The Sulawesi lowland rain forests harbor some of the most unique animals on Earth. The islands are located in the region known as Wallacea, which contains a distinctive fauna representing a mix of Asian and Australasian species.
A fruit-eating pig with huge tusks, a dwarf buffalo, endemic macaques, and cuscuses exemplify a truly unique mammal community.
Sulawesi, like the hub of a wheel, is surrounded by a variety of exotic ocean basins, including the Flores Sea, the Banda Sea, the Molucca Sea, the Java Sea, and the Straits of Makassar, as well as the diverse islands of Borneo, Java, Flores, Halmahera, and the Philippines. More than half of the original forest has been cleared, and most of the remaining forests have been reduced to fragments.
Location and General Description
This ecoregion represents the lowland forests (less than 1,000 meters (m)) on Sulawesi and the surrounding islands of Banggai and Sula to the east and Talaud and Sangihe to the north. Sulawesi is almost completely mountainous. There are no extensive lowlands on Sulawesi, with large areas above 1,000 m and the highest elevation at 3,455 m on Mt. Rantemario. Sangihe is mountainous, reaching an elevation of 1,784 m, whereas Talaud is low-lying. The physiography of the Sula Islands is hilly, with mountains over 800 m only on the island of Taliabu.
The upland areas (more than 1,000 m) of Sulawesi form a separate ecoregion, the Sulawesi montane rain forests. Based on the Köppen climate zone system, this ecoregion falls in the tropical wet climate zone. Sulawesi has a complex geologic history and is composed of three geologic provinces based on that history. West and East Sulawesi form two of the geologic provinces, separated by the Palu-Koro fault, which runs from the town of Palu to the Gulf of Bone. The third geologic province consists of the Tokala region on the northeast peninsula, the Banggai Islands, Butung Island, and the Sula Islands. East and West Sulawesi collided approximately 13-19 million years ago, and ultrabasic rocks were exposed as East Sulawesi overrode the western portion. The forces that caused the collision are still at work, and Sulawesi is being torn apart today. The surface geology of Sulawesi is a diverse patchwork of ophiolites, Mesozoic sedimentary rocks, Tertiary sedimentary and igneous rocks, and Quaternary volcanics and sediments. Active volcanoes are located on the northern arm of Sulawesi.
The lowland forest is predominantly tropical lowland evergreen and semi-evergreen rain forest, with some monsoon forests at the tip of the southeast peninsula and small areas of freshwater and peat swamp forest. Distinctive forest types on limestone are distributed around southern Sulawesi and on ultrabasic soils in scattered locations all around the island. The lowland and hill forests contain the most tree species, although these forests are not dominated by any one tree family; only seven dipterocarp species are found in Sulawesi (compared with 267 and 106 in Borneo and Sumatra, respectively). The dipterocarps include Anisoptera costata, Hopea celebica, H. gregaria, Shorea assamica, Vatica rassak, and V. flavovirens. Distinctive ebonies (Diospyros spp.) were common in dense clumps in the lowland forests. Palms are common in the lowland forest, including Oncosperma horridum, Liculala celebensis, Pinanga, Areca, Caryota, and Livistona rotundifolia.
Aopa Swamp, 100 kilometers (km) west of Kendari, is a major area of peat swamp that varies seasonally in extent from about 150 to 314 square-kilometers (km2). The dominant tree species in this forest include Casuarina spp., Eugenia spp., Geunsia paloensis, Premna foetida, Metroxylon sagu, Pholidocarpus spp., Licuala spp., Arenga spp., Oncosperma spp., and Corypha spp. Sedges such as Scleria spp. also occur along with 5-m tall Pandanus spp., at least two species of climbing rattan, and epiphytic Lecanopteris ant-ferns.
Freshwater swamp forest is characterized by grassy areas near open water, with palms and pandans on firmer ground and ubiquitous pitcher plants (Nepenthes). Riverine forest dominated by tall Eucalyptus deglupta is found in the Sopu Valley northeast of Lake Lindu and Mt. Nokilalaki.
This ecoregion also includes karst (limestone) areas that have a relative paucity of trees and tree species because of their shallow soils and steep slopes, resulting from the high solubility of limestone rocks. High calcium levels in the soil give rise to distinctive tolerant plant communities but support certain snail species limited to limestone forest as well as the large swallowtail butterfly (Graphium androcles).
