Predicting biodiversity loss in insular neotropical forest habitat patches
Neotropical forests have experienced high rates of biodiversity loss as a result of burgeoning land-use changes. Habitat conversion into cropland, pastures, and more recently hydroelectric lakes, are leading drivers of forest loss and fragmentation of pristine forests in the world’s most biodiverse region. This thesis aims to improve our understanding of the impacts of habitat fragmentation on biodiversity loss in Neotropical forests by evaluating the patterns of floristic changes and vertebrate extinctions in forest patches. Two approaches at different scales were conducted. First, a systematic literature review was carried out on the effects of fragmentation on Neotropical primates at a continental-scale. Second, biodiversity inventories were conducted on medium and large bodied vertebrates (including mammals, birds and tortoises) and trees ≥10 cm diameter at breast height at 37 islands and three continuous forest sites within the Balbina Hydroelectric Reservoir in Brazilian Amazonia. Patch area was a key driver of species persistence for all study taxa, yet other factors were also important. Hunting pressure exerted a strong influence on patterns of primate persistence within 760 fragments, and edge effects, including edge-related ground-fires, were the main predictors of floristic transitions using data from 87 quarter hectare forest-plots at Balbina. Additionally, matrix composition and species life-history traits played a key role in explaining patterns of species persistence. This study therefore highlights the importance of considering anthropogenic stressors in assessing the effects of land-use change to explain patterns of species persistence in forest patches, aside from including parameters related to the matrix and ecological life history traits of focal species. As conservation recommendations, prioritising large (>100 ha) patches, increasing their protection, and enhancing connectivity of surrounding habitats becomes clearly important. For future Amazonian dams, it is recommended that engineers should consider the overall topography of planned reservoirs to maximise landscape connectivity and/or reject plans targeting unfavourable river basins.
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