For years, the stretch of US Highway 93 between Missoula, Mont. and the Canadian border has had a nasty reputation.
The notoriety stems as much from the number of wild animals killed on the road as from the alarming number of dangerous encounters experienced by humans, crashing their vehicles into everything from deer and elk to imperiled grizzly bears.
But soon, Highway 93 and dozens of other travel routes in the United States could become less lethal as traffic engineers and biologists come together to design state-of-the-art wildlife overpasses and underpasses to keep peripatetic creatures from stepping onto the road.
With 3.9 million miles of major asphalt roads crossing the US, a small but growing number of ecologists point to highways as a major wildlife-management issue here and around the world.
One scientist believes that highways may be even more hazardous to the health of ecoysystems than local timber sales and mining. William Ruediger, a US Forest Service ecologist who specializes in forest carnivores, goes so far as to call the problem of roadkill, particularly for species pushed to the brink of survival, "the [wildlife] conservation issue of the 21st century."
As a result, environmentalists are searching for ways to help wildlife bridge the roads. They are taking lessons from Europe, where ecobypasses are called "green bridges," and from Canada, where researchers are studying how well over- and underpasses along the frenetic Trans-Canada Highway in Banff National Park work to reduce roadkill.
In the US, millions of dollars have already been invested in Florida's Big Cypress Swamp along Interstate 75 to provide passages for the endangered Florida panther, black bears, and alligators. In southern California, landscape architects have tried to make the gargantuan freeway system more sensitive to mountain lions. And now, in the northern Rockies, ecologists are trying to design safe bridges for grizzly bears, wolverine, lynx, and gray wolves.
Washington as traffic cop
For the first time ever, building ecobypasses has emerged as a national consideration in implementation of the $217 billion Transportation Equity Act.
"Highway underpasses were a very new concept 10 years ago, but only in the last year, with passage of a new federal highway bill in Congress, have they risen to a level of national interest," says Kim Davitt, a wildlife-corridor specialist with the Montana-based conservation group American Wildlands.
Highway engineers cite the potential safety benefits. More than 200 motorists are killed annually - and thousands more injured - in wildlife-auto collisions. Damage experts say the total cost per year exceeds $200 million.
But biologists believe the ecological savings could be even more profound. "Existing home ranges for some animals are not large enough to sustain a viable population," Ms. Davitt says. "Those animals need to link up with other habitat either for seasonal migration or natural dispersal.... Often that habitat is on the other side of a busy highway."
At present, the foremost global testing ground for wildlife crossings is in Canada, where 14,000 vehicles drive the Trans-Canada Highway through the heart of Banff each day. Until the park fenced the highway corridor, which funneled wildlife toward 22 underpasses and two overpasses, the annual carnage was high.
"This is the major east-west highway in Canada," says Parks Canada researcher Tony Clevenger. "Imagine if you had an interstate running through the middle of Yellowstone."
In 1996 alone, 11 Banff wolves died in collisions, a toll that could easily erase a net gain in population through natural reproduction. Since the latest overpasses were installed, wolves routinely pass safely, both below and above the highway.
But just because an overpass is built doesn't necessarily mean animals will use it. "I think we're learning what works and what doesn't," Mr. Clevenger says. "This is a field of applied ecology still very much in its infancy."
During a recent hike to one underpass, Clevenger found the footprints of wolves, a cougar, and coyotes. Since the end of 1996, scientists have documented more than 26,000 cases of wildlife using the artificial bridges, including 800 wolf passes, 600 cougar passes, and many grizzly bear passes.
Building the structures can be expensive, costing millions of dollars each to erect. Still, enabling animals to access more of the landscape is less pricey than buying more habitat to offset the damage caused by highways.
Within the US Forest Service, which manages 191 million acres, a movement is growing to identify important wildlife corridors in danger of being severed by highways. And placing ecoducts along Highway 93, which slices through some of the wildest country left in Montana, is one priority in the West.
"We're going to be wrestling with this for a long, long time," Davitt says.
(c) Copyright 2000. The Christian Science Publishing Society