To mow or to mow less: How landscaping behaviors influence bee diversity and ecosystem services in residential yards

Background/Question/Methods

Lawns (consisting primarily of Poa sp.) dominate residential yards, blanketing more than 163,800 km², roughly 50% of urban land cover in the US. Although many wildlife studies have dismissed lawns as inferior habitat, the sheer volume and pervasiveness of this land cover deserves consideration. Lawns receive intensive management including irrigation, fertilization, and mowing, with these decisions largely driven by the desire to create an aesthetically pleasing landscape. The primary goal of this study was to test whether different lawn mowing frequencies have the potential for improving bee habitat and promote ecosystem services for households. To achieve this goal we assigned yards to a lawn mowing treatment: every week, two weeks or three weeks. We monitored bees and documented flower abundance and soil conditions throughout the lawn mowing seasons of 2013 and 2014 in 17 suburban yards in Springfield, MA. We then tested whether lawn mowing frequency influenced bee diversity, soil conditions, and the interactions of these parameters.

Results/Conclusions

We documented 110 bee species in Springfield, MA lawns, representing nearly a third of the state’s species pool. Floral abundance reached its peak in yards mowed every three weeks, averaging 300% more lawn flowers than yards mowed weekly. Bee abundance was highest in yards mowed every two weeks, though species richness did not differ among mowing treatments. Soils in yards mowed every three weeks were the least compacted, implying more nesting opportunities for some ground-nesting bees. Our results suggest that frequent lawn mowing might suppress floral growth and compact soil, leading to a decline floral abundance, which provides pollen and nectar sources for bees and other pollinators, and ground-nesting opportunities in urban and intensively managed areas. We recognize some of the disservices bees and other wildlife might introduce (e.g., stinging allergies). However, given the stark decline in native bee populations coupled with the extent of private lawns, identifying immediate and short-term management solutions for supporting wildlife habitat in a socio-ecological system has the potential for improving the ecosystem services we rely upon in our cities and suburbs.