Wildlife crossings don’t just protect animals and biodiversity. They also can reduce the number of car collisions and save a community significant money, a new study finds.
Wildlife crossings are human-made structures that help animals move safely around their habitat. They are often underpasses, overpasses, or culverts that allow animals to get past roads and highways when they’re searching for food or evading predators.
When new roads are built, animals can be stranded in a part of their habitat as the new thoroughfares bisect animal populations and habitats. This can have a negative effect on ecosystem biodiversity as some animals are unable to migrate to survive. When they attempt to cross the new barriers, that can greatly increase the number of vehicle-wildlife collisions.
In the new study, researchers put a price tag on those events.
“I thought it would be useful to provide some information on the monetized benefits of wildlife crossing structures to policymakers, transportation planners, and conservationists,” Wisnu Sugiarto, a Washington State University economics doctoral student and author of the study, tells Treehugger.
“Building a wildlife crossing structure is typically an add-on project to an existing highway and project managers have to consider resource allocations and budget constraints. I hope having some information on the economic impact is useful for transportation planners, as they consider the cost and benefits associated with their projects involving wildlife crossing structures.”
Because wildlife crossings vary so much in type and size, Sugiarto says his study of their economic impacts isn’t targeted toward specific structural types of size. And his analysis didn’t look at the biodiversity impact.
“I only monetized the benefits based on the average reductions in wildlife-vehicle collisions,” he says. “Thus, my estimates are missing out on the benefits for animals and the ecosystem.”
Analyzing the Impact
For this study, Sugiarto studied collision information from the Washington State Department of Transportation. He looked at data from 2011 to 2020, before the start of the pandemic caused a shift in travel patterns. Then he made adjustments based on how close the crossings were to other structures and for the time it took to build them.
He examined data for 13 of the 22 wildlife crossings, including bridges and underpasses, in Washington state. He compared the number of wildlife-vehicle collisions each year before and after the construction of a wildlife crossing. He considered the area within 10 miles of a crossing.
The 10-mile radius was based on information from a 2004 study. Researchers found that female white-tailed deer wearing GPS collars migrate a minimum of 1.3 to 11.6 miles daily in spring.
Then he compared his analysis to a separate area in the state with no crossings at all.
“The findings reported that wildlife crossing structures reduced the number of wildlife–vehicle collisions by one to three accidents on average per mile per year, but not all structures had statistically significant effects,” Sugiarto says.
Using monetary estimates from other research, he determined that a wildlife crossing offers an annual benefit of between $235,000 and $443,000 every year, per crossing. Earlier studies focused on wildlife crossings in North Carolina, Utah, and Wyoming.
“They found that wildlife underpasses and fencing improve road safety,” he says. “My findings complement earlier studies from other states and are also in favor of improving road safety.”
The results were published in the journal Transportation Research Record.
Better Safety and More Lives Saved
Researchers think the findings are important for several reasons. They show, for example, that In addition to benefiting animals and the ecosystem, crossings improve road safety.
More than 350 deer are hit by cars each year on a 12.5-mile stretch of U.S. Highway 97 in Okanogan Valley in north-central Washington.
“Meanwhile, people continue to rely on highways for commerce and travel, and animals continue to have mobility needs for food, mating, and migration,” Sugiarto says. “Thus, identification of an effective mitigation strategy for reducing wildlife-vehicle collisions is essential for transportation safety.”
The findings are also timely. The Infrastructure Investment and Jobs Act passed in 2021 includes $350 million over five years for the construction of wildlife crossings.
“Prior to working on this research, I wasn’t aware of any mitigation strategies to reduce wildlife-vehicle collisions. I also thought we couldn’t do much about it, partly because we wouldn’t be able to communicate with wildlife and control their movement,” Sugiarto says.
“However, it turns out that there are multiple strategies to mitigate issues related to wildlife-vehicle collisions and we can do something about them.”
