Indonesia: Island of Sulawesi

The Sulawesi Lowland Rain Forests [AA0123] 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.

  • Scientific Code
  • Ecoregion Category
  • Size
    44,900 square miles
  • Status
    Relatively Stable/Intact
  • Habitats

Location and General Description
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).

Biodiversity Features
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.

Family Species
Phalangeridae Phalanger pelengensis*
Sorcidae Crocidura elongata
Sorcidae Crocidura lea
Sorcidae Crocidura levicula
Pteropodidae Acerodon humilis*
Pteropodidae Neopteryx frosti*
Pteropodidae Nyctimene minutus
Rhinolophidae Hipposideros inexpectatu
Vespertilionidae Pipistrellus minahassae
Vespertilionidae Hesperoptenus gaskelli
Tarsiidae Tarsius pelengensis
Cercopithecidae Macaca maura*
Cercopithecidae Macaca ochreata*
Cercopithecidae Macaca nigra
Suidae Babyrousa babyrussa
Bovidae Bubalus depressicornis*
Muridae Rattus koopmani*
Muridae Rattus xanthurus
Muridae Rattus bontanus*
Muridae Rattus elaphinus*
Muridae Maxomys hellwaldii*
Muridae Haeromys minahassae*
Muridae Margaretamys beccarii*
Muridae Taeromys celebensis*
Muridae Taeromys punicans*
Muridae Taeromys taerae*
Muridae Echiothrix leucura*
Muridae Melomys fulgens
Muridae Melomys caurinus*

An asterisk signifies that the species' range is limited to this ecoregion.

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.

Family Common Name Species
Accipitridae Small sparrowhawk Accipiter nanus
Megapodiidae Sula scrubfowl Megapodius bernsteinii*
Megapodiidae Maleo Macrocephalon maleo
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) (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.

Protected Area Area (km2) IUCN Category
Karakelang Utara 260 VI
Karakelang Selatan 80 VI
Gunung Sahendaruman 100 PRO
Dua Saudara 120 I
Pulau Taliabu 700 PRO
Pulau Seho 20 I
Pati-Pati 20 IV
Lombuyan I, II 1,070 IV
Gunung Lokon 20 VI
Gunung Manembo-Nembo 50 IV
Dumoga [AA0124] 940 ?
Mas Popaya Raja 40 I
Tanggale 10 PRO
Panua 410 I
Marisa 30 PRO
Pulau Una-una 70 PRO
Tanjung Api 50 I
Bangkiriang 390 PRO
Morowali [AA0124] 870 I
Mamuja/Tapalang 150 PRO
Danau Towuti 560 V
Lamiko-miko 280 PRO
Lasolo-Sampara 320 PRO
Lamedae 30 I
Rawa Aopa Watumohai 1,030 II
Tanjung Batikolo 30 IV
Lampoko Mampie 30 IV
Danau Tempe 310 PRO
Bontobahari 50 IV
Tanjung Peropa 300 IV
Polewai 100 PRO
Tanjung Amelango 10 IV
Kaya Kuku 40 PRO
Buton Utara 700 IV
Napabalano 10 I
Kokinawe 30 PRO
Lambu Sango NR 200 PRO
Tirta Rimba 30 V
Total 9,460  

Ecoregion numbers of protected areas that overlap with additional ecoregions are listed in brackets.

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).

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 (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.
Indo-Pacific Reference List

Prepared by: John Morrison
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.


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