How Are the Bees?

Chelsea Cook grew to love the low hum of the honeybees she studied as a graduate student in Boulder, Colorado. Their characteristic buzz, she learned, was audible cooperation, the result of worker bees fanning their wings at the colony’s entrance to circulate the air and cool the hive. Cook often watched as the insects responded quickly to minute adjustments in temperature: When a cloud drifted over the sun, the fanners disappeared, and when it emerged again, they promptly took up their places.

Fascinated by how strictly the insects were managing their environment, Cook conducted an experiment. “I found an old hot plate and a pickle jar, created mesh cages, put a bee inside, and heated them up,” she says. Previous research had established that honeybees regularly fan to control temperature, humidity, and carbon dioxide. But over and over, the bee on Cook’s hot plate sat still. Confused, she put two bees together. “Sure enough,” with a companion, “they fanned.” Honeybees, she found, use social information—paying attention to each other—to respond to environmental changes.¹

As global temperatures rise, understanding how bees will respond is becoming increasingly important. Back in 2006, beekeepers in Pennsylvania were mystified when their previously healthy hives suddenly emptied, a phenomenon dubbed colony collapse disorder. Beekeepers across the country soon saw similar disappearances: There were no dead bodies inside the barren hives to suggest starvation, and neighboring bees, who often rob hives, seemed to avoid the unprotected honey.

It’s a mystery that’s never been fully solved. But while reports of colony collapse disorder have waned over the last decade, the fate of bees has not improved. Honeybee mortality remains startlingly high, says Nathalie Steinhauer, the research coordinator for the Bee Informed Partnership, a nonprofit organization that started conducting extensive annual bee surveys in response to colony collapse. Steinhauer explains that for the last decade, around 30 to 40 percent of the United States’ honeybees have died every year.² While intensive management has been able to keep honeybee populations roughly stable, that’s much “higher than what beekeepers consider acceptable.” Nor are the 4,000 native bee species in North America doing any better: Nearly 1 in 4 of them is at increasing risk of extinction.³

From 2008 to 2013, wild bee populations plummeted by 23 percent.

Scientists have laid the blame for bee declines on a combination of factors, like the proliferation of pesticides, and parasites like the Varroa mite, which can carry deadly pathogens. While those are major stressors on their own, they are now exacerbated by climate change, painting a disquieting future.

“Honeybees are absolutely critical to our agriculture,” says Cook, now a biologist and founder of the Cook Lab at Marquette University in Wisconsin. Three-quarters of food crops rely on honeybees for at least some pollination,⁴ making honeybees more important than fertilizer.⁵ While some plants can self-pollinate, others, like tomatoes and potatoes, don’t release their pollen until bees arrive to vibrate their flowers⁶; others may require bumblebee saliva to encourage them to flower.⁷ Even trees previously thought to self-fertilize likely have pollinators contributing to their seed production. Yet globally, pollinators are now declining so quickly the Food and Agriculture Organization of the United Nations warns their loss may spark a food crisis.⁴

The problem extends far behind the dinner table: Over 80 percent of wild plants also depend on pollination, often from native bee species, which have evolved alongside the plants they serve. But from 2008 to 2013, wild bee populations plummeted by 23 percent.⁸ If these bees disappear, says Diana Cox-Foster, an entomologist and research leader with the United States Department of Agriculture, “the landscape would basically regress back to grassland.” Long before extinction, she worries about the feedback loops losing wild bee populations may spark: Fewer bees may encourage grass growth, for example, leading to worse wildfires. “Having healthy pollinators and pollinator plantings helps you avoid a tinderbox landscape.”

To forestall these crises, it’s critical to find ways to help bees navigate shrinking habitats and a warming world. Cook’s work is now focused on helping beekeepers manage their colonies as the climate shifts. “We’re stewards,” she says, “We have to figure out how to treat them better.”

American agriculture relies on the hard work of both managed hives and wild bees: Native bees can perform much of the pollination farmers need,⁹ and significantly contribute to crop production. But when most people think of bees, they think of the humble Apis mellifera, more commonly known as a European honeybee. They areessentially insect livestock, brought to the United States to pollinate Old World plants also introduced by colonists. They are as closely managed as other domesticated animals. Many commercial beekeepers transport their honeybee hives to multiple locations a year, servicing almond orchards in California in the early spring and returning to the Great Plains for honey production later in the summer. But for the last decade, the same number of bees have been making less and less honey—and, for beekeepers, less and less money. In 2021, because of extensive drought that withered crops across the Midwest, the USDA reported that honey production dropped by a staggering 126 million pounds, or about 14 percent per colony.

