Planting native wildflowers improves vacant land as bee habitat in a post‐industrial city

Abstract As people leave post‐industrial cities in search of better economic opportunities, abandoned homes are demolished and transformed into vacant lots. These greenspaces have been demonstrated to provide habitat for urban wildlife and supply ecosystem services to communities. In the post‐industrial city of Cleveland, Ohio, USA, approximately 37% of the state's bee fauna (Hymenoptera: Apoidea) has been collected within vacant lots. Our goal was to determine whether planting native wildflowers (‘pocket prairies’) on vacant land would improve these sites as bee habitat. We hypothesised that pocket prairies would support a greater proportion of the regional bee species pool, represented by Metropark grassland bee communities in the suburban landscape, compared to unaltered vacant lots. Using pan traps and hand vacuums, we sampled bees in each treatment from June to September 2019. We collected 1087 bees representing 24 genera and 81 species. Bees visited over 30 floral species, including native wildflowers and urban spontaneous vegetation. Metropark grasslands supported a higher bee species richness and diversity than urban pocket prairies. Both Metropark grasslands and pocket prairies supported a higher bee abundance, diversity and species richness than urban vacant lots. Synthesis and applications : Despite the substantially smaller extent of the pocket prairies, these habitats supported a similar bee abundance to the Metropark grasslands. Bee foraging on seeded native forbs also increased from representing <5% to >60% of plant–bee interactions over the course of this project, highlighting the importance of habitat establishment for urban bee conservation. Our results suggest that greening vacant land can improve post‐industrial cities as bee habitat.