Borneo lowland rainforests
Borneo lowland rainforests (Source: WWF)
Borneo lowland rainforests are the biologically richest rainforests in the world and rival the biodiversity of New Guinea and the Amazon. With 267 Dipterocarpaceae species (155 endemic to Borneo), Borneo is the center of the world's diversity for dipterocarps. These forests are home to the world's smallest squirrel, the eleven centimetre long pygmy squirrel, and the endangered orangutan. In northeast Borneo, populations of Sumatran rhinoceros and Asia's largest terrestrial mammal, the Asian elephant, still tenuously survive in the last pockets of forest. These forests contain the parasitic plant Rafflesia arnoldii, which produces the world's largest flower (up to one meter in diameter). These forests are globally outstanding for both bird and plant richness, with more than 380 birds and an estimated 10,000 plant taxa found within its boundaries. Unfortunately, these forests have been rapidly converted to oil palm plantations or commercially logged at unprecedented rates over the past ten years. In 1997-1998 fires intentionally set to clear the forest for commercial agriculture such as oil palm ravaged Kalimantan. If the current trend of habitat destruction continues, there will be virtually no remaining lowland forests in Borneo by the period 2012 to 2015; however, there is an incipient conservation movement to preserve some Malaysian lowland dipterocarp rainforests, particularly evident in the Kinabatan River basin.
Location and general description
Kalimantan (Borneo), Indonesia. (Photograph by WWF-Canon/Siegfried Woldhek) This ecoregion is made up of the lowland dipterocarp forests of Borneo. All of Borneo, Java, Sumatra, and mainland Malaysia and Indochina were once part of the same landmass during the Pleistocene Glacial period. Land bridges connected all of these islands, fostering waves of migrations of animals, plants, and humans. Today Borneo is geographically separate, but shares similarities in flora and fauna with these other landmasses. The geology of the Borneo lowland rainforests consists of limestones, volcanic rocks, schist-gneiss complexes, and sedimentary rocks. Soils are primarily ultisols and inceptisols, generally older, infertile soils. Based on the Köppen Climate Classification System, this ecoregion falls in the tropical wet climate zone. Monthly rainfall exceeds 200 millimetres year-around, and the temperature rarely fluctuates more than 10°C.
World Wildlife Fund The natural vegetation of this ecoregion is tropical lowland rainforest. The region's stable climatic conditions have given rise to some of the world's richest assemblage of flowering plants. Forests contain a high diversity of tree species, and dominant species are uncommon. As many as 240 different tree species can grow within a single hectare, with another 120 in the hectare adjacent. The general characteristics of these forests are canopies 24 to 36 metres (m) high, with emergents reaching up to 65 m.
Dipterocarpaceae is a dominant family in the emergent stratum. In the richest forests, up to 80 percent of the emergent trees are dipterocarps, although the white-barked Koompassia tree (Laurelaceae) is a readily identifiable emergent as well. Of the dipterocarp genera, Dipterocarpus, Dryobalanops, and Shorea are the emergents, and Hopea and Vatica usually are found in the main canopy. Berseraceae and Sapotaceae are other common main canopy families. Bornean ironwood Eusideroxylon zageri, or Belian, is a common and commercially valuable species. A third layer occurs below the canopy of shade-tolerant species, adorned with lianas, orchids, and epiphytic ferns. This layer includes many species from the Euphorbiaceae, Rubiaceae, Annonaceae, Lauraceae, and Myristicaceae families. In some cases Euphorbiaceae is more common than dipterocarps, being the second most common family in Borneo. Another unique feature of this layer is the prevalence of caulifory. Caulifory is a phenomenon in which trees bear their flowers and fruits on their trunks. The forest durian Durio testudinarum is a common example of caulifory. On the forest floor, herbs, seedlings, and shade-tolerant palms exploit the few places that receive sunlight (Solar radiation).
