Anthropogenic pressures drive the multidimensional homogenisation of bird diversity in a South Asian landscape

Understanding the impact of anthropogenic pressures and their interactions with landscape heterogeneity is crucial for avian conservation and for the development of effective management strategies. Despite widespread concerns over biodiversity loss, major gaps remain in understanding how these factors influence multiple dimensions of avian diversity in highly human-dominated landscapes. We examined their effects on taxonomic, functional, and phylogenetic diversity in anthropogenic (farmland and settlement) and natural (forest and riverine) habitats within the Parsa-Koshi Complex of Nepal, a South Asian landscape undergoing rapid environmental change. Our results revealed that anthropogenic habitats consistently support lower taxonomic (α and β), functional, and phylogenetic diversity, with pronounced functional clustering in settlements, suggesting environmental filtering that favours generalist species. In contrast, natural habitats, particularly forests, exhibited stronger phylogenetic clustering, possibly due to human-mediated disturbances that promoted the persistence of the dominant clades. Increased anthropogenic pressure reduced diversity across most metrics, whereas greater landscape heterogeneity enhanced them, indicating a buffering role. These findings emphasise the importance of reducing anthropogenic pressure and maintain landscape heterogeneity as key strategies for sustaining avian diversity, while providing insights into how landscape management could support conservation amid ongoing environmental changes.