Bees’ incredible ability to transform nectar into honey has long made them humanity’s friend. But hives also rely on honey to survive long after summer blooms have faded. If flowers have died off but winter cold doesn’t set in, bees may fruitlessly keep foraging, becoming nutritionally stressed. “If they used too many resources in the fall or emerge before flowers are available to feed on in the spring, there’s phenology mismatches,” a gap in the timing between bees and the flowers they depend on, says Christina Grozinger, the director of the Center for Pollinator Research at Penn State.

In the summer, honeybee workers transition through different states as they age, working as nurse bees when they are young, and foraging when they grow older. Winter bees, conversely, are physiologically different, and can survive for months. But if the colony is actively searching for nectar into the fall, they aren’t producing winter bees, meaning they aren’t as prepared to survive the winter.

“When spring comes, the older bees die at rates that exceed the replacement rate,” says Gloria DeGrandi-Hoffman, research leader at the Carl Hayden Bee Research Center. Thirty years ago, she adds, “If you’d lose 10 percent of your colonies, that was a bad year for you.” That’s in part because, like humans, bees are more likely to get sick when they’re mingling. Longer autumns and warmer winters are also extending bees’ flying time—helping spread Varroa mites and their diseases and causing surging numbers of deaths.

Fewer bees may encourage grass growth, leading to worse wildfires.

These climate impacts are likely exaggerated by land use changes, which reduce bees’ ability to adapt to new challenges. The increased use of herbicides and insecticides has reduced the diversity of plants bees used to depend on, while increasing their toxic load. Neonicotinoids, a class of insecticides that affect bees’ central nervous system, are particularly harmful. Bees can be exposed simply by visiting a field where they have previously been sprayed, bringing the chemical back to the hive with them. These chemicals are now used on most corn and soybean fields in the U.S., and persist in soil for years, which is why the European Union has banned three of the most common neonics.

In the U.S., a 2020 study by Penn State researchers found that in the last two decades, the toxicity to which bees are exposed rose by 121 times in the Midwest, primarily because of neonicotinoid use.¹⁰ While exposure may not immediately kill bees, even low doses of chemicals can exacerbate other stresses.¹¹ Glyphosate, the active ingredient in Roundup, for example, severely impacts bumblebees’ ability to control their temperature.¹²

While it may be hard to parse these various harms, DeGrandi-Hoffman uses a simple metric to understand how the beekeeping industry is doing. “If you look at companies that sell packages of bees or queens, they’re sold out every year. They can’t make enough to replace colonies that are lost.”

Honeybees evolved to survive winter by huddling into a thermoregulated cluster, surrounding their queen. When anthers stop releasing pollen and petals begin to shrivel, worker bees drag the male drones out of the hive into the crisp fall air, a sacrifice completed by chewing off their wings. The test of the hive’s endurance has begun. The bees’ huddle expands and contracts. It is a dying time.

To help slow these crippling winter losses, beekeepers are increasingly turning to cold storage. When honeybees are kept artificially cold, they don’t need to forage, be treated for mites, or be fed by their keepers, cutting down on costs and reducing mortality. As natural winters warm, states like Idaho and the Dakotas have been early adopters in adapting cold vegetable storage facilities for commercial beekeeping operations. Mike Lamoreaux, a business developer at Gellert, a climate control company that started out storing potatoes, says the practice has taken off over the last decade. Lamoreaux started overwintering bees in 2014. “We’d literally go to trade shows and people would stand in line, waiting to sign up,” Lamoreaux says.

Cold storage isn’t a catch-all solution. “It’s not a hospital,” Lamoreaux says. He warns people to make sure their bees are as healthy as possible before bringing them in. Like so much in modern agriculture, there’s also a question of scale: The costs and risks of these facilities work best for large-scale operations, who can afford to lose several hundred hives if something goes wrong.

