August 16, 2016

expert reaction to study investigating neonicotinoid use on long-term population changes in bees

Neonicotinoid insecticides have been implicated in the decline of bees, yet the evidence is derived from short-term laboratory studies on honeybees and bumblebees. Publishing in the journal Nature Communications scientists from the Centre for Ecology & Hydrology have investigated the long term, large scale impact of neonicotinoids on 62 wild bee species across England. These comments accompanied a briefing.

All our previous output on this subject can be seen here.

Dr Christopher Connolly, Reader in Neurobiology at the University of Dundee, said:

“This is a very interesting new paper that continues the growth of evidence supporting the role of the neonicotinoids in the bee decline. The evidence against neonicotinoids now exists in key bee brain cells involved in learning and memory, in whole bees, entire colonies and now at the level of whole populations of wild bees.

“The study investigated 62 wild bee species over 18 years on oilseed rape (the most likely source of exposure to bees). They found a three-fold increased negative effect on bees known to forage on OSR, compared to those that do not.

“In contrast to the laboratory studies, where the cause and effect of neonicotinoid exposure was established, this study performs an important nationwide correlation between OSR and bee populations. As the study is only a correlation, other causes for the decline in the bee species are possible. Among the caveats to this correlation is that bees foraging on OSR only benefit from this food source for 4-6 weeks and it is possible that they struggle to find food at other times (independent of pesticide exposure). The second major caveat is that other pesticides are used on OSR and the use of several, such as glyphosate and azoxystrobin, have also increased on OSR over the same timescale as the neonicotinoids. So, other chemicals used on OSR could be the drivers of bee decline observed in this study.

“Therefore, this study adds important new evidence on the safety of neonicotinoid use, but we still cannot exclude the impact of other pesticides and habitat loss on the current bee declines. There is still much that we need to know before we can stop the decline in the insect pollinators on which we depend for our food supply and ecosystem stability.”

‘Impacts of neonicotinoid use on long-term population changes in wild bees in England’ by Woodcock et al. published in Nature Communications UK time on Tuesday 16th August. 

Declared interests

Dr Christopher Connolly: “I have no conflicts of interest.”