Driving on the Interamerican Highway from Monteverde Biological Reserve to Rincón de la Vieja National Park, I couldn’t help but notice a series of rope bridges that crossed the six lanes of traffic. Each crossing structure featured traffic warning signs with silhouette images of monkeys or sloths as nonstop flows of diesel semitrucks and electric cars zoomed by.

Costa Rica is known for its protected areas, which cover one-third of the country and function as core zones for conservation, but the “green republic” should also be recognized for its corridors. What started as an NGO effort in the 2000s when organizations like Kids Saving The Rainforest started installing aerial bridges to improve habitat connectivity later became national policy with a 2024 presidential decree requiring electrical companies to build crossing structures so that animals like howler monkeys and kinkajous avoided electrocution from using power lines. These monkey bridges also keep tropical rainforest more intact for mobile creatures.

Beyond Central America, wildlife corridors are popular in the western United States. According to recent surveys from the Environment America Research and Policy Center and the Pew Charitable Trust, respondents approve creating more wildlife crossings at rates of 85-90%. And that support spans the political spectrum. In March 2026, the Idaho State Legislature passed Senate Concurrent Resolution No. 124, officially supporting the development of wildlife crossing infrastructure, such as highway overpasses and underpasses, to reduce animal-vehicle collisions. In December 2026, California’s Wallis Annenberg Wildlife Crossing is set to be completed across 10 lanes of Los Angeles freeway, making it the largest structure in the world.

Wildlife corridors could receive a financial boost by the bipartisan BUILD America 250 bill, considered by US House Transportation and Infrastructure Committee this week. If passed, it would increase funding for the Federal Highway Administration’s very popular Wildlife Crossings Pilot Program (WCPP) to $80 million annually ($400 million total). The 2021 Infrastructure Investment and Jobs Act allocated $350 million to 35 projects across 30 states, but demand far exceeded with $500 million in requests.

Today, the benefits of conserving wildlife corridors might be just as much about the social as the biological.

If we’re living in a worldwide golden age for wildlife corridors, where did this idea come from? I trace the origins of this dominant conservation strategy in my new book, Borders of Biodiversity: How Gray Wolves, Monarch Butterflies, and Giant Sequoia Transformed Large Landscape Conservation, published by University of North Carolina Press.

In the 1970s and 1980s, new technologies provided windows into animal mobility. For wolves, radio- and........

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