|Forêts guinéennes de l'Afrique de l' ouest|
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The lowland forests of West Africa are home to more than a quarter of Africa's mammals, including more than 20 species ofprimates. Logging, mining, hunting and human population growth are placingextreme stress on the forests, however, threatening species such as theJentinka's duiker, pygmy hippopotamus, and scattered populations of westernchimpanzees. Five Endemic Bird Areas lie partly or entirely within the hotspot.
The Guinean Forests of West Africa hotspot encompasses all of thelowland forests of political West Africa, stretching from Guinea and SierraLeone eastward to the SanagaRiver in Cameroon. This includes thecountries of Liberia, Ivory Coast, Ghana,Togo, Benin, and Nigeria, which maintain remnantfragments of the forests. The hotspot also includes four islands in the Gulf of Guinea:Bioko and Annobon, which are both part of EquatorialGuinea, and Sao Tomé and Principe, whichtogether form an independent nation. Bioko isa continental-shelf island, whereas the remaining three are oceanic.
The hotspot includes two distinct sub-regions, which incorporate severalimportant forest refugia created by the retraction and fragmentation of forestsduring the Pleistocene Epoch. The first sub-region, Upper Guinea, stretchesfrom southern Guinea intoeastern Sierra Leone andthrough Liberia, Ivory Coast and Ghanainto western Togo.The second sub-region, Nigeria-Cameroon, extends along the coast from western Nigeria to the SanagaRiver in southwestern Cameroon.The two sub-regions are separated by the Dahomeny Gap in Benin, an area of farmland,savannah and highly degraded dry forest. The hotspot supports several importantmontane regions, including the Cameroon Highlands (Mt.Cameroon, at 4,095 meters, is thehighest peak in West Africa) and the NimbaHighlands.
The Guinean forests consist of a range of distinct vegetation zonesvarying from moist forests along the coast, freshwater swamp forests (forexample, around the NigerDelta), semi-deciduous forests inland with prolonged dry seasons. Of all WestAfrican countries, only Liberialies entirely within the moist forest zone, although a substantial portion of Sierra Leonealso falls within the boundaries.
A unique and threatened biodiversity
The Guinean Forests hotspot is home to an estimated 9,000 vascular plantspecies, about 20 percent (1,800 species) of which are thought to be endemic(25 percent). The flora of this hotspot is closely related to the flora ofcentral Africa, and most genera are widespreadthroughout both regions. However, West Africahas high levels of local endemism at the species level. TaiNational Park in Côte d'Ivoire, MountNimba on the Liberia, Guineaand Côte d'Ivoire border, Cross River National Park in Nigeria,and Mount Cameroon are areas known to supportsignificant assemblages of endemic plant species. Nearly 2,500 plant specieshave been recorded on MountCameroon. Because oftheir relative isolation from the rest of the hotspot, the Gulf of GuineaIslands also support highly endemic flora; approximately 185 species areendemic to these islands, and São Tomé and Príncipe each have a single-islandendemic plant genus.
Among the many flagship plant species in this hotspot are a number ofeconomically important species. The oil palm ( Elaeis guineensis), widelyplanted throughout the tropics for oil production, is native to the hotspot,while valuable timber species include the African ebony ( Diospyros gracilis),two genera of African mahogany ( Entandophragma and Khaya), and iroko ( Miliciaexcelsa), which is widely exploited.
The Guinean Forests of West Africasupport nearly 785 bird species, of which roughly 75 species and seven generaare endemic. These forests are home to 10 species of hornbills, largefrugivores that fill an important ecological function in tropical forests asseed dispersers. Dozens of the region's bird species are threatened byextensive forest clearing that is occurring throughout the hotspot.