Limestone formations are found throughout Borneo and include extensive areas in the Sangkulirang Peninsula and the limestone hills of Sarawak. Detailed botanical surveys of the limestone areas have not been completed, but preliminary studies suggest that this habitat supports a tremendous number of flora species, many of them probably endemic. Although limestone forest has little commercially valuable timber, herbs such as Balsaminaceae, Begoniaceae, and Gesneriaceae (which are well represented in this ecoregion) have horticultural potential. The Labi Hills of the Brunei-Sarawak border support a diverse mosaic of forests on podzols and sandy yellow soils, and these are rich in endemics, including two palms, Livistona exigua and Pinanga yassinii, known only from podzolized ridges in the Ulu Ingei area. There seems to be no special vertebrate fauna associated with limestone in this ecoregion, although banteng Bos javanicus, orangutan Pongo pygmaeus, Bornean gibbon Hylobates muelleri, sambar Cervus unicolor, muntjac Muntiacus muntjak, and mousedeer Tragulus spp. all use limestone outcroppings.
Biodiversity features
The flora of Borneo alone consists of about 10,000 to 15,000 species, more than on any other island or region in Malesia and richer than all of Africa, which is forty times larger. Borneo has more than 3,000 tree species and 2,000 orchid species and is the center of distribution of dipterocarps, with 267 species, 60 percent of them endemic. Some of the most unique plants in the world are the five or six species of the parasitic Rafflesia plant found in Borneo. All Rafflesia produce large brown, red, orange, and white flowers. The largest in the world, Rafflesia arnoldii, is found in this ecoregion and produces flowers more than 3 feet wide. Rafflesia have no leaves, instead deriving all their energy from the tissues of the ground vine Tetrastigma, which it parasitizes. Large buds emerge from the vine and have five petals that surround spikes that smell like rotting meat. This smell attracts insects, which act as pollinators.
Bornean rainforests share much of their fauna with the Asian mainland and other Sunda islands but few with Sulawesi and the eastern islands. The wildlife in the Bornean lowland rainforests is not characterized by great spectacles of migrating or large charismatic species but by an enormous diversity of forest animals. As a whole, Borneo has a higher number of endemic mammals (forty-four) than the other islands in the Sunda Shelf and Philippines Bioregion, but fifteen are limited to lowland forests, and many of these are small rodents and bats. Twelve of these are endemic, and one is near endemic to these forests (Table 1).
Protected Areas That Overlap with the Ecoregion
- Apar Besar PRO Apo Kayan (1370)
- PRO Bukit Baka-Bukit Raya (470)
- II Bukit Batikap (800)
- I, II, III PRO Bukit Perai (5350)
- PRO Bukit Raya Perluasan X PRO Bukit Rongga (1830)
- PRO Crocker Range (1380)
- II Danum Valley (470)
- VIII Gunung Bentuang (270)
- II Gunung Berau (2212)
- PRO Gunung Lumut (1560)
- PRO Gunung Palung (500)
- II Gunung Penrisen/Gunung Niut (780)
- 640 IV Gunung Raya Pasi
- 50 I Gunung Tunggal
- 640 PRO Hutan Kapur Sangkulirang
- 2,150 PRO Hutan Sambas
- 220 PRO Kaya Kuku NR
- 70 PRO Kinabalu 190 II Kuala Kayan
- 610 PRO Kutai (extension)
- 320 PRO Kutai
- 1,370 II Long Bangun
- 1,720 PRO Meratus Hulu Barabai
- 980 PRO Pararawen Baru
- 520 PRO Pararawen I, II 40 I Pleihari Martapura 1,350 IV S. Kayan S. Mentarang 1,660 PRO S. Kayan S. Mentarang 6,400 ? Sangalaki 1 IV SAR (Sanctuary Reserve) 80 II SAR (Sanctuary Reserve) 90 II SAR (Sanctuary Reserve) 40 II SAR (Sanctuary Reserve) 160 UA SAR (Sanctuary Reserve) 30 UA SAR (Sanctuary Reserve) 3 PRO SAR (Sanctuary Reserve) 3 PRO SAR (Sanctuary Reserve) 30 UA SAR (Sanctuary Reserve)
- 540 PRO SAR (Sanctuary Reserve)
- 1,730 IV SAR (Sanctuary Reserve)
- 50 PRO SAR (Sanctuary Reserve)
- 100 PRO SAR (Sanctuary Reserve)
- 30 PRO SAR (Sanctuary Reserve)
- 220 II SAR (Sanctuary Reserve)
