Natural forest formations
Forest cover map
On the basis of Chevalier's floristic surveys between 1898 and 1933 and his work with Emberger, and then Aubréville's forest botany surveys between 1936 and 1939 (Aubréville; 1938, 1949, 1950), the vegetation of countries south of the Sahara with a long dry season can be divided into Sahelian, Sudanian and Guinean. Trochain's 1940 study Contribution à l'étude de la végétation du Sénégal is still the best available source for forests in the west of the continent. Giffard (1971, 1974) took it as the basis for classifying the different forest regions of Senegal, distinguishing three phytogeographic zones:
- The Sahelian zone in the north of the country, with a southern limit running from the Senegal River along latitude 15° 15´ N, then moving up to 15° 30´ N on a level with Coki and turning south-west to reach the coast in the Dakar area corresponding to isohyet 550 mm. The forest is "an open formation, very scattered, with large gaps between trees grouped in long, narrow, uneven patches" (Giffard, 1974).
- The Sudanian zone, covering almost two-thirds of the country and lying to the south of isohyet 550 mm, the limit of the Sahelian zone, and north of the BanjulKolda line, the limit of the Guinean zone. From the floristic point of view, the northern limit is indicated by the appearance of Bombax costatum, Combretum elliottii, Cordyla pinnata, Entada africana, Parkia biglobosa, Prosopis africana and Pterocarpus erinaceus. "The transition from the Sahel is gradual and imperceptible; more thornless species appear, forest stands become denser, grasses form a thicker carpet, and tree and shrub storeys tend to overlap one another." The southern limit corresponds roughly to the furthest southern extension of Acacia seyal and the furthest northern extension of Lophira alata. Aubréville (1950) estimates that there are 80 forest species specific to the Sudanian zone, and two sectors on either side of latitude 14° N (isohyet 900 mm) can be distinguished on the basis of how they are divided and grouped, with the Sudano-Sahelian sector to the north being marked by the presence of Acacia senegal, Balanites aegyptiaca, Boscia senegalensis, Commiphora africana and Grewia bicolor, and the Sudano-Guinean sector to the south by the appearance of Cassia sieberiana, Daniellia oliveri, Oxytenanthera abyssinica and Terminalia macrocarpa.
- The Guinean zone, covering about a million hectares west of a line from Banjul to Kolda, with an average annual rainfall of 1 250 to 1 700 mm. Its climax was a two-storeyed, closed, semi-dry forest but fire and human activity have resulted in a mixture of open forest and tree savannah similar to the Sudano-Guinean type.
Thus the vegetation of Senegal covers a large part of the range of tropical vegetation from closed forest to sub-desert steppe.
The above map is an extract from the Global Forest Cover map produced as part of FRA 2000. Please refer to FRA Working Paper 19 for a background to the production of the map.
The designations employed and the presentation of material in this publication do not imply the expression of any opinion whatsoever on the part of the Food and Agriculture Organization of the United Nations concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries.
Map source: Global Forest Resources Assessment 2000, base map: ESRI