Impacts of urban wildflower enhancements on pollinator population size and site occupancy

Habitat disturbance is a central driver of ongoing biodiversity loss, including the loss of insect pollinators. To reduce the negative impacts of habitat disturbance, many restoration efforts implement wildflower enhancements, which have been linked to increases in local abundance and diversity of pollinators. However, it is uncertain whether observed effects on local pollinator abundance and diversity are a consequence of flower enhancements transiently attracting pollinators from the surrounding landscape versus actually bolstering pollinator populations over the long-term by increasing reproduction and survival. To estimate how pollinator population dynamics respond to wildflower enhancements, we used metapopulation sampling designs with temporally replicated surveys to compare population size and site occupancy of bees and syrphid flies in nine urban parks in Vancouver, Canada, with approximately 1-hectare area no-mow meadows against nine paired urban parks that were mowed biweekly. We account for imperfect detection of abundance and occurance using N-mixture and multi-species occupancy models applied through a hierarchcial Bayesian statistical framework. Preliminary results suggest that after accounting for imperfect detection, these urban wildflower enhancements do not have significant impacts the abundances of common species, but may increase the equilibrium occupancy of pollinators. By identifying how pollinator population dynamics respond to the underlying changes in the plant community, these results will enable us to design management approaches that conserve pollinator biodiversity over the long-term and, moreover, test whether generalities about wildflower enhancements translate to urban ecosystems.