Bumblebee Diversity — ELSPETH HAY

By Elspeth Hay

For decades, Anne Averill has been researching how our agricultural systems impact native bees. More specifically, she's been studying the diversity and abundance of bumblebees for 30 years now.

"We’ve been studying the bumblebees—the diversity and abundance—for 30 years now. And what we see is that we’re losing diversity of species so that if you go back to 1900 there were 12 or 13 different species— Bombus perplexus and Bombus vagans, Bombus affinis, Bombus fervidus, Bombus terricola, Bombus sandersoni—but by 1950 about I don’t know maybe a third were already gone.”Today in Massachusetts, we’re down to seven species.

Anne explained that we have a lower diversity but about the same number of bumblebees and that’s because one species, Bombus impatiens. It’s the common eastern bumblebee and has become very, very common.

“So when you go out and see bumblebees and you see lots of workers out foraging, more and more often it’s the case it’s simply same species of bee instead of the wide diversity we used to have.”

Anne says this is a result of changes in the way we live on the land. Different species of bumblebees prefer different habitats. Our region went from mainly forest to mostly farms to being more and more built up and paved over, leaving little habitat for bee diversity. In terms of food security, this is worrisome.

"Systems are more stable when you have greater diversity. From the sole point of view of the farmer, they’re relying now on a single species of bumblebee and migratory beekeepers.”

Migratory beekeepers are honeybee keepers who travel the country with their hives. Most big farms rely on them for pollination—in cranberries for example, Anne estimates they pollinate 95 percent of the crop.

“And as we all know the honeybees are really challenged. So, that’s a weak link and then if we have a single species of bumblebee, Bombus impatiens, that common Eastern bumblebee, if a pathogen moves in or if there are bad years lots of times we see with native bees that there are these huge fluctuations in populations depending on weather events so that right now all the queen bumblebees of all the different species are establishing nests for this coming summer.” She added, "and if it was cold or rainy or windy or conditions weren’t good for those queens to set up nests then populations of the colonies, the colonies will be low over this coming season.”

This lack of diversity means our pollinators—and by extension a lot of our foods—are really vulnerable. I asked Anne—what can we do to rebuild diversity?

“I think the idea of setting up pollinator gardens and pollinator meadows it’s a good idea, but it’s kind of a simple band aid in the sense that these bees need nesting sites and they need landscapes where the populations are connected.”

What we really need, Anne says, is more wild lands. Historically we’ve defined wilderness as land set aside free from human touch. But it doesn’t have to be that restrictive. Increasingly creative farmers are rewilding their fields and growing food at the same time. For example, a British biologist who rewilded a meadow in France with the help of some goats counted sixteen species of bumblebees where there used to be only a handful. The more flower species he had, the more kinds of bumblebees showed up. Diversity it seems is contagious.

You can learn more about the idea of farming while rewilding here.

And more about bumblebee diversity on a French farm, and more on the bumblebee diversity in Massachusetts here.