Beekeepers in at least 24 states are reporting a huge number of empty honeybee hives this spring. Strangely, few dead bees are being found in the hives, so it appears that the hives are empty because bees are not returning from foraging. Since honeybees are the hard working pollinators of a lot of American crops, this is really bad news. But the cause for what is being called "colony collapse disorder" (CCD) is not at all clear.
Unfortunately, honeybees in the United States have been under pressure in recent years by new infestations of parasites, especially the varroa mite. The varroa mite, which sucks bee blood and which may pass along infectious diseases, was first identified in Java in the early part of the 20th century. The mite has been spreading around the globe and apparently made its way to Florida around 1987. Mites are now found throughout the United States and controlling them has become a major concern of beekeepers.
In their sadly predictable knee-jerk fashion, environmentalist ideologues cannot resist making biotech crops the bogeyman in this unfolding agricultural tragedy. The Sierra Club recently launched a letter writing campaign to Senate Agriculture Committee chairman Tom Harkin (D-Iowa) hinting that biotech crops may be responsible for CCD. The Sierra Club writes: "The cause of CCD is unknown. Although factors being considered include pesticides, mites, microbial disease and habitat decline, there's a possible link that's not being investigated. Highly respected scientists believe that exposure to genetically engineered crops and their plant-produced pesticides merit serious consideration as either the cause or a contributory factor to the development and spread of CCD. In searching for the cause of massive honey bee losses nationwide, we must leave no stone unturned to find the answer."
The vast majority of current biotech crops are enhanced with genes for herbicide tolerance (to ease weed control) and B.t. toxin to kill caterpillar pests. In its anti-biotech letter, the Sierra Club lists a number of studies that it suggests will show that biotech crops are harming bees. It either has not read the studies it cites or it's hoping nobody will actually read them. For example, the first study from the "highly respected scientists" the Sierra Club cites actually contradicts the notion that biotech crops hurt bees.
First, the study reports an experiment in which bee colonies were allowed either to feed from biotech herbicide-resistant oilseed rape (canola) or unenhanced varieties. The researchers begin by noting that ‘herbicide resistance is one of the most commonly-used traits in commercial cultivars of transgenic crop plants" and add that bees "are extremely unlikely to be harmed by these plants." The experiment bears out that prediction. "There were no significant differences that could be attributed to plant type in worker bee mortality, foraging activity, foraging preferences or colony health (bee population, brood area, presence of diseases or hive food stores)," report the researchers.
What about biotech crops enhanced for insect resistance by splicing in the B.t. toxin gene? The story is the same. The researchers evaluate various experiments in which bees fed on insect-resistant crops and conclude "B.t. transgene products are very likely to be safe for honey bees and bumblebees."
Another study cited by the Sierra Club worries about ecological risks posed by insect-resistant biotech crops. That study includes the Cornell University researcher, John Losey, who infamously poisoned monarch butterfy larva in the lab by force-feeding them B.t. corn pollen that was heavily sprinkled on milkweed leaves. In 1999, Losey's monarch research was published in Nature and provoked a firestorm of anti-biotech agitation complete with flocks of activists women at anti-biotech rallies dressed fetchingly as butterflies. Two years later six studies published in the Proceedings of the National Academy of Sciences showed Losey's research to be a bogus stunt with no relevance to field conditions. The lead PNAS study concluded "the impact of Bt corn pollen from current commercial hybrids on monarch butterfly populations is negligible."
So what does the Losey study cited by the Sierra Club letter say about biotech crops and bees? First, it notes "documentation for the EPA registration shows that pollen from Bt corn has no effect on survival of either larval or adult domesticated bees." Oddly, the study goes on to cite research from 1990 by Vandenberg on the effects of one variety of B.t. toxin on bees. Odd, because there were no biotech crops way back then. Vandenberg's research was on a B.t. toxin commonly used by organic farmers and even at high concentrations it only reduced adult bee longevity. This was not a study of biotech crops.
