This blog was written by Defenders of Wildlife Center for Conservation Innovation Intern, Bella Astin, with contributions from Defenders of Wildlife’s California team.
Hidden in plain sight above one of California’s busiest highways, a meaningful transformation is unfolding. A bridge is being built to reconnect wildlife. Over the past three years, I’ve driven beneath the construction of the Wallis Annenberg Wildlife Crossing nearly every day. When complete, it will turn a deadly stretch of freeway into a life-saving passage for mountain lions, deer and countless other animals. It is a truly hopeful reminder that even in one of the most developed parts of California, we can still choose to build a future where wildlife has a place to roam freely.
California is home to a wealth of wildlife and plants, supporting a wide range of endemic and imperiled species. At the same time, it is home to around 40 million residents plus an average of 250 million visitors each year. With this many people to accommodate, the state has developed a sprawling network of highways that cut through vital wildlife habitats. These roads span thousands of miles crisscrossing the state, along with other linear infrastructure like aqueducts, energy corridors and railroad tracks, which together disrupt the ability of wildlife to move freely and safely across the landscape.
Animals — from federally endangered gray wolves and San Joaquin kit foxes, to mountain lions, coyotes, bobcats and deer — rely on connected habitat throughout California to access essential resources including food, shelter and mates. Numerous animals attempt to cross the state’s roadways and infrastructure, but many do not survive the journey. According to the United States Forest Service, 2 million individual animals are killed in vehicle collisions annually across the U.S. The fragmentation caused by these roads also separates entire populations from each other, further accelerating biodiversity loss.
For instance, without being able to access their neighboring populations, inbreeding increases and consequently reduces genetic variation. These inbred populations are more susceptible to harmful traits, as seen in Southern California mountain lions, which are now exhibiting physical deformities and infertility issues.
The impacts of wildlife-vehicle collisions extend beyond wildlife, though. They also pose a serious risk to human safety. Research shows that the millions of wildlife-vehicle collisions occurring annually in the U.S. result in over 400 human fatalities and almost 60,000 injuries.
One solution to this growing crisis of habitat fragmentation is the creation of wildlife crossings. From naturally vegetated overpasses to culverts and tunnels, such infrastructure design features help animals to safely navigate barriers to habitat connectivity. Wildlife crossings are gaining momentum across the U.S. with a number of new laws passed in recent years. California is leading the charge both in policy and landmark projects already underway.
California’s Wildlife Habitat Connectivity Over the Years
In 2008, California became the second state — after Florida — to pass some form of wildlife habitat connectivity legislation. Since then, California has become the leading state on this issue, passing more legislation on wildlife habitat connectivity than any other. For instance, the state passed Senate Bill 790, the Wildlife Corridor Protection Act, in 2017. This law directed the California Department of Transportation and the California Department of Fish and Wildlife to identify important wildlife corridors and begin addressing barriers to wildlife movement.
As wildlife-vehicle collisions gained more attention, the state passed the Wildlife Traffic Safety Act (SB 395) in 2019. This Act established a pilot program that includes a statewide roadkill reporting system, allowing the public to report wildlife-vehicle collisions through an online portal. The data helps state agencies identify roadkill hotspot areas and determine where wildlife crossings or fencing are most needed.
Most recently, California further advanced its commitment with the passage of Assembly Bill 1889 in 2024, the Room to Roam Act. This law is designed to streamline wildlife crossing projects and prioritize protection for key movement corridors. AB 1889 simplifies the permitting process for building wildlife crossings, requires state agencies to prioritize key wildlife movement corridors and expands protections for the natural linkages on which animals rely. Currently, state legislators are considering AB 902, which would require the California Department of Transportation to identify wildlife connectivity barriers and assess the need for improved wildlife features in any state highway project that adds a traffic lane or could significantly impair wildlife movement in a known connectivity area. The bill aims to make wildlife movement a standard part of highway planning and ensure future road projects do not cut off critical migration routes or habitat linkages. It is set to be heard by the Senate Appropriations Committee in August 2025.
Despite California’s progress, federal and state efforts to roll back biodiversity protections – such as by rescinding the Roadless Rule, scaling back the California Environmental Quality Act and dramatically reducing federal funding for conservation — threaten to undermine habitat connectivity successes. These setbacks make the state’s continued commitment to solutions like wildlife crossings even more critical, especially as climate change shifts the range of suitable habitat for many animals.
California’s leadership in wildlife crossings and habitat connectivity demonstrates change is possible, but only if we continue to build upon it. With science, smart policy and continued public support, we can create a future where animals do not have to risk their lives just to move, migrate or survive.
Looking to learn about wildlife crossings in other regions of the U.S.? Check out this feature on the Southeast and Southwest.
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