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Western Africa: Western Cameroon extending into Ni

The Cameroon Highlands ecoregion comprises montane forest/grassland patches mainly above 900 m elevation, scattered in an archipelago along the border area between Nigeria and Cameroon. Habitat ranges with increasing altitude from sub-montane to montane forests and ultimately subalpine grasslands. The forests and grasslands contain exceptional levels of endemism in all taxa. The forests and montane grasslands in the ecoregion are poorly protected by reserves, but in some areas there is good traditional protection. Due to high population pressures the remaining natural habitats, especially the forests, are threatened by agricultural expansion.

  • Scientific Code
    (AT0103)
  • Ecoregion Category
    Afrotropical
  • Size
    14,700 square miles
  • Status
    Critical/Endangered
  • Habitats

Description
Location and General Description
Geographically this ecoregion encompasses the mountains and highland areas of the border region between Nigeria and Cameroon, excluding Mount Cameroon. Most of the ecoregion lies within a narrow rectangle of some 180 km by 625 km, oriented southwest to northeast and originating about 50 km inland of Mount Cameroon. At the southern extremity, the ecoregion covers the Rumpi Hills, the Bakossi Mountains, Mount Nlonako, Mount Kupe and Mount Manengouba. It then extends northeast towards the Mambila Plateau, with an extension north to the Bamenda-Banso highlands and outliers northeast to Mambila and northwest to the Obudu Plateau of Nigeria. The main trend of the ecoregion continues north-east along the western flank of the Adamawa Plateau to Tchabal Gangdaba with two small outliers further east (Stuart 1986, Gartlan 1989, Stattersfield et al. 1998).

The highest point within this ecoregion is Mount Oku at 3,011 m in the Bamenda-Banso highlands. Most of the remainder is below 2,600 m in elevation. At about 800 m to 1,000 m the ecoregion grades into lowland vegetation communities of other ecoregions. In the majority of cases, however, the lower boundary of these forests is now determined by conversion to agricultural land.

Although located in tropical Africa the mean maximum temperatures are below 20°C due to the effects of altitude. At the southern extremity, closer to the coast, rainfall is around 4,000 mm per annum, declining inland to 1,800 mm or less.

These mountains form part of a chain of former volcanoes that stretch inland from the sea. While there are currently no active volcanoes within the ecoregion, the effects of vulcanism are still present. In 1986, water from Lake Nyos, a crater lake in the Bamenda Highlands seeped into magma channels below and caused a massive explosion that killed 1,700 people and devastated the surrounding countryside. Soils derived from these volcanoes are fertile, which makes the land attractive to farmers. Combined with adequate rainfall, this contributes to a high human population density.

In White's (1983) phytogeographical classification, these mountain areas fall within the Afromontane archipelago-like regional center of endemism that spans the entire continent.

The elevational stratification that occurs along these mountains is quite distinct. Vegetation consists of submontane forests between 900 and 1,800 m, and above this a mixture of montane elements, including distinct montane forests and patches of montane grasslands, bamboo forests and subalpine communities. Five species of tree characterize the forested montane zone: Nuxia congesta, Podocarpus latifolius, Prunus africana, Rapanea melanophloeos, and Syzygium guineense bamendae, and these trees become increasingly covered with an epiphytic flora, especially orchids and mosses, at higher altitudes. Other important montane species include Crassocephalum mannii, Hypericum lanceolatum, Myrica humilis, Philippia mannii, and Schlefflera abyssinica.

Biodiversity Features
Although plant diversity and biogeography are poorly known, tree species diversity tends to be low, but the diversity of non-woody plants such as grasses is high. Highest levels of tree endemism are found in the submontane region and the higher elevations of the adjacent Mount Cameroon and Bioko Montane Forests [9] ecoregion. Overall tree diversity, however, decreases with increasing elevation. There is also a significant endemic flora in the grasslands, heathlands, moorlands and other non-forested habitats at higher elevations. These non-forested habitats share elements with the high mountain plant communities to the east, namely the Ruwenzori-Virunga montane moorlands. The Cameroon Highlands ecoregion is not high enough to contain pure Afroalpine elements, which are restricted to the mountains of East Africa.

