Where have all the bees gone?
The question has vexed farmers, beekeepers, regulators and scientists since the fall of 2006, when U.S. bee populations began their mysterious decline.
Approximately a third of U.S. bees have been dying in each of the last six winters, with a large percentage of deaths being linked to a phenomenon called Colony Collapse Disorder, in which entire populations of worker bees disappear.
The cause of the decline remains unclear, but environmentalists -- bolstered by several recent studies -- have begun pointing fingers at pesticides. Several coalitions are now urging U.S. EPA to ban certain pesticides that are part of the widely used neonicotinoid family, even as the agency and pesticide manufacturer Bayer CropScience say the chemicals are safe.
Dave Hackenberg, a Lewisburg, Pa., beekeeper who was one of the first to spot the large die-offs, says regulators need to step in even if the science implicating pesticides is not conclusive.
"Something is going on," said Hackenberg, who signed a petition asking EPA to ban the pesticide clothianidin last month. "Maybe the pesticides aren't killing them dead. But at the same token, something is breaking down their immune system and something is causing all types of things to happen."
If bee decline is left unchecked, its impact could be substantial because bees increase crop yield and value. Experts estimate that the disorder has affected honeybees in 35 states and could cause $15 billion in losses to U.S. crop production annually, since roughly a third of the North American diet relies on animal pollinators.
Neonicotinoids were developed in the 1990s to replace organophosphate insecticides that were causing harm to humans. They are now widely used on many crops, including corn and soy, and in home gardening products.
Environmentalists charge that bees are harmed by neonicotinoids because they are absorbed by crops and present themselves in pollen and nectar, which are then foraged by bees.
Their concern is that the chemicals then affect the bees' nervous systems, and some recent research bears that out.
A recent study by the French National Institute for Agricultural Research in Avignon, France, that was published in Science exposed bees to thiamethoxam, another neonicotinoid, and tracked their movement. They found that the bees exposed to the pesticide were more likely to die away from their nest than those that weren't, suggesting that the bees' homing system was compromised.
"Our study raises important issues regarding pesticide authorization procedures," said Mickael Henry, the study's author. "So far, they mostly require manufacturers to ensure that doses encountered on the field do not kill bees, but they basically ignore the consequences of doses that do not kill them but may cause behavioral difficulties."
Other research from the United Kingdom that was also recently published in Science suggested that exposure to imidacloprid, a widely used neonicotinoid also made by Bayer, drastically reduced a bumblebee hive's ability to produce new queens. And those studies come on the heels of a controversial Harvard University study earlier this month that found even low exposures to imidacloprid also have significant effects on bees.
The studies have led to two petitions. The first, from a coalition of beekeepers and environmental groups, calls for EPA to ban clothianidin because, the petitioners claim, Bayer never proved it is safe in a field study (Greenwire, March 22).
Similarly, Susan Mariner, a Virginia Beach, Va., gardener, started a Change.org citizen petition recently calling on EPA to ban Bayer's products. So far, Mariner has picked up more than 136,000 signees.
"This is a factor in Colony Collapse Disorder," Mariner told Greenwire. "It's killing bees in massive numbers. We know that. We need to act now."
Use as directed -- Bayer
The controversy surrounding these pesticides, especially imidacloprid, is nothing new for Bayer.
It first flared up in the late 1990s in France after reported problems with a product called Gaucho. The company acted quickly, immediately conducting several studies and eventually pulling the product off the market.
David Fischer, a Bayer environmental toxicologist, said the studies proved several things. First, the chemical does pose high toxicity to bees, but only at levels around 20 parts per billion or more. Typically, he said, bees in the field are exposed to the chemical in a range of about 1 to 5 ppb.
It can also be hazardous when sprayed onto crops, but Fischer pointed out that the product's labels all say not to apply it when the crop is in bloom.
"We had a lot of independent university researchers working with," Fischer said. "And nothing that's come up in the intervening decade or so has changed that outlook."
