A new study by the Harvard School of Public Health (HSPH) confirms what has long been feared: insecticides, in particular those in the neonicotinoid class, are causing the wide-scale collapse of bee colonies. According to the UN, bees are responsible for pollinating 70 of the 100 crop species that account for 90% of the world’s food – so it’s a scientific imperative to find and eliminate the cause of declining bee populations around the globe.
Colony Collapse Disorder (CCD), in which bees inexplicably leave the safety of their hive over winter and die en masse, was linked to the use of imidacloprid by the HSPH in a 2012 study. The new study has shown similar results with another neonicotinoid, clothianidin. Both studies showed that it only took low doses of the pesticides to cause abnormal behavior in the subject bees. The latest study also casts doubt on another popular theory: that pesticides cause bees to be more susceptible to mites and parasites. Bees in the pesticide test groups had just as many mites and parasites as control bees that weren’t exposed to the chemicals. This leads the Harvard team to surmise that “the neonicotinoids are causing some other kind of biological mechanism in bees that in turn leads to CCD.”
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In the latest study, scientists observed 18 bee colonies in three Massachussets locations between October 2012 and April 2013. In each location, one colony was exposed to imidacloprid, one to clothianidin, and one control colony had no pesticide exposure. As winter approached, each colony experienced a natural population decline. But in January, the control colonies began to increase again, whereas the pesticide-exposed colonies did not. By April, half of the neonicotinoid-exposed colonies had died out in circumstances that indicated CCD. However, only one of the control colonies had died, succumbing to a parasite invasion.
Lead researcher of the project, Chensheng (Alex) Lu, now hopes that further research will be able to shed light on exactly what the causal link is between the neonicotinoids and CCD. As he states, “Hopefully we can reverse the continuing trend of honey bee loss.”
Photos by Jeff Turner and Todd Huffman via Flickr