The forests have affinities with the highland forests of Angola on the southern fringes of the Congo Basin (Kingdon 1990) and especially with forests in East Africa. Most of the trees in the montane forests of Cameroon are also present in the mountains of eastern Africa, for example Alangium chinense, Albizia gummifera, Apodytes dimidiata, Cassipourea gummiflua, Croton macrostachyus, Ilex mitis, Olea capensis, Podocarpus latifolius, Polyscias fulva, Prunus africana, Schefflera abyssinica, Strombosia scheffleri, Xymalos monospora, and at edges Agauria salicifolia, Maesa lanceolata lanceolata, Myrica humilis, Nuxia congesta, Pittosporum viridiflorum, Rapanea melanophloeos and Scolopia zeyheri (Dowsett-Lemaire 1989). The liane Dregea schimperi (Asclepiadaceae), common in the drier type of montane forest of this ecoregion is widespread in the mountains of East Africa (Thomas and Thomas 1996).

The ecoregion contains exceptional levels of avian endemism,. There are seven strictly endemic bird species, the Bamenda apalis (Apalis bamendae), Bangwa forest warbler (Bradypterus bangwaensis), white-throated mountain-babbler (Kupeornis gilberti, EN), banded wattle-eye (Platysteira laticincta, EN), Bannerman's weaver (Ploceus bannermani, VU), Bannerman's turaco (Tauraco bannermani, EN) and Mt. Kupe bushshrike (Telophorus kupeensis, EN) (Bowden and Andrews 1994, Stattersfield et al. 1998). An additional nine montane endemics in common with Mt Cameroon and Bioko, these are Psalidoprocne fuliginosa, Andropadus tephrolaemus, Phyllastrephus poensis, Phylloscopus herberti, Urolais epichlora, Poliolais lopezi, Nectarinia oritis, Nectarinia ursulae, Nesocharis shelleyi. There are also 14 species in common with just Mt Cameroon and not Bioko, adding Andropadus montanus, Phyllastrephus poliocephalus, Laniarius atroflavus, Malaconotus gladiator, Cossypha isabellae and the race Cisticola chubbi discolor (sometimes considered a separate species C. discolor) (Dowsett 1989, Dowsett-Lemaire and Dowsett 1989, 2000, Fotso et al. 2001).

Eleven small mammal species are considered strictly endemic to this region: Eisentraut's striped mouse (Hybomys eisentrauti, EN), an African wood mouse species (Hylomyscus grandis), Mount Oku mouse (Lamottemys okuensis, EN), Mittendorf's striped grass mouse (Lemniscomys mittendorfi , EN), two brush-furred mouse species (Lophuromys dieterleni and L. eisentrauti), Oku mouse shrew (Myosorex okuensis, VU), Rumpi mouse shrew (M. rumpii, CR), western vlei rat (Otomys occidentalis, EN), Hartwig's soft-furred mouse (Praomys hartwigi, EN), and Isabella's shrew (Sylvisorex isabellae, VU). In addition to these smaller species, there is also a iolated population of an endemic subspecies of lowland gorilla (Gorilla gorilla diehli, EN). There are also populations of rare larger mammals – for example there are several groups of drill (Mandrillus leucophaeus, EN), in Bakossi, as well as healthy populations of Preuss's red colobus (Procolobus pennanti preussi, EN) and chimpanzee (Pan troglodytes, EN). One large group of drill was seen on Mount Kupe as recently as 2000 (Dowsett pers com).

Very high levels of endemism are observed among amphibians, with nearly 40 species as strict endemics (Gartshore in Stuart 1986): Hylarana longipes, Petropedetes parkeri, P. perreti, Phrynobatrachus cricogaster, P. steindachneri, P. werneri, Phrynobatrachus sp. (Oku), Phrynodon sp. 1 sensu Amiet (1975), Phrynodon sp. 2 sensu Amiet, Arthroleptis adolfifriedericii, Cardioglossa melanogaster, C. oreas, C. pulchra, C. schioetzi, C. trifasciata, C. venusta, Astylosternus nganhanus, A. perreti, A. montanus, A. rheophilus, Leptodactylodon axillaris, L. bicolor, L. boulengeri, L. erythrogaster, L. mertensi, L. polyacanthus punctiventris, L. perreti, Afrixalus lacteus, Hyperolius adametzi, H. riggenbachi (incl. hyeroglyphicus, now considered conspecific, J.-L. Amiet pers. comm.), Leptopelis nordequatorialis, Xenopus amieti, Xenopus sp., Bufo villiersi, Werneria bambutensis, W. tandyi, Wolterstorffina mirei. In addition, a new Leptodactylodon (wildi) was only named in 2000 and appears endemic to Bakossi (Amiet & Dowsett-Lemaire 2000). There are also a number of near-endemic amphibians, species found also on lower hills near Yaoundé (and some on Mt Cameroon): Leptodactylodon ornatus, Hyperolius koehleri, H. kuligae, Kassina decorata, Leptopelis modestus, Werneria mertensi, Wolterstorffina parvipalmata.

