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By David Schultz
April 3 — To our long list of polarizing, contentious national debates, add one more: bees and pesticides—specifically, a class of pesticides called neonicotinoids.
For some, these pesticides, chemically similar to nicotine, are the prime suspect behind the alarming decline in the numbers of bees and other pollinator insects in North America over the past decade.
For others, neonicotinoids are a superior alternative to an older, less effective and more toxic generation of pesticides—a crucial and ubiquitous agricultural tool that is unfairly under attack.
These are rough outlines of the two sides in a scientific debate that has begun to influence the public policy process.
In response to increasingly bleak pollinator numbers, the White House last year asked more than a dozen federal agencies to develop a national pollinator health strategy. According to the White House, U.S. honey bee colonies have declined from 6 million in 1947 to 4 million in 1970 and 2.5 million today.
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The Obama administration specifically asked the Environmental Protection Agency to “assess the effect of pesticides, including neonicotinoids, on bee and other pollinator health and take action, as appropriate, to protect pollinators.” The White House is expected to release this strategy sometime this spring.
However, scientists who are studying what's happening to the country's bees say this black-and-white debate is far more complicated than the simple question of whether or not one class of insecticides is to blame.
Bloomberg BNA conducted interviews with seven university-based scientists who have recently published studies on neonicotinoids and bees.
While they all brought their own perspectives to the issue, by and large the scientists said the debate over neonicotinoids has been a distraction from the more complicated suite of problems facing pollinators.
Though certainly not blameless, neonicotinoids are only one of many factors behind the bee decline, and possibly not even the most important factor, according to the scientists.
Bees, butterflies and other insects pollinate an estimated three-fourths of crops grown throughout the world, providing an estimated global economic benefit of $215 billion, according to a recent article in the journal Science.
All of these insects, but especially bees, are facing a number of different stressors at the moment, only one of which is the threat being poisoned by pesticides.
One of the primary factors working against bees are invasive, pathogen-carrying mites, mainly the species Varroa destructor, which have been infesting hives at a higher rate in recent years. These mites bring with them diseases that, in recent years, bees have had a more difficult time fighting off, the scientists said.
Additionally, many of the bees' natural habitat areas have been urbanized. Or, perhaps worse, their habitat has been converted to farms that grow a single crop, such as corn or soybeans, that is less nutritious for bees than the wildflowers they prefer to feed on.
Ironically, the recent increase in hobbyist or backyard beekeepers may also be hurting bees, according to Maryann Frazier, an entomologist at Penn State University.
“They put tremendous pressure on bee suppliers to produce queens” to start new colonies, Frazier said. “Then those queens end up being of poor quality because they're in such high demand.”
Though Frazier said this is just a theory at this point, it's an example of the diversity of the different factors affecting pollinators.
“They're quite amazing at being able to deal with what you throw at them,” Frazier said. “It's just that when you throw so much at them, their cup runneth over.”
But it's not just the number of stressors negatively affecting bees; it's that all the stressors interact with and amplify each other.
“It's become increasingly clear that these things don't act in isolation,” David Goulson, a biologist at the University of Sussex in the U.K. and the lead author of the Science article, told Bloomberg BNA. “You'd be daft to look at a single cause.”
For example, exposure to pesticides such as neonicotinoids has been shown to make bees more susceptible to the types of pathogens carried by Varroa mites. But a lack of appropriate forage areas for bees has also been found to reduce bees' immunity to pathogens, Goulson and his colleagues wrote in their article.
Additionally, Goulson and his team found, there are certain types of fungicides that aren't harmful to bees on their own but, when they come into contact with neonicotinoids, can boost the toxicity of these insecticides 1,000-fold.
And to add to all of this, the plummeting supply of bees has led to a spike in demand for their pollination services, which has led some beekeepers to cut corners, according to Washington State University extension researcher Tim Lawrence.
“I sat on a hill in California and looked at 84,000 colonies, all fed [artificial bee food] until almonds grew, with no flowers in sight,” Lawrence, a beekeeper himself, recalled. “They were there from September until February. … That's a great place to spread pathogens around.”
“We're doing some crazy things,” he added.
That said, neonicotinoids definitely cannot be excluded from any list of factors that are harmful to bees.
Like nearly all insecticides, neonicotinoids can kill bees if the insects come into direct contact with a large amount of the chemical.
