Billions of pollinating insects killed on North American roads each summer: study

A study of roadkill on the highway south of Sudbury surprise researchers who discovered tens of thousands of pollinating insects wind up squished on vehicle windshields each summer.

'If annually you're losing 9.3 billion butterflies, that has to have an impact'

Laurentian University biology students James Baxter-Gilbert and Julia Riley at the the start of their daily walk along Highway 69 in search of reptiles and insects on the road. (Markus Schwabe/CBC)
Featured VideoA Laurentian University study suggests billions of pollinating insects are killed on North American highways by speeding vehicles.

What started as a joke between two researchers crossing a highway in northern Ontario has turned into a published study on the number of insects killed by vehicles across North America. 

The study, published in the Journal of Insect Conservation, suggests billions of pollinating insects succumb to speeding vehicles each summer. 

PhD biology student James Baxter-Gilbert was a master's student at Laurentian University in Sudbury when he and a colleague were walking along a stretch of highway near the Magnetawan First Nation, looking for signs of reptile roadkill and noticed a lot of dead bugs.

"As a joke we started saying, 'Oh! There's a bee! Oh! There's a bee!' And it went from being a joke to realizing there are quite a few bees," said Baxter-Gilbert.

Pollinating insects collected after being hit by vehicles on Highway 69 south of Sudbury. (James Baxter-Gilbert)

Two years later while conducting an extensive daily road survey looking for snakes and turtles killed on the highway, researchers also kept their eyes peeled for any dead insects on the road.

Thousands of dead bugs were collected, dropped into sandwich bags and stored in crates for counting and categorization. 

"You can imagine if you're doing this every single day, all summer long, for two years, you amass quite a number of boxes filled with dead bugs," said Baxter-Gilbert, who joked they had a gross count, "in both it was a large amount and it was pretty smelly."

"It's not surprising that insects get hit. What was surprising was the number."

Close to 117,000 individual insects were collected along a two-kilometre stretch of highway over the two-year study.

By extrapolating those numbers with the number of highways across North America, Baxter-Gilbert said he estimates at least 9.3 billion butterflies and 24 billion bees and wasps are are killed by vehicles each year.

"If annually you're losing 9.3 billion butterflies, that has to have an impact. The crazy thing is we don't know what that impact is."

Baxter-Gilbert hopes this research spurs others to consider further study to determine how many insects can be removed from an area before doing before harming the sustainability of the population. 

"We know pollinators in general particularly bees are in trouble," said Baxter-Gilbert. "But what hasn't been looked at that much is the effect roads may play. It may not be the straw that breaks the camel's back, but it may be one of the straws."

"As the world becomes more urbanized ... and we have more traffic, this may eventually become an issue."

The paper concludes: "Ultimately, the continued survival of humanity depends on pollinating insects, and as roadways bring food to our tables, they may also be jeopardizing the future production of those crops."