With an area of over 700.000 square kilometers, Borneo is the third largest island in the world, stretching from about 4° south of equator to 7° north. Politically, Borneo is divide amongst three countries: Malaysia (the state of sabah and sarawak), Indonesia (the province of west,south,east and central Kalimantan) and Brunei.
Large tracts of Borneo, particularly the southern and eastern region, consist of hilly lowlands and swampy plains. The central and north western region are dominated by rugged mountain ranges with peak rising to between 1000 and 2000 m above sea level. Gunung Kinabalu,, at 4101 m, is the highest peak between the Himalayas and New Guinea.
Most of the island consist of geologically young sedimentary rock, including sandstones, mudstones and limestones. There are some volcanic rock, including in south eastern sabah, but no active volcanoes. The meratus mountain in South Kalimantan, the Schwaner mountains which straddle the boundary between inland Central and West Kalimantan, and scattered mountain in Sabah are of igneous rocks.
The natural vegetation of most of Borneo consist of evergreen rainforest of various types. Soil characteristics seem to be very important in influence forest composition. The amount and pattern of rainfall varies from place to place, but most area receive between 200 to 400 cm per year, with an average of at least 10 cm in most months. Mean temperature are roughly the same in all areas, for a given altitude, with a typical daily maximum of 30°C in the lowlands.
Tall lowland and hill forest up to about 1000 meters altitude are dominated by trees of the family Dipterocarpaceae. This family includes most of the commercially important timber trees. Many other type of tress occur, along with woody climbing plants. Small flowering plants and ferns grow as epiphytes on the larger trees.. This dipterocarp forest supports the highest diversity of mammals, and coastal and riverside areas are generally richer than the steeper hills in the interior.
In some areas, particularly substantial section of Sarawak and Brunei, the soil consist mainly of coarse silica which is poor in nutrients. The forest is lower, more open and more uniform in structure, and the stream are often stained dark reddish. Few mammals live in these heath or kerangas forests.
Much of the coast of Borneo is fringed by mangrove and nipah palm. In many areas further inland, extensive freshwater swamp occur. Peat swamp forest, where the soil consists largely of acidic organic material, are found in some area, especially between Sei . Kapuas in West Kalimantan and the Sei. Tutong in Brunai. This forest supports few mammal.
Lower stature montane forest replaces dipterocarp forest on hills and mountains at an average altitude of about 1000 meters, although the interface is lower in small mountains, and higher in extensive ranges and on large mountains. In some areas the division between dipterocarp and montane forest is distinct, while in others there is a more gradual reduction in forest stature with increasing altitude.
Traditionally, most of Borneo’s native peoples have been shifting cultivators, both in coastal and lowland riverine and in the upland far from the coast. As a result , the vegetation in many part of the island consist of a patchwork of essentially undisturbed forest, low stature forest in various stages of regeneration, and clear areas. On many steep on and upland areas where agriculture has been tried, the thin topsoil is inadequate to support regrowth of forest, and there are now extensive tracts of coarse lalang grasss which are unprodutive and vitually useless for both wildlife and Man. In some areas, attempts are being made to make such land productive again by planting exotic trees tolerant of poor conditions.
The most extensive and rapid change in Borneo’s vegetation has occured over the past 20 years or so through selective logging of the dipterocarp forest. Selective logging involves the removal of only trees from the forest, but in the process many smaller trees are killed or damaged. Regeneration of selectively logged forest to a state approaching its original condition may take decades.
Permanent agriculture is practised only in the lowland and more fertile upland valley in Borneo. It take many forms, ranging from wet rice paddies and small holding with mixed crops including fruit trees, vegetables and pepper, to large scale plantation of cocoa, oil palm and rubber.
Source:A Field Guide to the Mammals of Borneo by J. Payne, C.M. Francis and K. Phillipps (1985)