Most of the area within the Kilum-Ijim boundary is above 2000 metres in height, and consists of montane forest mixed with montane grassland and subalpine communities. At lower elevations, most of the submontane forest has been cleared for agriculture. Based on satellite images, between 1958 and 1988 about half of the forest was lost, although regeneration began soon after the conservation project was started in 1987. Since then there has been steady recovery of the forest reserve, which is under the direct management of the Kilum-Ijim communities. Endangered endemic species found exclusively on Mount Oku include the Mount Oku hylomyscus, the Dieterlen's brush-furred mouse, the Lake Oku clawed frog and the toad Wolterstorffina chirioi. The montane grassland above the forest belt is home to the endemic Mittendorf's striped grass mouse.