Mammal responses to habitat degradation induced by cashew expansion in West Africa

Tropical landscapes are perishing due to high rates of land-use change. In West Africa, Guinea-Bissau lost 77% of its closed-canopy forest over the last 25 years, mostly to the expansion of cashew monoculture. To date, understanding how species cope with such changes remains a conservation priority for the region. Here we examine mammal species composition, richness, and abundance, in addition to trophic-guild abundance across closed-canopy sub-humid forests and cashews orchards in the Cantanhez National Park, southwest Guinea-Bissau. Mammals were surveyed using one camera trap at each of the 24 sites, half in forest and half in cashew orchards, and their local and landscape-scale variables were measured. Based on 709 trap-nights, we collected 842 records from 25 mammal species. Local habitat structure--including canopy openness, floor obstruction, density of both lianas, palms and trees, tree species richness and height--sharply contrasted between forests and cashew orchards. As expected, mammal species composition differed between forests and cashew orchards, and the estimated, but not the observed, species richness declined towards cashew-like habitats. Although overall mammal abundance remained unaffected by the variables considered, carnivores were more abundant in cashew-like habitats, whereas insectivores and herbivores were more abundant in forest-like habitats. Human activity and distance to forest did not affect the response variables considered. Forest conversion into cashew orchards negatively affects mammals by profoundly changing the local habitat structure. Guild-level responses further unveiled specificity in their vulnerability to this form of land-use change, alerting for a potential disruption in the ecosystem functioning. We emphasize the need for policies that limit monoculture expansion, while safeguarding the remaining forests, thus maximising biodiversity persistence across the Afrotropics.