Historical trends show more declining than increasing species among European pollinators

Anthropogenic global change presents a growing threat to insect pollinators. Yet, long-term, continental-scale assessments of their population trends remain limited. Here, we leveraged a curated database of over four million occurrence records, covering 88% of extant bee and hoverfly species in Europe, to assess persistence, richness, and occupancy trends over the past century. Species persistence at the European level was relatively high, with modern records available for 87% of bee and 89% of hoverfly species. Regional richness changes were modest, with declines in the Atlantic and Continental regions for both pollinator groups. Recent increases were observed in the Alpine region for bees, but species richness remained largely stable elsewhere. At the species level, however, a more concerning picture emerged: Most bee species and about half of hoverfly species declined in occupancy. Species traits explained little variation in these trends, although there was a weak tendency for cold-adapted bees to show steeper declines than warm-adapted ones. Genera showing some of the steepest declines include parasitic or dietary specialists, though neither of these traits significantly predicted occupancy trends. Overall, we highlight clear warning signs of species population declines, but with potential recovery opportunities if we take urgent actions to reverse those trends.