Pollinator-friendly habitat enhancements in commercial agriculture are understood to be beneficial for wild bee community outcomes, yet little is known about the effects of management and implementation of pollinator conservation recommendations in urban farms and community gardens. Many cities support diverse wild bee communities, including species indicative of high quality habitat, with urban areas recently posed as potential refugia for pollinator conservation. Using a multi-disciplinary approach, we investigated the influences of plant community composition, farm and garden management priorities, and surrounding land-use on wild bee community structure and the pollinator conservation potential of urban agriculture in shrinking cities.
We collected wild bees every 4-6 weeks from mid-April – late-October across 18 sites each in Detroit, MI, St. Louis, MO and Chicago, IL. We recorded blooming vegetation and ground cover, and completed landscape analyses. We surveyed all site managers and over 600 additional farmers and gardeners across the three cities about pollinator management strategies, including perceived benefits and barriers to implementation.
We found community gardens, urban farms and vacant lots support diverse and abundant wild bee communities in Detroit, St. Louis and Chicago. Preliminary results indicate bee abundance was significantly predicted by bloom richness (p = 0.01) and the proportion of green space in the surrounding landscape (p = 0.03), but not by the type of urban agriculture (farm, vs. community garden). Overall, farmers and gardeners who are implementing more pollinator conservation recommendations more diverse and abundant wild bee communities. The pollinator conservation recommendations most likely to be implemented include not using pesticides (79%), planting additional wildflowers (71%), and allowing volunteer blooming plants to persist (43%). Our survey results indicate that farmers and gardeners are interested in pollinator conservation, and believe the biggest barriers to implementing pollinator conservation techniques are limited funds (30%) and lack of expertise (30%).