Neonicotinoids, a common and highly controversial class of insecticides linked to catastrophic bee deaths, could be significantly lowering the sperm count of male drone honey bees and cutting their life span by a third, Swiss researchers found.
Bees are dying in unsustainable numbers, and this latest study is further evidence that an extremely common pesticide might be behind it. Flickr
Researchers from the Institute of Bee Health at the University of Bern, Switzerland discovered that male drone honeybees that ate pollen treated with two popular "neonics"—thiamethoxam and clothianidin—produced nearly 40 percent less sperm than those that did not.
When sperm from both sets of drones were put under the microscope, the ones treated with neonics produced 1.2 million living sperm on average while the control group produced 1.98 million. The authors said that the insecticides "can serve as inadvertent insect contraceptives." A drone's main role is to mate with the queen bee.
"While no significant effects were observed for male teneral (newly emerged adult) body mass and sperm quantity, the data clearly showed reduced drone lifespan, as well as reduced sperm viability (percentage living versus dead) and living sperm quantity by 39 percent," the report states.
The results showed, for the first time, that neonicotinoids can negatively affect male insect reproductive capacity. The authors said their study might explain the declining population of wild insect pollinators as well as queen bee failure in managed fields.
"Because queen survival and productivity are intimately connected to successful mating, any influence on sperm quality may have profound consequences for the fitness of the queen, as well as the entire colony," the report said.
Geoffrey Williams, the study's co-author and University of Bernsenior bee researcher, told the Associated Press he does not know how exactly the insecticides might be damaging the sperm, but it seems to be happening after they are produced.
In another alarming discovery, the researchers found that 32 percent of the neonic-exposed drones died before reaching sexual maturity, compared to 17 percent of the unexposed controls. The average lifespan of insecticide drones was around 15 days, significantly lower than controls's lifespan of 22 days.
"This could have severe consequences for colony fitness, as well as reduce overall genetic variation within honeybee populations," the authors said.
The study was published today in the British journal Proceedings of the Royal Society B.
As the Associated Press pointed out, the worrisome population decline of pollinators can come down to a combination of many culprits, such as mites, parasites, disease, pesticides and poor nutrition. However, U.S. Department of Agriculture bee scientist Jeff Pettis, who was not part of the neonicotinoid study, suggested that poor sperm health may account for about a third of the growing crisis.
Neonicotinoid-maker Bayer Crop Science spokesman Jeffrey Donald told the AP that the company will review the study, but in general "artificial exposure to pesticides under lab conditions is not reflective of real-world experience."
Peter Campbell from Syngenta, the maker of thiamethoxam, told the Guardian that the study was interesting but added, "given the multiple mating of honeybee queens it is unclear what the consequences of a reduction in sperm quality would actually have on queen fecundity."
This latest study adds to the mounting scientific evidence that neonicotinoids—which are used on many crops in the U.S.—are harmful to pollinators. As Friends of the Earth wrote, bees are crucial to food production but are dying at unsustainable rates, with an unprecedented average of 30 to 40 percent loss of all honeybee colonies each year.
An investigation by the environmental group, Buzz Kill: How the Pesticide Industry is Clipping the Wings of Bee Protection Efforts Across the U.S., has found that the pesticide industry is stifling urgently needed reforms that would help these essential pollinators survive and rebuild their numbers.
For nearly 10 years, two nonprofits filed lawsuits, legal petitions and countless administrative actions to stop the U.S. Fish and Wildlife Service (FWS) in its tracks.
The issue that Center for Food Safety and Public Employees for Environmental Responsibility (PEER) took with the FWS? The regular use of genetically engineered (GE) crops and bee-killing neonicotinoid pesticides in national refuge farming programs—which ultimately interfere with the very plants and animals the refuge system is designed to protect.
Buffalo grazing in Niobrara National Wildlife Refuge. Photo courtesy of Shutterstock
Today, the FWS announced in an internal memorandum that the agency will ban neonic pesticides and phase out GE feed for wildlife by January 2016.
“GE crops and toxic pesticides violate the basic purposes of our protected national lands,” said Andrew Kimbrell, executive director of Center for Food Safety. “We applaud the Fish and Wildlife Service for recognizing what our legal challenges have repeatedly stated and courts have repeatedly held: that they must stop permitting these harmful agricultural practices.”
National Wildlife Refuge System Chief James Kurth acknowledged in the memorandum that the agency has demonstrated its ability to “successfully accomplish refuge purposes over the past two years without using genetically modified crops, therefore it is no longer possible to say that their use is essential to meet wildlife management objectives.” However, the temporary use of GE crops will be considered on a case-by-case basis for habitat restoration purposes.
Kurth also wrote that the FWS will follow a directive to use long-standing integrated pest management principles to evaluate and guide the agency’s pesticide use practices.
“We are gratified that the Fish and Wildlife Service has finally concluded that industrial agriculture, with GE crops and powerful pesticides, is both bad for wildlife and inappropriate on refuge lands,” stated PEER Executive Director Jeff Ruch. “Since refuges have already demonstrated that they do not need these practices, we would urge the Fish and Wildlife Service to make the ban immediate, not wait until 2016, and to eliminate the loopholes in its new policy.”
