This post was updated July 17 at 11:15 p.m.

After a decade of planning, the world’s largest wildlife crossing broke ground in Los Angeles.

Supported by a grant from Wallis Annenberg and the Annenberg Foundation, the crossing will be a habitat incorporated overpass allowing wildlife to cross 10 lanes of freeway on U.S. Highway 101. Construction began on Earth Day this year.

The Wallis Annenberg Wildlife Crossing, which is located northwest of LA between the Santa Monica Mountains and the Simi Hills, is meant to preserve species diversity across the Santa Monica mountains, said Beth Pratt, California regional executive director for the National Wildlife Federation. The National Wildlife Federation is an organization focused on preserving habitats, transforming wildlife conservation and connecting Americans with wildlife.

Pratt said that before planning for the crossing began, the National Park Service noticed the genetic diversity within species across the Santa Monica Mountains was beginning to collapse. The phenomenon was especially evident with the isolated mountain lion population, she added.

Professor of ecology and evolutionary biology Greg Grether said biologists with the National Park Service detected the effects of inbreeding negativities – reduced survival and fertility in mountain lion offspring because of relatives mating without a choice – in the Santa Monica Mountains beginning just prior to the COVID-19 outbreak.

According to the Santa Monica Mountains Conservancy website, highways restrict the movement of wildlife between different regions, causing deaths and preventing species from exchanging genetic material between populations.

The wildlife crossing will additionally help animals such as mountain lions, a species in which the males have to beat out other resident males, Grether said. Although these male mountain lions have to leave because of limited space within the mountains, the alternate path across Interstate 405 is impassable, he added.

Michael Comeaux, a public information officer at the California Department of Transportation, said in an emailed statement that Caltrans can oversee construction in a two-stage process since the campaign has sufficient funding.

First, Caltrans will manage the construction of a habitat-incorporated bridge over the Ventura Freeway, which is part of Highway 101, Comeaux said, adding that the second stage will include the building of a tunnel bridge over Agoura Road – which runs parallel to the Ventura Freeway nearby – along with additional utility features such as drainage equipment, irrigation water and soil.

The construction of a safe passage across the Ventura Freeway required $90 million in funding, said Pratt, who is also the leader of the Save LA Cougars campaign. The campaign centers around rallying support for the wildlife crossing and reconnecting natural habitats.

She said a mountain lion named “P22” played a large role in rallying support for the project.

In 2012, P22 successfully crossed I-405 from the Santa Monica Mountains into the Hollywood Hills and Griffith Park, Pratt said, adding that he is the only mountain lion to have successfully done so, giving him celebrity status among the wildlife preservation community.

“I call him the Brad Pitt of the cougar world,” Pratt said. “He’s helped inspire people all over the world to think differently about being able to live with large predators.”

The same year P22 made his crossing, the Save LA Cougars campaign began strategizing and planning the wildlife crossing, Pratt said. In 2014, the campaign went public and held a rally attended by 400 supporters, she said.

Over the next few years, the campaign received millions of dollars from the Annenberg Foundation, Wallis Annenberg himself and the California State Coastal Conservancy, a state agency that protects, restores and increases public access to coastal areas. Others who donated included state agencies endorsed by Gov. Gavin Newsom, Pratt said.

Grether said that although he believes the wildlife crossing is a huge accomplishment, more taxpayer dollars should be spent on conservation.

Pratt said she was happy to see LA leading California and the U.S. in wildlife conservation initiatives.

“It’s really cool that LA, in California, is showing this leadership because bottom line for me, selfishly, that’s good for wildlife … not just in LA but across the country,” Pratt said.