Mount Cameroon and Bioko montane forests
The Mount Cameroon and Bioko Montane Forests ecoregion comprises four areas of montane forest on volcanoes located in coastal Cameroon and the offshore island of Bioko. Mount Cameroon is the highest peak in sub-Saharan western and central Africa, with a vast dome that extends over 45 kilometers (km) and reaches just above 4,000 meters (m) in elevation. This ecoregion is unique in west Central Africa in containing a continuous altitudinal gradient from low-altitude (above 200 m on the western slopes) moist forest to subalpine vegetation at the highest elevations. While portions of this forest gradient persist intact, it is threatened at lower altitudes by subsistence and plantation agriculture. The ecoregion contains exceptional levels of species endemism and richness, in part due to the great altitudinal range and the resulting diversity of habitats. However, the forests of Bioko and Mount Cameroon are inadequately protected and threatened by conversion to agricultural lands, logging, and hunting (bushmeat).
Location and General Description
The Mount Cameroon and Bioko Montane Forests ecoregion is located in a volcanic chain that extends northeast along the border between Cameroon and Nigeria, and southwest towards the Guinea islands of São Tomé, Príncipe, and Annobon. Rising to 4,095 m in elevation, Mount Cameroon is the tallest peak in the region. The ecoregion occurs in the higher elevations of Mount Cameroon and Bioko, although on Mount Cameroon high rainfall and intense cloud cover depress montane habitats to as low as 500 m elevation on the southwest side of the mountain.
Mount Cameroon and Bioko are recent volcanoes compared to others in the region. Of these, Mount Cameroon is the only volcano that is still active, last erupting in 1982 and again in 1999. Etinde, on the south-western side of Mount Cameroon, is an older and non-active volcanic peak. The mountain's volcanic history is apparent in the areas of rifting on the north and south slopes, the barren lava fields from 1982 and 1999 eruptions, as well as the presence of collapse scars and cinder cone features.
The southwestern sides of both Mount Cameroon and Bioko have a virtually continuous wet rainy season, with rainfall locally reaching 10,000 millimeters (mm) per year and a tropical climate at lower altitudes. On the other hand, the north and eastern sides of Mount Cameroon lie in a relative rain-shadow. In general however, the ecoregion receives over 3,500 mm rainfall per annum. At higher elevations the rainfall gradually declines, with less than 2,000 mm falling at the summit of Mount Cameroon. At the base of the mountain, temperatures average 25.5 to 27°C, and can reach 32 to 35°C during the hottest months (March and April). Temperatures descrease at the rate of approximately 1°C per 150 m of elevation.
According to White's phytogeographic framework, this ecoregion falls within the Afromontane archipelago-like regional center of endemism. The ecoregion has close floristic affinities to the Guineo-Congolian forests and the Cameroon Highlands, the montane forests and [[alpine|subalpine] communities of the Ruwenzori-Virunga Mountains, and forests of the Angola Scarp.
A number of factors, such as elevation, aspect, and climate influence the diversity of vegetation types across the ecoregion. On Bioko, three distinct areas of montane forest occur above 1,500 m: Pico Basilé (maximum elevation 3,011 m), Gran Caldera de Luba (2,261 m), and Pico Biao (2,009 m). The montane forest has an open canopy and is characterized by Schefflera abyssinica, S. mannii, Prunus africana, and Nuxia congesta. On Mount Cameroon, montane forest extends from 1,675 m to between 2,200 and 2,400 m in elevation. This grades into montane scrub and ultimately into montane grasslands, subalpine communities and rocky habitats at the highest elevations. The well-drained slopes formed by porous lava flows on Mount Cameroon support meadows of tussock grass and sedge vegetation, including Pennisetum monostigma, Swertia abyssinica, Myrica humilis, and Agauria salicifolia. Lava outcrops above 2,000 m also support orchids such as Brownleea parviflora and Holothrix tridentata as well as other herbs. Subalpine grassland communities occur from c. 2,000-2,200 m on Mount Cameroon and 2,500 m on Bioko. Characteristic species include Andropogon amethystinus, Deschampsia mildbraedii, Agrostis mannii, Koeleria cristata, and Bulbostylis erratica.
This ecoregion contains high species diversity and endemism in its flora and fauna. The exceptional species richness is due to the diversity of habitats found within a restricted geographical area, ranging from submontane and montane forests to subalpine grasslands. There are also a relatively high number of endemic species in almost all taxonomic groups. Many of these endemics are recently evolved, although some paleoendemics are also present, mainly at lower altitudes.
At least 42 plant species and three genera are strictly endemic and another 50 species are near-endemic to Mount Cameroon. Twenty-nine of these near-endemic species are also found on the island of Bioko. Most of the endemics at higher altitudes are recently evolved, comprising 19 of the near-endemics and 19 of the strict endemics, whereas paleoendemic plants, including the three endemic genera, occur only in the foothills. A number of species that occur in nearby highlands are also missing on Mount Cameroon. Frequent volcanic activity in intervals of 20 years may explain why Mount Cameroon lacks stands of Arundinaria alpina and Podocarpus latifolius, common in the Cameroonian Highlands.