To make cold storage more accessible for hobbyists and smaller operations, Cook, along with her business partner Kimberly Drennan, an architect, recently designed a mobile climate-controlled apiary. The size of a horse trailer, it has insulated panels and smart sensors to control temperature, carbon dioxide, and humidity. After winning seed money from the USDA, along with a grant from the Advanced Industries Office of Economic Development in Colorado, their company HiveTech tested a prototype in apiaries this winter. Despite supply chain shortages, early results suggest the unit increased survival three times, compared to colonies that remained outside. Providing cold storage at home cuts down on the need to transport hives, reducing both costs and mortality, and helps beekeepers better manage mite populations and their hives’ nutrition. “It puts the control in the hands of the beekeepers,” Cook says.

To help slow crippling winter losses, beekeepers are turning to cold storage.

These kinds of practical solutions are increasingly urgent. As honey yields drop, financial pressures on beekeepers are increasing. If apiaries can’t stay in business, their efforts to keep bee populations stable will also vanish. “By adapting management—like cold storage—we can help bees make it,” says DeGrandi-Hoffman.

Wild bees, meanwhile, have fewer ways to adapt. Grozinger’s research suggests that across the country, many places that economically depend on wild pollinators will see their populations dwindle. Grozinger and her collaborators tracked wild bee abundance across the U.S., finding many of the places where bees are declining the fastest, like California’s Central Valley, are also places that currently rely on pollinators. “This means growers will be more dependent on purchasing managed pollinators, like honeybees, to produce their crops,” she says. This imbalance is already causing declining production: In another collaborative study, she found that poor seed generation in Pennsylvania black cherry trees may be due to the loss of wild andrenid bees, one of its most important pollinators.¹³

The urgency of understanding these relationships is heightened by how quickly some of these bees are vanishing from the landscape. The first bee added to the endangered species list was the rusty patched bumblebee, a wild bee which historically ranged from the upper Midwest to the East Coast, but others may soon join it. While honeybees are social animals, the majority of the United States’ 4,000 types of native bees are solitary, meaning they don’t have the help of a hive in sharing resources. “You can think about them like a single mom,” Grozinger says, “whereas honeybees are like a village.”

Adding to their vulnerability, many native bees also specialize on a small number of plants with a short blooming season, like the Mojave poppy bee, which U.S. Fish and Wildlife Service is currently considering listing as endangered. It is the only pollinator of the bearpoppy, a scrappy yellow flower that thrives in the harsh conditions of the desert, although mining, extreme heat, and drought have recently erased the wildflower from half its range.

The decline of wild bees will affect entire ecosystems, says Ellen Moss, a research associate at Newcastle University. Rising temperatures are increasingly disrupting the plants bees rely on, leading to food shortages. Moss recently conducted a study that simulated an increase in temperature of 1.5 degrees Celsius and a 40 percent increase in rainwater, over two growing seasons.¹⁴ She found that floral abundance was reduced by almost half—causing the hard-working pollinators to visit each flower more frequently to collect the same amount of pollen or nectar, while the wildflowers themselves produced fewer seeds. “I was surprised by how strong the temperature effect on floral abundance was,” Moss says.

Moss is concerned that writ large, each of these problems—climate change, habitat fragmentation, lower flower abundance—may compound. But so far, few researchers have looked outside of agriculture at the impact on non-crop plants, just as few studies have focused on wild bees and other pollinators. “No species exist in isolation,” she says. If climate change tips the balance, “it could permanently change the composition of communities.”

The unit of importance for bees is its society, not the individual.

Still, bee experts say it’s not too late to take steps to help wild bee populations. The silver lining is that bees reproduce quickly. “They can rebound from disaster surprisingly well,” Grozinger says. She hopes to find ways to design climate resilient landscapes for bees. “If we provide a diversity of options and identify places that may provide shelter from extreme climate variation, they can find what they need in the environment,” she says. In regions where increased rainfall is predicted, for instance, Grozinger is trying to determine where there might be natural rain shadows, preserving those key islands as habitat for pollinators. A recent study in Sciencesuggests that conserving forage for wild bees could also minimize the toxicity of glyphosate—further highlighting the importance of wildflower plantings and conserving native habitat.¹²

