The rainforest of tropical Africa extend from the coast of West Africa to the basin of River Congo. Its area of occurrence is identified as a regional centre of endemism. There are about 8,000 species of which more than 80 per cent are endemic. The Sudan, located south of the Sahara Desert, constitutes another regional centre of endemism (White, 1982).
The flora of the Sudanian centre of endemism consists of about 2,750 species of which about one-third are endemic (White,1982). Isoberiinia woodlands are common in the Sudan region but they do not dominate the vegetation. The Sudan region is separated from the forest region by a tranaitinn 7nno in whirh hnth tho finra and the vegetation are mixed.
One of the most recent work on the subject of biodiversity was published by works (FEPA) in 1992 under the title: Biological Diversity in Nigeria: A Country Study. A summary of the ecological status of the species shows that two species of animals and 20 species of plants had become extinct since 1950. These rates are unprecedented in comparison with the normal Natural History rates. They are indicative of an environmental disaster caused, presum- ably, by the current high rates of ecosystem modifi- cations resulting from human activities.
As of now, 48 species of animals and 431 species of plants are endangered; 16 species of animals and 45 species of plants are categorised as rare; 30 species of ani- mals and 20 species of plants are vulnerable; while 422 species of animals and 305 species of plants are endemic. All of these are of conservation con- cern to the country. The specifics of some of the endangered species include the following:
Reptiles and Amphibians:
The plants that had significant changes in their populations between 1981 and 1991, according to the Country Study, include Entandophragma utile, Pericopsis elata. Calamus spp, Diospyros sp, Pterocarpus osun, Khaya senegalensis, Sterculia setigera, Borassus acthiopium and Hyphaene spp. These are species exploited for timber, woodcarving, cane furniture, dyes and cosmetics, medicinal concoctions and food. The cause of the decrease in each population is given in each case as over exploitation.
Another recent attempt to update knowledge on the biodiversity of animal species in Nigeria is in Chapter 27 of the publication: IUCN Rain Forest: Africa. According to this publication, there are 248 species of mammals out of which 125 are found in the forest zone. The taxonomic affiliations of the 125 species are given as follows: insectivora, 11, chineptera, 38; carnivora, 11; Tubulidentata, 1; Proboscides, 1; Hyracoides, 1; Artiodactyla, 13. There are 83 bird species in the country with no information on their distribution between forest and savanna.
One of the species, which is forest- based, Mahimbus ibadanensis, is reported to be endemic to the country. Knowledge on the biodiversity status of reptiles and amphibians is sketchy. There are as many as 56 forest snakes out of which one, Mehelya egbensis, is reported to be endemic. Three crocodile species, including the Nile, the African dwarf and the slender snouted are present in various parts of the forest zone. There is a large number of amphibian species, 18 of these are rare, being found only in Nigeria and the Camerouns. One of the 18, Bufo perreft, is reported to be endemic to Nigeria. Stuart et al (1990) discuss the critical conser- vation sites and the critical conservation species for the country. The highlights of the critical species are given as follows:
-Primates: 24 species occur, nine of which are of concern. Among these, the following are of interest in the mixed forest area: the red-capped mangabey, the olive colobus and the white-throated guenom.
- Antelopes: 23 species occur, with two, the giant eland and scimitar-horned oryx, recently extinct. All but two of the sur- viving species are considered to be threatened.
- Fruit Bats: 18 species occur, including one of conservation interest: Epomops buet- tikoferi which is endemic to the West African forests in general.
-Other Mammals: The elephant and a species of the African fat mouse, steato- mysjacksoni, which occurs in the south- western forest zone are of conservation concern.
- Birds: The lbadan malimber is a very rare species, endemic to Nigeria where it occurs in the south-west.
- Reptiles: All three species of crocodile sur- vive in reduced numbers and are there- fore of conservation concern. The hinged tortoise also survives in much reduced numbers and should be of con- servation concern.
-Amphibians: There is one endemic species of toad, Bufo pemeti, only known from the Idanre Hills in Ondo State. This also is of conservation concern.