- 3 PRO SAR (Sanctuary Reserve)
- 3 IV SAR (Sanctuary Reserve)
- 60 II SAR (Sanctuary Reserve)
- 40 II SAR (Sanctuary Reserve)
- 6 UA SAR (Sanctuary Reserve)
- 4 UA SAR (Sanctuary Reserve)
- 110 PRO SAR (Sanctuary Reserve)
- 120 IV SAR (Sanctuary Reserve)
- 1,560 PRO SAR (Sanctuary Reserve)
- 1,560 PRO Sesulu
- 120 PRO Sungai Berambai 780 PRO Tabin
- 1,230 IV Unnamed
- 1,230 Unnamed
- Total 49,563 These areas have generally been heavily logged, with most logging occurring in the last thirty years. Commercial logging destroyed the forests while providing access to them. Massive agricultural (Borneo lowland rainforests) projects, such as oil palm, rubber, and industrial timber for pulp and plywood, soon followed. Smaller agricultural shareholders also filled in these areas by cutting and burning patches of forests. By the late 1980s Indonesia was the world's largest plywood producer. Private and state-owned forestry companies have stripped the land clear for pulp and palm oil plantations, destroying vast tracts of forest. They are replanting with a limited number of fast-growing exotic species. In 1982-1983 27,000 km2 of tropical rainforest was burned in Kalimantan. The cause of what was at the time the largest forest fire ever recorded was widespread logging activities over the previous decade. Logging had transformed the fire-resistant primary forest into a degraded and fire-prone landscape. The El Niño-driven drought of that year set that stage for catastrophe when small agricultural fires escaped and ignited the forest. Indonesia did not learn from its past lessons. In 1997-1998, another intense El Niño year, the same events unfolded. In 1997-1998 fires raged across Kalimantan and Sumatra as forests were being cleared to make way for agriculture and plantation lands. More than 23,750 km2 of lowland rainforest in Kalimantan was burned in these years alone. Primary tropical rainforests do not burn naturally, so few native plant or animal species are adapted to fire. Fires in pristine forests rarely escape the ground vegetation because of the high humidity and moisture. However, tropical rainforests that have been previously logged are fire-prone because large amounts of wood are left on the forest floor, and the forest canopy is opened, drying out the ground vegetation. These forests rarely escape fires such as those set throughout Indonesia in 1997.
Types and severity of threats
The prognosis for Borneo's lowland forests is bleak. With little to no law enforcement in Indonesia, large tracts of land will be susceptible to burning every year by commercial logging for agricultural projects such as oil palm, rubber, and industrial timber for pulp and plywood. Smaller agricultural shareholders threaten the forests through continued slash-and-burn agricultural practices. Little to no regard is given to the long-term environmental effects these actions will cause. Without immediate intervention to stem the loss of these forests, and given the current rate of destruction, there will be no primary lowland dipterocarp forests remaining in Indonesian Borneo within ten years. The current system of protected areas underrepresents the habitat, and, based on the actions from 1997-1998, even protected areas will become susceptible to illegal and rampant logging and burning activities. The loss and fragmentation of the forest habitat will have drastic effects on the wildlife populations. As the forests shrink, more and more primates will interact with humans, and many will be killed or sold into the international pet trade. Vast numbers of species will become extinct before they have even been described and their role in the ecosystem determined. This collapse of the ecosystem will occur long before the last dipterocarp is cut down or set afire. Exploration for oil and coal is a potential major threat to Gunung Lotung and the Maliau Basin in south central Sabah. On the Klias Peninsula, proposed development schemes will drain the wetlands for agriculture and pose the most serious threat.
