How do bees respond to anthropogenic disturbance? A meta-analysis

Background/Question/Methods The possibility of global pollinator declines is concerning because animal pollination is required by most of the world’s plant species, including most crops. Assessment of pollinator decline is limited by a lack of long-term pollinator monitoring data. Here, we take an alternative approach: we use meta-analysis to synthesize the literature on how bees, the most important pollinators, are affected by widespread human disturbances such as habitat fragmentation, grazing, logging, and agriculture. We found 54 published studies (130 effect sizes) recording bee abundance and/or species richness as a function of human disturbance.

Results/Conclusions

Both bee abundance and species richness were significantly negatively affected by disturbance; however, these effects were not strong (weighted mean effect sizes, Hedge's d = -0.32 and -0.37 respectively). Habitat loss and fragmentation had the strongest negative effect, but this effect was only statistically significant in extremely fragmented study systems. Social bees were more sensitive to disturbance than solitary bees. Our findings are consistent with other recent meta-analyses that show negative effects of habitat fragmentation on animal-pollinated plants, and on the abundance of crop-pollinating bees. In combination, these studies suggest that pollinators may be declining globally as a result of increasing human disturbance. Our study also shows that bees’ response to disturbance is heterogeneous and that low-intensity disturbance may be compatible with maintaining pollinators.