Sometimes You're the Windshield: USU Researcher Says Vehicles Cause Significant Number of Bee Deaths

When a large mammal such as a deer or a moose is struck by a motor vehicle, the damage is usually dramatic. To reduce these unfortunate events, transportation officials have teamed with wildlife researchers to place warning signs, and to construct wildlife underpasses and overpasses to mitigate mishaps along animal migration paths.

In contrast, collisions with much smaller bees often go unnoticed or are perceived by motorists as simply an annoying splat on a windshield. The significance, Utah State University researcher Joseph Wilson argues, is much greater.

"Bees play a pivotal role in our in ecosystem," says Wilson, an evolutionary ecologist and professor in the Department of Biology and USU Ecology Center, at USU Tooele. "The consequences of their frequent collisions with vehicles extend well beyond a minor travel inconvenience. In fact, the impacts of bee deaths, occurring minute-by-minute each day, may have a greater negative impact than we realized."

A new study by Wilson and colleagues suggests tens of millions of bees may perish every day as motorists zoom down busy highways of the western United States. He and USU alums Thomas Porter and Olivia Messinger Carril reported preliminary findings in the Nov. 7, 2024 online issue of Sustainable Environment.

"Unlike collisions with larger animals that are easy to measure, it is much harder to detect the extent of bee mortality caused by moving vehicles," Wilson says.

The team used sticky traps attached to car bumpers and extrapolated the data based on Department of Transportation statistics. Wilson says the large estimated numbers of bees being hit was sobering.

Why is bee mortality along roads so high?

"Roadsides, especially those in arid landscapes, have more flowering plants due to water runoff from roads," Wilson says.

In the desert, these roadside plant communities often house diverse bee communities. Further, the team's findings reveal roads with the highest bee mortality estimates are often near national parks, where visitation has skyrocketed with a steady stream of motor vehicles.

"The quality of the roadside habitat, however, determines if insects stay along the roadside or if they decide to cross the road, looking for better places to forage," he says.

Increased awareness of the importance of bees, as well as a growing number of studies suggesting some bee communities are declining, have led public managers and private organizations to encourage plantings along roads and in medians.

"This may not be the best solution in all areas, if those plantings encourage insects to cross roads to access those resources," Wilson says.

A challenging conundrum, then, is how to you create bee-friendly habitat without further imperiling bees?

"We've raised a lot of questions," Wilson says. "More research is needed to better understand how roads and roadside habitats are impacting insect movement, along with ways roadway design and maintenance, as well as vehicle designs, can be less detrimental to these pollinators."

And it's not all bad news, he says.

"Some studies show healthy roadside habitat facilitates movement of pollinators along the road," Wilson says. "So, with some awareness, landscapes can be restored along roadways to support pollinator communities and reduce the need for road crossings."

Still, habitat modification, habitat fragmentation and habitat loss are taking a grim toll on pollinator populations, he says.

"Bees are keystone species that support plant diversity and reproduction," Wilson says. "Understanding how we can support pollinators at a landscape scale is an important step toward the protection of these important insects."