The site is situated in the vast expense of forested country stretching from Yabassi (Nkam Department) to Ndikiniméki (Mbam Department). It consists mainly of three contiguous blocks of forest: Makombé (c.600 km²), Ndokbou (at least 1,000 km²) and Ebo (1,400 km²). Makombé Forest is immediately east of and contiguous with the forest of Mont Nlonako (CM023); their common boundary is formed by the Nkam river and the road from Yabassi to Nkondjock. The Makombé Forest is limited to the north, east and south by the Makombé river, a tributary of the Nkam. Ndokbou Forest stretches east from the middle Makombé river to Ndikiniméki, north to Tongo, and is contiguous to the south with Ebo Forest. The latter is traversed by the Ebo river in its centre, limited to the west by the Dibamba and to the east by the Iwouem river (a tributary of the Sanaga). These forests are fringed with a few hunting villages along their borders, but are otherwise uninhabited. The relief is steep, especially in Ndokbou and Ebo where many hills reach over 1,000 m (to 1,304 m). Away from river valleys where the forest can be impressively tall, the main forest-type is semi-evergreen with a low canopy: on steep gradients the soils are rather shallow, underlain with clay and rocks, thus the canopy reaches moderate heights (often around 20 m) and emergents are well spaced out. Common tall trees include Antrocaryon, Ceiba, Lophira, Piptadeniastrum, Pycnanthus, Scyphocephalum, Terminalia and Uapaca.
See Box and Tables 2 and 3 for key species. Some 310 species have been identified in a first survey; a few montane species inhabit the highest hills, i.e. two species of the Cameroon mountains EBA (086) and Afrotropical Highlands biome (A07) (see Tables 2 and 3), including Nectarinia oritis (an interesting extension of range to the south-east). Ceratogymna elata is common in the Makombé Forest; Hirundo fuliginosa is found commonly throughout and there are several breeding colonies of Picathartes oreas, especially in the north of Ebo. One Sudan–Guinea Savanna biome (A04) species has also been recorded (Table 3).
Non-bird biodiversity: Makombé Forest has been over-hunted, but the Ndokbou and Ebo Forests are still extremely important for their large populations of Loxodonta africana (EN) and several primates. These include Pan troglodytes (EN), Cercopithecus preussi (EN), Mandrillus leucophaeus (EN) still found in large groups throughout (this site probably harbours the most important population of drill in Cameroon today), a ‘new’ population of Procolobus (badius) preussi (EN) and, also most unexpectedly, a small population of Gorilla gorilla (EN) confined to the north-east hills of Ebo Forest and perhaps also in south Ndokbou. The frog Conraua goliath (VU) is much hunted for food, but is still widespread.
BirdLife International (2019) Important Bird Areas factsheet: Yabassi. Downloaded from http://www.birdlife.org on 23/04/2019.