The eerie mystery of the vanishing honeybees has not been put to rest.
In the last few weeks, three separate studies explored the effect of insecticides on honeybee and pollinator health. One paper linked neonicotinoids, a new class of systemic insecticides that have come into widespread use in recent years, to impaired honeybee navigation; a second noted the effects of low levels of the pesticides on bumblebee reproduction.
The most talked about study, from a Harvard team, found that the colonies fed neonicotinoid-laced corn syrup collapsed in a manner that appeared to mimic the effects of Colony Collapse Disorder, or CCD—the mysterious phenomenon in which otherwise-healthy bees simply vanish from their hives. Neonicotinoids, declared the Harvard team, were "the likely culprit in sharp worldwide declines in honeybee colonies since 2006."
Dramatic headlines soon followed: "Mystery of the Disappearing Bees: Solved!" announced a Reuters headline. Ah, if only that were true. Even if neonicotinoids were banned tomorrow, honeybees would still be in big trouble.
The recent studies add to mounting evidence that low levels of neonicotinoids may have "sub-lethal" outcomes—long-term effects on pollinators that haven't been measured in chemical-company testing submitted for EPA approval. What those papers don't prove, unfortunately, is that "neonics," as they are called, cause CCD—or explain the troubling colony losses we've seen in recent years.
CCD is defined as a condition in which the majority of bees disappear from a healthy hive in rapid fashion, usually within two weeks—leaving behind a queen, ample honey and brood, and little obvious sign of disease that might explain the colony's collapse.
Since the phenomenon was first named and made headlines in late 2006, however, the disorder has too often been conflated—by the media, and sometimes by beekeepers as well—with honeybee losses in general. "It's like saying that everyone's dying of a heart attack," explains Dennis vanEngelsdorp, the Pennsylvania entomologist who first discovered the disorder. "When in fact we die from all sorts of causes."
A Matter of Life and Deaths
Bees, too, die in all sorts of ways: they suffer from parasites and fungal and bacterial and viral infections; they starve to death; and yes, they also succumb to pesticides—sometimes when they are mistakenly sprayed and are poisoned outright, and also, perhaps, due to long-term neurological and developmental effects when exposed to lower amounts. Not many of them, however, actually die of CCD.
In fact, though about a third of the nation's honeybee herd has died each winter since 2007—a number much higher than the 15 percent loss beekeepers consider "acceptable"—few recent losses can be attributed to CCD. In 2008, beekeepers reported symptoms of CCD in 60 percent of colonies that died; in the last year, "I haven't seen one verifiable case of CCD," says vanEngelsdorp. Annual winter losses have been just as heavy in the last couple of years as they were in 2008. But "they can usually can be explained by something else," he says. And that's true even though neonicotinoid use continues apace.
The recent neonicotinoid studies have also come under fire. Bayer CropScience, which manufactures a number of widely used neonicotinoids, argued that the dosing given to the bees in all of the recent research was higher than what is considered to be "field realistic"—and most of the non-industry scientists I spoke with agreed with this assessment.
The Harvard study—which most explicitly linked neonics to CCD—has earned particular censure: "The study out of Harvard is sort of an embarrassment," vanEngelsdorp said, noting that the team fed colonies "astronomical" levels of CCD-laced corn syrup, that the sample sizes were way too small, and that the symptoms the colonies subsequently suffered did not, in fact, mimic the symptoms of CCD. Randy Oliver, a biologist and beekeeper in California, provided this in-depth exploration of the study's weaknesses on his website, Scientific Beekeeping. This study was "fatally flawed," both in its design and its conclusions, added Scott Black, executive director of the Xerces Society for Invertebrate Conservation.
Chensheng Lu, the author of the Harvard study, had no such reservations. He compared his findings to those of Rachel Carson, whose book Silent Spring, published 50 years ago, linked pesticides to plummeting bird populations and human cancer, and helped launch the modern environmental movement. "The hives were dead silent," Lu told Wired News of the failed colonies in his study. "I kind of ask myself: Is this the repeat of Silent Spring? What else do we need to prove that it's the pesticides causing Colony Collapse Disorder?"
