How Wildlife Corridors Protect Animals and People

Pew’s “After the Fact” podcast season, States of Innovation, has highlighted some of the ways that states are tackling big problems with creative solutions. One of those challenges is how to allow large herds of animals such as mule deer and elk to travel their ancient migratory routes, which are now often bisected by roads and highways, and protect animals—and drivers—from collisions. In an interview with Jodi Hilty, chief scientist and president of the Yellowstone to Yukon Conservation Initiative (Y2Y), we learn more about maintaining healthy ecosystems and safer roads. This interview has been edited for clarity and length.

Q: What is corridor ecology, and what does that mean today?

A: My first book was on corridor ecology—how wildlife moves from one place to another—back in the 1990s. We started to care about wildlife corridors because the technology had really changed. For the first time ever, we were able to put GPS collars on animals and could see how far they traveled.

To give you an idea of the breadth of movement: In the early 1990s, a wolf named Pluie was fixed with a GPS collar just south of Banff National Park in Canada. Researchers were able to track her 100,000-square-kilometer journey across two countries, three states, two provinces, and 30 different jurisdictions. She and other animals during the early days of GPS collars really taught us that animals moved much farther than we ever knew.

Q: Can you tell us more about what wildlife corridors are?

A: A wildlife corridor is designed to keep an open pathway for animals to travel from one place to another as safely as possible—both for them and their human neighbors. It’s not defined by a fence or closures. It might look like a stretch of public land and maybe one or two private lands. And the goal is to figure out how can we ensure that a grizzly bear, for example, can get from one mountain range to another mountain range through that corridor. To do this, we look at the terrain and determine what activities are compatible with ensuring grizzly bears and other wildlife can get through. Development of a major interstate through that corridor, for example, might be a big problem unless there are adequate overpasses and underpasses for those grizzly bears.

Through the Yellowstone to Yukon Conservation Initiative, we envision connecting and protecting the habitat from all the way down in Wyoming, from Yellowstone National Park, up to the Arctic Circle in the Yukon. This region still has all the large carnivores—grizzly bears, wolves, mountain lions, and wolverines—as well as all the hooved animals such as Dall sheep, caribou, moose, elk, and many more. It’s arguably the most intact mountain ecosystem in North America, and our goal is to keep it that way.

Q: Can you tell us more about overpasses and underpasses that help animals get safely across busy roads?

A: This is one of those solutions where it benefits both wildlife and people to have crossing structures. Different institutions have conducted economic research that clearly shows that the cost to society of animal-vehicle collisions is very expensive. It turns out that when you add them up, it’s cheaper for society to build these crossing structures.

Wildlife crossings are different from a standard bridge; they have a berm of dirt on either side with trees that allow the wildlife to go through the middle. This creates a quiet and secluded path for animals who might be sensitive to humans and to cars. While they’re less noticeable than the overpasses, there are underpasses that go beneath the road, too.

We’ve been studying these crossing structures long enough to know that they work; lots of animals are using them for multiple purposes. Wildlife-vehicle collision rates dropped dramatically. Research over many decades from Banff National Park—which has over 40 crossing structures—has shown that although it may take some time for animals to learn to use these wildlife crossings, once they figure it out, they are passing it on to their young.

Q: How can we accommodate for both wildlife and humans now that we know more about wildlife corridors?

A: I think there are several important things we are doing to help ensure wildlife corridors remain open. First is making sure that in protected areas, like the greater Yellowstone ecosystem, public lands are functioning for wildlife to get to the edges. In the corridors themselves, many times they are often going through private lands. That means working with private landowners to ensure wildlife can get across in a way that doesn’t interrupt their lives and ensures safe passage for the animal. And lastly, sometimes roads bisect these potential pathways. If they’re busy highways, like Interstate 90, they might not be passable for some wildlife. If that is the case, we need to work with the Department of Transportation to ensure that wildlife can either go over the highway safely with overpasses or underpasses.

Q: As a scientist, what excites you the most about the future of this conservation?

A: It is exciting that as of summer 2020 we now have globally agreed upon connectivity guidelines for the world. The United States and Canada are also both considering corridor legislation at the national level, and these guidelines may help guide that decision-making. And we’re already seeing countries moving forward with legislation; Tanzania, for example, recently passed wildlife corridor legislation to conserve animals like wildebeests.

And there have been many accomplishments, though we aren’t done yet. At Y2Y, we have worked with different partners and governments in the U.S. and Canada to increase protected areas from Yellowstone to Yukon by over 50%, with 116 overpasses and underpasses for wildlife to get safely across. The world sees the importance of ecosystem connectivity, in part not just for wildlife but also because of climate change. As ecosystems are beginning to shift, one of the top recommendations by climate scientists is to ensure that wildlife, as well as plants, can move freely and maintain connectivity. It’s not only important to plan where protected areas go but also ensure animals and plants can move between them.