Among the reptiles the following nine species are considered narrow endemics: Atractapsis coalescens, Chamaeleo eisentrauti, Pfeffer's chameleon (C. pfefferi), four-horned chameleon (C. quadricornis), Cnemaspis gigas, Leptosiaphos chriswildi, L. ianthinoxantha, angel's five-toed skink (L. lepesmei) and Panaspis duruarum.

In addition to the narrow endemics outlined above, there is also a significant overlap between the flora and fauna of this ecoregion and that of the nearby Mount Cameroon and Bioko Montane Forests ecoregion. Fifty near endemic plant species are shared between the two ecoregions. Similarly, 27 bird species are confined to these two ecoregions (Stattersfield et al. 1998). A similar pattern of overlap in taxa is seen in the plants, birds, reptiles, amphibians, invertebrates and small mammals.

In addition to their scientific interest, these mountains also form essential water catchments for Cameroon and Nigeria.

Current Status
While the different mountains and highlands that comprise this ecoregion are naturally geographically isolated, human activities are increasingly fragmenting, degrading and isolating the remaining forest patches. The area around Mount Oku in the Bamenda-Banso Highlands supports some 100 km2, and there are other patches in this region. The Bakossi Mts have at least 200 km² of mid-altitude and montane forest above the altitude of 1000 m; and the lowland forest ("Western Bakossi") covers some 400 km². The Mt Nlonako Faunal Reserve also contains a partial forest continuum from the montane section to the lower levels. Tchabal Mbabo, in the northern sector, has almost 50 km2 of virtually pristine montane forest (Thomas and Thomas 1996). In Nigeria, the biggest patch in the Gotel Mts covers 46 km² (peak Gangirwal) and there are other patches. Montane forest remnants also remain in gulleys of the Obudu Plateau and on the highland areas further to the north such as the Mambila and Mana Plateaux and Gashaka Gumti; all are smaller than the Cameroon patches (Sayer et al. 1992, Stattersfield et al. 1998).

Forest loss has been significant on many mountains in this ecoregion. Much of the Bamenda-Banso Highlands were once covered by forest, but cover has declined by more than 50% since the 1960s through conversion for cultivation, because of the relatively fertile soils and reliable rainfall in this area (Stuart 1986, Collar and Stuart 1988, Alpert 1993). Similarly, deforestation has also occurred on the Obudu Plateau.

This is one of the least well-protected ecoregions in Africa. No part of this ecoregion is under formal protected status in Cameroon, although local traditional rulers still exert considerable authority over land use. The main section of Bakossi (550 km²) has been proposed as "Protection Forest", banning all logging. Kupe has been proposed as a "Strict Nature Reserve", and the boundaries of this reserve were successfully delineated with the participation of the local people in 2000-2001. The forest at Oku has some form of protection and the boundaries are well demarcated; unfortunately the demand for firewood for neighbouring towns (including Bamenda) is so high that the forest may not have a long-term future. Nlonako Mountain is a Faunal Reserve, which gives them protection from logging, even if the hunting ban is not respected. In Nigeria The Gashaka Gumti National Park in Nigeria contains some montane forest and some fragments remain at Obudu in the Okwangwo section of the Cross River National Park.

Types and Severity of Threats
The natural habitats of this ecoregion are highly threatened and are being lost through conversion to agriculture, unsustainable use of timber, fires from farmland, and collection of firewood and construction materials (Collar and Stuart 1988, Gartlan 1989, Alpert 1993, Blom et al. in prep). Because volcanic rock produces good soils, there is considerable pressure to convert areas to farmland. However, these soils also dry easily, leading to desiccation during the dry season. Firewood collection is a major cause of degradation of forest patches. Hunting also threatens the remaining larger mammals.

