Vermont’s bumble bee populations declining

Yellow banded bumble bee.  Photo by Sam Droege/USGS.

Yellow banded bumble bee. Photo by Sam Droege/USGS.

Vermont’s bumble bees are in serious peril, according to a new study by the Vermont Center for Ecostudies. Three of the 15 bumble bee species found in Vermont are thought to be extinct and at least one other species is in decline. Bumble bees pollinate crops such as apples, blueberries and tomatoes, making them critical to Vermont’s agricultural economy.

Sara Zahendra, a field biologist with the Vermont Center for Ecostudies, says losing native bumble bees is cause for serious concern.

“There’s a lot that’s bad about losing native bumble bees,” she said. “One of the main things is that they are far and away the best pollinators of tomatoes. Where there aren’t a lot of native bumble bees, people have to hand-pollinate, which is incredibly expensive.”

Native bumble bees are more important than honeybees for crop pollination. Leif Richardson, an entomologist at Dartmouth College, said in a VCE news release that “Wild bees perform the majority of all pollination on Vermont farms, whether or not the managed honeybee is present.”

“As an ecosystem service, pollination is worth millions annually,” Richardson continued. “But we don’t know how the loss of native bee species will affect our food supply or overall environmental health.”

The bee declines cannot be attributed to one single cause. “There are probably a multitude of reasons,” Zahendra said. “All of them put together are causing a severe decline in some species.”

The causes include pesticides, the worst of which, for bees, are a class called neonicotinoids. The most commonly used neonicotinoid is imidacloprid, which is sold at lawn and garden stores.

Pathogens accidentally imported to the U.S. from Europe are also taking their toll. Between 1992 and 1994, commercial beekeepers shipped U.S. queen bumble bees to Europe. There, beekeepers reared colonies and then returned the queens and their colonies to the United States. Bee experts suspect that while in Europe, these bees picked up European pathogens against which our native bees have little resistance.

On top of these threats, changes in land use reduce food sources and nest sites for bumble bees. “The more flowers we cut down, the fewer bumble bees there are to gather pollen and nectar from those flowers,” Zahendra said.

Zahendra thinks what’s needed is for government to better regulate pesticides and oversee the importation of non-native species and pathogens. But she also says everyone can take steps to help bumble bees.

“Little things, like planting flower gardens and not mowing as often. Even just having small patches that don’t get mowed, that’s a small thing that everybody can do,” she said. She also says homeowners can be careful about what they spray on their gardens.

The VCE study was the most extensive bumble bee survey ever conducted in Vermont.

The VCE, based in Norwich, is a nonprofit organization that promotes science-based environmental conservation. Starting in 2012, VCE staff and volunteers gathered roughly 15,000 bumble bee observations from 1,500 sites across Vermont. Previously, university insect collections were the only source of information on bumble bee abundance, and most of those were from the University of Vermont, which meant little was known about bumble bees in most of the state.

The species thought to be extinct in Vermont are the rusty patched bumble bee (Bombus affinis), Ashton cuckoo bumble bee (B. ashtoni), and the American bumble bee (B. pensylvanicus). The yellow-banded bumble bee (B. terricola) is not far behind.

Many of these bees are struggling elsewhere, too. The rusty patched bumble bee, once common throughout the eastern U.S., has declined in nearly 90 percent of its former range since 2003, according to the Xerces Society, a nonprofit organization dedicated to conserving bees, butterflies and other invertebrates. The American and yellow-banded bumble bees are also in decline throughout much of their former ranges in the East and Midwest.

In the Netherlands and Britain, multiple native bee species have gone extinct and now the plants pollinated by those bees are less abundant, according to the Xerces Society.

Zahendra says there are many reasons to love bees, not just because they support our food supply. “They are so fantastic. Every time I learn something about bumble bees, it’s jaw-dropping,” she said. “Plus, they’re cute and fuzzy.”

Audrey Clark

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