borneo which is dominated by the chiroptera (102 species of bats) and rodentia (61 species of rats and mice), and 44 species are endemic to the island. There have also been 91 species of marine mammals recorded within the territorial boundaries of Malaysia, Indonesia and Brunei.