Urban agriculture is increasing in the United States, with vegetables and fruits often grown in private and community gardens as well as larger tracts of vacant land. These small-scale agricultural efforts may contribute to urban sustainability and can provide food security for those living in low-income inner city neighborhoods with limited access to fresh produce. Despite the potential social, nutritional, and ecological benefits of urban agriculture, little is known about the pollination services that support such efforts. Many crops grown in urban gardens benefit from or are dependent on pollination by insects, especially bees. However, while studies have found some bees to be prevalent in florally-diverse urban habitats, bee diversity or abundance also have been shown to decrease with increasing urbanization. Therefore, pollinator communities may vary across the urban landscape due to local management of floral resources (e.g., flower plantings along city blocks) as well as development intensity at larger spatial scales; these factors may then influence pollination services across the urban landscape. To determine how pollination services are distributed across the urban landscape, this research will (a) evaluate changes in pollinators and their response to floral resources across a gradient of urban development, and (b) determine how these biotic changes affect the consistency and magnitude of pollination services. The research will take place in Chicago, IL, the third largest city in the United States. In addition to sampling pollinator communities, this study will use an experimental "mobile garden" on the back of a pick-up truck to quantify directly pollination services across the city.
An assessment of pollination services in cities will increase understanding of the potential sustainability of urban ecosystems. This knowledge can be applied to increasing yield in urban agriculture, potentially contributing to food security in densely populated neighborhoods. This project will train undergraduate and graduate students through participation in research and educate Chicago residents about the importance of pollinators. Finally, the research will inform urban planners about the ecological attributes, at both neighborhood-block and landscape scales, that affect the ecosystem service of pollination.
This project examined the diversity and distribution of pollinators across an urban environment. We found at least 37 bee species inside Chicago city limits. In general, we found a greater abundance and diversity of bees in more densely-populated areas of the city (excluding downtown Chicago, which we did not include in our study) compared to less-densely populated areas. This pattern of increased bee abundance and diversity with more people appears to be due to the fact that densely-populated neighborhoods contain a greater diversity of flowering plants. We also examined the link between pollinator communities and pollination of three different plant species – cucumber, eggplant, and purple coneflower. We took the plants to various study sites across the city and allowed bees to visit them. The plants were pollinated at all study sites, but fruit and seed set was not the same everywhere. Increased pollinator abundance or diversity led to increased pollination of all three plant species. Pollination of purple coneflower was further increased in locations with more floral resources, suggesting that this species would benefit from being near other flowering plant species. Our work has examined insect and plant communities in residential yards, which are an understudied but potentially important part of the urban ecosystem. We have identified interesting links between socio-economic factors (e.g., income, race, rental status) and yard composition that may have important implications for urban biodiversity. We have found that these yards contain a surprising level of biodiversity, and our work shows that simple changes (e.g., planting more flowering plants) can increase biodiversity further. This research resulted in the training and education of one PhD student, one Masters student, one high school teacher, dozens of undergraduate students, and countless Chicago residents. We created brochures about our research, which we handed out to all interested passers-by during our field work. We held pollinator-identification training sessions, which were attended by numerous students and Chicago residents. We have given talks to the general public and presented our work at academic conferences and universities. To date, we have published one paper from our project, but we anticipate that 4-5 additional papers will come from this work.