Infertile ultrabasic substrates, with serpentine and peridotite rocks, contain unique forests with a high degree of plant endemism. Common species include ironwood (Metrosideros), Agathis, Calophyllum, Burseraceae, Sapotaceae, and dipterocarps (Vatica and Hopea celebica). Myrtaceae (Eugenia, Kjellbergiodendron, and Metrosideros) are dominant in the low and regular canopy. There is little marketable timber in such forests.
Wallace's Line, running from between Bali and Lombok and between Sulawesia and Borneo, marks the location of a deep oceanic trench and the point over which land animals and plants could not cross easily. Similarly, Lydekker's Line, running from between Timor and the Australian shelf to between Halmahera, Seram, and New Guinea, marks the point where Australasian flora and fauna could not easily pass. Sulawesi lies between these two lines. Sulawesi's location, geologic history, and long geographic isolation have created Sulawesi's distinctive fauna. There is variability, different among various animal and plant groups, in the amount of interchange between other biogeographic areas in the region, which led to the evolution of a large number of species endemic to the island. Although not species-rich relative to Borneo or Java, Sulawesi is high in endemicity because of its long isolation from Asia and Australia in Wallacea. This ecoregion exhibits high plant endemism, and the several distinct forest types provide habitat for the highest number of endemic mammals in Asia and several endemic birds.
|Table 1. Endemic and Near-Endemic Mammal Species.|
|An asterisk signifies that the species' range is limited to this ecoregion.|
Of the 104 mammal species in the ecoregion, 29 are endemic or near endemic (Table 1). Whereas the two cuscuses have Australasian affinities (i.e., the Peleng cuscus [Phalanger pelengensis] and dwarf cuscus [Strigocuscus celebensis]), the remainder of Sulawesi's mammals have Asian origins, including the crested macaque (Macaca nigra), moor macaque (M. maura), booted macaque (M. ochreata), lowland anoa (Bubalus depressicornis), spectral tarsier (Tarsius spectrum), and babirusa (Babyrousa babyrussa). The crested macaque, moor macacque, and lowland anoa are considered endangered.
Sulawesi contains a depauperate bird fauna but with high levels of endemicity. The origin of Sulawesi's birds is predominantly Asian. The bird fauna consists of about 337 species, of which 70 are endemic or near-endemic species (Table 2). The ecoregion also overlaps the lowland portions of the Sulawesi Endemic Bird Area (EBA) and completely overlaps both the Sangihe and Talaud and Banggai and Sula Islands EBAs and the Salayar and Bonerate Islands Secondary Area. Of the seventy restricted-range birds in these three EBAs, thirty-two bird species are found nowhere else in the world but this lowland ecoregion. Thirteen additional species are found only in this ecoregion and the adjacent montane ecoregion (and nineteen more species are found only in the uplands of Sulawesi). One species found on Sangihe, the cerulean paradise flycatcher (Eutrichomyias rowleyi), is critically endangered, and the red-and-blue lory (Eos histro), Sangihe hanging-parrot (Loriculus catamene), and elegant sunbird (Aethopyga duyvenbodei), all found on Sangihe and Talaud, are endangered.
