Effects of urbanization on forest arthropod abundance and diversity

Background/Question/Methods

Ecologists are increasingly interested in how human-dominated environments impact native communities.   Suburban development is one of the most rapidly expanding habitats in many areas of the world.  Although there is increasing evidence that urbanization can affect the abundance and diversity of native species, little work has focused on the effects of urbanization on mutualist species, such as pollinators.  Native bees are of particular interest due to concerns over possible worldwide declines and their importance in conferring a critical ecosystem service.  We investigated the effects of urbanization on the abundance and diversity of bees in and around the Raleigh/Durham area of North Carolina.   We established five paired plots in naturally occurring (forested) and suburban forested (suburban) sites.  Over two years, we sampled for bees and other arthropods using a combination of bee bowls, hand-netting, and pitfall trapping. 

Results/Conclusions

We found significantly higher insect abundance in suburban than in forested sites.  In particular, mean number of bees per sample was significantly higher in suburban sites; more than double that of forested sites.  Higher bee abundance in suburban areas may influence the nature and outcome of plant-pollinator interactions of bee pollinated plants growing in suburban vs. forested habitats.  Further investigation into the mechanisms driving this observed pattern will lead to a better understanding of the ecological impacts of urbanization on the abundance and diversity of arthropod communities and the nature of plant-insect interactions.  The results of this study also suggest that suburban habitats may be important in future studies interested in evaluating and monitoring the abundance and diversity of native bees.