Urban Hymenoptera Communities
Bees and wasps are beneficial insects that can support pollination of urban plants (and crops!) and control insect pests through predation. In Cleveland OH, we have a transformative opportunity to use an influx of vacant lots, generated from economic decline, as a tool for increasing the city’s quality green space and supporting beneficial insects. By managing some of Cleveland’s 27,000+ vacant lots as conservation plantings for beneficial insects (Figure 1), we aim to increase ecosystem functioning throughout the city and make Cleveland more sustainable.
Vacant lots are typically managed with turf grass and mowed monthly. We changed the plant composition of 40 vacant lots in Cleveland in order to test how urban green space design can influence wasp and bee diversity. Our lots span through eight Cleveland neighborhoods and represent five unique combinations of plants and grasses. These five green space designs vary by plant height, their plant richness, and how much they will bloom over a summer.
In summers 2015-2016, I sampled these 40 lots once a month from June-August with yellow pan traps and Malaise traps in order to collect the bees and wasps utilizing these habitats. Our hope is that these data will help elucidate the connection between beneficial insects and our conservation plantings so that the city of Cleveland can use what we learn to manage vacant lots their vacant lots more sustainably.
Cavity Nesting Wasp/Bee Reproduction
In summers 2015-2017, I also sampled these 40 lots with trap nests (Figure 2) in order to monitor solitary bee and wasp nesting and test what characteristics enable a vacant lot to support reproduction and population growth.
Trap nests consisted of PVC pipes filled with 20 cardboard straws with varying diameters and were placed in each lot on May 1st. Every month from May-August, we checked each nest, collected all filled or partially filled cardboard nesting straws, and X-rayed the individual nests to determine productivity (larvae/straw) (See Figure 3). We predict that wasps and bees will have greater nesting productivity in vacant lots with increased plant diversity and structural complexity. In short, that a diverse assemblage of plants will be critical to urban green space quality and ecosystem functioning provided by insects.
Pollen Use by Urban Solitary Bees
Starting in summer 2017, I will also be investigating urban bee’s pollen use in nine Cleveland farms (Figure 4). Urban agriculture is highly reliant on the pollination services that wild urban bees can provide. However, we don’t have a clear picture of what pollen wild bees feed their young in urban environments, and therefore we don’t know which flower resources will best support pollinator’s survival and reproduction around urban farms.
In order to test what bee larvae eat in urban farms of Cleveland, I am trap-nesting bees in nine urban farms, collecting all occupied straws every 2 weeks, and then completing a DNA analysis on the pollen provisions within these nesting straws. Through this DNA analysis, we can determine what floral resources are critical for solitary bee reproduction. With this insight into urban bee foraging behavior and reproductive success, our study will inform farmers about urban habitat management to support future generations of urban bees and urban farm sustainability.
What impact will this research have?
At the end of this research, we will be able to recommend which plant combinations Cleveland should grow in their vacant lots instead of turf grass. In the next 5-10 years you may see that many of the grassy lots in your neighborhood are planted with beautiful pocket prairies instead. We hope our vacant lot recommendations will also help Cleveland save money that could be invested in other community development projects and infrastructure that will help Cleveland grow into a stronger, more beautiful city.
“I wanted to work in Cleveland’s vacant lots because I like to contribute to win-win situations where both people and the environment are healthy and able to thrive. I hope that our work helps:
- More urban residents have access to diverse, beautiful green spaces and the ecosystem services they support (storm water control, pollination, pest-suppression), and
- Urban biodiversity (especially pollinators!) to continue to prosper and contribute to greater environmental quality.”
This material is based upon work supported by the National Science Foundation under Grant No. 1253197.
Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.