A bumblebee searches a lavender plant for pollen at Glendarragh Farm Lavender in Appleton. Credit: Gabor Degre / BDN

A key species of bumblebee is in trouble, especially in Maine. The loss of the American bumblebee is yet another sign that something is ecologically rotten in the state.

The U.S. Fish and Wildlife Service is beginning a one-year review to determine whether to declare the American bumblebee an endangered species after observing significant declines in its population — particularly in states like Maine, where they are all but gone.

Across the country, the American bumblebee population has plummeted by 89 percent over the past 20 years. The Center for Biological Diversity found that the American bumblebee has almost completely vanished from eight states, including Maine, as well as New Hampshire, Rhode Island, Vermont, Idaho, North Dakota, Oregon and Wyoming.

“The American bumblebee is a canary in the coal mine,” said Frank Drummond, Professor Emeritus of Insect Ecology and Insect Pest Management at the University of Maine. “It’s a warning that in general, all of the bumblebees are under stress and we’re starting to lose species.”

For bee researchers in Maine, the decline of the American bumblebee isn’t news. Kalyn Bickerman-Martens, PhD candidate in Ecology and Environmental Sciences at UMaine, is the co-coordinator of the Maine Bumble Bee Atlas, a citizen science initiative that has been tracking bumblebee populations throughout the state since 2015.

“We didn’t find any American bumblebee in Maine,” Bickerman-Martens said. “People say, ‘Hey, I see plenty of bumblebees in our garden,’ but a lot of people don’t realize we have multiple species of bumblebees and they all have their own specific ecological niches that they fill.”

Several factors contribute to bumblebee population decline. Research has shown that common agricultural chemical pesticides like neonicotinoids disrupt bees’ homing and communication systems as well as make them more susceptible to parasites.

Drummond said researchers in Maine have found relatively low exposure to pesticides, and instead credit the decline to other stressors like climate change and land use changes. Since they are adapted to cold climates, Drummond said bumblebees forage and reproduce less on hot days, which are increasingly common in Maine.

Extreme weather in the spring is another factor, from droughts that prevent wildflowers from producing adequate nectar, to support bee populations to unseasonably rainy stretches that keep bees from going out to find food.

“Another factor is that Maine’s landscape is changing,” Drummond said. “Maine used to have a lot of open land for dairy cow production and crop production, and what’s happened as agriculture has gotten more concentrated and we have become more and more forested. Bumblebees thrive on the edges of forests because there are lots of wildflowers on the edges of forests, but if you have solid contiguous forests, it’s not a lot of flowering plant forage to feed on.”

Bickerman-Martens said monoculture, or the cultivation of a single crop in an area, can be equally devastating for bumblebees because of the lack of plant diversity.

Another scourge for bumblebees: lawns.

“Many people are highly concerned about having weeds in their lawn and they utilize herbicides to get rid of the weeds,” Drummond said. “That’s basically a desert for bees because they can’t collect pollen and nectar from the grass in your lawn.”

Drummond said the decline in American bumblebee populations in Maine — and bumblebee species in general — is cause for alarm for several reasons. Unlike some other pollinators, bumblebees are uniquely adapted to cold weather.

“They can fly when it’s really cold and snowing outside and so they can pollinate a lot of our wildflowers and crops in the early spring. To lose this entire group of bees could be catastrophic to both our natural ecosystem but also for our agriculture.”

Bumblebees are also particularly good at pollinating certain plants, particularly those in the family Ericaceae, which include crops like blueberries and cranberries.

“If we lose our bumblebees we’ll be in trouble unless we bring in lots of honeybees, which is an expense,” Drummond said.

The American bumblebee wouldn’t be the first of Maine’s bumblebees to earn the endangered species designation. The rusty patched bumblebee was listed as federally endangered in 2017, though Drummond said the last was seen in Maine in around 2009.

In September 2021, Drummond co-authored a paper on a survey of bumblebees and their health throughout the state of Maine.

“Out of the 17 bumblebees that were originally found in Maine, we found 11 species,” Drummond said. “That doesn’t mean that there aren’t a few more that are low density and we didn’t pick up, but even so, it’s telling us that bumblebees are in trouble and stressed.”  

The bumblebee population situation isn’t black and white, though. The populations of other species of bumblebees, like the common eastern bumblebee, are doing well and have even increased in Maine. However, one bumblebee thriving isn’t enough for a stable ecosystem.

“If you only have one species of bumblebee and something happens — maybe a new pathogen is introduced into the area — all of a sudden we may suffer with pollination of crops and wildflowers,” Drummond said. “If you have 10 different species of bumblebees and there’s a stressor that hits one or two, there’s others there that can take their place.”

Different bumblebees have different skills, too. Some have longer proboscises that are better suited to collect nectar from and pollinate long, tubular flowers.

“The result is that you have a higher diversity of wildflowers whereas if you have a reduction of this bumblebee diversity, it may be that you have a reduction in the numbers of floral species that can be efficiently pollinated,” Drummond said. “The lack of diversity of bumblebees can result in a lack of diversity of wildflowers which can result in a lack of diversity of animals that depend on those wildflowers. It’s a domino effect.”

Drummond said there is a good chance the American bumblebee will be listed as an endangered species after USFWS review and then be protected under the Endangered Species Act. Developers and farmers who kill the insects, for example, would be legally liable and could be fined up to a maximum of $13,000 each time a protected animal is killed. The designation would also provide funding for federal and state agencies to conduct surveys of American bumblebee habitat and other projects that will help the species to thrive in Maine, like reducing mowing along freeways.

“It can make access to federal funding available which can enhance and increase the likelihood that the bees will come back from their decline,” Drummond said.