Conserving marine biodiversity on the African coast: Implications of a terrestrial perspective

Conservation principles developed for terrestrial habitats are frequently inapplicable in marine situations. This dichotomy arises because of different characteristics of the substratum and the existence of water as a ubiquitous marine dispersal medium. Physical differences are manifest in biological differences including reproductive mode, range requirements and levels of endemism. Marine systems differ further from terrestrial ones in that they have been subject to a very limited anthropogenic fragmentation, in contrast to land where many habitats have become highly fragmented. Estuaries and coral reefs, however, are naturally fragmented and particularly vulnerable because their substrata are strongly influenced by biological processes which are easily disrupted. One of the greatest threats to life in the sea is resource exploitation by man. In Africa, marine conservation is secondary to terrestrial conservation—only four countries in sub‐Saharan Africa have marine reserves. Marine reserves are effective in increasing population sizes of exploited stocks and supplementing stocks in adjacent areas through emigration. They also have the potential to provide recruits to exploited areas. Biogeographic patterns can be used to site marine reserves. We propose a middle/edge arrangement of ‘biodiversity reserves’, linked to biogeographical regions. Such reserves would achieve conservation of both representativeness (middle) and high diversity areas (edge). As a necessary corollary, we also suggest a second tier of reserves which has the specific purpose of improving local yields of exploited species. The sizes of biodiversity reserves should be determined by local habitat heterogeneity. Second‐tier reserves should be designed to maximize their benefit to adjacent areas while minimizing their size.