Karst Sangkulirang – Mangkahaliat lies between Berau and East Kutai district. It is known for its unusual geology with limestone being formed by ancient coral reefs, and is one of the largest karst topographies in Southeast Asia about 420,000 acre wide. With jagged limestone formation, the area also has cavernous structure, which is important for underground aquifers. The area has a significant amount of forest carbon stock, is home to unique biodiversity, and provides vital environmental services for local population.
Home to unique and endemic species, Karst Sangkulirang – Mangkahaliat is recognized by International Union for Conservation of Nature (IUCN) as a global center for plant biodiversity richness. It was also identified as one of the top 10 endangered karst ecosystems by international karst specialists.
TNC and the Indonesian Institute of Science (LIPI) conducted a rapid biological survey in 2004 on the area’s unique and rich biodiversity. The research found approximately 120 species of birds, 38 species of fish, 38 species of bats, dozens of aquatic troglobitic or troglophilic arthropods, 147 species of snails and several hundred species of cave arthropod in the area. The survey also found four endemic species of fish, 37 of snails, and hundreds of species of arthropods that are new to science.
Another research led by TNC in 2009 focused on the existence of endangered species in the area. The survey predicted a significant size of orangutan population exists in the Sangkulirang karst.
Karst Sangkulirang – Mangkahaliat has high economical value. The 240 caves in the areas are important for the collection of white and black swiftlets’ nests. The area also provides water sources for up to 90,000 people who inhabited the area. The population is spread into 8 villages and 3 new transmigration settlements.
There are five rivers from the area that flow to East Kutai district, and three rivers to Berau district. These rivers provide modes of transportation, clean water and irrigation to the communities.
Karst Sangkulirang – Mangkahaliat also provides a living to the residents, many of whom collect gaharu (Eagle wood), harvest wild honey – particularly among the Dayak communities- and other minor forest products. The area has its tourism potential, offering not only its beauty but also adventure through eco-tourism.
Karst Sangkulirang – Mangkahaliat provides an opportunity for sustainable financing and conservation through REDD mechanism. Preliminary estimate indicates that the vegetation and karst rocks store more than 339 million tones of carbon dioxide equivalent.
Social Cultural Heritage
Out of some 240 caves in the area, a total of 30 sites show invaluable evidence of prehistoric arts. The area especially in Marang area is an archeological treasure. The caves are famous for Mesolithic (Middle Stone Age) paintings that are estimated to be 9,800 years old. Decorating caves are known to be a part of spiritual and cultural activities in the prehistoric time.
Threats facing the area
But despites its ecological, scientific, socio-cultural and economic value, the area is constantly facing threats of degradation mostly caused by forest fire, illegal logging, treasure hunting, and conversion into farms, timber plantations and mines. The habitat alteration caused by these factors will have significant consequences for the biodiversity and also the people whose lives depend on the area.
Source: TNC reports on Karst
 Gilbert amd Deharveng (2002) from Salas et. al (2005). Biodiversity, endemism and the conservation of limestone karsts in the Sangkulirang Peninsula, Borneo.Biodiversity 6 (2), pg. 15 – 23.
 Pindi. Tantangan Kawasan Lindung Karst: Kerja Besar Pemda Kutim untuk Masa Depan. On Seminar of Rencana Aksi Pengelolaan Kawasan Kars Sangkulirang. Date: 9 August 2010.