The peat swamp forest in the south of Kalimantan is an unusual ecology that is home to many unique or rare species such as orangutans, as well as to slow-growing but valuable trees. The peat swamp forest is a dual ecosystem, with diverse tropical trees standing on a 10 to 12 m layer of peat - partly decayed and waterlogged plant material – which in turn covers relatively infertile soil. Peat is a major store of carbon.