Urban Pollination Study of Green Roofs on the UWM Campus

Amanda Pastirik and Meghan Wersel

Department of Biological Sciences, Conservation and Environmental Science Program, UW-Milwaukee, pastirik@uwm.edu, mwersel@uwm.edu

Can green roofs help pollinators thrive alongside urbanization? While our cities continue to grow and green space becomes sparse, it is imperative that we supply pollinators with a resource-rich natural habitat. By analyzing pollinator use, insect diversity, floral abundance, and floral diversity, we sought to discover if green roofs can provide crucial habitat for pollinating insects. In the first year of a long-term study, we monitored Annual Report 25 pollinator visitation at two different green roofs on the UWM campus, in comparison to a ground-level prairie planting, while developing a protocol for further monitoring.

Observations were made each week, including the identification and counting of all insects that came in contact with flowers inside of a 0.25 m2 quadrat, identification of all plant species in bloom at each of the three observation sites, and abundance rank of all blooming species. In addition, a flower count within each quadrat was made during each observation day. Contrary to our expectations, we found that all three sites were similar in visitation rates, with a dropoff in visitation on the green roofs near the end of the season. We also found that the ground-level prairie planting had the lowest amount of variability between observations but had fewer overall visits compared to the standard Sedum-rich green roof. Our results show that green roofs do play a critical role in providing pollinator habitat and are therefore important in an urban environment. However, the drop-off of visitation to the green roofs shows supplemental plantings are also vital, as the green roofs we studied only provided a short blooming period for local pollinator communities. Undergraduate research project, Dr. Gretchen Meyer and Dr. Mai Phillips, advisors.