| Borneo lowland rain forests | |
|---|---|
.jpg) Primary lowland forest atDanum Valley, Sabah | |
 Map of theBorneo lowland rain forests ecoregion | |
| Ecology | |
| Realm | Indomalayan |
| Biome | tropical and subtropical moist broadleaf forests |
| Borders | |
| Geography | |
| Area | 425,124 km2 (164,141 mi2) |
| Countries | |
| Conservation | |
| Conservation status | vulnerable,[1] nature could reach half protected[2] |
| Protected | 6.267%[3] |
TheBorneo lowland rain forests is anecoregion, within thetropical and subtropical moist broadleaf forestsbiome, of the large island ofBorneo in Southeast Asia.[1] It supports approximately 15,000 plant species, 380 bird species and several mammal species. The Borneo lowland rain forests is diminishing due to logging, hunting and conversion to commercial land use.
The Borneo lowland rain forests cover an area of 428,438 square kilometers, about 57% of Borneo's land area. They cover most of the island below 1000 meters elevation. Borneo is divided between Indonesia, Malaysia, and Brunei, and the lowland rainforests extend into all three countries.[3]
Other ecoregions cover portions of lowland Borneo, including theBorneo peat swamp forests,Southwest Borneo freshwater swamp forests, andSundaland heath forests. These other lowland ecoregions formed over specific soil conditions, and are home to distinct communities of plants and animals. TheSunda Shelf mangroves fringe the island's shores.[1]
The highlands of Borneo are home to theBorneo montane rain forests, which are distinct from the lowland forests in both forest structure and species composition.[1]
The lowlands are distinguished by climate (as the eastern side of the island is drier) or separated by the largeKapuas River andBarito River, which prevent animals and reptiles from spreading freely around the island.
Lowland Borneo has a stabletropical wet climate, with monthly rainfall exceeding 200 millimetres (7.9 in) throughout the year, and a temperature that rarely varies by more than 10°C.[1]
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The lowlands of Borneo are home to the richestrainforest in the world. The climate provides an ideal growing environment for approximately 10,000 species of plant (more than in the whole continent of Africa). Among these are some 2,000 species oforchids and 3,000 species of trees, including 267 species of dipterocarps (familyDipterocarpaceae), of which 155 are endemic to Borneo. This makes the island the center of the world's diversity for dipterocarps.[1]
Mixed dipterocarp forests, including lowland and hill forests, are the predominant plant community. The forests have a closed canopy 24 to 36 meters high, with emergent trees up to 65 meters tall extending above the canopy. Dipterocarps are the most common emergents, comprising up to 80% of the emergent stratum. The dipterocarp generaDipterocarpus,Dryobalanops, andShorea are typically emergents, while the dipterocarp generaHopea andVatica are common canopy trees.Koompassia excelsa (Fabaceae) is an emergent tree with a distinctive white trunk that can reach up to 85 meters high. Trees from the plant familiesBurseraceae andSapotaceae are also common in the canopy.[1]
There is an understorey stratum under the canopy, composed of shade-tolerant trees draped withlianas andepiphytic orchids and ferns. Understorey trees are commonly of the plant familiesEuphorbiaceae,Rubiaceae,Annonaceae,Lauraceae, andMyristicaceae.Cauliflory – trees which bear flowers and fruits on their trunks – is common among understorey trees, including the forest durian (Durio testudinarius).Forest floor plants include five species of the strong-smelling parasiteRafflesia, one of which,Rafflesia arnoldii, has flowers over a metre wide, making it the world's largest flower.[1]
The limestone uplands of theSangkulirang Peninsula and Sarawak support their own particular plant communities, as do the Labi Hills on the Brunei-Sarawak border.[1]
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The wildlife of this ecoregion consists of a large number of forest animals ranging from the world's smallest squirrel, theleast pygmy squirrel, to the largest land mammal in Asia, theAsian elephant. It includes the critically endangeredSumatran rhinoceros, the endangered and iconicBornean orangutan, twelve other species of primate,Bornean bearded pigs andBornean yellow muntjac deer. The primates of Borneo are: three apes (Bornean orangutan,Müller's Bornean gibbon andBornean white-bearded gibbon), fivelangurs, thesouthern pig-tailed macaque,long-tailed macaque,Horsfield's tarsier (Tarsius bancanus),Bornean slow loris (Nycticebus borneanus),Kayan slow loris (Nycticebus kayan),Philippine slow loris (Nycticebus menagensis),Bangka slow loris (Nycticebus bancanus), and the endangeredproboscis monkey (Nasalis larvatus). There are no tigers on Borneo; carnivores include the endangeredBornean clouded leopard (Neofelis diardi borneensis), thesun bear (Helarctos malayanus), theotter civet (Cynogale bennettii), and several othermustelids andviverrids.[1]
The 380 species of birds include eighthornbills, eighteenwoodpeckers and thirteenpittas. There are nine near-endemic and two endemic birds; theblack-browed babbler (Malacocincla perspicillata) and thewhite-crowned shama (Copsychus stricklandii). Among the rich variety of reptiles and amphibians are crocodiles and theearless monitor lizard (Lanthanotus borneensis). The sounds of the forest vary from day to night as different combinations of these birds and animals emerge to roam and feed.[1]
During thePleistocene glacial epoch, all of Borneo,Java,Sumatra, and mainlandIndochina were part of the same landmass, calledSundaland. This allowed plants and animals to migrate from one region to the next. Now Borneo is separated from theMalay Peninsula and the islands, but it still shares a lot of the same plant and animal diversity, while Sulawesi has less Borneo wildlife.
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Logging and conversion of natural forests to rubber, oil palm and industrial timber plantations and for small-scale farming have given rise to significant deforestation in recent decades. Borneo has lost more than half of its rainforests in the past half a century.[4] In 1982–83 and again in 1997–98, forest fires in Kalimantan cleared around 25,000 km2 (9,700 sq mi) each time for oil palm planting. Further threats in Sabah come from exploration for oil and coal in theMaliau Basin and the draining of the wetlands on theKlias Peninsula. In 2001, the World Wildlife Foundation forecast that "If the current trend ofhabitat destruction continues, there will be no remaining lowland forests in Borneo by 2010."[1] Although this forecast has not been fulfilled, in 2008 theIUCN Red List reported a 2005 prediction that "forest cover on the island of Borneo, if current deforestation rates continue, is projected to decline from 50% to less than one-third by 2020".[5]
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6.267% of the ecoregion is in protected areas. These include:[3]
Media related toBorneo Lowland Rainforests Ecoregion at Wikimedia Commons