How North America is Building the World's Largest Smart Wildlife Corridors

For decades, the expansion of North America's highway system has created an "infrastructure tsunami," slicing through ancient migration routes and fragmenting ecosystems. The consequences are measured in both ecological decline and human tragedy. In the United States alone, motorists collide with large wildlife between one and two million times each year. These accidents result in roughly 200 human fatalities, 26,000 injuries, and an estimated $8 billion to $10 billion in property damage and medical costs annually.[1][6]

To solve this, civil engineers and wildlife biologists have pioneered a deceptively simple solution: building roads for animals. Wildlife crossings—specially engineered overpasses and underpasses—are transforming how transportation networks interact with nature. What began as a niche experiment in the late 20th century has evolved into a continent-wide infrastructure shift, with over 1,000 dedicated wildlife crossings now operational across the United States and hundreds more in Canada.[6][8]

The crown jewel of this movement is the Yellowstone to Yukon (Y2Y) Conservation Initiative, an ambitious effort to reconnect a 2,100-mile corridor stretching from Wyoming to the Canadian Arctic. Spanning five U.S. states, two Canadian provinces, and dozens of Indigenous territories, the Y2Y region is the largest intact mountain system left on Earth.[4]

Progress within the Y2Y corridor has been staggering. According to the initiative's 2025 impact report, 204 wildlife crossings have been completed across the region. These structures are actively shrinking the isolation of vulnerable species. For example, the geographic gap between isolated grizzly bear populations in the Rockies has been reduced from 150 miles (240 kilometers) down to just 30 miles (50 kilometers), allowing previously separated groups to migrate and mate.[3][4]

The engineering behind these crossings is highly specialized. The Federal Highway Administration categorizes crossings into 11 distinct design types, tailored to the behavioral psychology of different species. Overpasses are typically wide, open, and landscaped with native soil, grasses, and trees. This design caters to prey species like elk, moose, and grizzly bears, which require a clear line of sight to feel secure against ambush predators.[5]

Conversely, underpasses are designed to be lower and darker, providing the concealed environment preferred by ambush predators like cougars and black bears. The infrastructure even scales down to the micro-level: specialized bottomless culverts and amphibian tunnels have been installed in states like California and Massachusetts to provide safe passage for migrating toads and salamanders.[5][7]

However, the secret ingredient to a successful wildlife crossing is not the bridge itself, but the fencing. Miles of high-tensile wildlife fencing run along both sides of the highway, acting as a funnel. Without fencing to physically block access to the pavement and guide animals toward the engineered structures, the crossings are largely ignored.[1][4]

When properly implemented, the evidence of success is overwhelming. In Canada's Banff National Park, which hosts the world's longest-running wildlife crossing research program, camera traps have documented more than 250,000 safe crossings. Along an 82-kilometer stretch of the Trans-Canada Highway, the combination of fencing and 44 crossing structures has reduced wildlife-vehicle collisions by more than 80 percent overall, and by 96 percent for elk and deer.[4]

The United States is rapidly scaling up its own mega-structures. In late 2025, the Colorado Department of Transportation opened the Greenland overpass spanning Interstate 25 south of Castle Rock. Measuring 200 feet wide, it is currently the largest wildlife bridge in North America. Combined with five nearby underpasses and extensive fencing, the project has already reduced wildlife collisions in the notoriously dangerous corridor by 91 percent.[2]

An even larger project is slated to open in late 2026: the Wallis Annenberg Wildlife Crossing in Southern California. Arching over 10 lanes of the heavily trafficked 101 Freeway near Los Angeles, the massive landscaped bridge is designed to save the region's genetically isolated mountain lion population from local extinction.[1][7]

This infrastructure boom is driven by a leap in tracking technology. Wildlife biologists now use lightweight GPS collars to monitor herd migrations in real-time, overlaying animal movement data with highway collision hot-spots. This precision allows state transportation departments to place multi-million-dollar structures exactly where animals naturally want to cross, guaranteeing high utilization rates.[6]

The movement has garnered rare unanimous bipartisan support, largely due to its undeniable economic logic. While structures like Colorado's Greenland overpass cost $15 million to build, the reduction in vehicular damage, hospital bills, and emergency response costs means the bridges effectively pay for themselves within a decade. Recognizing this, the federal Infrastructure Investment and Jobs Act (IIJA) allocated $350 million specifically for wildlife crossings.[2][6]

Despite these triumphs, the push for connectivity faces significant hurdles. The "infrastructure tsunami" of new housing developments, industrial logging, and road expansions continues to outpace conservation efforts in many regions. Crossings can safely route animals over a highway, but they cannot protect the habitat on either side of the bridge from being paved over.[1]

Furthermore, cross-border conservation is vulnerable to political headwinds. More than 500 migratory species regularly cross the U.S.-Canada border, requiring synchronized policy and funding. Recent proposals for budget cuts in cross-border environmental programs have alarmed conservationists, who warn that full continental connectivity requires sustained, rigorous investment from both nations.[3]

Ultimately, the proliferation of wildlife crossings represents a profound shift in how modern societies view their relationship with the natural world. By transitioning from barriers to bridges, North America is proving that human infrastructure and ancient ecological rhythms can successfully coexist.[8]