Biodiversity in a forest-agriculture mosaic – The changing face of West African rainforests

Abstract

The biodiversity of West African rainforests is globally significant but poorly described, little understood in terms of its functional significance, and under threat from forest loss and degradation. Estimates suggest that about 10 million ha of forest may have been lost in the 20th Century, and around 80% of the original forest area is now an agriculture-forest mosaic. These highly modified forests provide food, fuel, fibre and a range of ecosystem services for over 200 million people. As a consequence, the future of biodiversity in the region is intimately linked with the lives and livelihoods of local people. The available evidence suggests that forest loss and degradation has been caused primarily by agricultural expansion, sometimes facilitated by other human activities such as wood extraction. This expansion is a response to the demand generated by a growing and increasingly urbanised human population, but has been exacerbated by small increases in crop yields over recent decades. We synthesize and review our state of knowledge on the value of human-modified habitats for forest biodiversity in the region. Data on biodiversity are patchy, but we show that across plant, invertebrate and vertebrate groups, there is a significant loss of forest species as tree cover is reduced and vegetation structure simplified. Agricultural expansion clearly causes significant local biodiversity loss. We argue that replicated landscape-scale studies are now needed that describe changes a…