(original) (raw)

Mount Nimba

ID

513

Author(s)

Michele Thieme, WWF-US, Conservation Science Program, Washington, DC, USA

Countries

Guinea
Ivory Coast

Reviewer(s)

Christian Lévêque, Centre National de la Recherche Scientifique (CNRS), Paris, France

Major Habitat Type

Montane freshwaters

Main rivers to other water bodies

The Cavally and Ya rivers, as well as tributaries of the Sassandra and Cess Rivers, originate on Mount Nimba.

Boundaries

Mount Nimba forms part of the southern extent of the “Guinean Backbone” that stretches from northern Guinea to northern Côte d’Ivoire and rises 1,000 m above the surrounding lowland plains. This mountainous region is located at the intersection of Guinea, Ivory Coast and Liberia.

Topography

Mount Nimba is part of an ancient mountain range, the Guinean range, which was upthrust between the end of the Jurassic and the end of the Eocene (Lévêque 1997). Since then, erosion has worn away the softer schists and granito-gneiss, exposing the underlying ore-containing quartzite (Lamotte 1983). This large ridge is about 40 km long and 8-12 km wide. Steep cliffs and quartzite peaks are prominent features of the landscape, along with deep valleys, high plateaus, rounded hilltops, and granite blocks. The highest peak in the ecoregion is Mont Richard Molard at 1,752 m (WWF and IUCN 1994).

Freshwater habitats

Rivers descending the steep slopes of Mount Nimba run swiftly, often experiencing torrential floods during the rainy season. Rheophytes, plants that can live in running water, dominate the riparian vegetation (Hughes & Hughes 1992).

Terrestrial habitats

Vegetation of the Mount Nimba ecoregion changes with elevation. Grasslands cover the summits, dominated by Loudetia kagerensis and Protea occidentalis on the slopes. The plum tree (Parinari excelsa) dominates mid-altitude (above 1,000 m) forests. A cloud or “mist” hangs over the mountain for months at a time at elevations over 850 m, promoting a lush growth of epiphytes in these forests (WWF and IUCN 1994). The forests give way to plains savanna that covers the piedmont below altitudes of about 500 m (Lamotte 1983).

Justification for delineation

This ecoregion is defined by the high elevation Mount Nimba and distinguished by an endemic aquatic fauna. The Guinean Highlands, of which Mount Nimba forms a part, separate the coastal rivers and streams to the west from the northwards-flowing Niger River to the east. The highlands have effectively formed a barrier to movement of aquatic species between these systems (Hugueny 1989). The fish fauna of the highlands has affinities with the Upper Guinea bioregion (Daget 1963). Within the highlands, Mount Nimba’s relative high elevation, the presence of rapids and waterfalls that has led to isolation, and the stability of the aquatic environment over time have promoted speciation.

Level of taxonomic exploration

Poor. Although a biological research station exists on Mount Nimba, only a few studies have been completed on aquatic species.