When Gaucho was taken off the market, Fischer added, the health of the country's bees did not improve. He also pointed out that imidacloprid has been widely used in the United States since the mid-1990s, but the sharp decline in bees did not come until about a decade later.
Fischer's remarks were largely confirmed by the U.S. Department of Agriculture, which has done extensive research on the issue.
"What we've done, more than anything, is figure out what Colony Collapse Disorder is not," said Kim Kaplan, a USDA spokeswoman. "We have pretty much ruled out that it's any single cause."
Kaplan points to a series of other factors, including parasites such as the increasingly common varroa mites and tracheal mites as well as other diseases that may affect bees in the breeding process. Other factors may include loss of habitat or food sources, as well as diseases and fungi. In general, though, USDA has found that the larger the pathogen exposure, the worse off the bee hive is.
The agency has also questioned the methodologies behind some of the recent studies, including the levels of neonicotinoids to which the bees were exposed.
USDA's research is now trying to focus on two factors at a time and is currently researching whether exposure to imidacloprid and nosema, a disease, has a harmful effect.
Other experts suggest the answer may be even more complicated than that. Dennis vanEngelsdorp, a bee researcher at the University of Maryland, said there may be aspects of pesticides that are unexpectedly playing a role.
"There are a lot of suggestions that fungicides are playing a role and some inert components of pesticides, when they are mixed together, may have some toxicity," he said.
The scientist noted that traditional methods to combat diseases in hives are no longer working because they have developed a resistance. He also shot down the recent calls for bans on the pesticides.
"Just saying we are going to ban the product doesn't make a lot of sense to me because you need to have something that is going to replace it," he said. "It's implying that when you get rid of these chemicals, all our problems go away. I don't think that's the case. That's naive."
VanEngelsdorp did call for taking a closer look at how these pesticides are registered with regulatory agencies.
EPA said it is "concerned" about the issue. The agency has grouped all neonicotinoid pesticides together in its periodic registration review process and has moved up that review to this year. However, the agency echoed USDA in saying that multiple causes appear to be contributing to the bee problems. EPA also appeared to side with Bayer in saying that the pesticides are safe.
"Our review of these studies is underway," EPA said in a statement to Greenwire, "but at this time, we do not have data indicating EPA-registered pesticides, when used according to label directions, have caused Colony Collapse Disorder."
That's not enough to satisfy Charles Benbrook of Boulder, Colo.'s Organic Center.
Benbrook has a simple way to resolve the issue: Ban the pesticides from some areas and watch what happens to the bees.
He bases the idea on stories he has heard coming out of Europe, where France, Germany, Italy and Slovenia have taken steps to suspend the use of certain neonicotinoids. In those areas, Benbrook said, bee populations appear to be on the rebound.
"If that is really true," Benbrook said, "we don't have to do a lot more science to determine what the logical policy response is."
Benbrook said that even if EPA did not think the science justified what he called a "moratorium," the agency could work out an agreement with certain states -- like, say, Missouri and Arkansas -- as a test case.
"It would be a very low-cost experiment," he said.
Benbrook pointed out, however, that EPA may face a legal hurdle if it tries to regulate the chemicals based on bee problems. Simply put, it is not EPA's job to prevent harm to bees, which it regards as personal property.
"Under EPA policy, they do not strive to minimize damage to personal property when they evaluate the label of a new use pesticide," Benbrook said. "So it's not really clear at all whether EPA has a statutory and regulatory leg to stand on."
John Kepner of the nonprofit Beyond Pesticides, which is also involved in one of the petitions, added that EPA's process for studying these effects is flawed.
"We know that there are these sub-lethal effects. They may be confusing the bees, causing fatigue or making it so they don't reproduce," he said. "But EPA doesn't have testing ... for 'makes bees lazy.'"
He added that the honeybee problems could be providing insight to future problems.
"The honeybees," he said, "are definitely an indicator of what could be happening in the broader environment."