The latest tally of honeybee colonies shows a lessening in deaths of the crucial pollinators — and suggests at least one way to keep bees healthier, researchers reported Thursday.
The annual report from the Bee Informed Partnership adds a new twist to the debate over the mysterious disappearance of honeybees, a phenomenon known as colony collapse disorder.
The fate of the bees is a huge issue because their pollinating role adds $15 billion to the value of U.S. crops, from almonds to zucchini. Bees and other pollinators play a role in producing a third of the world's foods and beverages. As a result, colony collapse disorder has spawned publicity campaigns and counter-campaigns, backed up on both sides by stacks of reports.
"Bees are the canary in the coal mine for our food system," said Lisa Archer, director of the food and technology program for Friends of the Earth U.S.
Some scientists blame a class of nerve-poisoning pesticides known as neonicotinoids — and that has resulted in a ban on their use in European countries. Just last week, a trio of researchers published a study claiming a strong link between the pesticides and colony collapse in healthy hives.
"We're really encouraging Congress to look at the science."
However, the Bee Informed survey of more than 7,000 beekeepers focused on a different threat to the bees: parasitic Varroa mites. The survey found that bee mortality was much lower for beekeepers who carefully treated their hives to control the mites.
"We think we could take a bite out of some of these losses if you control the mites properly," Dennis vanEngelsdorp, an entomologist at the University of Maryland and the director of the Bee Informed Partnership, told NBC News.
Complexities of colony collapse
In a report issued last year, the U.S. Department of Agriculture and the Environmental Protection Administration said colony collapse disorder, or CCD, is the result of a combination of factors — including pesticides, mites, other parasites, viruses and even changes in land use. "A lot of land that used to support foraging sources for bees has been plowed under," vanEngelsdorp explained.
The toll on the honeybees varies widely from year to year: Over the past winter, beekeepers said they lost 23 percent of their bee colonies. That's much better than the 31 percent loss recorded for the winter of 2012-2013, or the 29 percent average loss for the eight-year history of the survey.
However, the losses were still above the levels that beekeepers regard as tolerable. About two-thirds of the beekeepers surveyed said their losses were beyond an acceptable level — a level that was set at 19 percent on average.
This year, for the first time, the survey also asked beekeepers about colony losses during the summer. That figure was a surprisingly high 20 percent.
"We used to think that winter was the critical period," vanEngelsdorp said in a news release. "But during our field studies, beekeepers told us they were also losing colonies in the summer months. So we expanded the survey and found that, in fact, colonies are dying all year round."
When vanEngelsdorp and his colleagues analyzed the subset of surveys from beekeepers who reported both summer and winter losses, they came up with a year-to-year average loss of 34 percent.
What is to be done?
The new reports set the stage for renewed debate over the causes of and the remedies for the bee die-off. Last week's study, published online in the Bulletin of Insectology, claimed that the use of two types of neonicotinoids heightened the risk to honeybee colonies over the winter, particularly during colder winters.
"Neonicotinoids are 'our new DDT' and should be banned from use until they have been demonstrated, independently and conclusively, to be safe for the environment and for human health."
The report provided ammunition for those who want to ban neonicotinoids in the United States, as the Europeans have done.
"Neonicotinoids are 'our new DDT' and should be banned from use until they have been demonstrated, independently and conclusively, to be safe for the environment and for human health," said Eric Chivian, who is a beekeeper as well as the founder and former director of the Center for Health and the Global Environment at Harvard Medical School.
Archer, the policy expert at Friends of the Earth, said she hoped the study would give a boost to a proposed ban currently under consideration in Congress. "We're really encouraging Congress to look at the science," she told NBC News.
However, other bee experts said the study had serious shortcomings — including small sample size, the lack of replication at each location, and the use of pesticide doses that were larger than bees would get under realistic field conditions. These researchers said more rigorous studies are needed to trace the causes of bee colony loss.