Location and General Description
The Albertine Rift forms the epicenter of Africa’s montane rainforest circle. Both its fauna and flora have links to the west and southwest with Cameroon and Angola, to the northeast with the Kenyan Highlands, and the southeast with the Eastern Arc Mountains, and ultimately via the Malawi Rift with southern Africa (Dowsett 1986, Kingdon 1989). On the western side it abuts the Guinea-Congolian lowland rainforest. Collectively, its central location within Africa, juxtaposition of habitats, and prevalent altitudinal zonation, makes the Albertine Rift globally outstanding for its high species diversity and large numbers of endemics; highlighted by the ecoregion containing the world’s last population of Mountain Gorilla.
The Albertine Rift is dominated by a series of mountain chains, originating on the Lendu Plateau in northern Uganda/DRC (Bober et al. in press), and running south through the Ruwenzori mountains of Uganda and the eastern part of the Democratic Republic of Congo (03o N, 30o E), western Rwanda and Burundi, to some isolated massifs on the shores of Lake Tanganyika (to 08o S). The Albertine Rift has been formed from a combination of uplifted Pre-Cambrian basement rocks and recent volcanic activity. The uplift and volcanism are associated with the origins of Africa’s great rift valley and famous valley lakes, that were created by the clockwise rotation of the African continent into Europe, producing cracks extending down the eastern side of Africa. These large cracks in the crust are generally filled by lakes, including Lake Tanganyika, and are flanked by uplifted mountain areas. The intense crustal movement has also been accompanied by upwelling of volcanic material, most spectacularly in the volcanoes within the Parc de Volcans areas of the Albertine Rift. The Ruwenzori Mountains have the highest peak at 5110m, but above 3500 m the habitats are placed within the Ruwenzori-Virunga Montane Moorland ecoregion.
The severe geological history has resulted in a diversity of climatic regimes. While the Rift is located in the center of tropical Africa the high mountain regions extensively modify the climate, with a more temperate climate occurring in the highlands. Average rainfall throughout the mountain range varies between 1,200 to 2,200 mm per annum, although it is locally more in some mountain areas.
The ecoregion is dominated by montane rainforest (White 1983), but in the west, marginal fringes of the Guineo-Congolian rainforest impinge on the lower slopes (down from 500-800m), and forest/savanna mosaic habitats border it to the east in Uganda, Rwanda and Burundi. At altitudes above 3500 m, montane rainforest grades through Juniper forest and Ericaceous Heathland into the tussock grass and Giant Lobelia dominated altimontane vegetation of the the Ruwenzori-Virunga Montane Moorland ecoregion. Some details of the vegetation composition in the Albertine Rift Mountains are found in Lind and Morrison (1974), Langdale-Brown et al. (1964) and White (1983).
Throughout much of the ecoregion, especially in Burundi and Rwanda, the rural human population density is amongst the highest in Africa. This places considerable pressure on the remaining forest resources as most families live on shambas undertaking subsistence farming. Population densities are lower on the DRC side of the Rift, but considerable human movements have occurred in recent years and some areas that used to have few people (e.g. Itombwe) may now have considerable population densities.
The Albertine Rift is one of Africa’s most species rich and endemic rich regions, despite being one of its most poorly documented.
The botanical values of the area are poorly known and there is no overall synthesis of botanical richness or endemism in the ecoregion. Currently the total number of strictly endemic plants is estimated as around 1000-1200 species, which is of similar magnitude to the number of endemics known from the Eastern Arc Mountains and the Cameroon Mountains. At sites that have received higher levels of botanical exploration the floral values are better known. For example, Bwindi Forest in Uganda supports an estimated 1000 plant species; eight of these are tree species only found locally (WWF and IUCN 1994), yet botanical collections have only been made at Bwindi on a few occasions. Even less is known from the huge expanse of Itombwe Forest which occupies the southern Rift. It is expected that further botanical exploration will lead to the discovery of additional new species of plants and the botanical importance of the area may well change over time.
