Do pathogen spillover, pesticide use, or habitat loss explain recent North American bumblebee declines? Nora D. Szabo, Sheila R. Colla, David L. Wagner, Lawrence F. Gall, Jeremy T. Kerr Conservation Letters, ¬©2012 Wiley Periodicals, Inc.
[Quoted for review purposes only]
> We consider pesticide use and habitat loss, other factors that have been proposed as potential causes of North American bumblebee declines (Colla & Packer 2008). If either were causing declines, we predict that species should generally have been lost from areas with high pesticide use or habitat loss, while persisting in areas with low pesticide use or habitat loss.
> We did not find significant relationships between losses and pesticide use or the relationships were in the opposite direction than predicted. We also did not detect significant relationships between losses and change in human population density for Bombus affinis or Bombus pensylvanicus.
> Although habitat loss and pesticides have well-established negative effects on bumblebees (Goulson et al. 2008; Williams & Osborne 2009), they are unlikely to be main drivers of recent North American declines. We did not find significant relationships between patterns of bumblebee losses and pesticide use, or the relationships were in the opposite direction than predicted.
> While pesticides have negative impacts on bumblebees at the individual or colony level (e.g., Morandin et al. 2005), our results suggest that pesticides are not a main contributor to declines of these species when their entire ranges are considered. Therefore, there remains an urgent need to identify other causes of North American bumblebee declines.