Quantifying the impacts of land-use change and management on tropical biodiversity across scales

Tropical forests harbour exceptional biodiversity and are vital for sustaining future human needs, yet they face severe threats, particularly from agricultural land-use change. In this thesis, I examine the impacts of livestock agriculture on tropical biodiversity using a comprehensive field-based dataset across local, regional, and near-national scales. Birds are used as a model taxon due to their ease of sampling, extensive data availability, and their representation of broader ecological impacts. I assess phylogenetic and functional diversity to reflect biodiversity’s multidimensionality and identify land-use practices that best conserve it.
Chapter 1 introduces the broader context and key aspects of the research problem. Chapter 2 examines the local scale in lowland tropical forests, finding that deforestation reduces both phylogenetic and functional diversity, with land-sparing practices offering better conservation outcomes. Chapter 3 assesses land sharing and sparing strategies across a topographically diverse region spanning elevational gradients, showing that land sparing remains the more effective approach despite elevational differences. Chapter 4 explores forest conversion impacts at regional spatial scales, revealing phylogenetic diversity loss driven by impoverishment within clades, though entire lineages are not systematically lost, a pattern that is generally scale independent. Chapter 5 explores functional diversity change, finding that although functional richness declines, the overall functional structure remains resilient. However, forest loss is especially detrimental to dispersal-limited forest birds. Chapter 6 synthesises the main findings of the thesis, discusses their implications, and highlights potential applications along with directions for future research.
Overall, losses of phylogenetic and functional diversity appear less severe than those typically reported using taxonomic metrics at local scales. Nonetheless, the findings highlight the need for more sustainable agricultural practices that prioritise forest conservation. Approaches that share land with wildlife appear incompatible with species dependent on intact habitats, suggesting that strategies to spare and restore native forest may be more effective.