by | Sep 13, 2022 | Conservation, Fauna, People

Bumblebees (Bombus spp.), like the one pictured here on a sunflower (Helianthus sp.), are decreasing in relative abundance as the summers get hotter. PHOTO Dr. Gabriella Pardee

Dr. Gabriella Pardee’s decision to study bees was partially one of self-preservation. As an undergraduate at the University of Toledo, she conducted research on Azteca instabilis ants, a particularly aggressive species that is a friend to farmers hoping to eliminate coffee pests, but a foe to researchers wanting to avoid the need for anti-inflammation lotion. 

“I loved doing research, but I hated working with ants,” Pardee explains. “If you got too close to the nest, they’d just come out and attack you.” 

Countless bites later, she knew it was time for a change. At the suggestion of her mentor, Pardee turned her attention to bees.

“There was a little community garden on campus, so I went out that day with a net, caught some bees, and thought, ‘Bees are amazing!’” she remembers. “From there on out, I’ve spent every single summer standing in meadows with a net, looking for bees.” 

Dr. Gabriella Pardee and Dr. Sean Griffin on a bee collecting excursion at the Nachusa Grasslands in Franklin Grove, Illinois. PHOTO Sean Griffin

That may sound quaint, but Pardee’s research is cutting-edge. From 2013 to 2018, she and her husband, Dr. Sean Griffin, director of Science and Conservation at the Wildflower Center, joined an ongoing research project at the Rocky Mountain Biological Laboratory in Gothic, Colorado that seeks to understand how various bee species respond to climate change. Their work consisted of collecting bees at an elevation of 10,000 feet and was physically challenging. Griffin says he got terrible altitude sickness on one of the excursions. 

“I wasn’t used to [the elevation],” he explains. “I went in and hiked eight miles in one day on snowshoes and it laid me out.” 

But temporary discomfort is a small price to pay for impactful science. By the time Pardee began writing her doctoral dissertation, which examines the effects of climate change on insect populations, the Colorado project had amassed nearly 20,000 bees of approximately 154 species. She and her team analyzed the collection closely and made an interesting, if disconcerting, discovery: As summers get hotter and drier, large-bodied bee populations decrease, and small-bodied bee populations increase in relative abundances. Pardee and Griffin, along with several other researchers, co-authored their findings in a paper titled, “Life History Traits Predict Responses of Wild Bees to Climate Variation,” recently published in the journal, Proceedings of the Royal Society B. 

“We focused on body size, because body size has been shown to affect bees differently in response to global change,” Pardee explains. “Then we looked at their nesting behaviors.” 

Bumblebees, which tend to be larger-bodied, are comb-building cavity nesters, while solitary bees, which tend to be smaller-bodied, are soil-nesting.  

“Bumblebees are one of our best pollinators, so [their decline in relative abundance] is concerning,” Griffin says. “They are the largest [bees] and they have the most hair. They can transport a lot of pollen.” 

The genus can also transport that pollen much more widely than their soil-nesting counterparts. 

“Smaller bees usually have a foraging radius of about 200 to 500 meters, whereas bumblebees can travel about six kilometers from their nest,” Pardee says. “That’s good for plants, because if [the bumblebees] are visiting flowers farther away, then it could help with gene flow.” 

Of course, the fact that smaller bees are increasing in relative abundance under warmer conditions may compensate for the decline in bumblebees and create what Pardee tentatively calls “pollination security.” But she says only time will tell, and it’s essential for people to take action to protect bees of all species. These winged insects are independently responsible for pollinating about 75% of the Earth’s crops, so losing them could devastate the ecosystem. In fact, Albert Einstein is believed to have said, “If the bee disappears from the surface of the Earth, man would have no more than four years left to live.” Griffin and Pardee are more optimistic.

LEFT One of Pardee and Griffin’s research subjects, a bumblebee (Bombus sp.) pollinates a bluebell (Mertensia sp.). RIGHT Small-bodied, solitary bees like this one are increasing in abundance as temperatures rise. PHOTOS Dr. Gabriella Pardee

“I bet humans could survive,” Griffin speculates, “But eating wouldn’t be as much fun, because it’s all the best things [that bees pollinate], like fruits and vegetables.” 

Luckily, there are actions people can take now to protect bees and the flavorful meals they make possible. Pardee says that, in addition to climate change, one of the biggest threats to bees is habitat loss. That’s why she encourages gardeners to fill their beds with native plants that bloom in succession.

“Bees are just emerging from their nests [in early spring, when there aren’t many flowers available],” she explains. “They’re hungry, they’re trying to build their nests, so having plants that bloom from early spring up until the late fall is really, really important.” 

Pardee and Griffin also recommend checking out “citizen science” websites like iNaturalist ( and Bumblebee Watch (, where user-submitted photos of bees are used by researchers to monitor population changes. The more data collected about wild bees, like those in Pardee’s study, the better. 

“Wild bees are actually better pollinators than domesticated honeybees in many crops and natural systems, but we don’t know as much about their trajectory because there are just so many different species and they all have different responses to global change,” Griffin explains. “So, this is an exciting field because I feel like we can really make a difference. And bees are just super cool … they’re interesting animals.”

Shop pollinator plants at the Wildflower Center’s Fall Native Plant Sale.