Restoring habitat with native flowering plants benefits wild bees in an urban landscape
Native bees provide critical pollinator services for both crop and wild flowering plants, yet the status of many bee populations is either poorly understood or has declined in the past 30 years. Habitat degradation and urbanization, especially the loss of floral and nesting resources, is hypothesized to negatively impact wild bee populations. In a sea of urbanization, college campuses in cities have the potential to be native habitat islands for wildlife. To improve natural habitat in an urban landscape, Massasoit Community College has converted mowed lawns to native plant sanctuaries. We conducted an experiment to better understand how habitat restoration impacts wild bee populations. The bee community at Massasoit was sampled along a 120m transect that began at the native meadow and extended further than the maximum foraging distance of most small bees. We collected bees using pan traps and measured wild bee abundance, diversity, and richness.
Wild bee abundance, diversity, and richness was differentially impacted by distance from the native meadow. Two of the most abundant bees collected were small carpenter bees from the genus Ceratina and green sweat bees from the genus Agapostemon. The abundance of Ceratina was much higher at or within 40m of the meadow, while the abundance of Agapostemon did not appear to be influenced by distance. Ceratina nests in cavities of stems and dead wood, while Agapostemon nests in loose to compact soil. Our results indicate that abundance might be correlated with nesting preference. Although nesting resources are often overlooked in landscape restoration, our study suggests that planting native flowering forbs increases the availability of nest sites in an urban landscape and may benefit cavity-nesting bees.