Temporal shifts in bumblebee community composition more likely explained by climate change than by increasing urbanization

Abstract Bumblebees ( Bombus spp.) play an essential role in pollinating a wide range of flowering plants, but many bumblebee species have declined across Europe. Here, we assessed temporal changes in farmland bumblebee community composition alongside increased urbanization of the landscape context over a 19-year period. We repeated a bumblebee survey in 2024 that was originally conducted in 2005 in a farmland area in Helsinki metropolitan area in Finland. We found a significant increase in species richness and a shift in bumblebee community composition over the period. These changes took place in parallel with a significant change in temperature preferences but not tongue lengths or habitat preferences of the bumblebee species. Based on Community Temperature Index (CTI) estimates, the relative abundance of warm-dwelling bumblebee species increased. Most of the new species observed in the study area were species with southern distributions in relation to Finland, suggesting that the increase in species richness may be related to climate change rather than to increased urbanization in the surrounding landscape. Our results suggest that bumblebee community composition may change rapidly with rising temperatures. The increase in species richness and the persistence of several bumblebee species that have declined strongly elsewhere in Europe also suggest that farmland bumblebee species are not necessarily particularly sensitive to urban land use in the surrounding landscape, and suitable habitats in urban areas might play a role in bumblebee species conservation.