BirdLife International has recognized six Endemic Bird Areas as lyingpartly or entirely within the hotspot. The Upper Guinea Forests EBA has 15endemic bird species, and the Cameroon Mountains EBA, which includes the island of Bioko, is the sole habitat of nearly 30bird species. These montane regions support a number of endemics: the MountCameroon francolin ( Francolinus camerunensis, EN) and the Mount Cameroonspeirops ( Speirops melanocephalus, VU) are endemic to Mount Cameroon, whilethe Mount Kupe bush-shrike ( Malaconotus kupeensis, EN) is largely confined toMount Kupe, where only 21 square kilometers of habitat remains (it has recentlybeen discovered at two additional localities). The conservation of the forestsof Mount Oku is the last remaining hope for two species, Bannerman's turaco (Tauraco bannermani, EN) and the banded wattle-eye ( Platysteira laticincta,EN), which are restricted to montane forests in the Bamenda-Banso highlands.The islands of Sao Tome, Principe and Annobon in the Gulf of Guinea,each of which is an entire EBA, add several endemic and interesting birdspecies to the region's avifauna including the dwarf olive ibis ( Bostrychiabocagei, CR). The giant sunbird (Nectarinia thomensis, VU), the giant weaver (Ploceus grandis), and two endemic genera, Amaurocichla and Neospiza, bothrepresented by threatened single species, are also restricted to these islands.The sixth EBA, the Cameroonand Gabonlowlands, is marginal to the hotspot.
Mammal diversity in the hotspot is very high. West Africa's estimated320 species represent more than a quarter of the roughly 1,100 total mammalspecies found on the entire continent of Africa.More than 60 of these mammals are endemic to the region, including 18 speciesof primate.
The Guinean Forests are renowned for their primate diversity, withnearly 30 distinct species. These forests have been identified as some of Africa's most critical primate conservation areas. Asmany as six species are endemic to the Upper Guinea forests, and nine areendemic to the forests of Nigeriaand Cameroon.There are four endemic subspecies on BiokoIsland. Among the speciesfound within the Guinean Forests the striking Diana monkey ( Cercopithecusdiana, EN) is an important indicator of forest health because of its dependenceon high-canopy forests, while the olive colobus ( Procolobus verus) is theworld's smallest colobine monkey. The hotspot also has populations of two ofAfrica's great apes, including remaining scattered populations of chimpanzees (Pan troglodytes, EN) and a small population of western lowland gorillas (Gorilla gorilla gorilla, EN) on the Nigeria-Cameroon border.
While the West African forests are famous for their primates, they arealso the home of seven endemic genera, including the rare pygmy hippopotamus (Hexaprotodon liberiensis, VU) and the Liberian mongoose ( Liberiictis kuhnii,EN). Other flagship species include two species of duiker, Jentink's duiker (Cephalophus jentinki, VU) and the zebra duiker ( Cephalophus zebra, VU),endemic to the Guinean forest and two of the rarest antelopes in the world. Thecountries that make up the hotspot have a combined population of some 5,000elephants ( Loxodonta africana, VU), though many populations reside in savannahhabitats outside to the hotspot.
While reptiles are not adequately documented in West Africa, preliminaryanalysis suggests that more than 200 species, a quarter of which are endemic,are found in the region, including more than 100 species of snakes and allthree species of African crocodiles. Among the distinctive endemics are the LosArchipelago worm lizard ( Cynisca leonina), Benson's mabuya ( Mabuya bensonii),and the Liberiaworm snake ( Typhlops leucostictus).
Amphibians are also poorly documented in the region, but it is estimatedthat almost 225 amphibians inhabit the hotspot, including more than 80endemics. Many additional species are likely to be discovered; for example, 11new frog species have been discovered in the last decade alone. It is clear thehotspot supports a high diversity of tree frogs. One distinctive endemicspecies is the MountNimba toad (Nimbaphrynoides occidentalis, CR), which gives birth to fully developedtoadlets after a gestation period of nine months. The huge and threatenedGoliath frog ( Conraua goliath, EN) also occurs in this hotspot; this speciescan grow as large as 30 centimeters long and weigh 3.3 kilograms.
Fish diversity is quite remarkable in the Guinean Forests hotspot, withmore than 510 freshwater fishes, 35 percent of which are thought to be endemic.About a quarter of the world's 350 species of killifish live here, half ofwhich are endemic. Cichlid fishes are also prominent, with more than half ofthe over 60 species endemic to the hotspot. Four of the five endemic genera ofcichlids are found only in Lake Barombi Mbo in northwest Cameroon.
For moreinformation on theHotspot, concerning Human Impacts, Conservation Action and species gotohttp://www.biodiversityhotspots.org/xp/hotspots/west_africa/Pages/biodiversity.aspx