Since at least 2011, scientists have been warning of widespread decline in bumblebee populations in North America.1 Such declines have only continued in 2020, with researchers now warning that their rate of decline is consistent with a mass extinction.2

Bumblebees — those fuzzy bees that likely frequented the flowerbeds of your childhood — are vital pollinators of both wild plants and agricultural crops across the globe. Unique features, like their large size, long tongues and high-frequency buzzing, help to release pollen from flowers and make them efficient players in transferring pollen among crops like tomatoes and berries, which bring in billions of dollars.3

In 2011, researchers found that relative abundances of four bumblebee species declined by up to 96% over a three-year period, with reductions in geographic ranges between 23% and 87% — in some cases occurring within the last two decades.

A 2020 study using long-term data for 66 bumblebee species across North America and Europe found similarly disturbing statistics,4 including that, compared to prior to 1974, you are close to 50% less likely to see a bumblebee today.5

Temperature Changes Blamed for Declining Bumblebee Populations

The data, which spanned a 115-year period, revealed that the likelihood of a bumblebee population surviving in any given area has declined by 30% over the course of a human generation.6

Lead study author Peter Soroye of the University of Ottawa, further told The Guardian, “We found that populations were disappearing in areas where the temperatures had gotten hotter. If declines continue at this pace, many of these species could vanish forever within a few decades.”7

Bumblebees’ fuzzy exteriors and ability to generate heat while they fly signal a preference for cooler weather. It’s unknown exactly how much heat and fluctuations in temperature they can tolerate, but Soroye said the declines “are linked to species being pushed beyond temperatures they haven’t previously had to tolerate.”8

It’s possible that bumblebees could overheat or be affected by related changes to vegetation and flowers, leading to starvation. Queen bees also overwinter in leaf litter or in the ground and may be affected by early ice melts and subsequent freezing, according to study co-author Jeremy Kerr, who is also with the University of Ottawa.9

Writing in the journal Science, researchers explained that changes in climate are contributing to widespread declines among bumblebees across continents. As the number of days with extreme heat increase, so do local bumblebee extinction rates.

Colonization and site occupancy within a region, along with species richness, also decrease, independent of changes in land use and condition. Further, the researchers noted:

“Increasing frequencies of temperatures that exceed historically observed tolerances help explain widespread bumble bee species decline … As average temperatures continue to rise, bumble bees may be faced with an untenable increase in frequency of extreme temperatures.”10


Pesticides Also Harming Bumblebees

Systemic neonicotinoid pesticides have also made headlines for their role in bee deaths. One study suggested that the chemicals may prevent the formation of new colonies by reducing egg-laying by queen bees.11 Bumblebee queens exposed to the neonicotinoids were 26% less likely to lay eggs, a number big enough to increase the chance of extinction for wild bumblebee populations.12

Two weeks of exposure to the neonicotinoid thiamethoxam also resulted in a reduction in feeding in two out of four bumblebee species, suggesting “anti-feedant, repellency or toxicity effects,” the study found.13 In separate research, exposure to another neonicotinoid, imidacloprid, led to social behavior changes in bees,14 making them less active and less likely to contribute to the welfare of their colony, such as caring for larvae or maintaining the nest.15

Research published in Proceedings of the National Academy of Sciences also suggests that pesticides like glyphosate may be disturbing specialized bee gut microbiota that is necessary for proper growth and defense against pathogens.16

What Can You Do to Help Bees?

More than half of bee species are declining and nearly 1 in 4 is imperiled and at increasing risk of extinction, according to an analysis by the Center for Biological Diversity.17 A loss of bees would have major ramifications on the ecosystem and food supply, as pollination from bees and other insects is responsible for between $235 billion and $577 billion worth of annual global food production.18

Managed honeybees alone provide an estimated $20 billion in economic value, but even native bees contribute, including bumblebees, by pollinating foods such as berries, alfalfa and citrus fruits to the tune of $4 billion.

“Although their actual economic value is much smaller than honey bees, the value of wild bees is significant,” Forbes noted. “Aside from maintaining habitats that attract pollinators, native bees arrive at no cost to farmers yet still help improve the quality and quantity of their harvest.”19

To help bees in your area, reduce the use of chemical pesticides and grow native, non-GMO plants and flowers — especially those that provide nectar and larval food for pollinators.

You can also leave leaf litter in your yard until spring; this natural substrate provides shelter for many insects. On a larger scale, by planting trees, shrubs and other plants, you can provide a cooler spot for bees on hot days, protecting them from extreme temperatures and hopefully helping to stave off extinction.