Grozinger’s lab has developed a public tool where you can get a bee’s eye view of the landscape near you, gauging the quality of pollinator habitat across the U.S. and encouraging people to make bee-friendly gardens. Many efforts to increase “bee pasture,” as Cox-Foster calls it, have added rippling benefits. For example, sowing cover crops—plants intended to cover the soil rather than be harvested—under almond trees not only doesn’t compete with almond blossoms, but improves the soil quality. Similarly, adding native plantings to solar and wind farms has been highly effective at alleviating their environmental impacts.¹⁵ Even neighborhood projects to plant flowers for bees along curbs and roadways can help reduce habitat fragmentation.¹⁶ Tucked into the recent infrastructure bill is a five-year program that provides $10 million in grants to replant roadsides for pollinators, and an additional $250 million will be distributed for invasive plant removal along transportation routes.¹⁷

Helping bees navigate a quickly shifting climate is a daunting task. But as a honeybee knows well, even minute actions add up. “The reason I study honeybees is their complex societies,” Cook says. The monarchy metaphor—the queen rules the hive—is misleading. The hive’s elegant division of labor is controlled by its thousands of workers, who make decisions at a local level that, when acted out, affect the entire colony. This wasn’t inevitable; like many social insects, honeybees evolved from a solitary ancestor. To survive, they adapted to persist through difficult conditions communally. “Everyone is working toward the collective good,” Cook says. “The unit of importance for bees is its society, not the individual.” These are choices, she adds, “that change how we view solutions.”

Lois Parshley is a journalist and photographer. Follow her work @loisparshley.

Lead image: Santypan / Shutterstock

References

1. Cook, C.N., Kaspar, R.E., Flaxman, S.M., & Breed, M.D. Rapidly changing environment modulates the thermoregulatory fanning response in honeybee groups. Animal Behaviour 115, 237-243 (2016).

2. Woods, J. US beekeepers continue to report high colony loss rates, no progression toward improvement. ocm.auburn.edu/news (2021).

3. Kopec, K. & Burd, L.A. A systematic status review of North American and Hawaiian native bees. Center for Biological Diversity (2017).

4.  Why bees matter: The importance of bees and other pollinators for food and agriculture. Food and Agriculture Organization of the United Nations (2018).

5. Albert-Ludwigs-Universität Freiburg. Bees can be more important than fertilizer. Science Daily (2018).

6. Nevard, L., Russell, A.L., Foord, K., & Vallejo-Marín, M. Transmission of bee-like vibrations in buzz-pollinated plants with different stamen architectures. Scientific Reports 11, 13541 (2021).

7. Daley, J. Bumblebees bite plants to force them to flower (seriously). Scientific American (2020).

8. Koh I., Lonsdorf, E.V., Williams, N.M., & Ricketts, T.H. Modeling the status, trends, and impacts of wild bee abundance in the United States. Proceedings of the National Academy of Sciences 113, 140-145 (2015).

9. Garibaldi, L.A., et al. Wild pollinators enhance fruit set of crops regardless of honey bee abundance. Science 339, 1608-1611 (2013).

10. Douglas, M.R., Sponsler, D.B., Lonsdorf, E.V., & Grozinger, C.M. County-level analysis reveals a rapidly shifting landscape of insecticide hazard to honey bees (Apis mellifera) on US farmland. Scientific Reports 10, 797 (2020).

11. Traynor, K.S., et al. Pesticides in honey bee colonies: Establishing a baseline for real world exposure over seven years in the USA. Environmental Pollution 279, 116566 (2021).

12. Weidenmüller, A., Meltzer, A., Neupert, S., Schwarz, A., & Kleineidam, C. Glyphosate impairs collective thermoregulation in bumblebees. Science 376, 1122-1126 (2022).

13. McLaughlin, R., et al. Insect visitors of black cherry (Prunus serotina) (Rosales: Rosacease) and factors affecting viable seed production. Environmental Entomology 51, 471-481 (2022).

14. Moss, E.D. & Evans, D.M. Experimental climate warming reduces floral resources and alters insect visitation and wildflower seed set in a cereal agro-ecosystem. Frontiers in Plant Science 13, 826205 (2022).

15. Pustkowiak, S., Banaszak-Cibicka, W., Mielczarek L.E., Tryjanowski, P., & Skórka, P. The association of windmills with conservation of pollinating insects and wild plants in homogenous farmland of western Poland. Environmental Science and Pollution Research 25, 6273-6284 (2018).

16. Fitch, G. & Vaidya, C. Roads pose a significant barrier to bee movement, mediated by road size, traffic and bee identity. Journal of Applied Ecology 58, 1177-1186 (2021).

17. Raichel, D. Infrastructure bill boosts bees, butterflies. NRDC.org (2021).

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