The fourth study referenced by the Sierra Club letter makes some suggestions for further research but notes that current research finds that honeybees actually preferred herbicide resistant oilseed rape, perhaps because the biotech variety produced more nectar. In any case, the experimenters detected no difference in the diversity pollinators and their foraging behavior between the biotech and unenhanced crops.
The Sierra Club also lists a 2005 study that evaluates the effects of B.t. toxin, deltamethrin and imidacloprid insecticides. Keep in mind that in this experiment B.t. toxin is not fed to bees in the form of biotech crops but as plain old toxin in syrup. Even so, the study found that B.t. toxin did not affect bee mortality, syrup consumption or learning capacities, although foraging activity was reduced. However, both of the synthetic insecticides affected syrup consumption and foraging activity and deltamethrin also reduced bee learning capacities. But here's the kicker: "Our study suggests that for honeybees, synthetic insecticides such as deltamethrin may induce a greater hazard than [B.t. toxin] protein, potentially expressed in B.t. corn pollen."
Being interested in what the most recent research says about the effects of insect resistant biotech crops on bees, I looked at the 2006 review cited in the Sierra Club letter. In that review I discovered that all of the data cited find no observational differences between bees that fed from biotech crops and those that didn't. The review does cite studies from the 1960s and 1970s in which bees forced to eat actual B.t. bacteria or spores died. Checking the references in that review turned up a 2003 study in which pollen from B.t. corn was fed to bees and wax moth larvae. The researchers found no significant differences in all the parameters tested between bee larvae fed transgenic B.t. corn pollen and non-transgenic corn pollen. However, since B.t. toxin is targeted to caterpillars, it was expected that the moth larvae that ate B.t. corn pollen would die and they did.
Again, didn't the Sierra Club folks read the studies they cited? If they had and they were honest, they'd be a lot more sanguine about the effects that biotech crops have on bees. In any case, the Sierra Club managed to overlook plenty of other studies that consistently find that biotech crops do not harm bees and other non-target insects.
By the way, colony collapse disorder is not confined to biotech-friendly United States. Hives are collapsing in biotech-free Europe too. The head of the German beekeeper's association says there has been a 25 percent drop in bee populations in Germany. Bizarrely, one particularly irrational German beekeeper blames biotech corn even though the Germany's biotech corn is only 0.06 percent of the total crop. Last week, the Irish Times (subscription required) reported that in Britain 30 per cent of hives inspected so far have been lost and that hundreds of thousands of colonies have collapsed in Spain. Beekeepers in Poland, Greece, Croatia, Switzerland, Italy and Portugal have also reported heavy losses.
A very interesting and disturbing comprehensive analysis of CCD by bee researchers from Florida and Pennsylvania failed to pinpoint the cause, but did note that several live bees taken from nearly collapsed hives were massively infected with a number of viruses and fungi. Of course, it is possible that at the margins, biotech crops may be somehow harming bees, but the overwhelming evidence suggests that it would be far more scientifically profitable to look elsewhere for why colonies are collapsing. Leaving no stone unturned in the search of the causes of CCD is a good idea, but as even the studies cited in the Sierra Club's dishonest letter make clear, a lot of the biotech stones have already been turned over and nothing harmful was found. Evidently it is more important for environmentalist ideologues to bash biotech and mislead the public and policymakers than it is to actually find out why bees are disappearing.
Ronald Bailey is Reason's science correspondent. His book Liberation Biology: The Scientific and Moral Case for the Biotech Revolution is now available from Prometheus Books.
Disclosure: When I was growing up on my family's farm my father had over 30 hives of bees. Because I'm a big wimp, I never enjoyed helping him to rob the hives of their honey, though I must say that locust and sourwood blossom honey are particularly tasty. As I recall I sold my Monsanto stock 8 years or so ago. I own no stocks in bee or honey companies and I am not in the pay of Big Honey or Big Pollination.
Discuss this article here.