Bees are stressed out! Scientists say climate change is part of the problem.

Both wild bees and honeybees are being pummeled by stressors that can act alone or together to pack a powerful and even deadly punch. Now a study in the journal Science by an international team of fourteen scientific experts has analyzed the historical and current geographical range of bumble bees and confirmed a steep decline due to climate change.(Kerr et al 2015) The southern edge of their range has moved northwards, away from the equator, and upwards to cooler, higher elevations. This has resulted in an overall intercontinental 'range compression' that has resulted in a loss of about 185 miles (300 km) across Europe and North America. These global stressors are in addition to more local stressors like pesticide poisonings, say the scientists.

These findings are bad news for our food security. Bumble bees pollinate many food crops, as well as forage like clover that feeds livestock, gardens, and wild flowers that provide food and habitat for all sorts of wildlife. Climate change can disrupt the timing between bees and bloom, so that when pollinators come out of hibernation, the flowers they need to start the season are not in bloom. Climate change may also shift the range of bees and plants, creating a mismatch between bees and their food.

"Pollinators are vital for food security and our economy, and widespread losses of pollinators due to climate change will diminish both," stated Jeremy Kerr, a biologist from the University of Ottawa, who led the new study. "We need to figure out how we can improve the outlook for pollinators at continental scales, but the most important thing we can do is begin to take serious action to reduce the rate of climate change." (Univ Vermont press release)

Bee on flowers Scottland - Mel Peffers.jpg

Other researchers have identified the following factors - in addition to climate change - as likely contributors to bee decline (see NRDC fact sheet for details and scientific sources):

  • Poisoning from an onslaught of toxic insecticides used on field crops and home gardens as well as pesticides used in bee hives to control bee pathogens;
  • Loss of habitat from land use change and the widespread use of herbicides like atrazine, glyphosate (Roundup), and 2,4-D that kill off the blooming wild flowers and groundcover like clover that bees rely on for food;
  • Diseases from rapidly spreading bee parasites like the deadly Varroa destructor mites, small hive beetles, and Nosema fungus;

Any one of the above factors may be enough to injure and kill bees, but various combinations are almost certain to cause serious harm or death. For example, disease can weaken a colony and make it more susceptible to pesticide poisoning, and vice-versa.

Either disease or pesticide poisoning can jeopardize a colony's ability to survive a particularly cold winter or an unexpected heat wave, when bees emerge but food is not available. This situation is compounded with a shrinking healthy habitat for bees. We know from our own experiences that combined stressors are more harmful than one stressor alone.

Just think how much more likely you are to catch a cold when you haven't slept well for several days. That's what life is like now for the stressed out bee!

Photo of Bumble Bee in Scotland by Mel Peffers.

Selected resources:

More info on NRDC's bee website, and direct link to NRDC fact sheet, "Bee Deaths, Pesticides, and a Stalled Regulatory System".

Goulson D, Nicholls E, Botías C, Rotheray EL. Bee declines driven by combined stress from parasites, pesticides, and lack of flowers. Science. 2015 Mar 27;347. Full article pdf.

Kerr JT, Pindar A, Galpern P, Packer L, Potts SG, Roberts SM, Rasmont P, Schweiger O, Colla SR, Richardson LL, Wagner DL, Gall LF, Sikes DS, Pantoja A. 2015. Climate change impacts on bumblebees converge across continents. 10 July 2015, Vol 349 Issue 6244.

Friends of the Earth have information on bee-friendly gardens and landscaping.

Pesticide Action Network has information on bee declines and pesticides.

Center for Food Safety has information on pollinators and pesticides.

About the Authors

Jennifer Sass

Senior Scientist, Health program

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