In the past decade, scientists have raised alarms about the decline in pollinators, including the semi-domestic honey bee.
There seems little doubt that honey bees are dying off at alarming rates. It would be surprising if similar trends were not occurring across many species of bee, wasp, beetle, and butterfly.
Data point: in my pollinator friendly yard, we get lots of insects. Up to two years ago, we had honey bees and at least three other species of bees, as well as butterflies, and numerous identified insects. Every day, all summer.
Last year, there were no honey bees. None this year, either. From hundreds to zero in one year. I assure you that the flowers are the same, so where are the bees?
Suspicions fall on agricultural chemicals, insecticides intended to protect crops from being eaten by insects. But with a bazillion dollar industry and possibly huge crop losses at stake, trivial ideas like, “just stop using pesticides” are neither reasonable nor feasible. We need to know exactly what is happening to bees, and we need to know as soon as possible.
For one thing, there are a number of stressors for bees, including the familiar refrains of habitat loss and climate shift. For that matter, there are a lot of human introduced chemicals that might be involved. And, in the end, the bees must contend with the combination of all these.
But out of all the troubles plaguing our bees, fingers have pointed to neonicotinoid chemicals which are applied as a coating on crop seeds. Bees don’t have much to do with seeds, but the worry is that these chemicals persist for months, and small quantities are on the flowers that bees and other insects visit. Visiting hundreds of flowers, a bee may be exposed to tiny amounts of chemical many times. Furthermore, insects may carry the chemicals to other flowers and back to nests, spreading small amounts of the toxins.
An assessment of the problem requires examining how tiny amounts of chemicals persist and spread, as well as how much pollinators pick up from these sources. Investigating this in real settings is a non-trivial challenge, because the amounts of chemicals are small and must be measured over long periods of time. There are many possible variables, including how the chemicals are used, weather and soil conditions, and who know what else.
This month a European team reports a large scale study of these effects, comparing the effects over two years of neonicotinoid with control . The careful study found a rather complicated set of results, different for different countries in the study. In some cases, there was clear losses of the bees, in others there were no differences between conditions. In the case of the UK, so many bees died in all conditions that there could be no statistical comparison of the effects. The study also found traces of the chemicals in the nests of wild bees, which appears to be related to reduced populations.
Overall, their results seem to show that there definitely are losses of bees, and these chemicals may contribute to the losses, at least in some cases. Most likely, neonicotinoids weaken some of the bees, making them more vulnerable to other challenges.
This study also confirms that the chemicals persist for months, and seem to accumulate in the nests of wild bees, far from the location of the deployment, and far from the intended target. This is consistent with other studies .
There is certainly cause for concern here. The EU and Canada are moving to stop using these chemicals, with a calculus that even with uncertainty, the benefits don’t outweigh the risks .
With the current administration, the US EPA will almost certainly not act to restrict these chemicals, study or no study. Sigh.
If you still have bees, be sure to say goodbye to them this summer. There won’t be very many left in a few years.
- Rebecca Morelle, Large-scale study ‘shows neonic pesticides harm bees’, in BBC News – Science & Environment. 2017. http://www.bbc.com/news/science-environment-4038208
- Erik Stokstad, Controversial pesticides can decimate honey bees, large study finds, in Science – News. 2017. http://www.sciencemag.org/news/2017/06/controversial-pesticides-can-decimate-honey-bees-large-study-finds
- B. A. Woodcock J. M. Bullock, R. F. Shore, M. S. Heard, M. G. Pereira, J. Redhead, L. Ridding, H. Dean, D. Sleep, P. Henrys, J. Peyton, S. Hulmes, L. Hulmes, M. Sárospataki, C. Saure, M. Edwards, E. Genersch, S. Knäbe, and R. F. Pywell, Country-specific effects of neonicotinoid pesticides on honey bees and wild bees. Science, 356 (6345):1393, 2017. http://science.sciencemag.org/content/356/6345/1393.abstract