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Humboldt-Universität zu Berlin (2019)

Understanding the immediate and time-delayed effects of deforestation on biodiversity in the Gran Chaco

Semper-Pascual, Asunción

Titre : Understanding the immediate and time-delayed effects of deforestation on biodiversity in the Gran Chaco

Auteur : Semper-Pascual, Asunción

Université de soutenance : Humboldt-Universität zu Berlin

Grade : Doctor rerum naturalium (Dr. rer. nat.) 2019

Résumé
Land-use change is a primary driver of biodiversity loss. During recent decades, the tropics and subtropics have witnessed accelerating deforestation rates, resulting in widespread extinctions. Even if further deforestation was to be avoided, species would likely continue to disappear due to delays in their responses to land-use change. The goals of this thesis were to provide a better understanding of the effects of past and contemporary land use on biodiversity in the Argentine Dry Chaco, and to develop approaches that capture the impacts of land-use change on biodiversity before local extinctions occur. The Argentine Dry Chaco provides an excellent scenario for this purpose due to its dynamic land-use history, the high deforestation rates, and its high biodiversity levels. At the community level, I found that species richness of birds and mammals was influenced by past landscape patterns, suggesting time-delayed responses to land-use change and the evidence of an extinction debt. These time-delayed responses were due to habitat fragmentation rather than habitat loss. At the population level, I found that giant anteater occupancy decreased particularly after 2000 when agriculture expanded rapidly. My results further suggested that land-use change had substantial indirect effects on species’ populations. Finally, I assessed the effects of deforestation on collared peccaries at the population and individual level. Peccary occupancy was highest in areas with high woodland cover. Where peccaries were present, physiological stress was negatively correlated with food availability. Overall, this thesis shows that deforestation is driving species to extinction in the Argentine Dry Chaco. While some species may disappear quickly following deforestation, extinctions of others may not be immediate, providing an opportunity to prevent those extinctions. The approaches presented in this thesis help to identify those opportunities in dynamic landscapes such as deforestation frontiers.

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