Unveiling how herpetofauna cope with land-use changes—Insights from forest-cashew-rice landscapes in West Africa

Abstract

Agricultural induced land-use change comprises a key driver of biodiversity loss across tropical forests. Guinea-Bissau, among Afrotropical West Africa, was formerly occupied by native forest-savanna mosaics. While savannas have long given place to traditional rice agroecosystems, forests are now being transformed into cashew monocultures at unprecedented rates. The ecological impact of such rapid change is largely unknown. Here, we examined how rarefied species richness, encounters, and composition of amphibians and reptiles varied across forest remnants, cashew orchards, and rice paddies in northern Guinea-Bissau. To do so, visual encounter surveys were carried across 21 standardized sampling sites, seven in each habitat type. A total of 703 amphibian and 266 reptile encounters was recorded from nine and 14 taxa, respectively. The results show class-specific responses to habitat type. Amphibian richness was similar across habitat types, but rice paddies held more encounters and distinct composition compared to forest remnants. Reptile richness and encounters were lower in rice paddies than in forest remnants, but cashew orchards had the most encounters and a different composition compared to forest remnants. Overall, our results do not support the expected detrimental impacts of cashew expansion, which might be due to the still high heterogeneity of habitat types within the landscape. Rice paddies proved particularly important for amphibians, and for open-habitat reptiles, boosting the landscape-scale species diversity. In face of the eminent habitat conversion, maintaining heterogeneous landscapes, including the persistence of both forest remnants and rice paddies, is critical to minimize biodiversity loss in West Africa.