Atlantic Equatorial coastal forests
The Atlantic Equatorial Coastal Forests ecoregion has exceptionally high levels of species richness and endemism, contains large blocks of evergreen lowland moist forest, and the central portion has one of the lowest human population densities in Africa. Most of the floral and faunal assemblages are intact, including assemblages of threatened large mammals, such as the western lowland gorilla (Gorilla gorilla gorilla), mandrill (Mandrillus sphinx), and sun-tailed monkey (Cercopithecus solatus). Important centers of endemism are found in this ecoregion, particularly in some of the coastal mountain ranges.
Location and General Description
This ecoregion extends from the Sanaga River in west-central Cameroon south through Equatorial Guinea into the coastal and inland areas of Gabon, the Republic of Congo, and the Cabinda Province of Angola, ending in the extreme west Democratic Republic of Congo, just north of the mouth of the Congo River. At its southern extremity, the last 400 kilometers (km) of the ecoregion is a tongue of forest lying inland of the coastal plain and surrounded by the Western Congolian Forest-Savanna Mosaic.
Low undulating hills and plains characterize the topography of the northern portion of the ecoregion. Altitude increases gradually inland from the coast up to 800 meters (m) on the eastern margins. Coastal mountain ranges are also found, particularly in the southern sector of the ecoregion. These include Monte Alén, Monts de Cristal, and Monts Doudou which have altitudes in excess of 1,000 m.
The ecoregion lies within the wet tropics and receives high rainfall with limited seasonality throughout its extent. Rainfall is approximately 2,000 millimeters (mm) per annum, falling to 1,200 mm in the southern sector. Temperatures range from an annual mean maximum of 24 to 27°C, to an annual mean minimum of 18 to 21°C, and there is little seasonal variation; in fact, diurnal temperature variation often exceeds the annual range. Humidity is typically high throughout the year, except in the south.
The geology of the ecoregion is characterized by Precambrian metamorphic rocks such as schists, amphibolites, quartzites, and gneiss. The southern extent is delineated by the limits of these Precambrian rock outcroppings, with younger rocks on either side. In the northern part of the ecoregion the soils are ferrasols, whereas towards the south they are replaced by cambisols and some nitosols.
A number of important river systems cross the ecoregion. The Sanaga River, a significant biogeographical boundary comprises the northern limit. Further south, because of the lowland coastal alignment and heavy silt loads, many of the rivers form extensive coastal deltas and are prone to significant flooding, including the Ogooué, the Nyanga, and the Kouilou just north of the Congo River. These rivers and their associated habitats are an important component of this ecoregion.
Human population densities are low through much of the ecoregion. Densities of only 1-10 persons per km2 are typical, with an exception in the southern mountains where there are more than 50 persons per km2. Gabon and the Republic of Congo rank first and second as the most forested countries in Africa, with an average of one person per 19.3 and 12.6 hectares (ha) of national territory, respectively.
The ecoregion falls within the Lower Guinea Forest Block of the Guineo-Congolian regional center of endemism. Coastal evergreen moist forests characterize the vegetation, with mixed semi-evergreen moist forests in the drier southern extension. The lowland forests are multi-layered, with tall trees and canopies up to 60 meters (m) high. Near the coast the vegetation is somewhat different, especially in Gabon, where there are long strips of coastal savanna mosaic known as Guineo-Congolian edaphic grassland. These coastal savannas intergrade with low coastal forest and scrub, which gradually give way to continuous moist forest cover further inland. On the mountain ranges embedded within the ecoregion the vegetation is also somewhat different, and has floral elements more typical of montane forest habitats elsewhere in Africa.
This ecoregion supports exceptionally high species richness and has many endemic species. The endemics are concentrated in the mountains in the southern part of the ecoregion, although there are other strict endemic and near-endemic species in the lowland forest habitats. Some of these are found only in the western and eastern margins of the Congo Basin, and are apparently absent from the central Congo Basin forests.
