Predicting the pattern of decline of African primate diversity: an extinction debt from historical deforestation

Populations that have survived extensive habitat loss may still face extinc tion owing to a time lag between initial habitat loss and eventual populati on collapse. Using island biogeography theory, I investigated the potential existence and magnitude of such "extinction debts" among African forest pr imates as a result of historical deforestation. Forest primate species exhi bited a classic species-area relationship (S = cA(z)) with forest habitat a cross African countries I conducted three tests based on the species-area r elationship that indicate extinction debts are likely to exist in African f orest primates; in particular several national extinctions should have alre ady occurred solely as a result of forest loss in the last 50 years (if ext inctions occurred simultaneously with habitat loss), but none of these exti nctions have yet taken place. I also used the species-area relationship to predict the number of species that make up the total debt accumulated since deforestation began in these countries. My, results suggest that in most c ountries the debt currently consists of over 30% of the forest primate faun a, which usually constitutes between four and eight species. These figures are likely to be accurate because the same model pl edicts with a reasonabl e degree of precision (1) the severity of threat of extinction from defores tation faced by country endemics, (2) the distribution of regional communit y endemics threatened by deforestation, and (3) the total number of African species threatened by deforestation (according to the 1996 IUCN Red List). My findings indicate that although protected areas are an essential part o f conservation, the protection of the remaining forest alone may not be eno ugh to prevent extinctions caused by habitat loss.