|Table 2. Endemic and Near-Endemic Bird Species.|
|Accipitridae||Small sparrowhawk||Accipiter nanus|
|Megapodiidae||Sula scrubfowl||Megapodius bernsteinii*|
|Rallidae||Platen's rail||Aramidopsis plateni|
|Rallidae||Bare-faced rail||Gymnocrex rosenbergii|
|Rallidae||Isabelline waterhen||Amaurornis isabellinus|
|Columbidae||Dusky cuckoo-dove||Macropygia magna|
|Columbidae||Sulawesi ground-dove||Gallicolumba tristigmata|
|Columbidae||Maroon-chinned fruit-dove||Ptilinopus subgularis*|
|Columbidae||White-bellied imperial-pigeon||Ducula forsteni|
|Columbidae||Pink-headed imperial pigeon||Ducula rosacae|
|Columbidae||Grey-headed imperial-pigeon||Ducula radiata|
|Columbidae||Grey imperial-pigeon||Ducula pickeringii|
|Columbidae||Silver-tipped imperial-pigeon||Ducula luctuosa*|
|Psittacidae||Yellowish-breasted racquet-tail||Prioniturus flavicans*|
|Psittacidae||Moluccan hanging-parrot||Loriculus amabilis|
|Psittacidae||Sangihe hanging-parrot||Loriculus catamene*|
|Psittacidae||Pygmy hanging-parrot||Loriculus exilis*|
|Loriidae||Red-and-blue lory||Eos histrio*|
|Loriidae||Yellow-and-green lorikeet||Trichoglossus flavoviridis|
|Cuculidae||Sulawesi hawk-cuckoo||Cuculus crassirostris|
|Cuculidae||Bay coucal||Centropus celebensis*|
|Strigidae||Ochre-bellied hawk-owl||Ninox ochracea|
|Strigidae||Speckled hawk-owl||Ninox punctulata|
|Tytonidae||Minahassa owl||Tyto inexspectata|
|Tytonidae||Taliabu owl||Tyto nigrobrunnea*|
|Tytonidae||Sulawesi owl||Tyto rosenbergii|
|Caprimulgidae||Diabolical nightjar||Eurostopodus diabolicus|
|Caprimulgidae||Sulawesi nightjar||Caprimulgus celebensis*|
|Alcedinidae||Sulawesi kingfisher||Ceyx fallax*|
|Alcedinidae||Lilac kingfisher||Cittura cyanotis*|
|Alcedinidae||Black-billed kingfisher||Pelargopsis melanorhyncha*|
|Alcedinidae||Talaud kingfisher||Todirhamphus enigma*|
|Alcedinidae||Green-backed kingfisher||Actenoides monachus*|
|Alcedinidae||Scaly kingfisher||Actenoides princeps|
|Meropidae||Purple-bearded bee-eater||Meropogon forsteni|
|Coraciidae||Purple-winged roller||Coracias temminckii|
|Bucconidae||Sulawesi hornbill||Penelopides exarhatus*|
|Bucconidae||Knobbed hornbill||Aceros cassidix|
|Acanthizidae||Rufous-sided gerygone||Gerygone dorsalis|
|Pachycephalida||Sulphur-bellied whistler||Pachycephala sulfuriventer|
|Pachycephalida||Drab whistler||Pachycephala griseonota|
|Rhipiduridae||Rusty-flanked fantail||Rhipidura teysmanni|
|Monarchidae||Cerulean paradise-flycatcher||Eutrichomyias rowleyi*|
|Monarchidae||White tipped monarch||Monarcha everetti*|
|Dicruridae||Sulawesi drongo||Dicrurus montanus|
|Corvidae||Banggai crow||Corvus unicolor*|
|Campephagidae||Cerulean cuckoo-shrike||Coracina temminckii|
|Campephagidae||Pied cuckoo-shrike||Coracina bicolor*|
|Campephagidae||White-rumped cuckoo-shrike||Coracina leucopygia|
|Campephagidae||Sula cuckoo-shrike||Coracina sula*|
|Campephagidae||Slaty cuckoo-shrike||Coracina schistacea*|
|Campephagidae||White-rumped triller||Lalage leucopygialis*|
|Turdidae||Rusty-backed thrush||Zoothera erythronota*|
|Sturnidae||Pale-bellied myna||Acridotheres cinereus|
|Sturnidae||Sulawesi myna||Basilornis celebensis|
|Sturnidae||Helmeted myna||Basilornis galeatus*|
|Sturnidae||White-necked myna||Streptocitta albicollis|
|Sturnidae||Bare-eyed myna||Streptocitta albertinae*|
|Sturnidae||Fiery-browed myna||Enodes erythrophris|
|Sturnidae||Finch-billed myna||Scissirostrum dubium*|
|Muscicapidae||Henna-tailed jungle-flycatcher||Rhinomyias colonus*|
|Muscicapidae||Rufous-throated flycatcher||Ficedula rufigula*|
|Zosteropidae||Sulawesi white-eye||Zosterops consobrinorum*|
|Zosteropidae||Black-ringed white-eye||Zosterops anomalus|
|Sylviidae||Sulawesi leaf-warbler||Phylloscopus sarasinorum|
|Dicaeidae||Crimson-crowned flowerpecker||Dicaeum nehrkorni|
|Dicaeidae||Red-chested flowerpecker||Dicaeum maugei|
|Dicaeidae||Grey-sided flowerpecker||Dicaeum celebicum*|
|Nectariniidae||Elegant sunbird||Aethopyga duyvenbodei*|
|An asterisk signifies that the species' range is limited to this ecoregion.|
Four of Sulawesi's amphibians have Sundaland affinities, and two have Australasian roots. Thirty-eight of Sulawesi's sixty-three snake species are found on both sides of Wallace's Line. There are large reptiles of conservation significance: the sailfin lizard (Hydrosaurus amboinensis), saltwater crocodile (Crocodylus porosus), and reticulated python (Python reticulatus).
