Urbanisation is increasing worldwide, with major impacts on biodiversity, species interactions and ecosystem functioning. Pollination is an ecosystem function vital for terrestrial ecosystems and food security, however, the processes underlying the patterns of pollinator diversity and the ecosystem services they provide in cities have seldom been quantified. Here, we present a comprehensive meta-analysis, using 133 studies, on the effects of urbanisation on pollinator diversity and pollination. Our results confirm the widespread negative effects of urbanisation on pollinator diversity, particularly of Lepidoptera. Additionally, pollinator responses were found to be trait-specific, with below ground nesting, solitary, and spring flyers more severely affected from urbanisation. Meanwhile, cities promote a greater diversity of non-native pollinators, which may exacerbate conservation risks to native ones. Surprisingly, despite the negative effects of urbanisation on pollinator diversity, pollination services in cities are enhanced and mediated by the high flower visitation rates of abundant generalists and managed pollinators. We highlight that the richness of local flowering plants could mitigate the negative effects of urbanisation on pollinator diversity. Overall, the results demonstrate the varying magnitudes of multiple moderators on urban pollinators and pollination service provision and could help guide conservation actions for biodiversity and ecosystem function for a sustainable future.

An understanding of the influence of competition on bumble bees’ foraging strategy is essential to understand the coexistence of multiple bee species in the context of pollinator declines, but remains unclear. We conducted a field survey in an isolated meadow in eastern Himalaya with10 bumble bee species and more than 55 flowering plants they visited. In 2018 and 2019 we measured abundance of the three dominant bumble bees (one mainly foraging for pollen and two for nectar) and recorded the identity and frequency of flowering plants they visited. The intensity of competition of species pairs was evaluated by niche overlap. A composite index of flower depth of plants visited by each bumble bee was calculated on each sampling day. Results indicated that foraging strategies of the three bee species shifted differentially in response to increasing competition; the pollen-seeking bee was forced to forage for more nectar while the nectar-seeking bees were impelled to change target flowers in order to match proboscis length and flower depth. The coexistence of multiple bumble bee species in a community can thus be achieved by adjusting foraging strategy in response to intensity of competition for floral resources.