Borneo, the third largest island in the world, is one of the mega-bio diversity hot spots with a myriad of plant and animal species, many of which are endemic to the island. The island of Borneo is well-known for its rich natural resources and lush tropical rainforests, providing an ideal natural habitat for thousands of wildlife; however this natural jungle was deemed as hostile to the Westerners who previously colonized North Borneo. The western part of Sabah is generally mountainous, containing the three highest mountains in Malaysia. The most prominent range is the Crocker Range which houses several mountains of varying height from about 1,000 metres to 4,000 metres. At the height of 4,095 metres, Mount Kinabalu is the highest mountain in South East Asia. Kinabalu National Park was inscribed as a World Heritage Site in 2000 because of its richness in plant diversity combined with its unique geological, topographical, and climatic conditions.
The central and eastern portions of Sabah are generally lower mountain ranges and plains with occasional hills. Kinabatangan River begins from the western ranges and snakes its way through the central region towards the east coast out into the Sulu Sea. It is the second longest river in Malaysia at a length of 560 kilometres. The forests surrounding the river valley also contains an array of wildlife habitats, and is the largest forest-covered floodplain in Malaysia. The areas of Lahad Datu, Sandakan and Kota Kinabalu are especially abundant with native as well as endemic plant and animal species. Sabah's forest is divided into four broad categories of vegetation type of habitat:
Coastal and Mangrove Forest – Includes mangrove forest, freshwater swamp forest, riverine forest and beach vegetation. These types of habitats are found from zero to 100 feet above sea level. The distribution is all along the coast and on major rivers in Sabah. Mangrove forests and swamp forests are important breeding grounds for fish and provide nesting and roosting sites for wetland birds such as egrets and herons. They are critical for the survival of Borneo's famous Proboscis Monkey.
Dipterocarp Forest – This type of habitat is sub-divided into three categories: The Lowland Dipterocarp Forest (100 - 500 feet above sea level), Upland Dipterocarp Forest (500 - 1,500 feet above sea level) and Highland Dipterocarp Forest (1,500 - 3,000 feet above sea level). Dipterocarp Forests are among the most diverse ecosystems on earth, and are home to most of Sabah's unique and famous wildlife species, such as orangutan and rhinoceros.
Heath forests and limestone forests – These are special lowland forest types. Although these forests may be low in stature, they are rich in unique plant species.
Montane Forest – This forest is sub-divided into Lower Montane Forest (3,000 - 4,500 feet above sea level) and Upper Montane Forest (4,500 - 11,000) feet above sea level). Upper montane habitat type in Sabah is basically restricted to Kinabalu and Trus Madi mountains. Many rare and restricted range species occur in these unique habitats.