The cultivation of perennial cash crops is fast expanding in the tropics, but for most crops and
regions there is very limited understanding about their biodiversity impacts. This is the case of
cashew nut cultivation, which is occupying ever larger areas, particularly in West Africa. Here
we investigated the impacts of cashew cultivation on biodiversity using butterfly assemblages
sampled across a gradient of cashew expansion in Guinea-Bissau (West Africa). The overall
species richness and abundance of butterflies was only slightly lower in cashew orchards than in
native woodland habitats, but whereas the former were dominated by generalist species, the
latter showed a much higher richness and abundance of trophic and habitat specialists. The
landscape context significantly affected butterfly assemblages, with reduced richness and
abundance of generalist species recorded within woodland habitats in heterogeneous landscapes
with low woodland cover. Increases in land cover by cashew cultivation were associated with
reduced abundance of specialist species within woodland habitats, and reduced abundance of
generalist species within cashew orchards. Overall, our study provides the first evidence that
cashew expansion may have serious negative consequences for biodiversity in West Africa,
suggesting that this is an unfolding conservation problem that needs to be fully evaluated.
Retaining woodland patches within production landscapes might help reducing the negative
impacts of cashew expansion on biodiversity.