Associate Professor University of British Columbia, British Columbia, Canada
Abstract: As cities around the world rapidly expand into surrounding landscapes, there is a need to better understand the major drivers of urban biodiversity dynamics and the spatial and temporal scales at which these drivers operate. This is especially true for functionally important species such as insect pollinators, which are experiencing global declines. Although previous studies have determined that natural habitat and floral resources drive locally observed patterns of urban pollinator biodiversity, no study to date has explored whether these drivers influence urban pollinator biodiversity patterns at the landscape-scale. To test the hypotheses that greater total area of undeveloped natural habitat and greater average income (where income is a proxy for plant diversity and management resources) in an urban landscape promote pollinator biodiversity at the landscape scale, we applied an integrated Bayesian occupancy model to 12 years of natural history collections records, comparing occupancy rates of bumble bee and hoverfly pollinator species across 459 urban landscapes in the continental United States. We found that landscape-scale occupancy rates for the average bumble bee species was not associated with the area of natural habitat in an urban landscape (95% BCI = [-0.21, 0.42] change in occupancy rate), however, there was a weak, positive association with landscape income (50% BCI = [0.06, 0.23]). In contrast, we found a positive association between natural habitat area and the average hoverfly occupancy rate (95% BCI = [0.03,0.53]), emphasizing that natural habitat remnants such as greenbelts and nature reserves are critical for the maintenance of pollinator biodiversity in urban landscapes. Together, these results support the idea that landscape-scale, city-wide characteristics mediate urban biodiversity patterns, and that policies that promote habitat conservation and restoration within urban regions are necessary for the successful conservation of urban biodiversity.