In terms of the flora, this area and the adjacent Cross-Sanaga-Bioko Coastal Forests ecoregion to the north support about 50 percent of the 7,000 to 8,000 plants endemic to tropical West Africa, mainly in the coastal area of Cameroon. Three of the four families of plants endemic to tropical Africa (Huaceae, Medusandraceae, and Scytopetalaceae) are also abundant in the same area. Sites of importance for plant conservation include the Monts de Cristal of Gabon, a Pleistocene refuge for xerophytes and orophytes and one of two distinct Centers of Plant Diversity in this ecoregion. The Monts de Cristal are characterized by wet evergreen coastal rainforests and the site is estimated to have more than 3,000 species of vascular plants; over 100 of these are strict endemics. Another montane site is the Monts Doudou with more than 1,000 vascular species, of which 50 are strict endemics.
The second Center of Plant Diversity is the Mayombe region, occurring along the borders of the Republic of Congo, Cabinda Province (Angola), and western Democratic Republic of Congo in the southern sector of the ecoregion. A mosaic of lowland semi-evergreen forests, savanna, and wetlands characterizes this region. Over 1,100 species of plants occur, with well-represented families including Apocynaceae, Caesalpiniaceae, Euphorbiaceae, and Rubiaceae.
The species richness of forest mammals is exceptional. Several near-endemic and restricted-range mammals occur, including the sun-tailed monkey (Cercopithecus solatus, VU), long-footed shrew (Crocidura crenata), lesser Angolan epauletted fruit bat (Epomophorus grandis, DD), and African smoky mouse (Heimyscus fumosus). This is a critical area for the conservation of large forest mammals of Africa. Globally important populations of gorillas (Gorilla gorilla gorilla, EN) occur, along with those for chimpanzees (Pan troglodytes, EN) and forest elephant (Loxodonta africana cyclotis, EN). Other important larger mammals include mandrill (Mandrillus sphinx VU), black colobus (Colobus satanas), bongo (Tragelaphus euryceros), forest buffalo (Syncerus caffer nanus), and various duikers (Cephalophus spp.). A number of other small mammal species restricted to the Congo Basin forests also occur.
The avian species richness is high, particularly for forest restricted species. The ecoregion forms part of an Endemic Bird Area, the Cameroon, and Gabon lowlands. Although no strict endemics are known, eight near-endemic, and restricted-range species occur: Verraux's batis (Batis minima), black-necked wattle-eye (Platysteira chalybea), forest swallow (Hirundo fulginosa), Rachel's malimbe (Malimbus racheliae), Ursula's sunbird (Nectarina ursulae), African river martin (Psuedochelidon eurystomina), Bates' weaver (Ploceus batesi, EN) and the Dja River warbler (Bradypterus grandis, VU). Most of these species are shared only with the Northwestern Congolian Lowland Forests, and a few only with the Cross-Sanaga-Bioko Coastal Forests ecoregions.
Herpetofauna species richness and diversity is pronounced, particularly among the amphibians where there are over 13 endemic species. Of these, seven are considered strict endemics, including the Apouh night frog (Astylosternus schioetzi), Perret's shovelnose frog (Hemisus perreti), Gabon dwarf clawed frog (Hymenochirus feae), Ogowe River frog (Phrynobatrachus ogoensis), and Andre's clawed frog (Xenopus andrei). Among the reptiles there are also many endemics, eight of which are considered strictly endemic. These include the French Congo worm lizard (Cynisca bifrontalis), Haugh's worm lizard (Cynisca haughi), Boulenger's feylinia (Feylinia boulengeri), and the Cameroon racer (Poecilopholis cameronensis). In the Gamba complex of protected areas, it is noteworthy that all three species of African crocodiles are found (Crocodylus niloticus, Crocodylus cataphractus, Osteolaemis tetraspis) and at least four species of marine turtles frequent the beaches during the nesting season (Lepidochelys olivacea, Eretmochelys imbricata, Chelonia mydas, Dermochelys coriacea).
Extensive areas of forest also remain, and because human populations are often low, the fauna can be largely intact, especially in the southern parts of Equatorial Guinea and in Gabon. Migrations of forest animals still occur between this and adjacent ecoregions. Important elephant migrations are likely. Portions of the ecoregion are included in one of the world's largest remaining wilderness areas. Top predators, such as crowned eagle (Stephanoaetus coronatus), leopard (Panthera pardus, VU) and golden cat (Felis aurata) are still found at levels close to their natural range of variation.