Justification of ecoregion delineation
The large island of Borneo was divided into seven [[ecoregion]s]. Most of the island's lowland and submontane forests are dominated by dipterocarp species. MacKinnon and MacKinnon divided the island's lowland forests into six subunits, with a central subunit representing the montane forests. MacKinnon revised the boundaries of these seven subunits but retained the same general configuration. These authors used the major rivers, the Kapuas and Barito, to represent zoogeographic barriers to a few mammal species and based subunits largely on these barriers but also used climatic regimes for the drier eastern biounits. Because ecoregions are based on biomes, we first isolated the central montane ecoregion-the Borneo Montane Rain Forests-above the 1,000-meter elevation contour using the DEM. We then assigned the large patches of peat forests, heath forests, freshwater swamp forests, and mangroves, in the lowlands and along the periphery of the island, into their own ecoregions: the Borneo Peat Swamp Forests, Sundaland Heath Forests (which also includes Belitung Island and the heath forests in Bangka island), Southern Borneo Freshwater Swamp Forests, and Sunda Shelf Mangroves, respectively. The alpine [[habitat]s] of the Kinabalu Mountain Range were represented by the Kinabalu Montane Alpine Meadows. The remaining lowland dipterocarp forests in Borneo were combined into a single ecoregion, Borneo Lowland Rainforests. This deviates from MacKinnon's use of subunits (25a, b, f, g, h, i) to divide Borneo.
Current status
This ecoregion is the second largest ecoregion in the Indo-Pacific region, yet more than half of the natural habitat in this ecoregion has been cleared or degraded. In recent years there has been extensive habitat loss, and current assessments predict further widespread destruction of forests. There are sixty reserves on paper that protect almost 12 percent of the region, but many are small (less than 100 km2) or are still proposed (Table 3). Only six reserves have been gazetted that protect more than 1,000 km2 of contiguous lowland rainforest. The remaining reserves are proposed. These include Gunung Bentuang, Kutai, Pleihari Martapura, S. Kayan, S. Mentarang, Tabin, and one SAR (Sanctuary Reserve). The protection of these reserves and the gazetting of the proposed reserves are essential to the conservation of biodiversity in this ecoregion.
References
- Li and Sun. 1999. Palynological records since Last Glacial Maximum from a deep-sea core in the southern South China Sea. Quat. Sci. Rev. 23: 2007-2016
- Pinxian Wang. 2009. The South China Sea: Paleoceanography and Sedimentology (Google eBook) Springer. 506 pages
- Eric D.Wikramanayake. 2002. Terrestrial ecoregions of the Indo-Pacific: a conservation assessment. Island Press. 643 pages
Citation
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Table 1. Endemic and Near-Endemic Mammal Species. Family Species Vespertilionidae Pipistrellus kitcheneri* Tupaiidae Tupaia montana* Tupaiidae Tupaia picta* Vespertilionidae Pipistrellus cuprosus* Vespertilionidae Murina rozendaali* Cercopithecidae Presbytis hosei* Sciuridae Callosciurus adamsi* Sciuridae Petaurillus hosei* Muridae Aeromys thomasi* Muridae Maxomys ochraceiventer* Muridae Maxomys baeodon* Muridae Haeromys pusillus* Rhinolophidae Hipposideros doriae An asterisk signifies that the species' range is limited to this ecoregion. Borneo also lacks some of the larger predators found in Asian mainland ecoregions (Borneo lowland rainforests) , such as the tiger (Pantera tigris) and the leopard (P. pardus). In their absence, several small-medium carnivores dominate these forests, including the endangered clouded leopard (Neofelis nebulosa), sun bear (Helarctos malayanus), Sunda otter-civet (Cynogale bennettii), and other mustelids. The Asian elephant (Elephas maximus) and critically endangered Sumatran rhinoceros (Dicerorhinus sumatrensis) are found in northeastern Borneo. The Asian elephant and Sumatran rhinoceros are the largest forest herbivores, and they need a large amount of forest to survive. The intense human pressure on the natural forests will challenge their ability to survive in the