From what we know about the fauna of these mountains, mainly from older taxonomic studies, it is remarkably rich. Exceptionally large numbers of endemic species occur in all taxonomic groups. Unlike the Andes of South America, endemism is found at all altitudes, and extends markedly into the lower altitude forests on the western margins which form a border to the Congo Basin lowland forests (Prigogine 1985, Vande weghe 1988a & b). Among vertebrates the amphibians with 32 strict endemics spread across 12 genera, and a further seven near endemics, have the highest number of range-restricted species. The bulk of these endemics consist of the highly variable Reed Frogs (Hyperolius, 9 strict endemics), the Screeching frogs (Phrynobatrachus, 7 strict endemics) and the River Frogs (Anthroleptis, 5 strict endemics) and Clawed Toads (Xenopus, 3 strict endemics). Birds also possess exceptional levels of endemism with 30 strict endemics and another 16 near endemics, although no one genus dominates (Bober et al. in press and references therein). The endemic mammalian community contains 25 strictly endemic species and a further 11 species regarded as near-endemics (WWF database). The endemic mammal fauna is dominated by small-mammals, with 10 of the species being shrews and 12 species being rodents. One of only two species of the family Tenrecidae on mainland Africa is also strictly endemic to these mountains, the Ruwenzori otter shrew (Micropotamogale ruwenzorii, EN). The large number of endemic species, some occupying only a small portion of the ecoregion, also need consideration in any conservation plan for the area.
Although there are few endemic or near-endemic large mammals in the ecoregion, it does harbor the few remaining populations of the mountain gorilla (Gorilla gorilla beringei), one of the most critically threatened large mammals in Africa. This species is the obvious flagship species in this ecoregion, and the research already conducted provides a firm foundation from which to develop conservation strategies (Aveling and Aveling 1987, 1989, Aveling and Harcourt 1984, Doran and McNeilage 1998, Fossey 1983, Fossey and Harcourt 1977, Harcourt et al. 1981, Harcourt et al. 1983, McNeilage 1996, Schaller 1963, Schaller 1964, Watts 1984, Watts 1985, Watts 1991, Watts 1994, Watts 1995a, Watts 1995b, Watts 1998a, Watts 1998b, Watts 1998c).
The primate fauna also includes the owl-faced monkey (Cercopithecus hamlyni) which has an endangered subspecies (C. h. kahuziensis) in the ecoregion, and L’Hoest’s monkey (Cercopithecus lhoesti). Some of the easternmost populations of chimpanzee (Pan troglodytes, EN) also occur in this ecoregion (Aveling and Aveling 1989, Aveling and Harcourt 1984, Harcourt et al. 1983, McNeilage 1996, Hall et al. 1998a&b). The Albertine Rift endemic duiker Cephalophus rubidus may also venture into the upper parts of this ecoregion from the higher altitude heathland areas that are its more typical home.
In comparison to the other vertebrate groups the number of endemic reptiles is relatively low, with 11 strict endemics. These include four species of chameleons (Chamaeleo spp.) and four species of skinks in the genus Leptosiaphos. However, given the very high rates of endemism in other vertebrate groups the number of endemics may more reflect the relatively low rates of biological collecting, rather than the true numbers of reptile endemics
Despite its high biological importance, much of the forest of this area remains poorly studied. Specific references on the biodiversity of the Albertine Rift are rare (Bennun et al. 1994, Lovett and Wasser 1993, Stuart et al. 1990, WWF and IUCN 1994, Moreau 1966, Stattersfield et al. 1998; Bober et al. in press and references therein). For all taxonomic groups additional field studies as well as synthesis of existing collections and inventories need to be undertaken. It is expected that additional vertebrate, and especially invertebrate endemics are present in these mountain forests.
Some of the highest population pressures in Africa are to be found within the Albertine Rift with many families living on small farms originally cleared from the forest. Consequently, remaining blocks of habitat range from undisturbed to highly disturbed. For Rwanda alone, 1998 logged a minimum of 55% of the original extent of afromontane forest in 1934.
The forests of the Lendu Plateau in the northern reaches of the Albertine Rift have almost completely disappeared. Further south some relatively intact forests can be found within the Rwenzori Mountain range. From here the ecoregion passes through the Bwindi forest of southwest Uganda, the Volcanoes National Park, Gishwati-South and Nikura forests of northern Rwanda, the Nyungwe Forest Mountains area in Burundi and Rwanda, and the Itombwe Mountains of the southeastern portion of the Democratic Republic of Congo (DRC). Further to the south, there are only isolated mountain blocks, such as Mtbuuri in southern Burundi, Mahale Mountains and Mtkungwenahke in western Tanzania, and Mount Kabobo and the Marungu mountains in the eastern Democratic Republic of Congo on the shores of Lake Tanganyika. Outside protected areas these forests have been under severe human pressure and even within national parks they are not safe from serious disturbances. The ongoing conflicts in this region have made management extremely difficult. Especially the war in Congo and the genocide of Rwanda have caused major refugee problems, which has resulted in serious environmental problems.
