Browsing by Subject "tropics"
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(2023)Land-use change stands behind the current biodiversity crisis and all it entails in terms of ecosystem services. Guinea-Bissau, in West Africa, is originally characterized by a forest- savanna mosaic biome. However, while savannas have long been planted with rice, both rice paddies and forest remnants are now being converted into cashew monocultures – the only cash crop in the country – at unprecedented rates. The ecological impact of such rapid change is largely unknown. To help fill this gap, we examined how three diversity metrics – rarefied species richness, abundance and composition – varied across forest remnants, cashew orchards and rice paddies for amphibians and reptiles in northern Guinea-Bissau. To do so, visual encounter surveys were carried across 21 sampling sites, seven of 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. Amphibians’ diversity in forest remnants and cashew orchards was similar across all metrics, but rice paddies had a higher abundance and unique composition compared to forest remnants. Reptiles’ abundance was highest in cashew orchards and this habitat had a distinct composition, when compared to forest remnants. Rice paddies sustained both lower reptile richness and abundance. Overall, our results are not in agreement with 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 overall species diversity. In face of the eminent habitat conversion, maintaining heterogeneous landscapes, including the persistence of both forest remnants and rice paddies, will allow minimizing biodiversity loss in West Africa.
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(2023)Driven by the growing world population and increased food demand, the conversion of natural habitats into agricultural lands is occurring at an unprecedented rate. This is in turn the leading driver of the current biodiversity crisis, particularly in tropical forest areas characterised by prominent species diversity. Due to an accelerating cash-crop expansion, the once forest-savannah landscape of Northern Guinea-Bissau is now notably occupied by cashew orchards, in addition to scattered forest patches and floodable rice paddies. So far, it remains unknown how these kinds of human-modified landscapes can sustain mammal species over contrasting seasons, and how the habitat use varies across feeding guilds. To address this gap, this study aimed to understand how medium-sized mammals make use of mosaic-like landscapes in Northern Guinea-Bissau by considering the interactive effects of (1) habitat type: forest patch, cashew orchard and rice paddy and (2) season: before (June-July 2022) and after (October-November 2022) the peak of the rainy season. To do so, in each of the two seasons we conducted a 30-day consecutive camera-trap survey across seven landscapes, each of which comprised the three habitat types, amounting to 21 sampling sites. I evaluated mammal species richness, abundance (number of records) and composition across habitat types and seasons at the assemblage-level and discussed the species-specific habitat dependency. I further analysed species abundance across four feeding guilds: carnivores, insectivores, herbivores and omnivores. Based on a sampling effort of 1200 camera-trap days and 940 records, I identified 21 mammal species from 10 families and five orders. At the assemblage-level, species richness and abundance were similar between habitat types, but higher after the peak of the rainy season, except for rice paddies. Forest and cashew habitats shared similar species composition, which differed from rice paddies. Habitat-dependent species were found in each of the habitat types. At the feeding guild-level, in both seasonally periods carnivores and insectivores were less abundant in cashew orchards, while omnivores were more abundant. The results demonstrate that habitat conversion is likely to disrupt the functional structure of mammal assemblages. Maintaining heterogeneous landscapes, including both forested and open-area habitats, is crucial to maximize the integrity of mammal assemblages in Northern Guinea-Bissau. These findings can be used as baseline information in effective conservation measures in Guinea-Bissau and other tropical regions undergoing rapid conversion for cashew cultivation.
Now showing items 1-2 of 2