On any given day, Americans drive over millions of miles of roadways, rarely noticing what’s left splattered on their windshields. Yet, unbeknownst to most drivers, their vehicles are unwittingly contributing to the deaths of tens of millions of bees each day, according to a new study by researchers at Utah State University (USU).

Bees pollinate nearly 75 percent of all the food crops humans grow globally. Suffice it to say, they’re a big deal!

A previous report reveals that the cost of pollinating services that bees provide in the US alone comes out to be a whopping $20 billion a year. However, the real question is: bees do so much for us and nature, but are we treating them well in return?

“Bees play a pivotal role in our ecosystem. 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,” Joseph Wilson, lead study author and a professor at USU Tooele, said.

Generally, when a vehicle strikes a large animal such as a rodent, cat, deer, or dog, it is quite noticeable. To help prevent such accidents, road and wildlife authorities put up warning signs, develop alternate pathways, and construct tunnels to enable free and safe travel of animals. 

However, when a car hits a bee, no one pays attention as the collision leaves only an insignificant mark on the windshield. Even if dozens of such marks appear, they are simply wiped away.

Estimating the number of bee deaths caused by vehicles

To get a rough idea of how many bees die like this, the study authors conducted an interesting experiment.

They pasted sticky papers on the bumpers of some mid-sized vehicles. Using these vehicles, they completed 29 trips covering 9,344 km (~5,800 miles) across Utah, a state that is home to over 1,000 bee species. At the end of each trip, they looked at the sticky paper and counted the dead bees on it. 

Then, considering the size of the sticky trap and the distance traveled by the vehicle, the study authors calculated the number of bee collisions per unit area and for each kilometer. Next, they multiplied this number by the total front surface area of a typical vehicle to estimate how many bees would hit the entire front of the car per kilometer.

The result was further multiplied by the total distance traveled by a single car and the average number of cars traveling that particular route each day. This calculation provided an approximate daily number of bee collisions along the route, using both average and minimum values for accuracy.

“Our data suggest that, when including smaller bee species, over 5 million bees are killed by all vehicular traffic along a single stretch of highway on any given day during the bee flight season.

“Even if we apply our minimum estimates of bee mortality across sampled Utah roads to the entire spring and summer season, and accounting for only daytime drivers, we estimate that hundreds of millions of bees could be killed every summer,” the study authors note.

Busy roads don’t kill the most bees

The sticky paper captured bees belonging to 14 different genera. This suggests the extent of destruction vehicular traffic is causing to bee populations across multiple species. 

From this data, one might also assume that the highest number of bees are killed on the roads with the most traffic. However, this is where it gets interesting. It is not the busy roads but the routes leading to popular national parks that kill the most bees. 

“One interesting pattern seen in our data is that some of the routes with the highest bee mortality estimates are in parts of Utah that are home to busy national parks. For example, the route that had the highest bee mortality estimates, with up to 16 million bees hit per day along the route from Salt Lake City to Moab, Utah, near Arches National Park,” the study authors said.

Even the short route from St. George to Zion National Park (~33 miles) witnesses nearly 1.4 million bee-car collisions. Compared to regular roads, the traffic on such routes is much lower. However, since the area surrounding national parks has a high bee population density, the likelihood of vehicles hitting large numbers of bees on such routes is high. 

The time to act is now

Commercial beekeepers claim that for the last two decades, honey bee colonies have been declining at a rate of 30 percent annually in the US.  Studies suggest that similar trends have been observed in wild bee species. For instance, according to research published in 2023, in the last 15 years, the number of individual bees has dropped by a staggering 60 percent. 

The current study highlights another important factor contributing to declining bee population. However, it also hints that if we somehow manage to save bees from vehicular traffic, we can save the lives of hundreds of millions of bees each year. How to do this we still haven’t figured out. But considering the rate at which bees are dying, something must be done soon.

Hopefully, further research will reveal some practical solutions to this problem.

The study is published by Taylor & Francis.