Wildlife: The bridge will help prevent wildlife deaths, including mountain lions, in the local mountains. Santa Monica Mountains National Recreation Area

Associated Press

Construction has begun on what’s billed as the world’s largest wildlife crossing for mountain lions and other animals caught in Southern California’s urban sprawl.

Officials held a ceremony Friday to mark the start of construction of a $90 million bridge over a freeway and feeder road near downtown Los Angeles.

“This wildlife crossing could not have come at a better time. It is truly a game changer,” said Jeff Sikich, biologist for the National Park Service. “Today’s groundbreaking sets a path toward saving our local mountain lions and supporting the diversity of wildlife in this whole region.”

The bridge will stretch 200 feet over the U.S. 101 to give big cats, coyotes, deer and other wildlife a safe path to the nearby Santa Monica Mountains. It is expected to be completed by early 2025 and will be named the Wallis Annenberg Wildlife Crossing for the philanthropist whose foundation donated $25 million.

“No challenge poses a greater threat to our way of life, prosperity, and future as a state than climate change,” said Governor Newsom. “With our rich natural heritage on the front lines of this crisis, California is building on our global climate leadership with bold strategies that harness the power of nature to fight climate change and protect our communities and ecosystems. Strong partnerships across the board will be critical to these efforts, and the project we’re lifting up today is an inspiring example of the kind of creative collaborations that will help us protect our common home for generations to come.”

Some 300,000 cars a day travel that stretch of the 101 in Agoura Hills, a small city surrounded by a patchwork of protected wildland that the new crossing will connect.

The star of the fundraising campaign to build the bridge was mountain lion P-22, who traveled across freeways and made his home in a huge Los Angeles park. While he’s unlikely to use the span because he lives many miles away, P-22 became a symbol of the shrinking genetic diversity of wild animals that must remain all but trapped by sprawling development or risk becoming roadkill.

Officials said that from the beginning, it was clear that the 101 Freeway was a major barrier to movement, even for wide-ranging species like carnivores. Later, National Park Service and UCLA studies found that the barrier effect extended to gene flow. They found genetic differentiation because of urban development and roads for bobcats and coyotes, smaller, more abundant species such as western fence lizards, and even for a bird, the wrentit.  

 Thus far, the most significant genetic effects have been seen in mountain lions.  

The population in the Santa Monica Mountains has one of the lowest levels of genetic diversity in the state or across the west. More recently, biologists have begun to see the physical effects of that low genetic diversity, specifically kinks at the end of tails, a male with only one descended testicle, and poor sperm quality, documented through research conducted by scientists at UCLA. These were all common characteristics linked with inbreeding depression in mountain lions in Florida that nearly went extinct in the early 1990s.

Scientists tracking mountain lions fitted with GPS collars found over decades that roadways are largely confining animals in mountains that run along the Malibu coast and across the middle of Los Angeles to Griffith Park, where P-22 settled.

On Thursday, a mountain lion was struck and killed on a nearby freeway. J.P. Rose, a senior attorney at the Center for Biological Diversity, said these deaths are preventable if the state invests in more wildlife crossings.

Wildlife crossings — bridges and tunnels — are common in western Europe and Canada. A famous one in Banff National Park in Alberta spans the Trans-Canada Highway and is frequently used by bears, moose and elk.

Cara Lacey, project director for wildlife corridors and crossings project at the Nature Conservancy, said her organization has been mapping out other wildlife crossings that she hopes can also be built so animals can seek out mates and food sources.

“We can do this everywhere,” she said. “We and our partners have a vision for reconnected California where wildlife does not have to compete with cars to cross roads.”

Santa Monica Mountains National Recreation Area (SMMNRA) is the largest urban national park in the country, encompassing more than 150,000 acres of mountains and coastline in Ventura and Los Angeles counties. For more information, visit www.nps.gov/samo.