Wetlands are found in most African countries, the largest including the Okavango Delta, the Sudd in the Upper Nile, the Lake Victoria and Chad basins, and the floodplains and deltas of the Congo, Niger and Zambezi rivers. Despite being among the most biologically-productive ecosystems in Africa, wetlands are often regarded locally either as wasteland, habitats for pests and threats to public health or as potential areas for agriculture. As a result many wetlands are being lost. Coastal wetlands in Egypt and Tunisia and freshwater wetlands in the Sudan are also under increasing threat. Freshwater ecosystems found in lakes, rivers and wetlands may be the most endangered ecosystems of all.
Environmental pollution is an increasingly major threat to biodiversity in many countries.
Pesticide residues have reduced the populations of several bird species and other organisms. Both air and water pollution stress ecosystems and reduce populations of sensitive species, especially in the coastal zones where there is a high population density and industrial activity. As the region continues to industrialize, the adverse impact of pollution on biodiversity will become even more severe unless cleaner production technologies are adopted. The introduction of exotic species over the past century also contributed to biodiversity loss as some alien species 'out-competed' native vegetation. However, the introduction of undesirable exotic species is declining, a positive trend that will probably continue as regulations on the importation of biological resources become increasingly stringent.