However, the vast majority of neonicotinoid use is via seed treatments—a seed is coated with the insecticide, which then enters into the plant's systems and protects it from insects from the inside out.
Initially, this method was considered safer and more effective than spraying plants with insecticides because it reduced the amount of chemicals that drift into the air.
However, there is still the possibility that the neonicotinoids used in seed treatments will rub off the seeds during planting and create a dust cloud that can land on nearby plants that the bees feed on, according to Dennis vanEngelsdorp, an entomologist at the University of Maryland.
More potentially troubling is the possibility that pollen and nectar from seed-treated plants might contain small amounts of neonicotinoids, which bees consume and then bring back to their hives.
However, vanEngelsdorp and others said there's not yet enough evidence to definitively say that bees regularly consume enough of the chemical in this manner to cause hive-level damage.
If neonicotinoids aren't the only factor negatively affecting bees, are they the factor affecting them most acutely?
“That's not really a productive discussion,” said Christian Krupke, an entomologist at Purdue University. “We've looked beyond, ‘Here's the smoking gun: It's Varroa. No, it's habitat. No, it's neonicotinoids.' The conversation has moved beyond that.”
Krupke said he believes neonicotinoids have received the lion's share of the attention in this debate because pesticide use is more easily controllable through public policy than an invasive mite or nationwide land use.
“We've been working on Varroa for decades,” he said. “There's not an easy, low-hanging-fruit thing that we can do. It's the same with replanting the prairies. That's not going to happen.”
Nearly all of the scientists interviewed said an across-the-board ban on the use of neonicotinoids would be unwise. The chemicals can kill a wide variety of insects, but are particularly effective on aphids and other sucking insects.
Organophosphates and carbamates, the classes of pesticides that were widely used before neonicotinoids came on the scene in the late 1990s, are far more toxic, not only to bees but also to birds and mammals.
Tjeerd Blacquiere, an ecologist at Wageningen University in the Netherlands, said a neonicotinoid ban would actually accelerate declines in bee populations if it caused farmers to revert to these older pesticides.
Among the scientists interviewed, Chensheng Lu, an environmental biologist at the Harvard School of Public Health, was the only one to differ on this point. He said neonicotinoids should be banned immediately because they are what's behind the phenomenon known as Colony Collapse Disorder, in which entire colonies suddenly disappear.
“The chemical industry wants to blame the causes on mother nature,” Lu said. But “neonicotinoids are the primary cause of pollinator declines. It could be the only reason we have for CCD.”
Though Lu may be an outlier in calling for a neonicotinoid ban, all the scientists agreed that the EPA should make some changes to how the insecticides can be used.
For example, they said the EPA should only allow farmers to use neonicotinoids to respond to a pest outbreak, not to prevent one.
“You have to look at what the risk of a pest is at a particular time and deal with that,” Frazier said. “Now we just put pesticides out there willy nilly into the environment. … It's hard to think of a crop where it's not used.”
An Oct. 15 study from the EPA reflected this sentiment; it found that treating soybean seeds with neonicotinoids provides farmers with little to no economic or agricultural benefits.
In addition, several scientists said the EPA should rethink whether neonicotinoids should be allowed in non-agricultural settings, such as on ornamental plants in residences.
“I do wonder why we would use such highly toxic products when there's no food or human safety risk involved,” vanEngelsdorp said.
EPA officials have said they are considering including new restrictions on neonicotinoid use as a part of the national pollinator health strategy, but they have yet to fully flesh out what form those restrictions might take.
Also, on April 2 the EPA placed a moratorium on approving new uses for neonicotinoid products until it receives more data on exactly how the insecticides affect pollinators.
Though the scientists said they found the tone of the current debate over these insecticides frustrating, several said they're noticing that it is beginning to change—for the better.
That's largely a function of the increased attention on the issue, both from high level government officials and from the public, vanEngelsdorp said.
As a result, “there are more people at the table with more diverse interests, and there seems to be more engagement,” he said. “There seems to be a willingness to look at this more comprehensively.”
Ultimately, he said, the conversation over the fate of pollinators in this country needs to avoid the binary, are-they-good-or-are-they-bad trap that has ensnared so many other recent political discussions.
“We have to move away from this polarization, which seems to happen everywhere,” vanEngelsdorp said.
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