Interactions between land-use change and climate warming drive long-term wild bee declines

Long-term data on species dynamics are scarce, limiting our understanding of biodiversity changes. We analysed over 17,500 museum records of 342 wild bee species collected between 1910 and 2021 at eight sites. Linking temporal distributions to land-use and climatic data, we show that continuous species turnover has reduced diversity over time. Early 20th-century landscape alterations primarily drove local extinctions of habitat-specialist species, initiating declines before global warming began. Subsequent climate warming has exacerbated these losses by reducing habitat suitability for already fragmented populations. While rising temperatures facilitate the immigration of thermophilic generalist species, land-use changes hinder this process; immigration would be faster in less altered landscapes. Habitat generalists with broad climatic niches show greater resilience, contributing to the observed species turnover and functional homogenization as their proportion increases. Climatic traits strongly influence species turnover, and the combined impacts of warming and land-use change further reduce species richness and functional diversity. Improving habitat connectivity and quality can enhance resilience to climate change, providing a clear target for conservation and policy.