SoCal Building the World’s Largest Wildlife Crossing

When a motorist found yet another dead mountain lion on Highway 101 in the Los Angeles County town of Agoura Hills earlier this summer, it highlighted the risks faced by wildlife trying to survive in Southern California’s increasingly fractured natural landscapes.
For wildlife conservation proponents, it also hammered home the need for a wildlife crossing being built nearby – the world’s largest.
Construction on the Wallis Annenberg Wildlife Crossing began in 2022 to much fanfare. The project is hailed as a way for wildlife to cross the 101 freeway, which bisects the Santa Monica Mountains.

The wildlife crossing, estimated to cost $87 million, will allow animals to pass over 10 lanes of fast-moving traffic, re-establishing ecological connectivity in a critical wildlife corridor. Installation of massive steel girders over Highway 101 began this April, a major milestone for the project, and construction is expected to be complete in 2026.
“This project is truly incredible,” said Wade Crowfoot, California secretary for natural resources. “As the largest wildlife crossing of its kind in the world, it will provide lifesaving habitat connectivity to a broad array of animals for decades to come.”
The project is a partnership between the National Wildlife Foundation (NWF) and Caltrans and received financial support from over 3,000 entities. Major funding came from the Wallis Annenberg Foundation, hence the crossing name.
Creating an area to protect the mountain lions and other animals and plants in the region has been a long-term project, as much of the area was privately owned decades ago.

Over several decades, the Santa Monica Mountains Conservancy, the Mountains Recreation and Conservation Authority, and the National Park Service systematically acquired much of the private land and permanently protected a critical mass of habitat that will now make it possible to link the mountains with the Wallace Annenberg Wildlife Crossing.
Public support for the project has, in part, been driven by wildlife deaths in the area in recent years, which have received a lot of media attention in recent years, in part thanks to programs to monitor the area’s dwindling mountain lion population. In December 2022, the celebrated mountain lion P-22 was euthanized after suffering from severe injuries likely caused by a vehicle collision.
Known as the “Hollywood Cat,” P-22 had lived in Griffith Park for over a decade, navigating some of Los Angeles’ busiest freeways. For many, his death underscored the urgent challenges of protecting Southern California’s wildlife amidst urban development and climate change. The death of yet another mountain lion this summer ads to the grim toll of highways on the animals.

A survey of the California mountain lion population released earlier estimated that the population was smaller than previously thought, at 3,200 to 4,500 cats. Southern California’s cats are at high risk of going extinct in the next 50 years, according to a 2019 study that found multiple threats – roads, pesticides, inbreeding, etc. – create an “extinction vortex” that collectively represents a serious risk to the animals.
You can follow progress on the crossing via images from webcams posted here.