It’s been a decade since wildlife biologist Miguel Ordeñana spotted the unmistakable tawny rump of a mountain lion in a photo captured on a trail camera in California's Griffith Park. It was the rear end of a now-famous cougar known as Puma 22 (or P-22 for short) who has been sighted hundreds of times since that balmy February evening back in 2012. The celebrity cat, now firmly ingrained in Los Angeles culture, has become something of a symbol for Angelenos: both a sign of hopefulness that we can learn to live alongside wild animals and a cautionary tale about the dangers of overdevelopment and exploitation of the environment.

P-22’s celebrity and the fact that his home range has become fragmented by LA’s vast road network became catalysts for an idea to build an ambitious wildlife crossing. The planned overpass would be constructed over one of the busiest highways in California – the ten-lane 101 north of Los Angeles – and would effectively create a corridor between two parts of the Santa Monica Mountains. Now, almost ten years since P-22’s butt turned up on camera, plans are in place to break ground on the massive wildlife crossing this Earth Day (April 22, 2022).

Highways like the 101 are notoriously dangerous for mountain lions (and other species) that are often killed in collisions with cars as they try to cross into new territory. Los Angeles freeways have claimed the lives of at least 25 pumas since 2002. Just last month, a young mountain lion lost its life when it was struck by a vehicle on the Pacific Coast highway. The situation is particularly problematic for California’s pumas that have been shown to be suffering from low genetic diversity as they struggle to reach one another in the shadow of human development.

One of only two megacities in the world that are home to big cats, Los Angeles is crisscrossed with roadways. For the mountain lions that live in this highly urbanised space, the odds are stacked against them. "Simply put, we won’t have mountain lions in the Santa Monica Mountains in the future if we don’t connect the landscape," Beth Pratt, a conservation leader with the National Wildlife Federation who has spearheaded the corridor campaign told us last year. Pumas in the LA area, especially those south of the 101 freeway, may go extinct in the near future unless they can join up with other cats outside of their bloodlines. "The science is now clear that wildlife need large landscape connectivity in order to have a future," says Pratt.

The goal of the new 210-foot-long, 165-foot-wide wildlife crossing is to provide safe passage for not only mountain lions, but also lizards, snakes, toads, deer, coyotes, and just about any other species that needs to roam. Plans include an acre of local foliage that will be planted on either side of the overpass as well as vegetated sound walls to dampen light and noise for nocturnal animals as they creep across.

Pratt has spent much of the last decade strategising the project, gathering funding and gaining the support and approval of transportation officials. “I’m a little dizzy still, but I feel relieved: we have the chance to give these mountain lions a shot at a future,” she told The Guardian.

The construction of the bridge comes with a cool $90 million price tag, 60% of which is being covered by private donations while the rest coming courtesy of public funds allocated to conservation projects. The new overpass has been described by California’s Governor Gavin Newsom as an “inspiring example” of public-private partnership.

Wildlife corridors have been created with some success in other areas, most famously the overpass in Canada’s Banff National Park or the tunnels and bridges erected for red crabs on Australia’s Christmas Island. But LA’s new overpass will be unlike anything built to date. The crossing is designed to mould perfectly into the surrounding mountains and includes the work of a soil scientist who will ensure that local trees are grown successfully on the bridge and a mycologist responsible for integrating fungi and plants into the design.

For Robert Rock, a landscape architect who led the design, the nature-centred approach could pave the way for future designs that play a restorative role in the natural world. “As both a tool for and a symbol of connection, it will stand as an alluring challenge to future generations to pick up the mantle of design to bridge the gaps elsewhere in our world,” he told The Guardian.

Construction on the overpass is likely to continue until 2025 and it may be some time after that before wildlife begin to adapt to the new design, but Pratt is hopeful that it will all be worth it. “Someone could be in rush-hour traffic, and there could be a mountain lion right above them,” she said to The Guardian. "I think that’s such a hopeful image, and one that inspires me that we can right some of these great wrongs.”

The groundbreaking will be livestreamed here.