World’s Largest Wildlife Crossing Gets First Layers of Soil Across California Freeway

The Wallis Annenberg Wildlife Crossing — the largest wildlife crossing of its kind in the world — has reached a new milestone, as workers laid the first layers of soil on the historic California overpass on Monday.

The crossing stretches over California’s 101 freeway and is designed to help bobcats, mountain lions, deer and other creatures safely traverse the busy, 10-lane road.

“I imagine a future for all the wildlife in our area where it’s possible to survive and thrive and the placement of this first soil on the bridge means another step closer to reality,” Annenberg, philanthropist and president of nonprofit the Annenberg Foundation, said in a statement, as the Los Angeles Times reported. “This extraordinary structure will serve not only animals, but it will reconnect an entire ecosystem and protect this global biodiversity hotspot — this moment marks another wonderful milestone toward that goal.”

Located in Agoura Hills, between the Santa Monica Mountains and the Simi Hills, the wildlife passage will allow mountain lions and other animals to expand their ranges to find food and mates.

“Time is running out for these mountain lions, and the National Wildlife Federation is so grateful to the Annenberg Foundation for showing extraordinary leadership to help make this crossing a reality,” said Beth Pratt, the California regional executive director of the National Wildlife Federation (NWF), in a press release from the Annenberg Foundation.

The 101 freeway has isolated small populations of pumas, and their offspring have been showing indications of having birth defects.

“Wildlife crossings restore ecosystems that had been fractured and disrupted. They reconnect lands and species that are aching to be whole. I believe these crossings go beyond mere conservation, toward a kind of environmental rejuvenation that is long overdue,” Annenberg said on the wildlife crossing’s website.

First conceptualized over three decades ago, construction on the wildlife overpass started in 2022 and is projected to be finished next year. The bridge spans 200 by 165 feet and stands 21 feet, eight inches above the 101 freeway. The Annenberg Foundation was a major contributor to the $92-million project.

“There’s been a growing awareness in California as we’re working to protect our nature, our biodiversity, that we can’t just restore and protect habitat. We actually have to build connectivity between habitats,” said Wade Crowfoot, California Natural Resources Agency secretary, when the project was announced, as reported by the Los Angeles Times.

Annenberg Foundation

Workers began placing a mixture of sandy loam and lightweight volcanic aggregate on the crossing Monday morning. It is expected that the process will take several weeks and an enormous amount of soil — 6,000 cubic yards — over roughly one acre.

Once the soil is placed, native plants such as wild grape, buckwheat, coastal sage, wildflowers and milkweed will be planted. Other plants and trees like oaks will be planted on a dozen acres flanking each side of the new passageway.

“Wallis Annenberg’s grant will protect this global biodiversity hotspot — recognized as one of only 36 biodiversity hotspots worldwide — and ensure that California’s iconic mountain lions and other wildlife can find the food and mates they need to survive by reconnecting the Santa Monica Mountains and the Simi Hills and beyond,” said Collin O’Mara, president and CEO of NWF, in the press release.