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An estimated 1 million animals are killed on U.S. roads every year. Mostly, that's because of vehicle collisions. But roads can also kill in more subtle ways. NPR's Nathan Rott explains.
NATHAN ROTT, BYLINE: Mountain lion researchers Seth Riley and Audra Huffmeyer started noticing something troubling last year in the cats they were observing in Southern California's Santa Monica Mountains.
AUDRA HUFFMEYER: Over the course of one year, our combined efforts identified nine individuals with reproductive abnormalities or physical abnormalities.
ROTT: Mountain lions were seen with kinked tails; others with something called cryptorchidism.
HUFFMEYER: It is when one or both of your testes fail to drop during puberty.
ROTT: Huffmeyer, a researcher at the University of California, Los Angeles, decided to go deeper, looking at five deceased males. All of them had reduced fertility. For Riley, a biologist with the National Park Service, it was like an oh-no moment.
SETH RILEY: We've known that there was low genetic diversity. I mean, we knew even before we started the studies that that was sort of a possibility, right? But we were kind of hoping not to get to the point where we were starting to see these physical manifestations. And it definitely ramps up the urgency of doing something about it.
ROTT: The problems Huffmeyer and Riley observed were related to inbreeding. Mountain lions in this small coastal range were and had been mating with close relatives, not because they wanted to, but because they had no other choice. They had been hemmed in and cut off, trapped by subdivisions, shopping malls and roads like Highway 101.
BETH PRATT: The 101 freeway has become this impenetrable barrier for wildlife.
ROTT: Beth Pratt is with the National Wildlife Federation. A mountain lion is tattooed on her left arm. We're standing just north of the 10-lane freeway in an open patch of ground while a red-tailed hawk circles overhead.
PRATT: This is really deceptive because you're looking at a lot of open space right here, yet the Kardashians live right over there in Calabasas. And, you know, you have 10 million people surrounding us. And then this really busy freeway - 300- to 400,000 cars a day.
ROTT: A report by the United Nations' Convention on Biological Diversity found that human development, not climate change or consumption, is the biggest driver of extinction in the world. Our sprawl is driving species out of their habitats or, in the case of the Southern California mountain lions, constricting them in place.
PRATT: You know, we don't think of how animals need to move.
ROTT: Pratt has spent the last decade working on a solution. And in just over a month, it's going to happen. Construction workers and engineers will break ground on a 200-foot long wildlife crossing, a bridge for wildlife, complete with sound barriers and vegetation.
PRATT: We're putting in the first urban crossing in the world of this scale.
ROTT: The goal is to reconnect a fragmented landscape in one of the most urbanized areas on the planet.
PRATT: You're going to see this ecological transformation and that part of it is going to be over one of the busiest freeways in the world - that, to me, is just such a hopeful statement for what's possible.
ROTT: And there's new hope that many more projects are to come. In the recently passed infrastructure bill, Congress allocated $350 million for wildlife crossings. Renee Callahan, executive director of ARC Solutions - ARC standing for Animal Road Crossings - says it's the first time ever the federal government has allocated big money to the issue.
RENEE CALLAHAN: We know that wildlife vehicle collisions cost Americans close to $10 billion - and that's, you know, billion with a B - every single year.
ROTT: So, she says, it's an investment well worth making. Research from Montana State University has found that wildlife crossings, if used with other infrastructure, like roadside fencing, can reduce animal vehicle collisions by 97%.
CALLAHAN: To my knowledge, there's not a whole lot of infrastructure investments out there that you can make that are going to be that effective in terms of fixing the issue that they're targeted at.
ROTT: Callahan's hope is that eventually, crossings for wildlife will be baked into all infrastructure plans going forward.
Nathan Rott, NPR News, Los Angeles.
(SOUNDBITE OF OKAMI (O)'S "UNDERGROWTH") Transcript provided by NPR, Copyright NPR.
