World’s Largest Wildlife Crossing Game Changer

Big progress. Big Milestone.

The Wallis Annenberg Wildlife Crossing is “going to start looking like the bridge it will become” said Beth Pratt, California Regional Executive Director for the National Wildlife Federation. In March she spelled out the night time freeway closures details coming in April. For six to eight weeks one direction of the 101 Freeway will close every night, 11p.m. – 4a.m., Monday through Friday. The opposite direction will stay open for traffic.

These ‘Closures for Cougars’, 10 lanes of freeway where 300,000 vehicles roar every day, are for a good cause — saving the Santa Monica Mountains mountain lions and other vulnerable species from extinction and ensuring a future for this ‘biodiversity hot spot’. The Santa Monica Mountains are one of 36 ‘hot spots’ in the world, regions that contain a high level of species diversity, many not found anywhere else, and a significant number of threatened or endangered species. This corridor will connect the small population of mountain lions in the Santa Monica Mountains and the larger and genetically diverse populations to the north as well as the genetically isolated bobcats, birds, deer, snakes, toads, insects, coyotes, lizards and species that pollinate plants and keep pests in check.

On April 17th Beth Pratt posted this video along with these comments on Facebook: “Hard to describe the elation I feel to now be driving UNDER the first supports for the Wallis Annenberg Wildlife Crossing. We will make things right for wildlife!”

Construction broke ground in 2022, on Earth Day. Two wet springs have pushed the opening into 2026. P-22’s legacy passageway is halfway done with more than 6,100 tons of concrete poured. Now the installation begins of massive concrete beams. Each concrete beam is 140 tons, equivalent to 14 elephants! 82 of these horizontal supports will stretch across the freeway.

Another effort to restore connections between biological communities and save threatened wildlife is at the San Diego-Riverside County line. Here, Caltrans and The Nature Conservancy are leading the planning of 2 wildlife crossings for Interstate 15 in collaboration with San Diego State University Field Station Programs and other partners, SDSU, USGS, UC Davis Wildlife Health Center & Road Ecology among them. The goal of the wildlife crossings is to reconnect the Santa Ana Mountains west of I-15 with the Peninsular Ranges east of I-15, establishing a viable network of connectivity known as the Santa Ana-Palomar Mountains Linkage. Should this sole remaining natural habitat area be severed, mountain lions will likely become extinct in the Santa Ana Range (Paul Beier, Conservation Biology, 1993).

Linkage Design for Santa Ana – Palomar Connection. This zone, 4 miles wide, 16 miles long,
encompasses the best areas for movement and reproduction of
a diverse assemblage of species.

At roughly 500,000 acres of natural habitat, the Santa Ana Mountains are still not large enough to sustain populations of wildlife that inhabit the area and the I-15 is a nearly impenetrable barrier to wildlife populations in other mountain ranges leading to genetic isolation. Both crossings are essential for San Diego connectivity and for multi-species connectivity. Caltrans is working on completing planning and environmental documents by the end of 2026 for a new vegetated wildlife overcrossing for I-15 about 1.5 miles south of Temecula Creek Bridge. Caltrans is also creating crossing structure alternatives with public circulation of the environmental document in the next 6 months. Meanwhile, The Nature Conservancy has completed plans to enhance the function of the existing I-15 Temecula Creek Bridge at the northern edge of the linkage as a wildlife corridor which will provide a shorter term wildlife connectivity solution for the linkage while plans for the wildlife overcrossing move forward.

Nature needs room to roam and SoCal wildlands are one of the world’s great biological warehouses of species diversity so many crossings are planned to restore fractured ecosystems. Together we can ensure a future for an ancient species, the mountain lion, and countless others.

More information is available at 101 Wildlife Crossing and Save LA Cougars.
For construction progress updates, sign up for a weekly newsletter or contact Michael Comeaux at Caltrans: or call 213-897-9372
For Episode 2 of Destination Nature podcast discussing the importance of the Santa Ana-Palomar crossings, click here.

Be the first to comment on "World’s Largest Wildlife Crossing Game Changer"

Tell readers what you think

This site uses Akismet to reduce spam. Learn how your comment data is processed.