Diverse urban pollinators and where to find them

Urbanization affects the occurrence, abundance and distribution of pollinators worldwide. Although urban green spaces support many pollinators, global estimates of urban pollinator diversity are still lacking. Here, we present a global overview of urban pollinators, characterizing the most frequently recorded species and functional groups, as well as the types of urban green spaces where these pollinators were most frequently recorded. A systematic review of the literature revealed a total of 11,560 pollinator records in urban green areas. These comprised 3148 species from 255 cities in 46 countries, with more than half of the studies (similar to 67 %) carried out in non-tropical cities. Hymenoptera was the main pollinator group recorded, especially bees, followed by Lepidoptera and Diptera worldwide. However, birds were more commonly reported in tropical than non-tropical regions, highlighting their importance as pollinators in the tropics. The most frequently recorded species were social and generalist bees, including invasive and managed species. Hence, while some bees may be able to persist in urban areas, other groups may face challenges that need to be considered when planning urban pollinator conservation. Considering the urban habitat types where pollinators were sampled, university campuses and gardens were the most common types investigated in tropical and non-tropical regions, respectively. These results may reflect regional differences in urban landscape characteristics, as well as a research bias caused by greater investment in urban ecology research in non-tropical countries. Our review synthetizes the diversity of urban pollinators worldwide and highlights the gaps and challenges in promoting their conservation more inclusively.