Bees facing a barrage of chemical and environmental burdens

Bees facing a barrage of chemical and environmental burdens

Wild and domesticated bees are under pressure from pesticides, diseases and habitat degradation, but it remains challenging to quantify their impacts and understand how they act together.

‘We’re measuring habitat loss, emerging pathogens, competition and new agricultural pesticides individually, but we are much less good at really understanding how they interact with each other,’ says Mark Brown, parasitologist and bee biologist at Royal Holloway University of London, UK. Open questions include whether a landscape with meagre flower resources renders bees more susceptible to parasites or to pesticides, and whether specific combinations of stresses harm bees more than others.

Brown and his colleagues combed through 15,000 relevant studies and selected experiments that looked at more than one stressor. They pooled data from 90 lab studies in their meta-analysis, from the last two decades, where bees were exposed to combinations of agrochemicals, nutritional stress and/or parasites.1 They looked at effects on mortality, foraging behaviour, memory, mortality and colony reproduction. They found an overall synergistic effect between multiple stressors on bee mortality, and concluded that we are underestimating the negative repercussions for bees of the multiple stresses they face.