Land Use Change Consistently Reduces α‐ But Not β‐ and γ‐Diversity of Bees

ABSTRACT Land use change threatens global biodiversity and compromises ecosystem functions, including pollination and food production. Reduced taxonomic α‐diversity is often reported under land use change, yet the impacts could be different at larger spatial scales (i.e., γ‐diversity), either due to reduced β‐diversity amplifying diversity loss or increased β‐diversity dampening diversity loss. Additionally, studies often focus on taxonomic diversity, while other important biodiversity components, including phylogenetic diversity, can exhibit differential responses. Here, we evaluated how agricultural and urban land use alters the taxonomic and phylogenetic α‐, β‐, and γ‐diversity of an important pollinator taxon—bees. Using a multicontinental dataset of 3117 bee assemblages from 157 studies, we found that taxonomic α‐diversity was reduced by 16%–18% in both agricultural and urban habitats relative to natural habitats. Phylogenetic α‐diversity was decreased by 11%–12% in agricultural and urban habitats. Compared with natural habitats, taxonomic and phylogenetic β‐diversity increased by 11% and 6% in urban habitats, respectively, but exhibited no systematic change in agricultural habitats. We detected a 22% decline in taxonomic γ‐diversity and a 17% decline in phylogenetic γ‐diversity in agricultural habitats, but γ‐diversity of urban habitats was not significantly different from natural habitats. These findings highlight the threat of agricultural expansions to large‐scale bee diversity due to systematic γ‐diversity decline. In addition, while both urbanization and agriculture lead to consistent declines in α‐diversity, their impacts on β‐ or γ‐diversity vary, highlighting the need to study the effects of land use change at multiple scales. We analyzed a global dataset of 3117 bee assemblages across 157 studies to assess how bee diversity varies among natural, agricultural, and urban habitats. We measured diversity using both the number of bee taxa (taxonomic diversity) and their evolutionary relationships (phylogenetic diversity). Compared to natural habitats, agricultural and urban habitats showed a 16%–18% reduction in local taxonomic diversity and an 11%–12% reduction in local phylogenetic diversity. At broader spatial scales, agricultural habitats exhibited a 22% decline in taxonomic diversity and a 17% decline in phylogenetic diversity compared to natural habitats, while urban habitats showed no consistent decline.