The media is buzzing this morning with the nth edition of What’s-Been-Killing-The-Bees:
…the mysterious mass die-off of honey bees that pollinate $30 billion worth of crops in the US has so decimated America’s Apis mellifera population that one bad winter could leave fields fallow. Now, a new study has pinpointed some of the probable causes of bee deaths and the rather scary results show that averting beemageddon will be much more difficult than previously thought.
Ever since Colony Collapse Disorder surfaced in late 2006, we’ve been treated to story after story proclaiming that scientists have finally discovered the cause: pesticides, viruses, cell phones, parasitic flies, fungi, mites, GMOs. Each story has the same formula. A study documents cause X killing bees, the media runs X as causing CCD, and the activist community amplifies the connection with increasingly alarming rhetoric.
The trouble is a simple logical fallacy. X kills bees, and CCD kills bees, but that doesn’t mean that X = CCD. After all, cigarettes kill people, but not all people die from cigarettes. To bring any of these causes full circle requires not only establishing that X can replicate CCD symptoms- that’s the easy bit- but that X was present in documented CCD cases and that experimental treatment of bees with X leads to CCD. Anything short of that, however interesting, is hypothesis rather than fact.
As you might imagine, beekeepers themselves have become rather cynical about any science on CCD. After being burned, say, five or ten times, can you blame them?
Keeping in mind an appropriate level of caution, though, the most recent study in the mix is a good one. Writing in PLoS One, Pettis et al document a shocking quantity and diversity of pesticides gathered by honey bees in real agricultural settings. When they fed the most abundant of these- a fungicide- back to the bees at realistic doses, they found affected bees were more susceptible to the parasite Nosema ceranae. This observation is intriguing, as Nosema ceranae infections are known to kill foraging bees away from the hive, one of the signatures of colony collapse. Not only that, but Nosema ceranae is also a recent import to our continent, potentially explaining the sudden appearance of CCD.
As a cause of colony collapse, though, the science behind the pesticide/pathogen double whammy isn’t quite there yet. To move beyond a promising hypothesis, bee researchers must still document the presence of the relevant pesticides and pathogens in collapsed hives, and then re-create collapse at the colony level in field experiments. We owe it to the bees, and the beekeepers, to do the science right.
source: Pettis JS, Lichtenberg EM, Andree M, Stitzinger J, Rose R, et al. (2013) Crop Pollination Exposes Honey Bees to Pesticides Which Alters Their Susceptibility to the Gut Pathogen Nosema ceranae. PLoS ONE 8(7): e70182. doi:10.1371/journal.pone.0070182