Sulawesi's flora is most closely related to the floras of dry areas in the Philippines, Moluccas, Lesser Sundas, and Java. The lowland forests have affinities to New Guinea, whereas the upland areas are more related to Borneo. Three Centres of Plant Diversity are located in lowland Sulawesi: Dumoga-Bone National Park, Limestone Flora of Sulawesi, and Ultramafic Flora of Sulawesi.
More than half of the original forest has been cleared, and the remaining forests have been reduced to fragments except for a few fairly large blocks that are still intact. There are thirty-eight protected areas that cover 9,460 square-kilometers (km2) (8 percent) of the ecoregion area (Table 3). Seven of these reserves are more than 500 km2, but none are more than 1,100 km2.
Sulawesi still supports some lowland moist forests on steep slopes that are unsuitable for agriculture. However, large areas in the south and some parts of the center and north of the island have been cleared for permanent and shifting cultivation. The lowland peneplain dry forest is completely gone because of large-scale agricultural plantations, transmigration, logging, and local clearance. The riverine forest in the Dumoga Valley is now the site of a major irrigation scheme, and some of the limestone vegetation has been destroyed by quarrying to supply the Tonasa cement factories. During the dry season, cattle farmers set fires to encourage the growth of young grass, and repeated burnings have resulted in a persistent grassland vegetation in some areas and a savanna with fire-resistant trees in others. Uncontrolled exploitation for the oil in its heartwood has depleted stands of the sandalwood tree Santalum album, even in protected areas such as Paboya Reserve.
Sangihe and Talaud were largely deforested by 1920, and there is minimal natural forest remaining on these islands. A survey has been proposed to determine appropriate locations for additional protected areas around remaining forest.
Most of Taliabu, the largest island in the Sula Islands, is still forested, but there has been large-scale logging in the lowlands. The other main Sula Islands, Sanana and Mangole, have been heavily degraded. Extensive lowland forest still remains on the Banggai Islands.
|Table 3. WCMC Protected Areas That Overlap with the Ecoregion.|
|Protected Area||Area (km2)||IUCN Category|
|Lombuyan I, II||1,070||IV|
|Mas Popaya Raja||40||I|
|Rawa Aopa Watumohai||1,030||II|
|Lambu Sango NR||200||PRO|
|Ecoregion numbers of protected areas that overlap with additional ecoregions are listed in brackets.|
Types and Severity of Threats
Uncontrolled and illegal logging will continue to be the biggest threat to the integrity of the remaining forests. This situation has been and will be exacerbated by lack of authority and implementation of existing environmental laws.
Justification of Ecoregion Delineation
There have been several attempts to divide the bioregion into biogeographic units. Because many of the islands have distinct natural faunal communities and a high degree of endemism, the more recent attempts have used faunal dissimilarities--especially birds--to identify distinct biogeographic units. Because detailed floral data are largely unavailable across most of the bioregion, we followed these authors in delineating ecoregions based on distribution of biomes and vertebrate communities.
On Sulawesi Island we delineated two ecoregions: the Sulawesi lowland rain forests and Sulawesi montane rain forests. These represent the tropical lowland and montane tropical moist forests, respectively. The small patch of monsoon forests on the southwest peninsula of Sulawesi and on Butung Island were included in the Sulawesi lowland rain forests but should be considered a distinct habitat type in an ecoregion-based conservation assessment to ensure representation.
Additional information on this ecoregion
- For a shorter summary of this entry, see the WWF WildWorld profile of this ecoregion.
- To see the species that live in this ecoregion, including images and threat levels, see the WWF Wildfinder description of this ecoregion.
- World Wildlife Fund Homepage
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