Afforestation of tropical savannas has mixed consequences for bird communities

Abstract Land‐use change is a key driver of tropical savanna biodiversity and one such widespread change is the conversion of ancient (i.e., old‐growth) savannas to tree plantations. While the recognition of tropical savanna biodiversity continues to grow, our understanding of the consequences of savanna afforestation on biodiversity, and how these consequences vary across broad rainfall gradients occupied by tropical savannas, remains limited. We studied the consequences of savanna afforestation for bird communities in western‐Maharashtra, India at n = 15 sites—each consisting of an old‐growth savanna and tree plantation pair—stratified across a 459–1007 mm rainfall gradient. We found that overall, without factoring in rainfall, afforestation neither changed bird species richness nor abundance. But across the rainfall gradient, afforestation increased total species richness in the rainfall extremes while decreased richness in the intermediate rainfall range. Savanna‐specialist birds declined with afforestation whereas woodland‐specialists and nectarivorous birds increased. Afforestation consistently altered bird community composition across the rainfall gradient. Our results warrant a nuanced outlook toward impacts of savanna afforestation on native biodiversity. On one hand, our findings imply that conserving savanna‐specialist birds necessitates urgently halting ongoing large‐scale savanna afforestation. On the other hand, we urge scientists and policymakers to acknowledge the role of some tree plantations as supplementary habitats for native biodiversity.