Wildlife Crossings: Bridging the Great Concrete Divide

Enhancing Animal Safety and Genetic Diversity on America’s Highways

Wildlife Crossings

Interstate 90, stretching over 3,000 miles from Seattle to Boston, stands as the longest interstate highway in the United States. This colossal stretch of asphalt not only connects major cities but also serves as a significant barrier for wildlife. For many animals, I-90 represents a perilous divide, impeding their natural movement and endangering their lives.

Recognizing this issue, the U.S. Forest Service and the Washington State Department of Transportation have collaborated to create a series of “critter crossings” in Washington. These innovative overpasses and underpasses aim to provide safe passage for wildlife, mitigating the highway’s impact on animal movement and genetic diversity.

The project spans a 15-mile section of I-90 near Snoqualmie Pass, a region surrounded by national forest land. This habitat supports a variety of creatures, from mule deer and elk to smaller animals like toads and salamanders. Wildlife biologist Patty Garvey-Darda explains the importance of these crossings: without them, isolated animal populations face the threat of localized extinction due to a lack of genetic diversity.

Wildlife crossings are designed to mimic the natural habitat on both sides of the road, incorporating native plants and reducing sensory disruptions with high concrete walls to block headlights and traffic noise. These measures help animals navigate the crossings without hesitation. The results are promising. In 2022 alone, cameras documented over 5,000 crossings by animals, proving the effectiveness of these structures.

The success of the I-90 project draws inspiration from the wildlife crossings in Banff, Alberta, Canada. There, a network of 38 undercrossings and six overcrossings along the Trans-Canada Highway has reduced wildlife collisions by 80%. This model has been replicated worldwide, demonstrating the potential of well-designed crossings to protect wildlife and enhance road safety.

Across the United States, approximately 1,500 wildlife crossing structures exist in 43 states. From pronghorn in Wyoming to panthers in Florida, these crossings provide critical safe passage for a variety of species. While many of these structures are subtle and go unnoticed by motorists, some, like the upcoming Wallis Annenberg Wildlife Crossing near Los Angeles, are hard to miss. Once completed, this 200-foot structure will span 10 lanes of the 101 Freeway, accommodating one of the busiest traffic corridors in the world.

Beth Pratt of the National Wildlife Federation sees the Wallis Annenberg Wildlife Crossing as a hopeful project, inspired by the famous mountain lion P-22 who navigated two freeways to reside in L.A.’s Griffith Park. Such crossings are vital for preventing inbreeding and supporting genetic diversity, crucial for the survival of many species.

The human benefits of wildlife crossings are equally significant. Annually, there are approximately one million collisions involving large wildlife on American roads, resulting in about 200 human fatalities. The economic impact of these accidents includes road closures and repair costs. Reducing wildlife collisions through crossings not only saves animal lives but also enhances human safety and reduces travel delays.

How wildlife crossings protect both animals and people

Federal support for these initiatives is growing, with Transportation Secretary Pete Buttigieg announcing a $350 million grant program to build more crossings and improve road safety. Brian White of the Washington DOT notes that these structures quickly pay for themselves by preventing accidents and minimizing road closures.

Wildlife crossings have gained widespread public support across political lines, reflecting a common desire to protect animals and reduce roadkill. These structures symbolize a rare point of unity in a divided time, underscoring the shared value placed on preserving our natural world and ensuring safe passage for all its inhabitants.

By investing in wildlife crossings, we are not only safeguarding biodiversity but also enhancing the coexistence of humans and animals. As these projects continue to expand, they offer a glimpse into a future where highways no longer divide but instead connect the natural world.

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