SNOQUALMIE PASS, Wash. — Interstate 90 cuts through a mountain pass of old growth forests and wetlands before descending the Cascade Mountains on its final stretch to Seattle.
The busy highway is a border for countless wildlife species, constraining their movements and posing a fatal risk should they dare to cross it.
“Everything from an elk down to a small salamander, they need to move to find food, to find mates, to find new places to live as their populations expand or just when conditions change, like a fire breaks out,” said Jen Watkins of Conservation Northwest.
Soon, animals will have a safer option for crossing the road: They’ll be able to go above it.
Washington state is finishing work on its largest wildlife bridge. The 35-foot-tall, 66-foot-wide structure emerges from the forest and forms two arches above the highway, one for each direction of traffic.
Fencing and landscaping will be installed to guide animals across the bridge, and 8-foot walls will block car noise.
At least one animal has already used it. Washington’s Transportation Department tweeted last week that a wildlife camera captured video of a coyote scampering over I-90 on the new structure. “Excited to see what other species cross!” the agency wrote.
Scientists pinpointed the area as part of a natural migration route from the Cascades to Keechelus Lake, about 60 miles east of Seattle, said Meagan Lott, spokes-woman for the project. Animals, especially elk, move to the lower lands as the season change and the mountains get colder and snowier.
“Providing habitat reconnection will prevent some of the wildlife from accessing I-90 and keep drivers safe,” she said.
The I-90 bridge is part of a growing number of wildlife crossings across the U.S.
The crossings —a combination of fencing, overland bridges and underpasses — aim to keep drivers and animals away from each other as increased human population, a boom in the number of deer and development encroaching on natural habitat have meant more cars on roads and more crashes with animals.
A 2008 U.S. Transportation Department study found collisions between animals and humans have steadily increased, totaling 5 percent of all crashes nationwide and, at the time, costing about $8 billion to the economy, including everything from car repairs to emergency room visits and carcass disposal.
Renee Callahan of the Montana-based Center for Large Landscapes Conservation said driver-animal collisions remain vastly under reported. She points to a 2017 study by Virginia’s transportation agency that showed law enforcement tallies of deer-driver collisions were 8.5 times lower than the number of carcass removals. An adjusted tally showed deer collisions ranked fourth among the 14 types of costliest collisions in Virginia, adding up to more than $500 million per year.
“This is an issue that’s perennially undermeasured, and that means it’s not ranked properly among priorities,” Callahan said.
Collisions between animals and drivers are rarely fatal to people, but often deadly to wildlife. The 2008 federal study also found 21 endangered or threatened species in the U.S. are affected by vehicle hits.
In Canada’s Banff National Park, research has found bridges, underpasses and fencing cut the area’s animal-driver collisions by 80 percent. Another set of crossings and fencing in Wyoming built for a pronghorn migration has seen drops beyond 85 percent.
All but four of the two dozen overland wildlife bridges are in Western states, but dozens of other locations have been pinpointed as needing corridors, Callahan said.
“The No. 1 obstacle is funding,” said Watkins, whose organization has helped campaign for animal crossings.
Patty Garvey-Darda, a biologist with the U.S. Forest Service has worked on the I-90 crossing from the beginning. She said the $6 million bridge will pay for itself when the highway is not fully or partially closed by animal hits.
“If you shut down Interstate 90, you shut down interstate commerce,” Garvey-Darda said.