Human interventions like fences and roads kill wildlife. But human intervention can also help save wildlife.
When the Wallis Annenberg Wildlife Crossing opens Dec. 2, it will be the largest in the world. Spanning 10 lanes on the 101 Freeway in Agoura Hills, Calif., the $114-million project covers roughly 200 feet of the highway to reconnect fragmented mountain lion and local animal habitats.
More than two decades of study by the National Park Service has shown roads and development are not only proving deadly for animals trying to cross, but have also created islands of habitat that can genetically isolate all wildlife—from mountain lions and bobcats to birds and lizards.
Research and planning efforts identified the 101 Freeway as the most significant barrier to the ecological health of the region. The crossing will reconnect an entire ecosystem that has long been fragmented. By building a wildlife crossing over 10 lanes and an access road — in the last 1,600 feet in the area that has protected land north and south of the 101 — this project will re-establish ecological connectivity for a wide variety of native plant and animal species in the Santa Monica Mountains ecosystem.
The structure will be built using native plants and paths for the animals to feel safe on. The whole project is expected to serve as a global model for urban wildlife conservation.
As of now, the I-25 Greenland Wildlife Overpass in Colorado is North America’s largest, measuring 200 feet wide and 209 feet long over six lanes of I-25.
Studies have found that overpasses and underpasses work exceptionally well. When paired with directional fencing, they routinely reduce animal-vehicle collisions by up to 90 percent or more, successfully restoring migration paths and reconnecting fragmented habitats. Decades of tracking data from the Banff Wildlife Crossings Project in Canada prove an 80 percent drop in total collisions, with a 96 percent reduction specifically for deer and elk.
How they work:
- The fencing installed alongside highways blocks animals from entering traffic and funnels them directly toward the crossing structure.
- Overpasses are blanketed with native soil, trees, shrubs and logs so that animals step onto a natural extension of the landscape rather than a concrete bridge.
- Different species have distinct preferences; open, wide overpasses favor herd animals and open-country species like deer, elk, and moose, while shier predators often utilize discreet underpasses.
- Animals quickly learn to integrate these safe corridors into their daily ranges and seasonal migration routes.
While constructing multi-million dollar overpasses requires a massive upfront investment, they quickly pay for themselves by preventing human fatalities, injuries and the billions of dollars lost annually to animal-vehicle crashes.
