Bee diversity in the shrinking city: The influence of infrastructure, economic status and ethnicity

Background/Question/Methods

Currently, over 50% of the world’s population resides in cities, and over two-thirds by the middle of the century.  Alternatively, the cores of many cities, especially in the Midwest of the United States, are shrinking (losing >1% per year for over 10 years). Shrinking tends to occur spatially clumped with regards of socio-economic status and ethnicity. In the city of St. Louis the majority of the shrinkage has taken place in the north side, which is predominantly African-American and poor. Many city leaders have proposed the conversion of empty lots into community gardens as a strategy to stabilize neighborhoods and combat urban food deserts. We surveyed the bee community weekly (via aerial nets) of a nine community gardens along a North-South gradient in order to determine how socio-economic factors influence bee diversity. Finally, is hypothesized that empty lots and decaying buildings can serve as potential habitat, and thus increase diversity. The surrounding infrastructure at each garden was visually inspected whereas ground cover was assessed with ArcGIS. We built a spatial model at four scales, 100m, 500m, 1000m and 1500m to determine at what scale is infrastructure, as well as social and economic variables, influencing bee species diversity.

Results/Conclusions

We identified over 80 different species of bees in five families across St. Louis city, with an average of 36 ± 6.7 species per garden. There were differences in infrastructure with significantly more empty lots and abandoned and/or decaying buildings in the north side of the city. These differences were also consistent with differences in ethnic and economic status, i.e., poorer and mostly African-American. There was a correlation, although weak and not across all bee families, between increased bee diversity and increased abandoned or decaying infrastructure.  It seems that this relationship is complex and may be also influenced by the functional traits of the various bee families. The results of our study have implications for city managers on how to implement “smart shrinking” policies in urban cores.