This past winter has been exceptionally rough for honeybees — and although it's too early to say exactly why, the usual suspects range from pesticides that appear to cause memory loss to pests that got an exceptionally early start last spring.
Friday marked the start of an annual survey that asks beekeepers to report how many bees they lost over the winter, conducted by the Bee Informed Partnership, the Apiary Inspectors of America and the U.S. Department of Agriculture. The advance word is that the results will be brutal. The New York Times, for example, quoted beekeepers as saying the losses reached levels of 40 to 50 percent — which would be double the average reported last year.
One beekeeper in Montana was quoted as saying that his bees seemed health last spring, but in September, "they started to fall on their face, to die like crazy."
Dennis vanEngelsdorp, an entomologist at the University of Maryland who is one of the leaders of the survey team, said he can't predict what the past winter's average loss figure will be. The beekeepers' reports are being solicited online for the next two weeks, and the figures are due for release on May 7.
"What I can say is, when we were in California this year, the strength of the colonies that were there was significantly lower than it was in previous years," vanEngelsdorp told NBC News.
Pesticides at issue
That's consistent with a mysterious ailment known as colony collapse disorder, which has stirred scientists' concern for the past decade. The malady almost certainly due to combination of factors — including the Varroa mite, a single-celled parasite known as Nosema, several varieties of viruses, and pesticides. Researchers point to one particular class of pesticides, known as neonicotinoids, as a prime suspect.
Neonicotinoid-based pesticides are commonly applied as a coating on corn seeds, but the chemicals can persist in the environment. Although they have low toxicity for mammals, they've been found to have a significant neurotoxic effect on insects, including bees. Several European countries have banned neonicotinoids, the European Union has been looking at a wider ban, and the Environmental Protection Agency is considering new limitations as well. Just last week, a lawsuit called on the EPA to suspend the use of two types of neonicotinoids immediately.
Two recently published studies add to the concern: This week, researchers report in Nature Communications that neonicotinoids block the part of a bee's brain that associates scents with foods. They suggest that without that functionality, the bees effectively forget that floral scents mean food is nearby, and thus die off before they can pollinate. A study published in January in the Journal of Experimental Biology found a similar link to problems with scent-related learning and memory.
Mild winter, dry summer
Although neonicotinoids are currently front and center in the debate over colony collapse disorder, they're not necessarily the primary reason for this winter's dramatic dip in bee colonies.
VanEngelsdorp noted that the winter of 2011-2012 was easy on the bees: Losses amounted to just 21.9 percent, compared with a 2006-2011 average of 33 percent. However, the mild winter was kind to the bees' pests as well. VanEngelsdorp speculated that Varroa mites may have gained an early foothold in the hives last spring. By the time beekeepers started their treatments on the usual schedule, it was too late to keep the mites from weakening the colonies. That would help explain why the past winter's losses were worse than usual.
California beekeeper Randy Oliver, who discusses industry trends on the Scientific Beekeeping blog, said the past summer's drought was also a factor: "When there's a drought, the bees are in poor shape with the food," he told NBC News. He said he and other beekeepers predicted that there'd be heavy winter losses last July, when the scale of the drought became clear.
Heavy losses are bad news, and if bee colonies are becoming progressively weaker, that's worse news. It's not just because of the honey: The Department of Agriculture says that bee pollination is responsible for more than $15 billion in increased crop value each year. A bee scarcity increases costs for the farmers who need them for pollination, and that could lead to higher food prices. But Oliver said it's important to keep a sense of perspective about the bad news.
"The situation with the bees is not dire," he said. "The bees are doing OK. There's no danger that the bees will go extinct. ... That's just not true."
More about bees:
- Neonicotinoids tied to crashing bee populations
- Zombie bees spread to Washington state
- Mites and virus team up to wipe out beehives
Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.