Within the five countries encompassing the boundaries of the Albertine rift, the level and degree of protection is variable. In Uganda, parts of the forest are protected in the Rwenzori Mountains National Park and in the Bwindi-Impenetrable Forest National Park. In the case of Bwindi, WWF and other agencies support the Ugandan government in the management of the park. In the Democratic Republic of Congo, some forest on the Lendu plateau are supposedly protected in Forest Reserves, and the montane forests on the western side of Lake Kivu are protected by the Kahuzi-Biega National Park and the Virunga National Park. In Rwanda and Burundi, forests are protected in the Volcanoes National Park, and in the Nyungwe proposed National Park. Forests further to the south, particularly those of the Itombwe Mountains in the Democratic Republic of Congo, are currently unprotected. To some extent, this lack of protection is offset by the fact that these forests are remote and the population density is reported to be relatively low. In Rwanda, the proposed Nyungwe Forest and Kibira National Parks would join to the existing Volcanoes National Park forming a central African transfronteir-park. In Tanzania, the Mahale Mountains are protected as a National Park, mainly for the local populations of chimpanzee. Available information on the protected areas of this 70,166 km2 ecoregion are summarized below. It should be noted that part of Kahuzi-Biega National Park is also lowland, and that details of some of the sites mentioned above were not available. Although it is difficult to give accurate overall statistics for this ecoregion, roughly 13,500 km2 is gazetted, representing around 14 % of the ecoregion.
In both Rwanda and Burundi there are very high human population densities and in many areas the only stands of forest remaining are within Forest Reserves or National Parks, or those stands found in the most mountainous and therefore inaccessible areas. In Uganda, a similar situation occurs, where forest habitat has been lost from the majority of areas that are not protected by National Parks or which do not have Forest Reserve status (Howard 1991, Hamilton 1984). However, in the more eastern and southern portions of the Itombwe Mountains in the Democratic Republic of Congo, the population density is lower, and far greater areas of forest exist, including complete transition zones between lowland and montane forest types. There remains a worry that some of these areas may be logged and this should form a focus of any future conservation initiatives within the ecoregion. However, on each mountain block within the range the habitat has also been fragmented through the activities of man, specifically subsistence farming. Probably the least fragmented and most extensive area of habitat is found within the Itombwe Mountains of the Democratic Republic of Congo. In other areas, the forests are typically confined within protected areas, with the land between these areas largely farmed and occupied by people.
Types and Severity of Threats
The farming activities of rural people are destroying and fragmenting habitats of this ecoregion in many areas, and this issue is the largest and most overriding concern for conservation in the area. Coupled to high human population density and destruction of habitat, is hunting and poaching, which is causing major problems in several protected areas and is even more intense outside these areas. Fire wood collection is also a serious problem in several areas (Aveling, Schoorl, pers comm.).
Populations of elephant (Loxodonta africana), as well as many other large mammal species, have been decimated during the regions turbulent political past. This is especially the case in the DRC Virunga national park. An update of the situation is urgently needed to be able to implement and design appropriate conservation strategies.
There is an additional problem associated with the recent wars in Rwanda/Burundi, the Democratic Republic of Congo, and the overspills into western Uganda and Tanzania. These wars prevent the effective management of some protected areas in the ecoregion, thereby further increasing problems of encroachment and illegal activities, such as the killing of mountain gorillas. Large numbers of refugees from the Rwanda/Burundi/DRC wars are known to be deforesting some areas, and bands of rebels are known to use the forest to hide in between periods of raiding and fighting. In the more remote parts of the Democratic Republic of Congo, the threats are less severe, but even here there has been considerable intensification of the threats due to mass movement of refugees in recent years. In Kahuzi-Biega, GTZ is trying to continue conservation efforts, but many other areas have been virtually abandoned in the DRC. In Rwanda the situation is only slightly better, due to the continued tensions in this country. All large mammals need particular attention, by improving anti-poaching efforts and re-establishing control in the gazetted areas.
Justification of Ecoregion Delineation
This ecoregion largely follows the ‘undifferentiated montane vegetation’ unit of White (1983), including the western boundary adjacent to the Northeastern Congolian Lowland Forest, the southern polygon encompassing Monts Malimba and Magiba, and the three areas to the east of Lake Tanganyika (the Mahali Mountains). However, the northern montane forest area to the west of Lake Albert was enlarged to encompass the whole of the Lendu Plateau region, as depicted by Birdlife’s Endemic Bird Area for this region (Stattersfield et al. 1998). The boundary just north of the Ruwenzori-Virunga Montane Moorland areas was also delineated using the 1500 m contour, again, to better reflect the Endemic Bird Area. The polygon directly north of Lake Tanganyika that White portrays as a ‘mosaic of East African evergreen bushland and secondary Acacia wooded grassland’ was subsumed within the montane forest ecoregion, as this was considered more representative of the potential (non-anthropogenically influenced) vegetation.
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Prepared by: Allard Blom and Rauri Bowie
Reviewed by: In progress