Geographic Patterns

Centres of species richness

Species distribution maps for fishes, molluscs, odonates and crabs were overlaid to identify those river basins holding the highest richness of species for each taxonomic group.

 Species richness of African freshwater taxa

Species richness of four taxonomic groups mapped to Hydro1K level 6 sub-basins. The species are mapped 'Low' to 'High' using Jenks Natural Breaks, to reflect the differing number of species included represented by each of the taxonomic groups.

Although species distributions vary, three areas came out as species rich across all of the taxonomic groups; the Congo Basin, the east Africa Great Lakes (Particularly Lakes Victoria, Tanganyika and Malawi), and the coastal basins of western Africa.

Distribution of threatened species

Whilst species richness across the four taxonomic groups show similar trends, mapped distributions of regionally threatened taxa differ considerably.

Distribution of regionally threatened freshwater taxa in Africa

The distribution of regionally threatened species of four taxonomic groups mapped to Hydro1K level 6 sub-basins. The species are mapped 'Low' to 'High' using Jenks Natural Breaks, to reflect the differing number of species included represented by each of the taxonomic groups.

Whilst the Great Lakes support the highest number of threatened fishes and molluscs in Continental Africa, these areas are less important to threatened crabs and odonates. One area of uniform importance to each taxonomic group was southwestern Nigeria and the Niger Delta; this area is home to several endemics, and is heavily threatened by deforestation (causing sedimentation of the waterways) and oil drilling.

The Western Cape of South Africa is a unique ecosystem and also an area of high endemism. It has a number of threatened species, and is particularly important to threatened Odonata. More information on the threats to this region is available on the southern Africa pages.

A particularly rich area of threatened species is noticeable in northern Africa, especially for the odonates. Many of the more mobile species are actually Mediterranean endemics, and their distribution extends into southern Europe, but this is not universally the case, and major threats such as drought are an issue for many endemics. More information on the threats to this region is available on the northern Africa pages.

Distribution of restricted range species

For fishes, molluscs and crabs, species with restricted range were defined as those regionally endemic species restricted to any level 3 river basin as defined in the Hydro1K data layer. The average area of a level 3 basin is approximately 36,000 km2. As odonates are generally more mobile, and found in freshwater and terrestrial habitats, restricted range species were defined as those with a range of less than 50,000 km2, plus those that qualify for a threatened category under the restricted range Criteria of B or D.

Restricted range species richness of Africa's freshwater taxa

Richness of restricted range species mapped to single Hydro1K level 3 sub-basins

Again, the Great Lakes are shown to support a large number of restricted range species, particularly for fishes and molluscs, with the Congo basin being important for odonates. The Western Cape also reflects a high number of restricted range species, particularly for endemic crabs.

Data Deficient species

Although large amounts of information have been made available as a result of this project, it has also highlighted the extent of information still lacking.

Data deficient species richness of African taxa

The distribution of Data Deficient species mapped to river catchments

These maps show an under representation of Data Deficient species, as many do not even have any locality information available in order to map their known or inferred range. Key areas recognised as lacking in information recognised both by these maps and by local experts and scientists are the Congo basin, and northeastern Africa.