One Piece of a Bigger Puzzle
What we need, sadly, is better evidence—and so far, it's not there yet. This is not to say that anybody working with pollinators believes insecticides aren't a big issue for bee health. It makes perfect sense that systemic pesticides—which are absorbed throughout plants' vascular systems and into their pollen and nectar, and remain toxic to insects for a year or more after application—might present issues not seen with traditional pesticides. Perhaps chronic exposure to low doses of poisons disorients bees, or interrupts brood-production, or weakens them so that another pathogen—one that would under normal circumstances cause only limited mortality—can finish them off.
In a recent review of neonicotinoid research, the Xerces Society noted that neonicotinoids upended conventional wisdom about safe pest management. This is because pesticides can't be avoided by relocating hives during application, or by not spraying during the bloom. Still, while the organization advocates a more critical look at these pesticides, especially revisiting the high dosages permitted for horticultural use—"we should have a better sense of the risk before we start spreading poisons around our kids, our pollinators and our farmworkers," the Xerces Society's Scott Black told me. The group doesn't recommend an outright ban, because neonicotinoids are still considered safer for wildlife and human health than the organophosphate pesticides they replaced.
"One of the biggest concerns," notes University of Minnesota entomologist Marla Spivak, a Macarthur fellow and tireless advocate for honeybee health, "is that if all neonics are banned, other much more harmful pesticides will be registered."
And things won't necessarily get any better for the honeybee. This vital pollinator is suffering "death by a thousand paper cuts," as beekeeper John Miller, about whom I wrote a recent book, The Beekeeper's LamentThe Beekeeper's Lament, once described the malady of the honeybee.
Pesticides and other chemicals may provide a nasty gash, but so do the stresses of long-distance pollination to which many commercial beekeepers must subject their bees to stay afloat, and poor nutrition, and all varieties of pests and pathogens that have accompanied the globalization of modern agriculture and apiculture.
Indeed, in places where neonicotinoid pesticides have been banned, such as France, Italy and Germany, there's no evidence that honeybee populations have rebounded. And in Australia, which has among the healthiest bee herds in the world and has never reported a case of CCD, neonicotinoids have been in widespread use for over a decade. Australian agriculture isn't as industrialized as in the U.S., where beekeepers make a living by dragging their hives from monocrop to monocrop, feasting their bees on one single nectar and pollen source, and then moving them on to the next. "The only situation in Australia where honeybees used for pollination are strongly restricted to one crop," Australian bee pathologist Denis Anderson told me, "is in the pollination of almonds. However, we don't see losses among those colonies, even though neonicotinoids are used in the almond industry."
The other thing they don't see in Australia—but do see everywhere else in the world—is the varroa mite, a nasty, tick-like creature that latches onto a bee's exoskeleton and sucks the life out of the bee, and then the colony, and the apiary, and eventually, the entire beekeeping outfit. Since varroa was first found in the U.S. in 1987, American beekeeping has changed dramatically—inalterably. Indeed, this tiny mite has been the major cause of honeybee mortality across the United States. The nation's CCD losses pose no comparison. For most beekeepers and bee scientists, it is the varroa mite, not CCD, that occupies most of their worrying hours.
Here are the conclusions of another recent bee study—one that hasn't seen nearly as much play in the press. The paper, published in the Journal of Apicultural Research, puts it this way: "In many cases, bee mortality appears to be the product of many interacting factors, but there is a growing consensus that the ectoparasitic mite Varroa destructor plays the role of the major predisposing liability. We argue that the fight against this mite should be a priority for future honeybee health research."
Until we deal with that problem, all the pesticide bans in the world won't make it right with the honeybee.
Are Neonicotinoids Killing Bees? [xerces.org]