Nimba Range

The Nimba Range is a range of mountains in West Africa, where the borders of Guinea, Ivory Coast, and Liberia meet.

The Nimba Range forms part of the southern extent of the Guinean Highlands, a highland region that stretches from northern Guinea to northern Côte d'Ivoire, and rises 1,000 m above the surrounding lowland plains. The highest peak is Mount Richard-Molard, on the border of Côte d'Ivoire and Guinea, at 1,752 m (5,750 ft), which is the second highest point in West Africa, west of Cameroon. "Mount Nimba" may refer either to Mount Richard-Molard or to the entire range. Other peaks include Grand Rochers in Guinea at 1694 meters (5558 feet), Mont Sempéré in Guinea at 1682 meters (5518 feet), Mont LeClerc in Guinea at 1577 meters (5174 feet), Mont Tô in Guinea at 1675 meters (5495 feet), and Mont Piérré Richaud in Guinea at 1670 meters (5479 feet).[1]

The headwaters of the Cavalla, Cestos, Saint John, and Sassandra rivers originate in the Nimba Range.

Geology

The Nimba Range is narrow ridge approximately 40 km long, which runs northeast-southwest. It is composed mostly of Precambrian rock, including granite and quartzite which contain deposits of iron ore.[2] The iron ore deposits in the range have been mined since the early 1960s, and diamond mining also takes place.[3]

Climate

Rainfall varies greatly with elevation and season. About 3,000 mm of rain falls at the highest altitudes, and between 700-1,200 mm at the lower elevations. Most of the rainfall occurs between May and October.[4]

Ecology

Nimba Range lies within Guinean Forests of West Africa biodiversity hotspot. It harbour an especially rich flora and fauna, it is the home of more than 2000 vascular plants, 317 vertebrate species, 107 of which are mammals, and, to more than 2,500 invertebrate species with a strong endemism level. Notably endemic vertebrates such as the Micropotamogale of Mount Nimba (Micropotamogale lamottei), the viviparous toad of Mount Nimba (Nimbaphrynoides occidentalis), and Lamotte's roundleaf bat (Hipposideros lamottei). Other threatened animals are West African lion (Panthera leo senegalensis), pygmy hippopotamus (Choeropsis liberiensis), zebra duiker (Cephalophus zebra), and western chimpanzees that use stones as tools.[5]

Terrestrial ecoregions including Guinean montane forest, Western Guinean lowland forests, and Guinean forest-savanna mosaic. Nimba Range has distinct freshwater ecoregion, because of high portion of endemic aquatic species.

Terrestrial

The plant communities of the Nimba Range change with elevation.

The Guinean montane forests ecoregion covers the portion of the range above 600 meters elevation. Major plant communities in the ecoregion include montane grasslands and savannas, cloud forests, and lower montane forests.

High-altitude grasslands and montane savannas cover the highest peaks, dominated by the grass Loudetia kagerensis. The grasslands are home to one endemic fern, Asplenium schnellii, and two endemic flowering plants, Osbeckia porteresii and Blaeria nimbana. Shrubs, including Protea occidentalis, inhabit the slopes.[6] The endemic frog species Nimbaphrynoides occidentalis, which inhabits the montane grasslands of the range, is totally viviparous. The Guinea Screeching Frog (Arthroleptis crusculum) is a threatened species found on Mt. Nimba and other peaks in the Guinea Highlands. It is found in high-altitude grassland and in gallery forests during the dry season.[7] Ptychadena submascareniensis is another frog species that has been found only on Mt. Nimba and in the Loma Mountains of Sierra Leone.[8] Below the highest peaks, montane grasslands interspersed by gallery forests, between 1,000-1,600 meters.

Above 850-950 meters elevation, near-daily mist and clouds support cloud forests, dominated by the Guinea Plum tree (Parinari excelsa), trees of the Myrtle family (Myrtaceae), including Syzygium guineense, and species of Ochna and Gaertnera. The moist climate supports many epiphytes, including an endemic orchid, Rhipidoglossum paucifolium.

Lower montane forests of Lophira procera, Tarrietia utilis, Mapania spp.,Chlorophora regia, Morus mesozygia and Terminalia ivorensis occur between 550 and 900 meters elevation.[9]

Below 600 meters, the montane forests transition to the Western Guinean lowland forests ecoregion to the south of the range, and the Guinean forest-savanna mosaic to the north.

Freshwater

Swift-running streams descend steep slopes of the range, and often experience torrential floods during the rainy season. Rheophytes, plants that can live in running water, dominate the aquatic vegetation.

The endemic aquatic animals in the Nimba Range includes frogs, fish, the Nimba Stream Crab (Liberonautes nimba), and the endangered Nimba otter shrew (Micropotamogale lamottei). The African clawless otter (Aonyx capensis) also inhabits the mountain streams.Species richness is high among aquatic invertebrates, including 81 species of dragonflies.[10]

The WWF designates the Nimba Range a distinct freshwater ecoregion because of its moderate species richness and high proportion of endemic aquatic species, particularly among fish and amphibians. The Nimba Range's high elevation, its rapids and waterfalls that isolate habitat areas, and the stability of the aquatic environment, have promoted speciation.

The Guinean Highlands, of which the Nimba Range are part, separate the coastal rivers and streams of Upper Guinea from the upper Niger River basin. The highlands form a barrier to movement of aquatic species between these freshwater regions. The fish fauna of the Nimba Range shares affinities with that of Upper Guinea.[11]

Mount Nimba Strict Nature Reserve

In 1943, the colonial government established a Strict Nature Reserve, which prohibits tourism, in the Côte d'Ivoire section of the range. It was extended into Guinea the following year. The area remained protected after Guinea and Côte d'Ivoire became independent. UNESCO declared Mount Nimba a biosphere reserve in 1980, and a World Heritage Site shortly thereafter.

References

  1. ↑ "Grand Rochers, Guinea." Peakbaggers. Accessed 27 September 2015.
  2. ↑ "Mount Nimba Strict Nature Reserve, Guinea and Côte d'Ivoire". Encyclopedia of Earth. Accessed November 10, 2012.
  3. ↑ "Guinea Highlands". Encyclopedia Brittanica. Accessed 27 September 2015.
  4. ↑ "Mount Nimba". Freshwater Ecoregions of the World. Accessed November 10, 2012.
  5. ↑ Centre, UNESCO World Heritage. "Mount Nimba Strict Nature Reserve - UNESCO World Heritage Centre". whc.unesco.org. Retrieved 2016-02-23.
  6. ↑ "Mount Nimba Strict Nature Reserve, Guinea and Côte d'Ivoire". Encyclopedia of Earth. Accessed November 10, 2012.
  7. ↑ "Arthroleptis crusculum" IUCN Red List. Accessed 28 September 2015.
  8. ↑ "Ptychadena submascareniensis". IUCN Red List. Accessed 28 September 2015.
  9. ↑ "Mount Nimba Strict Nature Reserve, Guinea and Côte d'Ivoire". Encyclopedia of Earth. Accessed November 10, 2012.
  10. ↑ "Mount Nimba". Freshwater Ecoregions of the World, accessed November 10, 2012
  11. ↑ "Mount Nimba". Freshwater Ecoregions of the World, accessed November 10, 2012

External links

Coordinates: 7°34′N 8°28′W / 7.567°N 8.467°W / 7.567; -8.467

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