Just 30 miles west of the iconic Hollywood sign in Los Angeles, a bold new landmark is rising—not for people, but for wildlife. Stretching over ten roaring lanes of the US Highway 101, the Wallis Annenberg Wildlife Crossing is quickly taking shape. 

Once finished, this vegetation-covered bridge will be the largest wildlife overpass in the world. Designed to reconnect the Santa Monica Mountains with the Simi Hills, it offers animals like mountain lions, deer, bobcats, and even birds and insects a safe way to travel, hunt, and breed—without risking deadly road crossings.

Time to spread soil on the crossing

Millions of animals are hit by vehicles on highways every year, posing serious risks to wildlife and human lives. In the US alone, about two million such accidents happen annually. Decades-long research has shown that one of the most practical and effective ways to avoid such collisions is to make wildlife crossings. Essentially, special bridges or tunnels that facilitate safe movement of animals across roads.

“Wildlife crossings are unique because they allow people and nature to thrive together. By building the Wallis Annenberg Wildlife Crossing, Caltrans is supporting transportation infrastructure that will not only reconnect and restore habitats but also reduce vehicle collisions with wildlife and enhance highway safety,” Tony Tavares, Director of California Department of Transportation (Caltrans), said.

The idea for this massive project started years ago, when scientists and residents noticed that animals, especially mountain lions in the Santa Monica Mountains, were becoming isolated by freeways. A famous example is P-22, a mountain lion that managed to cross two freeways but lived the rest of his life isolated in Griffith Park. 

His story, along with some other studies, highlighted severe genetic problems among local wildlife triggered by isolation and inbreeding. This motivated the locals, conservationists, and wildlife authorities to take some action.

In April 2022, construction of the Wallis Annenberg wildlife crossing officially began. Since then, the project has made major progress. In the early 2025, crews lifted and placed massive concrete beams, and now they are laying soil on the structure. 

A boon for biodiversity

In the coming weeks, about 6,000 cubic yards of carefully engineered soil will be spread on the crossing. This special soil is a precise blend of sand, silt, and clay infused with compost and native fungi. It is prepared such that it has the same biological characteristics as the natural soil surrounding Highway 101. Once the soil is in place, the crew will begin planting seeds of native trees, shrubs, and grasses. This vegetation will eventually span across 12 acres of land over LA’s busiest highway.

“Basically, they’re restoring the mountain to what it once was, so wildlife won’t even know they’re crossing the freeway,” Jeremy Wolf, a scientist and one of the proponents of the LA wildlife crossing idea, told the Los Angeles Times.

The crossing is expected to open for animals by the end of 2026. It will reconnect natural habitats that have been divided for decades. Scientists hope the overpass will help reverse the harmful effects of isolation, particularly among mountain lions, whose populations have shown signs of inbreeding and genetic decline.

Moreover, beyond large predators, the crossing is designed to support free movement of a wide range of species, including bobcats, deer, birds, reptiles, and even pollinators. It could become a powerful boost for biodiversity, allowing native plants and animals to reclaim lost ground.

Previous research has shown that wildlife crossings can reduce collisions between animals and vehicles by more than 90 percent, improving both animal welfare and human safety. Hopefully, the Wallis Annenberg Wildlife Crossing will achieve similar results and play a big role in restoring the natural environment around Highway 101.