Quantifying dung beetle responses to anthropogenic disturbances in tropical forest regions

Abstract

Tropical forests sustain most of Earth’s biodiversity and provide numerous ecosystem services. However, these forests have long been impacted by human activities, following the growing demands for resources to satisfy human needs. For instance, the Brazilian Amazon is the largest tropical forest remaining and currently has approximately 60 million ha of forests converted to pastures, and other 50 million ha under timber concession. In order to move towards a more sustainable use of this tropical forest region, we need to understand biodiversity responses to human activities, and the underlying mechanisms that determine those responses. This thesis aims to address this knowledge gap by quantifying dung beetle responses to anthropogenic changes in the Amazonian state of Pará, Brazil. In Chapter 2, my objectives were to investigate dung beetle responses to disturbances such as selective logging and wildfires, and identify environmental and/or historical characteristics influencing the observed patterns. Chapter 3 assess the impacts of forest conversion to pastures on dung beetle communities, identifying the main drivers of species occurrence in this open land-use. Finally, in Chapter 4 I assess the choice of variables for dung beetle studies on anthropogenic changes in tropical landscapes, identifying gaps between variables importance and use in the literature. For this thesis, I used data on dung beetles sampled across 273 independent sites, across multiple scales and encompassing undisturbed primary forests, logged primary forests, logged and burnt primary forests, secondary forests and introduced pastures (Chapter 2 and Chapter 3). In total, I sampled a total of 74,926 dung beetles belonging 149 species. I also, used data from a literature review and a structured survey of 25 authors (Chapter 4). Overall, this thesis demonstrate that anthropogenic disturbances promote impoverishment of dung beetle communities in tropical forests, following changes in forest canopy openness and biomass, and a strong dependence of natural open habitats to serve as source of populations for the introduced pastures. This work also shows that there are some discrepancies in relation to variables importance and use in the dung beetle studies on consequences of tropical forest modification. I use the findings from this thesis to discuss the impacts of human activities in tropical forests, presenting alternatives for future research and applied management initiatives.