The avifauna of this ecoregion is diverse, with over 370 species recorded from Mount Cameroon, a number of which are endemic. Two of these species are strictly endemic to Mount Cameroon: Mount Cameroon francolin (Francolinus camerunensis, EN) and the Mount Cameroon speirops (Speirops melanocephalus, VU). Two important bird areas are recognized on Bioko: Luba Caldera Scientific Reserve with over 120 recorded species, and Basilé Peak National Park with over 70 species. Notable species include Nectarinia ursulae, Psalidoprocne fuliginosa, Picathartes oreas, and the endemic Fernando Po speirops (Speirops brunneus, VU), which is confined to Basilé Peak in Bioko. An additional 18 restricted range bird species are shared by this ecoregion and the Cameroon Highlands Forests ecoregion.
Mammals display moderate levels of diversity and endemism. The Cameroon soft-furred mouse (Praomys morio, VU) is one near-endemic species that is confined to narrow altitudinal bands. Two other mammals, the arrogant shrew (Sylvisorex morio, EN) and a brush-furred mouse species (Lophuromys roseveari) are strict endemics. Other species found in the ecoregion include red-eared nose-spotted monkey (Cercopithecus erythrotis, VU), Preuss's monkey (Cercopithecus preussi, EN), black colobus monkey (Colobus satanas, VU on Bioko), drill (Mandrillus leucophaeus, EN), Hun shrew (Crocidura attila, VU), Cameroon climbing mouse (Dendromus oreas, VU), and Eisentraut's mouse shrew (Myosorex eisentrauti, EN, only on Bioko).
Although the herpetofauna is diverse, there is only one strictly endemic toad, Werneria preussi. Two additional amphibians are considered near endemics, the four-digit toad (Didynamipus sjotstedti) and the frog, Athroleptis bivittatus. Other near-endemic species include Cameroon mountain chameleon (Chamaeleo montium), Sjöstedt's five-toed skink (Leptosiaphos gemmiventris), and Tandy's smalltongue toad (Werneria tandyi). Mount Cameroon is also important for butterflies, including the endemic Charaxes musakensis.
The forests of Mount Cameroon are not currently protected under formal park status. Much of the foothills of Mount Cameroon are the property of the Cameroon Development Corporation (CDC), a parastatal agroindustrial institution in process of privatization. Forest reserves on the flanks of the mountain provide little protection as they are becoming increasingly degraded. These reserves were established for timber production and are also encroached upon for farming and subject to illegal logging and hunting pressures. Three further reserves have been proposed by the Mount Cameroon Project, a collaboration between the Government of Cameroon, DFID, GTZ, GEF. However, despite much work over the last decade to gazette the reserves of Mabeta-Moliwe, Etinde, and Onge, there has been little substantive progress. These projects are aiming at sustainable use of these forests. As the soils of the region are fertile, further conversion of some forest to agriculture is regarded as inevitable, especially in view of the proposed CDC privatization.
The montane forest of Bioko is protected by Basilé National Park (Parque Nacionale de Pico Basilé – 330 km2) and Luba Crater Scientific Reserve (Reserva Cientifica de la Caldera de Luba - 510 km2), which were both given legal status in 2000. Habitat loss on the mountains of Bioko is low and the southern slopes of the mountain are almost completely undisturbed from sea level to the summit at 2,261 meters. Fire is a threat to some montane forest and grassland, as it is on Mount Cameroon.
Types and Severity of Threats
Habitat loss and hunting of native fauna are the principal threats to this ecoregion. Habitat loss is caused by the unsustainable exploitation of firewood, overgrazing, fire damage, agricultural encroachment, and collection of medicinal bark (Prunus africana). On the eastern side of Mount Cameroon it has been estimated that up to half of the forest cover has already been lost. Less forest habitat has been lost on the southern slopes of Mount Cameroon.
In some areas larger mammals have nearly disappeared (southern, eastern, and northern slopes of Mount Cameroon). The Mount Cameroon project, trying to develop parameters for sustainable hunting, was unable to come up with a database for calculating sustainable offtake, as numbers were so low. Hunting pressure is also rising on Bioko. Due to its inaccessibility the southern part of the island still has a largely intact mammal fauna, including an endemic subspecies of drill (Mandrillus leucophaeus poensis). There is also an active trade in live animals from the ecoregion to supply the pet trade, including amphibians, reptiles, mammals, and birds.
An expanding human population seeking new agricultural land and bushmeat is the main cause of the threats to the remaining habitats of the ecoregion. The areas that receive slightly lower rainfall, and hence have better agricultural potential, are in the most demand and are the most likely to be converted into agricultural lands. The collection of non-timber forest products, including firewood and pygeum (Prunus africana), occurs, although the killing of Prunus (previously over-exploited for its bark) has largely stopped . Oil palm, rubber, and banana plantations are found across much of the Mount Cameroon foothills. Environmental impact studies carried out by the Mount Cameroon Project may impose constraints on further plantation creation, but some expansion is inevitable. The fact that none of this ecoregion is found within a National Park on the mainland is a major concern and a threat to the future of this important area.
Justification of Ecoregion Delineation
The chain of volcanoes that stretch from Bioko to Cameroon and along the Cameroon/Nigerian border form part of White's Afromontane archipelago-like regional center of endemism. They are also recognized as an Endemic Bird Area. The Mount Cameroon and Bioko Montane Forests ecoregion is considered distinct from the Cameroonian Highlands because of the younger age and activity of Mount Cameroon, reflected in the distributions (or absence) of many restricted-range taxa. The ecoregion was delineated from White's Afromontane undifferentiated montane woodland unit. The montane area (above 1,500 m elevation) of Bioko was included because it shares biological affinities with Mount Cameroon. Bioko was connected to the mainland during lower sea levels towards the end of the last Ice Age.
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