long term. Borneo's lowland forests are home to the globally recognized orangutan. The prehistoric race of orangutan distribution reached mainland Asia through Indochina and Thailand to southeastern China. Today the orangutan is limited to northern Sumatra and Borneo. Unlike other apes, orangutans are solitary and arboreal. They feed primarily on fruit but also feed on leaves, flowers, insects, and, during times of food stress, specifically bark. The orangutans move throughout the forest, following the fruiting of numerous trees. They have the ability to catalog the location and degree of a fruit's ripeness for a large number of trees and species. The orangutan is not the only primate in Borneo's lowland forests. They are home to thirteen primate species: three apes (the orangutan and two gibbon species), five langurs, two macaques, the tarsier (Tarsius bancanus), the slow loris (Nycticebus coucang), and the endangered proboscis monkey (Nasalis larvatus). Most of these species have overlapping ranges, but they vary with respect to dietary content and foraging strategy. {| border="1" cellpadding="3" align="center" ! colspan="3" align="center" | Table 2. Endemic and Near-Endemic Bird Species. Family Common Name Species Zosteropidae Javan white-eye Zosterops flavus Timaliidae Black-browed babbler* Malacocincla perspicillata* Pycnonotidae Blue-wattled bulbul Pycnonotus nieuwenhuisii Phasianidae Red-breasted partridge Arborophila hyperythra Phasianidae Crimson-headed partridge Haematortyx sanguiniceps Strigidae Mantanani scops-owl Otus mantananensis Capitonidae Mountain barbet Megalaima monticola Pachycephalidae White-vented whistler Pachycephala homeyeri Muscicapidae White-crowned shama* Copsychus stricklandii* Zosteropidae Pygmy white-eye Oculocincta squamifrons Timaliidae Chestnut-crested yuhina Yuhina everetti An asterisk signifies that the species' range is limited to this ecoregion. The fauna communities are divided into those that are active during the day and those that are nocturnal. Orangutans, pig-tailed macaques (Macaca nemestrina), and the white-rumped shama (Copyschus malabaricus), with its melodious calls, can be seen or heard during the early part of the day. Many birds, reptiles (Borneo lowland rainforests) , and amphibians browse throughout the day. As night approaches, bats such as the large flying-fox (Pteropus vampyrus) and flying squirrels begin to appear. Pangolins (Manis javanicus) search for ants on the forest floor, while civets and the clouded leopard (Neofilis nebulosa) hunt for food. Bearded pigs, though occasionally active during the day, are predominantly nocturnal animals. The tarsier (Tarsius bancanus), one of Borneo's strangest animals, with its large eyes searches out smaller animals and leaves for food. The bird fauna, like the mammal fauna, is similar to that of peninsular Malaysia and Sumatra. In Borneo there are eight hornbill species, eighteen woodpecker species, and thirteen pitta species. The 385 bird species attributed to the ecoregion include nine near-endemic species and two endemic species: the black-browed babbler Malacocincla perspicillata and the white-crowned shama (Copsychus stricklandii) (Table 2). Hornbills such as the bushy-crested (Anorrhinus galeritus), helmeted hornbill (Rhinoplax vigil), and great rhinoceros (Buceros rhinoceros) are important seed disperses of many fig (Ficus spp.) trees. Figs act as a keystone resource, providing food for many animals such as monkeys, arboreal mammals, squirrels, civets, and birds. The high diversity of fig trees in the rainforest assures food during fruiting throughout the year. Borneo is probably the richest island in the Sunda Shelf for reptile and amphibian diversity. Because detailed studies of the entire island have not been done, an incomplete picture emerges. For example, the earless monitor lizard (Lanthonotus borneensis) spends most of its life in underground caves and has been recorded in only a few places in Borneo. However, it probably has a widespread distribution throughout the island. Many populations of amphibians and reptiles are also hunted toward the brink of local extinctions. == |
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