Bonga forest is in Keficho-Shekicho Zone, south-west Ethiopia. The zonal capital, Bonga, is c.100 km south-west of Jimma. Bonga forest cloaks the highland area to the east of the Dincha river. The area comprises ridges and valleys through which the Guma, Sheko, Bittno and Ihina rivers and several small streams drain into the Dincha. Habitats include rivers and streams with riverine forest, upland montane forest and an Erica arborea zone above 3,000 m. The main forested area is broadleaf (Afro-montane) forest, which lies between 1,500 and 2,500 m and has many large tree species forming a canopy 10–>30 m high. The tallest trees are Aningeria adolfi-friderici. Other canopy species include Ocotea kenyensis, Olea capensis, Sapium ellipticum, Macaranga capensis, several species of Albizia, Euphorbia ampliphylla, Polyscias fulva, Schefflera abyssinica and several different Ficus spp. There is a rich understorey that includes the tree-fern Cyathea manniana found in moist ravines and near waterfalls, Dracaena steudneri and Coffea arabica. The higher parts of the forest support smaller trees such as Hagenia abyssinica and Prunus africana. Bonga forest has long been exploited for its large timber species and this is continuing. Some areas have been left to regenerate naturally, but over 2,000 ha have been planted with exotic and native species such as Eucalyptus, Hagenia abyssinica, Cordia africana, Cuppressus, Grevillea and Pinus patula. Local people make extensive use of the forest and many non-timber forest products are collected, particularly coffee and honey.
See Box and Table 3 for key species. The forest avifauna in south-west Ethiopia is less diverse than in the country’s bushland habitats. During surveys in December 1995, 100 species were recorded at this site. Afrotropical Highlands biome species include Lybius undatus and good numbers of Poeoptera stuhlmanni. Other interesting forest species present are Apaloderma narina and Coracina caesia. Cisticola troglodytes has also been recorded from the area.
Non-bird biodiversity: Although there are no endemic tree species in these forests, undergrowth and epiphyte diversity is high and includes endemics such as cardamom Aframomum corrorima.
Pressure/threats to key biodiversity
High-altitude forest is severely threatened in Ethiopia. Although Bonga forest is designated a National Forest Priority Area, little has been done to enforce the existing legislation. The current forest extent is unknown, but it has decreased since the 1970s. The forest is next to two major roads, making the removal of timber relatively easy. The more accessible parts of the forest are highly disturbed and now comprise thick undercover that could certainly be a hindrance to the larger mammals reported to occur. The fact that any forest remains is almost certainly due to the broken terrain within the Dincha watershed. Major threats include the introduction of exotic tree plantations, clearance for agriculture, and some grazing. The effect of grazing is currently not serious, but could become so, severely affecting the potential for forest regeneration. The forest coffee, Coffea arabica, of Bonga is genetically important, as it was from this area, near Wushwush, that the first plants with natural resistance to coffee berry disease were identified. Tree-ferns Cyathea manniana are known from only a few locations in Ethiopia; they require well-shaded and moist conditions to grow and would disappear if the forest were destroyed.
BirdLife International (2020) Important Bird Areas factsheet: Bonga forest. Downloaded from
http://www.birdlife.org on 31/10/2020.