Neonicotinoids and colony collapse disorder - err on the side of caution, or just a distraction??

The cause of colony collapse disorder (CCD) in honey bees is not yet understood, but even so the European Commission decided on Monday to ban the use of neonicotinoid insecticides starting in December, for at least the next two years.  This past winter was particularly hard on bees in the US, even given the losses over the last 10 years or so since CCD was first described, with 40 to 50 percent and more decline in the bee population around the country, and the EPA is being asked to reconsider the use of these compounds in the US as well.

CCD, the sudden disappearance of worker bees from a beehive or colony, is characterized by little or no build-up of dead bees in or around the affected hives, and by the early death of adult worker bees away from the hive, leaving affected hives populated primarily by young adults.  The queen is usually still there, but without worker bees the colony can't sustain itself, and the remaining bees eventually die.

Varroa mite on honeybee larva;
Wikimedia

It's possible that a build-up of factors causes CCD. Mite and parasite infestation seems to contribute, as do viral infection and the widespread use of pesticides and fungicides, and there's some thought that the stresses involved in frequently moving hives used for pollination of commercial crops might also contribute.  Bees might be able to survive just mites or a viral infection, but if they are already weakened by one or more stressors they are more likely to succumb when more are piled on. 

A third of everything we eat depends on pollinators, so the losses are significant commercially, with the potential to become even more significant.  Many people are becoming increasingly concerned about the impact of CCD on the world food supply.  Just this spring California almond growers have had to scramble to find enough bees to pollinate their crop, after a particularly hard winter for bees, but additional crops worldwide are at risk.   

It was to prevent agricultural losses that the European Commission decided to act. “I pledge to my utmost to ensure that our bees, which are so vital to our ecosystem and contribute over 22 billion Euros [$29 billion] annually to European agriculture, are protected,” said European Union Health Commissioner Tonio Borg.

Do they or don't they?
Neonicotinoids, as we wrote in a recent post, are the newest class of insecticides in use today, and the most widely used.  They affect insect nervous systems, though are less toxic to mammals than older classes of insecticides.  Derived from nicotine and developed 2-3 decades ago, seeds are coated with these compounds and they remain within the plant as it grows, or they are sprayed on fields.

More than 30 studies have demonstrated a connection between bee deaths and neonicotinoid usage.  Two high profile studies determined that they are likely to have a negative effect on bees.  A paper published online in Science March 29, 2012 (Whitehorn et al.) reported growing evidence that neonicotinoids are involved.  Researchers exposed bees in the laboratory to levels of insecticide that mimicked what bees would encounter in the field, and found reduced growth rates and an 85% reduction in new queens produced.

A second paper published in Science at the same time  (Henry et al.) found effects of a sublethal dose of a neonicotinoid on the homing behavior of honeybees.  One of the hallmarks of CCD is that whole hives empty out, suggesting that bees might be disoriented and unable to retrace their flight paths home. 

The definitive role of neonicotinoids in CCD has not been demonstrated, but the evidence seems to be mounting.  Pesticides are at "unprecedented levels" in honeybee colonies, and because neonicotinoids are the most frequently used pesticide today, and are applied on "approximately 75 percent of the acres devoted" to the most important fruit and vegetable crops grown in the US, their role has to be considered. 

On the other hand, these compounds are in widespread use in Canada and Australia, and CCD is not nearly the problem in these countries as it is in the US and Europe, though mites are not a problem in Australia either, so it's impossible to know which essential variable in the CCD equation is missing.  Indeed, a number of studies have not shown a definitive link, or suggest other causes (e.g., this paper reporting that metals in the soil, due to vehicle exhaust, might be the cause.)  

Manufacturers maintain that neonicotinoids are safe if used as directed -- applied to seeds, in small amounts.  They will break down as the plant develops, and no longer be biologically active when pollinators are visiting the plants.  But two nicotinoids have been found in the pollen and nectar of flowers of squash plants after being applied to soil as directed, and they've been found on riverbanks as well, suggesting that the compounds aren't breaking down as supposed.

To some, there is enough evidence of the detrimental effects of neonicotinoids on bees that it is time to ban their use.  Several European countries had already done so before the European Commission banned them through the EU, and the EU ban is welcomed by many.

To others, there is insufficient evidence that these compounds are a core cause of CCD, and this ban is premature and even detrimental because it means that farmers will now have to use older insecticides, whose effects on bees have not been studied.  It's no surprise that neonicotinoid manufacturers lobbied hard against the ban and are among those most vociferously protesting it.

Win-lose or lose-lose?
The New York Times reports that worldwide sales of neonicotinoids is in the billions of dollars.  Bayer CropScience and Syngenta are two European companies that make these compounds.  The Times reports their representatives saying:

“The proposal is based on poor science and ignores a wealth of evidence from the field that these pesticides do not damage the health of bees,” John Atkin, Syngenta’s chief operating officer, said Monday in a statement. “Instead of banning these products, the commission should now take the opportunity to address the real reasons for bee health decline: disease, viruses and loss of habitat and nutrition.”

Bayer CropScience called the commission’s plan “a setback for technology, innovation and sustainability,” and warned of “crop yield losses, reduced food quality and loss of competitiveness for European agriculture.”

The view of the industry, and their interpretation of the science of CCD, and in particular the role of neonicotinoids, is of course colored by their vested interests.  But, the view of the European Commission and agribusiness is also colored by their vested interests.  They just happen to be diametrically opposed to those of the neonicotinoid industry.
 
In all of this, it is rather surprising that something that seemed to have come on suddenly just a few years ago and hence might be expected to have a rather simple, strong cause, is so hard to understand, despite many large, carefully designed studies.  A lot of the evidence we just mentioned would indeed suggest that neonicotinoids really are not the cause, or even a cause, of CCD (whether or not they should be used, based on other considerations).  Erring on the side of caution, which is what the ban is doing, may be risky because of the other costs that entails, but the problem is so serious that any chance of improving it is probably worth taking.  This is another instance of the elusive problem of identifying natural causation, and as so often happens, the evidence is largely statistical and hence difficult to interpret.

As with climate change, this has become not a strictly scientific decision but a political decision driven by business interests.  The science is rather more equivocal than with climate change, but still the approach should be the same.  When the stakes are so high, and perhaps even irreversible, the precautionary principle, erring on the side of caution, should drive decision making.  Which is just what happened with this ban.  Whether or not a two year ban is enough time to pin down the science is certainly a question, but if neonicotinoids might be part of the problem, they should be banned.