Although considerable areas of rainforest still remain in southern Cameroon, Gabon, and the Republic of Congo, most of these areas have been selectively logged, some several times over. Logging has been particularly severe in Equatorial Guinea, which has lost approximately half of its forest cover, and logging is now becoming widespread in Cameroon and Gabon. Logging has even occurred within protected areas and only recently was an agreement reached to halt the logging of Gabon's Lopé Reserve core area. It is unlikely that any substantial areas of unlogged forest remain outside of protected areas, and the area of untouched primary forest is small. However, most of the logged forests have not suffered extensive human infiltration and thus are recovering.
In Gabon, apart from the logging camps, the forests are inhabited at low densities by agricultural and fishing people as well as small groups of forest dwelling Bakola and Bagyeli peoples. The total area under protection is 28,664 km2 or 15.1 percent of the ecoregion. This is higher than in most other forest regions of Africa. Major protected areas in the northern part of the ecoregion are the Campo-Maan National Park and Douala-Edéa Wildlife Reserve in Cameroon, and the Monte Alén National Park in Equatorial Guinea. Further south in Gabon, protected areas include part of the Lopé Reserve, the large Gamba complex of protected areas and the Wonga-Wongué Presidential Reserve. An additional 13 forest National Parks are in the process of being established in Gabon. The Republic of Congo contains the Conkouati and Dimonika-Mayombe Reserves. However, given the vast forest areas remaining in the ecoregion and its exceptional importance, the number of protected areas is insufficient, their level of legal protection too low, and they are not representative of the entire range of existing habitats. Proposals have been made as to where additional protected areas should be located within areas of high biological priority.
Despite widespread logging and other human-related conversion, the degree of fragmentation in this ecoregion is much less severe than that of the Upper Guinea forests of West Africa, or the forests of eastern and southern Africa.
Types and Severity of Threats
The current distribution of logging concessions covers almost the entire ecoregion, including many protected areas. This seems to indicate that logging will continue intensively. Extensive logging poses a serious threat to the continued existence of primary stands of rainforest. In the southern and northern areas of the forest where human population density is higher (Cameroon, northern Equatorial Guinea, Democratic Republic of Congo, and Republic of Congo), logging has opened up the forest and native agriculturists have colonized some areas. The human population is low in the central portion of this ecoregion, and the threat from agricultural conversion is not as pronounced.
The main threats to the larger mammals of the ecoregion come from hunting for both bushmeat and fetishes, including the supposed magical properties of certain species. In the Gamba complex of protected areas, a large portion of protein and iron in the human diet is provided by protected species. Large, charismatic mammals such as mandrill, forest elephant, and lowland gorilla are relatively easy to hunt but reproduce slowly, and populations do not increase quickly after hunting. The logging and oil industries facilitate hunting, poaching, and the trade in bushmeat, by providing markets, transport, and access to remote forests. Recently some logging and oil companies have shown willingness to address some of the major environmental impacts of the industry. There are also oil exploration and production facilities in Gabon, that are fragmenting the forest to some extent and favoring human settlements.
Elephants are poached throughout the ecoregion for their meat and ivory. In the past, elephant poaching was less pronounced in Gabon than elsewhere, but now seems to be on the increase. The trade in African grey parrots (Psittacus erithacus) is also highly developed in some parts of this ecoregion, especially in Cameroon, where the trade is seriously threatening the survival of this bird.
Justification of Ecoregion Delineation
The Atlantic Equatorial Coastal Forests ecoregion is a part of White's Guineo-Congolian regional center of endemism. The southern boundary of the ecoregion follows White's delimitation of lobes of rainforest stretching into the forest-savanna mosaic to the south. The northern limit of the ecoregion is bordered by the Sanaga River, which represents a significant biophysical boundary for many vertebrates (e.g., Mandrillus sphinx). The ecoregion stretches approximately 200 km inland, and encompasses the ranges of some large mammal fauna. The coastal littoral forest and the forests on the mountain ranges in the south of the ecoregion both contain distinct biological features, and may be separated into new ecoregions in the future.
Additional Information on this Ecoregion
- For a shorter summary of this entry, see the WWF WildWorld profile of this ecoregion.
- To see the species that live in this ecoregion, including images and threat levels, see the WWF Wildfinder description of this ecoregion.
- World Wildlife Fund Homepage
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