For World Bee Day, take a moment to appreciate native bees - National Geographic

Clay Bolt first laid eyes on a rusty patched bumblebee impaled on a pin in an insect collection at the Great Smoky Mountains National Park in 2014. Brown and dull yellow with a faded rust-colored patch on its abdomen, the fuzzy, dime-sized relic got him thinking about the species' precarious status in the wild.

Once common in flower-rich grasslands and prairies across the eastern United States and southeastern Canada, this bee now buzzes about in only 0.1 percent of its historical range—a trend documented among many other North American bee populations as well.

There are nearly 4,000 native bee species in North America, including 47 species of bumblebees, and many are declining or are at risk of extinction. 

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Left: Franklin's bumblebee, a close relative of the federally protected rusty patched bumblebee, was last seen in 2006 on Mt. Ashland in southern Oregon. This specimen was photographed at the Smithsonian Museum of Natural History in Washington, D.C.

Right: A greenhouse in Madison, Wisconsin, houses commercially reared common eastern bumblebees to pollinate tomato plants. To collect pollen, many bumblebees vibrate their wing muscles to shake out pollen lodged in the flower's anthers.

A rusty patched bumblebee forages on a hydrangea flower in a public garden in Madison. Once common in 28 states, D.C., and two Canadian provinces, the species now lives in only 13 states and one province. It was declared an endangered species in 2017.

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A natural history and conservation photographer, Bolt wanted to highlight their plight. He decided to start by focusing on the rusty patched bumblebee, telling its story through photographs and a 2016 film titled A Ghost in the Making.

"It broke my heart to think that if something wasn't done to protect it, specimens like that one would be all we had left," Bolt says. "I felt like I could use my photography and filmmaking skills to really bring attention to this species declining in the darkness."

His efforts, and those of conservationists, paid off in this case. In 2017, thanks to a petition filed by the Xerces Society and the Natural Resources Defense Council, the rusty-patched bumblebee became the only bee in the continental United States to get protection under the Endangered Species Act.

The plight of the bumblebee

Much attention has focused on dwindling honeybees, a nonnative species that's domesticated and heavily managed for their pollination services in agricultural settings. But the loss of wild bees, which are also crucial crop pollinators and possibly better suited to help native plants reproduce, is less recognized. (Read more about nature's "gold dusters.") 

Large-scale agricultural intensification has contributed substantially to this decline. Conversion of bees' natural foraging and nesting habitat to corn and soybean fields, plus heavy pesticide use, has not only decimated native bee populations but has also impaired the insects' reproduction and colony growth. 

In a laboratory experiment, for instance, spraying neonicotinoid pesticides—one of the most widely used classes of insecticides since their introduction in the 1990s—led to an 85 percent reduction in new buff-tailed bumblebee queen numbers. These chemicals dissolve in water and can be easily taken up by plants from the soil. 

"Every time a bee drinks nectar or eats pollen, which is their only source of food, they're getting a microdose of the insecticides," says Rich Hatfield, a conservation biologist with the Xerces Society.

Scientists are also concerned about a fungal pathogen, Nosema bombi, detected in several plummeting North American bumblebee populations, including the rusty-patched bumblebee. Commercial breeding, which brings together tens of thousands of queen bumblebees from the wild to start colonies in close proximity, may have allowed the naturally occurring pathogen to spread among and between species. "These colonies would get taken out to farms and the pathogen could spread to wild populations," says entomologist Sydney Cameron at the University of Illinois Urbana-Champaign.

Extreme temperatures, driven by climate change, are also linked to bumblebee declines across North America. In a recent study, researchers found these pollinators missing from many locations where they had previously been recorded. Those sites  experienced increased warming and more frequent unusually hot days over time. (Read how bumblebees are going extinct in a time of climate chaos.)

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Left: A black and gold bumble bee visits a clover flower on the National Mall, in Washington, D.C. Many bumblebee species can do well in populous towns and cities, as long as they have safe sites to forage and spots to nest on or below the ground.

Right: A black-tailed bumblebee flits through flowering plants near San Francisco's Golden Gate Bridge. Such foraging habitat can also benefit butterflies, birds, and many other critters.

A queen common eastern bumblebee visits a wild azalea in Highlands, North Carolina. Found through much of eastern North America, this native species is an important pollinator for wild plants. It's also commercially reared to pollinate tomatoes, blueberries, and other crops.

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Saving more bees

On a cool September morning in 2015, Bolt spotted his first rusty-patched bumblebee in the wild, at University of Wisconsin at Madison's arboretum. 

Such pollinator-friendly and pesticide-free gardens teeming with wildflowers are helping conserve native bees. The Xerces Society has region-specific pollinator plant lists that can help backyard gardeners choose plants that are bee-friendly as well.

Bolt has since turned to photographing other native bumblebee species in peril. Both the Franklin's bumblebee, which was once found across northern California and southern Oregon and was last spotted in 2006, and the western bumblebee, whose numbers have plummeted since the 1990s, are on his list.

"People tend to identify readily with large fauna," he says. "But over 99 percent of life on Earth is smaller than your finger, and those things are so incredibly important."