This is one of the largest and best-protected rainforests in Africa, with 90% of its area left undisturbed. Almost completely surrounded by the Dja River, which forms a natural boundary, the reserve is especially noted for its biodiversity and a wide variety of primates. It contains 107 mammal species, five of which are threatened.
The site is situated on the Dja which almost completely encircles the reserve, forming its natural boundary, except to the south-west.
Except in the south-east of the reserve, the relief is fairly flat and consists of a succession of round-topped hills. A major fault line on the southern edge of the reserve, which is followed by the Dja River, has lead to the formation of rather deeper cut valleys on the south-eastern edge of the plateau. Cliffs run along the course of the river in the south for some 60 km, and are associated with a section of the river broken up by rapids and waterfalls. Dja is located in a transition zone between the forests of southern Nigeria, south-west Cameroon and the forests of the Congo Basin. It seems likely that the forests of the region are essentially undisturbed.
The vegetation mainly comprises dense evergreen Congo rainforest with a main canopy at 30-40 m rising to 60 m. The shrub layer contains over 53 species. The forest is also rich in lianes. The herbaceous layer is composed principally of Marantaceae and Mapania species. The Congo rainforest is also characterized by almost pure stands of Gilbertiodendron dewevrei forest.
Other main vegetation types are swamp vegetation, and secondary forest around old villages (which were abandoned in 1946) and recently abandoned cocoa and coffee plantations. Composition of the secondary forest is noticeably different as a result of the relative scarcity of species of the Meliaceae .
Although the area is poorly studied, it is known to have a wide range of primate species including western lowland gorilla, greater white-nosed guenon, moustached guenon, crowned guenon, talapoin, red-capped mangabey, white-cheeked mangabey, agile mangabey, drill, mandrill, potto, Demidorff's galago, black and white colobus monkey and chimpanzee. Other mammals include elephant, bongo, sitatunga, buffalo, leopard, warthog, giant forest hog and pangolin.
Birds include Bates's weaver, which is endemic to southern Cameroon, and grey-necked picathartes probably also occurs in this reserve. The type locality of Dja River warbler is near the reserve and there are few other records of this kind. Reptiles include python, lizard and two species of crocodile (both of which are threatened species).
A population of pygmies lives within the reserve, in small sporadic encampments, maintaining an essentially traditional lifestyle.
Protected as a 'reserve de faune et de chasse' by Law No. 319 of 25 April 1950, and then as a 'reserve de faune' lrnder the National Forestry Act Ordinance No. 73/18 of 22 May 1973. ,<eported to have received some protection as early as 1932, protection for certain species within Dja was stipulated by Decree No. 2254 of 18 November 1947, which regulated hunting in the French African territories. Accepted as a biosphere reserve in 1981 and inscribed on the World Heritage List in 1984. Proposed as a national park.