The Center for Biological Diversity, Beyond Pesticides and Sierra Club have also been involved in petitions and litigation leading up to the FWS’s policy reversal.
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In addition to previous research on the direct impacts of pesticides on pollinators and other beneficials, a recent study published by Dutch scientists establishes an additional indirect link between neonicotinoid use and insect-eating birds. The report, which came out on Wednesday, provides evidence that neonicotinoids, a class of systemic pesticides, are indirectly hurting larger creatures by reducing insect prey populations such as mosquitoes and beetles.
Researchers found that in certain areas of the Netherlands where water is contaminated with high concentrations of imidacloprid, a commonly used neonicotinoid, bird populations tend to decline by an average of 3.5 percent every year. Further analysis found that this spatial pattern of decline appeared only after the introduction of imidacloprid to the Netherlands in the mid-1990s, even after correcting for land-use changes that have been known to affect bird populations in farmland.
“To our surprise we did find a very strong effect on birds”, said lead author of the study, Caspar Hallmann, a Ph.D. student from Radboud University in the Netherlands, to Reuters. In fact, according to the study, which was published in the journal Nature, nine of 15 bird species studied only eat insects and all feed insects to their young. Hallmann added, “We cannot say this is proof (that the pesticide causes the decline in bird numbers) but we cannot explain the… decline of birds by any other factors.” The study also looked into other possible causes like pollution.
Bayer CropScience issued a speedy response expressing disagreement with the study findings. The company writes that the study did not “demonstrate that there is a causal link between the use of neonicotinoids and the development of bird populations in Europe.” The company went on to say that neonicotinoids “have gone through an extensive risk assessment which has shown that they are safe to the environment when used responsibly according to the label instructions.” The company, along with Syngenta, has been accused of forestalling attempts to ban neonicotinoids via the proposal of bee health plans that call for more research, implementing agricultural best management practices and planting new habitat. These solutions fail to address the real problem that their products are highly toxic to bees.
The recent report titled, Worldwide Integrated Assessment (WIA), undertaken by the Task Force on Systemic Pesticides, indicates otherwise. Twenty-nine scientists representing multiple disciplines analyzed more than 800 peer-reviewed publications on the impacts of systemic pesticides. The report emphasizes that neonicotinoids and their metabolites are persistent and harmful, even at very low levels, and that the chemicals have far-reaching impacts on entire ecosystems, from direct exposure to persistence in soil and water. Bees, butterflies, worms and other pollinators and non-target organisms are also put at risk. Scientists concluded that even when neonicotinoids were used according to guidelines on their labels, the chemicals’ levels in the environment still frequently exceeded the lowest levels known to be harmful to a wide range of species.
The European Union (EU) began implementation of a two-year moratorium in April on neonicotinoids used on flowering crops stemming from scientific evidence that the chemicals are harmful to bees. The pesticides can still be used legally in the E.U. on non-flowering crops, such as barley and wheat, the scientists said. Germany’s Bayer and Switzerland’s Syngenta, the two main producers of the pesticides, have contested the moratorium. They suspect that “colony collapse disorder,” which has resulted in the large drop in bee populations in Europe, Asia, the Americas and the Middle East, are due to a virus spread by a parasitic mite. Opposition to neonicotinoid use remains strong, however. Syngenta recently withdrew its emergency application to allow the use of neonicotinoids on UK oilseed rape crops (known as canola in the U.S.) in face of public outcry. According to Reuters, more than 200,000 people protested against the request, with around 35,000 more writing to environment secretary Owen Paterson.
The Dutch study recommends that future legislation consider and take into account the wider impact of pesticides on wildlife. Dave Goulson, Ph.D., of Sussex University, writes in a commentary in Nature that the study was “the first to provide direct evidence that the widespread depletion of insect populations by neonicotinoids has knock-on effects” on larger animals. Goulson has done work on the far-reaching effects neonicotinoids have on biodiversity and ecosystem health; a review of his from last year found that not only are neonicotinoids the most widely used insecticides in the world, but they persist and accumulate in soil, are prone to leaching into waterways, commonly exceed the LC 50 (the concentration which kills 50 percent of individuals) for beneficial organisms, and the consumption of small numbers of treated seeds presents a direct risk of mortality in birds and mammals.
Sound familiar? The link between pesticide use and birds is not a new one. Rachel Carson’s book, Silent Spring, chronicled the profligate use of pesticides and their effects on the environment and on birds in particular. While Carson wrote specifically about DDT, an organochlorine pesticide, the message is similar—neonicotinoid pesticides effects have been shown to have widespread consequences on beneficial insects, the environment and birds.
Read more about how neonicotinoids affect non-target organisms, or Pierre Mineau’s, Ph.D., in-depth presentation with the American Bird Conservancy on the impact of insecticides on birds. You can also visit our BEE Protective page to learn more about how honey bees and other pollinators are going through rapid population declines, and what you can do to help.
