The Pulai River starts at the Mount Pulai and drains into the Tebrau Straits. At the mouth of the river is the largest seagrass bed of the country. A vast mangrove ecoregion is also located here. Intensive research is carried out in the ecoregion to study the unique collection of flora and fauna here.

Located on the islands of Borneo, the Lower Kinabatangan Segama Wetlands span an area of 788.03 square km. The site was added to the Ramsar List on October 28, 2008. The wetland area constitutes three Forest Reserves, the Kuala Maruap and Kuala Segama Forest Reserve, Kulamba Wildlife Reserve, and the Trusan Kinabatangan Forest Reserve. These wetlands serve as an important habitat for numerous resident and migratory birds. They are also a vital habitat of the Bornean orangutans and are significant for the conservation of orangutans.