Justification of Ecoregion Delineation
This ecoregion forms part of the Afromontane archipelago-like regional center of endemism (White 1983). This ecoregion is delineated as montane areas above 900 m elevation, capturing submontane and montane forest habitat and subalpine communities. The lower elevation forests were included to capture elevational migrations of species as well as transition zones that appear to be a crucial component of speciation and of the development of endemism (Schneider et al. 1999). The Cameroonian Highlands are distinct from Mount Cameroon and Bioko Montane Forests because there are no active volcanoes and numerous endemic species are confined to one or other region.

References
Alpert, P. 1993. Conserving biodiversity in Cameroon. Ambio 22: 44-49.

Amiet, J.-L. 1975. Ecologie et distribution des Amphibiens Anoures de la région de Nkongsamba (Cameroun). Ann. Fac. Sci. Yaoundé 20: 33-107.

Amiet, J.-L. and F. Dowsett-Lemaire. 2000. Un nouveau Leptodactylodon de la Dorsale camerounaise (Amphibia, Anura). Alytes 18: 1-14.

Bowden, C.G.R., and S.M. Andrews. 1994. Mount Kupe and its birds. Bulletin African Bird Club 1: 13-16.

Collar, N.J., and S.N. Stuart. 1988. Key forests for threatened birds in Africa. ICBP, Cambridge, UK.

Dowsett, R.J. (ed.). 1989. A preliminary natural history survey of Mambilla Plateau and some lowland forests of eastern Nigeria. Tauraco Research Report No. 1, 56 pp. Tauraco Press.

Dowsett-Lemaire, F. 1989. The flora and phytogeography of the evergreen forests of Malawi. 1: Afromontane and mid-altitude forests. Bull. Jard. Bot. Nat. Belg. 59: 3-131.

Dowsett-Lemaire, F. and R.J. Dowsett. 1998. Zoological surveys of small mammals, birds and frogs in the Bakossi and Kupe Mts, Cameroon. Unpublished report for WWF-Cameroon, 46 pp.

Dowsett-Lemaire, F. and R.J. Dowsett. 2000. Further biological surveys of Manenguba and Central Bakossi in March 2000, and an evaluation of the conservation importance of Manenguba, Bakossi, Kupe and Nlonako Mts, with special reference to birds. Unpublished report for WWF-Cameroon, 45 pp.

Fotso, R., F. Dowsett-Lemaire, R.J. Dowsett, Cameroon Ornithological Club, P. Scholte, M. Languy, and C. Bowden. 2001. Cameroon. Pp. 133-159 in L.D.C. Fishpool and M.I. Evans (eds). Important bird areas of Africa and associated islands: priority sites for conservation. BirdLife Conservation Series No. 11. Pisces Publications and BirdLife International, Newbury and Cambridge, UK.

Gartlan, S. 1989. La conservation des écosystèmes forestiers du Cameroun. IUCN, Gland and Cambridge.

Kingdon, J. 1990. Island Africa; the Evolution of Africa's Rare Animals and Plants. Collins, London.

Sayer, J.A., C.S. Harcourt, and N.M. Collins. 1992. The Conservation Atlas of Tropical Forests: Africa. IUCN and Simon & Schuster, Cambridge.

Schneider, C.J., T.B. Smith, B. Larison, B., and C. Moritz. 1999. A test of alternative models of diversification in tropical rainforests: ecological gradients vs rainforest refugia. Proceeding of the National Academy of Sciences, vol. 96, No. 24, pp 13869-73.

Stattersfield, A.J., M.J. Crosby, A.J. Long, and D.C. Wege. 1998. Endemic bird areas of the world: priorities for biodiversity conservation. BirdLife Conservation Series No. 7., BirdLife International, Cambridge, UK.

Stuart, S.N. (ed.) 1986. Conservation of Cameroon montane forests. Cambridge, UK. International Council for Bird Preservation.

Thomas, D. and J. Thomas. 1996. Tchabal Mbabo Botanical Survey. Consultants' Report to WWF Cameroon Program Office. 44 pages plus annexes.

White, F. 1983. The vegetation of Africa, a descriptive memoir to accompany the UNESCO/AETFAT/UNSO Vegetation Map of Africa (3 Plates, Northwestern Africa, Northeastern Africa, and Southern Africa 1:5,000,000). UNESCO, Paris.

Prepared by: Allard Blom
Reviewed by: In progress

 

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