The Rapid Decline of Bumble Bees Threatens U.S. Agriculture

A recently released study found that climate change may cause bumble bees in North America and Europe to become extinct. Researchers analyzed the data collected from 1900 to 2015 on 66 bumble bee species in North America and Europe. What they discovered is that in just one human generation, the likelihood of a bumble bee population surviving in a given place has declined by an average of over 30 percent.

This decline in bumble bees is occurring rapidly in both North America and Europe. The study links the decline of bumble bees to climate change, which increases the frequency of higher temperatures occurring that exceed what bumble bees can tolerate. “Climate change could increase species’ extinction risk as temperatures and precipitation begin to exceed species’ historically observed tolerances,” researchers wrote.

“We find that species extinctions across two continents are caused by hotter and more frequent extremes in temperatures,” said lead author Peter Soroye said in a statement.

Other studies link climate change to the decline of bumble bees

A previous study published in 2018 conducted the first species-specific assessment of future climate change impacts on North American bumble bee distributions. What researchers discovered is that in all the models analyzed, large losses of bumble bee ranges occurred. “Few bumblebee species are likely to maintain stable geographical range sizes, let alone track warming rapidly into historically-unoccupied areas beyond species’ current ranges,” researchers concluded.

Researchers from Florida State University studied bumble bees in the Rocky Mountains of Colorado. They used models to test direct and indirect climate change effects on three subalpine bumble bees species and examined long-term data to look at how the climate and floral resources of the bumble bees have changed. They discovered that climate-driven changes in floral resources play a “critical role” in how bumble bee populations respond to climate change.

Several other studies show that habitat loss is a significant problem for bumble bees. One study found that the effects of climate change on the range of bumble bees cause them to decline. While many species will move their ranges north, bumble bees do not. Researchers looked at data for 67 bumble bee species in North America going back to 1901 and found that some southern species of bumble bees are disappearing, including the rusty patched bumble bee, which was the first bee put on the endangered species list.

In another study, researchers looked at 15 bumble bee species in the Pacific Northwest and found that 80 percent of the species studied are projected to experience habitat loss within the next 50 years.

The economic importance of bumble bees

Bumble bees are amongst the pollinators important to food company supply chains, and about 30 percent of the food and fiber crops grown globally depend on pollinators for reproduction. The fruits and seeds from those crops provide 15 to 30 percent of the foods and beverages humans consume. That means that one in every four mouthfuls of food and drink consumed is produced thanks to pollinators. Between $235 and $577 billion worth of annual global food production relies on pollinators.

Bumble bees are native bees and about 15 percent of the value of U.S. fruit, nut, vegetable and field crop production depends on native bees. Native bees, including bumble bees, added $4 billion in value to crops dependent on pollinators.

Understanding just may be the key to stopping the decline of bumble bees

Understanding where and why the decline of bumble bees is occurring can help develop ways to stop it. Jeremy Kerr, professor at the University of Ottawa, one of the researchers that worked on the most recently published study, believes that the research they did “holds out hope by implying ways that we might take the sting out of climate change for these and other organisms by maintaining habitats that offer shelter, like trees, shrubs, or slopes, that could let bumble bees get out of the heat.”

Or as the researchers for the 2018 study wrote, “Broad-scale strategies are likely to be necessary to improve bumblebee conservation prospects under climate change.”

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