Deforestation and bird extinctions in the Atlantic forest

Abstract

The Atlantic forests of South America hold a great concentration of biodiversity, but most of this habitat has been destroyed. We therefore expect many species to become extinct, and yet no bird extinctions have conclusively been recorded. There could be three explanations for this. First, birds may be able to adapt to deforested landscapes. Second, many species may have become extinct before they were known to science. Third, there may be a time-lag following deforestation before extinction occurs. We present the most complete list to date of the endemic birds of the Atlantic forests (124 forest-dependent species), and then use the species-area relationship to predict how many species we expect to become extinct through deforestation (51 species i.e. 41%). We also count how many Atlantic forest endemic birds are independently considered 'threatened' with 'a high risk of extinction in the wild in the medium-term future' (45 species i.e. 36%). We compare these totals and find that they are similar, suggesting that there is a time-lag between deforestation and extinction. We go on to test the robustness of this result by varying the parameters used to make our predictions. The only parameter that varies enough to substantially weaken predictions based on deforestation is the habitat classification of Atlantic 'forest' birds. If we include species that can survive in secondary and non-forest habitats then, unsurprisingly, we find that deforestation overestimates threat. Overall, not only does deforestation accurately predict threat to Atlantic forest endemic birds, but this result is robust enough to accommodate considerable variability within our data.