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This ecoregion represents the lowland forests (less than 1,000 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 (Stattersfield et al. 1998). 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 (National Geographic Society 1999). 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 (Whitten et al. 1987). 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 (Whitten et al. 1987; Stattersfield et al. 1998). 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 (Whitten et al. 1987). The isolated Sula Islands, just off Sulawesi's east coast, receive rain from both the northwest and the southeast and have volcanic soils that create excellent growth conditions (Monk et al. 1997). Aopa Swamp, 100 km west of Kendari, is a major area of peat swamp that varies seasonally in extent from about 150 to 314 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 (Whitten et al. 1987). 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 (Whitten et al. 1987). 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) (Whitten et al. 1987). 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 (Whitten et al. 1987).
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 (Whitten et al. 1987). 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) (Flannery 1995). The crested macaque, moor macacque, and lowland anoa are considered endangered (IUCN 2000). Table 1. Endemic and Near-Endemic Mammal Species.
Sulawesi contains a depauperate bird fauna but with high levels of endemicity (Stattersfield et al. 1998). The origin of Sulawesi's birds is predominantly Asian (Whitten et al. 1987). 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 EBA and completely overlaps both the Sangihe and Talaud and Banggai and Sula Islands EBAs and the Salayar and Bonerate Islands Secondary Area (Stattersfield et al. 1998). 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) (Stattersfield et al. 1998). 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 (Stattersfield et al. 1998). Table 2. Endemic and Near-Endemic Bird Species.
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) (Whitten et al. 1987). 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 (Whitten et al. 1987). Three Centres of Plant Diversity are located in lowland Sulawesi: Dumoga-Bone National Park, Limestone Flora of Sulawesi, and Ultramafic Flora of Sulawesi (Davis et al. 1995).  Current Status
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 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. Table 3. WCMC (1997) Protected Areas That Overlap with the Ecoregion.
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 (IUCN 1991). 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 (Whitten et al. 1987; Whitten, pers. comm., 2000). 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 (Stattersfield et al. 1998). 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 (Stattersfield et al. 1998). 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.
There have been several attempts to divide the bioregion into biogeographic units (MacKinnon 1997; Stattersfield et al. 1998; van Balgooy 1971, cited in Monk et al. 1997; MacKinnon and Artha 1981; MacKinnon and MacKinnon 1986; MacKinnon et al. 1982; van Steenis 1950; Udvardy 1975). Because many of the islands have distinct natural faunal communities and a high degree of endemism (Monk et al. 1997), the more recent attempts have used faunal dissimilarities-especially birds-to identify distinct biogeographic units (MacKinnon 1997; Stattersfield et al. 1998; MacKinnon and Artha 1981; MacKinnon and MacKinnon 1986). 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 [AA0123] and Sulawesi Montane Rain Forests [AA0124]. 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 (Whitmore 1984) were included in the Sulawesi Lowland Rain Forests [AA0123] but should be considered a distinct habitat type in an ecoregion-based conservation assessment to ensure representation.
References for this ecoregion are currently consolidated in one document for the entire Indo-Pacific realm. Reviewed by: This text was originally published in the book Terrestrial ecoregions of the Indo-Pacific: a conservation assessment from Island Press. This assessment offers an in-depth analysis of the biodiversity and conservation status of the Indo-Pacific's ecoregions. For more general information on this ecoregion, go to the WildWorld version of this description. All text by World Wildlife Fund © 2001 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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