Editor's Note: (This story was identified by Patricia Zurita, who is guest editor for Call to Earth's "Nature's Highways" theme. )
(CNN) How did the grizzly bear cross the road? With difficulty. It took Lingenpolter, a young male grizzly bear, 46 attempts to safely cross the Interstate 90 highway in Montana.
Wearing a GPS tracker fitted by researchers, the bear was spotted approaching the highway time and time again between the fall of 2020 and spring of 2021, but always turning back. Until eventually, he got lucky, crossing the road beneath a bridge north of the town of Drummond.
Lingenpolter's story is not a rare one. For animals that need space to roam, busy highways are a dangerous obstacle. If they cross they risk being hit by a vehicle, but not crossing can restrict an animal's range, leading to populations fragmenting and declining.
"(Highways) represent a real barrier for all sorts of different wildlife," says Jodi Hilty, president and chief scientist of Y2Y, an initiative that aims to conserve prime habitat across 2,000 miles of land between Yellowstone National Park in the US and Yukon in northwestern Canada. Connectivity is vital for a species' survival -- "to sustain their genetics, find the resources they need, and help maintain healthy populations," she adds.
One simple yet effective method to overcome these barriers is wildlife crossings -- bridges or underpasses that provide safe passage for animals across a highway. Y2Y has helped to pioneer this approach across its range.
"When Y2Y started in 1993, there were exactly zero wildlife crossing structures. Today, there are 117," Hilty tells CNN.
In April, ground was broken on the 118th -- the Bow Valley overpass that will cross the Trans-Canada Highway in Alberta.
This highway, which spans nearly 5,000 miles, cuts through some of the country's most scenic landscapes, including the majestic Canadian Rockies and breathtaking Banff National Park -- home to grizzly bears, wolves, elks, deer and other wildlife.
According to Y2Y, 22,000 cars use the road each day, and this swells to more than 30,000 in the summer, when tourists pour in to witness the region's natural beauty. But this intrusion of traffic into the wilderness has led to high numbers of wildlife-vehicle collisions.
In one 25-mile stretch of highway, which has no fencing or wildlife crossings, Y2Y has recorded around 70 roadkills a year -- and the true number is likely to be far higher as injured animals often move off the road and die later, says Hilty.
Yet in places where there are wildlife crossings and roadside fencing, roadkill has dramatically reduced. Take Banff National Park, where there are 41 underpasses and seven overpasses across a 55-mile stretch of highway. Here, wildlife-vehicle collisions have dropped by more than 80% and, for elk and deer, by more than 96%.
As well as helping animals, crossing "improve safety for people," says Jesse Whittington, a wildlife ecologist for Parks Canada, which manages Banff National Park.
Whittington has studied the effect of the crossings in and around the park for years. Camera traps capture which animals are using them, and radio collars attached to grizzlies and wolves have shown how crossings can help to enable long-range movements.
Animals don't learn where a crossing is immediately, he says, but highway fencing -- with foundations built two meters underground, so that animals can't dig under it -- helps to funnel them towards it. Over time, grizzlies and wolves learn to use the crossings and they pass this knowledge on to their offspring.
Since 1996, Parks Canada has documented animals using overpasses and underpasses on 187,000 occasions, according to Whittington -- "a sign that these crossing structures work."
Banff National Park and the Y2Y project have set an example for others to follow, says Hilty.
"I really hope that our model gets picked up continually, because I think that together we can ensure that both people and nature can thrive," she says.
There are signs of momentum. In 2021, the US government announced its Infrastructure Investment and Jobs Act which will provide $350 million over five years for the construction of wildlife bridges, tunnels, fencing and other infrastructure. And in April of this year, construction began on the world's largest wildlife crossing, which will span over 10 lanes of Highway 101 in northwest Los Angeles, linking the Simi Hills with the Santa Monica Mountains and giving wild animals like cougars more space to roam.
Hilty hopes the use of wildlife crossings will become standard practice across the planet. "We need to get to a point where when roads are busy, it becomes part of normal societal practice that we create safe passage for wildlife," she says.