Kabaena Island

A(i)Site contains one or more globally threatened species

Kabaena is an important habitat for globally threatened plants, with two Endangered and one Vulnerable. There are also several species endemic to Kabaena Island which are likely to be threatened since all parts of the island are unprotected. This island also holds populations of Sulawesi endemics like Grevillea elbertii, Lasjia erecta, and Vaccinium kjellbergii which are located in the disturbed shrubland. Larger parts of the island, i.e. around 70 percent of the island, have been designated as concessions for nickel mining areas, which surely threaten the presence of endemic or important species. In some areas, Some native species including large trees are being used by the local people as the source of traditional medicines.

Kabaena is an outer island in Southeast Sulawesi. It is an 880 km square island with undulating terrain with its highest point located on Mount Sabampolulu at 1533 m asl. Some areas of the mountain consist of rocky outcrops which are very hard to climb like Mount Batu Sangia. The lowland areas have mostly been converted into developed areas, with the upper elevation still in the form of forest and shrubland or savanna. The vegetation on the island is threatened by tin mining and many plants in the open area are threatened by pastoral activities like cattle grazing. Mount Sabampolulu is an area for hiking and will attract more visitors shortly due to the increasing popularity of mountain climbing in the country.

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Kabaena harbours the entire global populations of at least six species from several families and is an important area for 3 globally threatened species. The globally threatened species are all endemic to Sulawesi phytogeographical regions: the Endangered Goniothalamus majestatis and Callicarpa cinnamomea as well as the Vulnerable Dehaasia celebica. This area is also an important habitat for some Sulawesi endemic species like Grevillea elbertii, Lasjia erecta, Sartotheca celebica, and Vaccinium kjellbergii.

The vegetation of Kabaena Island belongs to the Sulawesi moist forest ecoregions. Barthlott et al. (2005) scored 6 out of 10 for diversity zone, which means there are 1500 to 2000 plant species per 10,000 km square. Vegetation of Kabaena is divided into two types the Sulawesi lowland rainforest, and Sulawesi montane rainforest ecoregions, alongside the scattered distributed savanna in some areas, especially in the lowlands. In the coastal area, mangrove belts developed in some parts of the island. Kabaena is a Mesozoic-Australian derived, or in other words, it was once part of the Gondwana supercontinent. All summits on this island are non-volcanic and have a similar geological origin to the likes of Sula Island, Buton, Tukang Besi, and some parts of the SE arm of Sulawesi (Hall 1996, Satyana et al. 2011). There are five main rock formations in Kabaena Island: (1) ultramafic being the most prominent component of the island, from north to south; (2) two metamorphic rocks, i.e. the Pompangeo formation in the central northern and Langkowala formation in the western coast; (3) central karstic mountain that includes the Mount Batu Sangia; and (4) alluvium plain scattered along the coastal areas (Simandjuntak et al. 1993).

Kabaena is rich in nickel and has been subjected to rapidly growing mining since 2009. This resulted in habitat degradation in many places, especially the lowland areas and ultramafic mountains in the southern half of the island including the highest point, Mount Sabampolulu.. The destruction of habitats from mining activities is projected to increase for many years to come. The concession area covers an area of around 75 per cent of the total area of the island (Afra 2024). The nickel mining activities seem not to threaten forests of northeastern montane ranges as they are made of metamorphic rocks.
Besides that, cattle grazing and relevant activities also threaten some vegetation in many parts of the island, with the most intense being the Mount Batu Sangia area, reaching the base of the summit rock cliffs. This includes the area that becomes the habitat of the Kabaena, e.g. Vernonia kabaenensis, or Sulawesi endemic, e.g. Vaccinium kjellbergii. Besides that, vegetation surrounding the Batu Sangia rocky summit has been converted into clove (Syzygium aromaticum) plantations that could be misinterpreted as forests with good tree stands.

Kabaena is an outer island of Sulawesi where the forest provides many ecosystem services for the people living on the island. Forests are important for water catchment including for drinking water. Many parts of the island have been used for a long time as pastoral areas, e.g. cattle grazing. The mangrove in the coastal area is also important for providing habitat for the commercially important fauna. The island is also a habitat for 27 Sulawesi endemic birds, around 30.3 per cent of the total 89 species recorded for the island, with one Endangered and three Near Threatened (O’Connell et al. 2017). Several native plant species have also been used by the local people as sources of medicine, this includes common Wallacean large trees like Kjellbergiodendron celebicum and Pterospermum celebicum (Rahayu & Rugayah 2010).

Wendy Mustaqim, Universitas Samudra, Indonesia

Arman, Tumbuhan Asli Nusantara Foundation, Indonesia

Wisnu H. Ardi, National Research and Innovation Agency, Indonesia

Liam Trethowan, Royal Botanic Gardens, Kew

Laura Jennings, Royal Botanic Garden Kew

Date of first assessment: 2nd Jun 2025