Conservationists have already built more than 1,000 wildlife crossings throughout the U.S. and are planning many more. In some places, larger strips of natural habitat known as wildlife corridors are being created. These often provide access to seasonal migration routes, allowing animals to freely move between breeding and feeding grounds. To determine where corridors and crossings are most needed, scientists examine vehicle collision statistics as well as movement data from animals tagged with GPS locators.
Patty Garvey-Darda, a wildlife biologist with the U.S. Forest Service, oversaw an ambitious project in Washington State that included multiple highway crossings. Several years ago, workers began constructing routes to help animals bypass Interstate 90, a highway that cuts through Snoqualmie (snoh-KWAHL-mee) Pass. The road divides the habitats of hundreds of animal species, including black bears, elk, fish, mountain goats, salamanders, and toads. When it came to designing each crossing, “the first step was identifying what habitats we were trying to restore and what areas needed to be connected,” says Garvey-Darda. She worked with a team of biologists, engineers, and hydrologists—scientists who study Earth’s waters—to determine where the landscape was best suited for wildlife crossings.