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Largest Wildlife Overpass in the World Now Under Construction in California

It'll span 10 lanes of traffic to connect the area's mountain lion population.

Construction broke ground this past Friday on what will soon become the world’s largest wildlife overpass in Agoura Hills, California. The $87 million structure will span all 10 lanes of U.S. Highway 101 at Liberty Canyon Road, connecting the Santa Monica Mountains with the Simi Hills, providing safe passage for all types of critters.

Mountain lions seem to be the main concern, as researchers estimate the area’s mountain lion population could go extinct in 50 years without genetic diversity. The 101 freeway separates and isolates the mountain lion populations, which is what the Wallis Annenberg Wildlife Crossing is designed to fix.

“It’s an engineering marvel,” said Beth Pratt, regional executive director of the National Wildlife Federation, to CBS LA. “I mean, to put this living landscape on top, you have to put soil on top so that the vegetation can grow. And one of the other unique things about our crossing: nobody has ever tried to do it in such an urban area as well. So we have to do special design considerations to mitigate that sound you can hear. Because if an animal hears that, he’s not gonna wanna go on top of it. The light from the headlights. I mean, all that stuff. We have to trick the animal into thinking they’re not going over a freeway, or else they’ll not use it.”

To convince those animals of the crossing’s safety, trees and bushes will fill the overpass, while sound barriers isolate it from the noise of the freeway.

This overpass is a jointly funded project with both private and public donations, including contributors such as the National Park Service, National Wildlife Federation, and Annenberg Foundation. The project is expected to be finished by 2025.

It’s fitting that the Wallis Annenberg Wildlife Crossing project kicked off in earnest on Earth Day. Tragically, the day before, a mountain lion was struck by a car and killed on U.S. Highway 405. The National Parks Service has been studying the dangers that Los Angeles roads and freeways pose to wildlife for nearly 20 years, so it’s good to see this finally being built.

It’s proven to work in other parts of the world, after all.

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