Short Wave - Animal Crossing: The Destructive Nature of Roads

Episode Date: September 13, 2023

40 million miles of road unite us. They also cause mass destruction for many species. Today, environmental journalist Ben Goldfarb and host Aaron Scott go on a tour of that destruction — the subject of Ben's new book Crossings: How Road Ecology Is Shaping the Future of Our Planet. But don't worry, it's not all grim! Along the way, we learn why fewer insects are hitting our windshields, talk about the breakthrough that is highway overpasses, and how at least one bird has adapted to avoid 18-wheel semi-trucks. Listen to Short Wave on Spotify, Apple Podcasts and Google Podcasts.See pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences.NPR Privacy Policy

You're listening to Shortwave from NPR. I want you to picture the Earth. Really zoom out like you're taking a photo from space. Then shatter that image into 600,000 fragments. These fragments are carved out by roads, highways, streets, country lanes. All together, they stretch across about 40 million miles of the Earth's surface. There were new roads being built all the time. There are something like 15 million miles.

of roads scheduled for construction by the middle of this century. So roads are ubiquitous and everywhere, and we're only getting more of them. Ben Goldfarb is an environmental journalist and the author of the new book, Crossings, how road ecology is shaping the future of our planet. As he puts it, to us, roads signify connection and escape. To other life forms, they spell death and division. A point made clear through the experience of amphibians. Amphibians like frogs, toads, salamanders

tend to migrate between, you know, sort of upland forests and breeding pools on big spring nights when it's warm and wet. But many of those habitats are severed by roads. He discusses what comes next in a passage in the book. In some places, the emergence occurs over weeks. In others, in a bacchanal known as the big night. And a salamander on a big knight will cross any road in her past. come hell, high water, or Honda.

When an aggregation of libidinous amphibians boils over a road, the outcome is what biologists call, none too scientifically, a massive squishing. Probably never heard one pop beneath your tires, but in many places it's reptiles and amphibians, not deer, not squirrels, that make up most vertebrate roadkill. For years, biologists didn't see that as a problem. They thought that the amphibium populations made up for it through producing more tadpoles or losing fewer animals to predators,

until one scientist started to question that assumption. Lenore Farrag, who's a great road ecologist, a Canadian, kind of the fascinating thing that she observed driving around her home in Canada, was that the busiest roads had the least frog roadkill. And that was sort of surprising because you would expect that busy roads have more traffic and there would be more dead animals. But what she figured out was that the busiest roads had the fewest road kills because roads had already reduced the population, right?

Busy traffic was capable of reducing populations and even extirpating them, you know, causing local extinctions that nature can't actually compensate. And it's not just frogs. So today on the show, how roads are blocking migrations, playing a role in the insect apocalypse and shaping the very way animals evolve. I'm Aaron Scott, and you're listening to Shortwave from NPR. Okay, Ben, so I'd like to step back to the early days of the automobile, early 20th century. Who are the first people to realize that cars were not going to be a great invention

from the perspective of America's wildlife? Cars are kind of this new technology in the early 20th century. You know, people aren't good at driving them. They don't have any safety features. They're taking over cities that aren't really ready for them. And the rates of pedestrian fatality are enormous. You know, people are getting killed left and right at, you know, at per capita rates, they're actually much higher than today's. And there are these big demonstrations and safety parades where thousands of people go out in the streets of cities like Milwaukee and Pittsburgh in New York and, you know, sort of campaign against the car. And, you know, this concern about the car's impacts on wildlife really comes. out of that in a lot of ways. You know, some biologists start to observe, you know, dead garter snakes and woodpeckers and ground squirrels and say, you know, hey, to wait a second, you know, the same thing that cars are doing to human beings and to cities, you know, they're doing to animals out, out in the countryside. And of course, roadkill becomes an even bigger problem by the middle of the century is deer populations rebound and road animal collisions

become a lot more dangerous for humans, too, beyond the safety issue. What were the major problems that biologists started to focus on and kind of the negative impacts that this growing road system was having on wildlife like deer. One of the first things that biologists notice, especially in the American West, is the kind of the truncation of animal movement. You know, in states like Colorado and Wyoming, you know, there are these big herds of migratory mule deer and elk and pronghorn antelope that have to move across the landscape seasonally. And, you know, as all of these new giant interstates pop up, the kind of the moving fence of traffic, as one biologist put it, basically cuts off animals from these migratory routes and winter ranges. And, you know, there are cases of mass starvation along the shoulders of interstates like I-80 in Wyoming or I-84 in Idaho. And suddenly people realize that it's not just roadkill. That's a problem. It's actually the traffic itself. And, you know, in some ways, that challenges our perception of the problem of roads.

You see the dead deer lying by the side of the road, and that's a very visible manifestation. But, you know, what you don't see are all of the animals who never even attempt to cross the road. But in some ways, that moving fence, that traffic barrier is an even bigger problem because it causes entire herds of deer and elk and antelope to die out. You write about how it also cuts off populations of animals from each other, which means that their genes are not. no longer going back and forth, to the point that in certain places, biologists can tell what side of a road a bear comes from by a snippet of its DNA. So take us through some of the solutions people tried. I mean, the underpass and the overpass that a lot of us recognize now, particularly out here

in the West, they were pretty winding processes to get these even close to right. Yeah, some of the first wildlife underpasses are actually built along I-80 in Wyoming. designed to allow these migratory herds of mule deer to cross. Those early underpasses were, you know, they were very long and dark and narrow. Biologists were able to coax deer through them eventually, but, you know, the deer didn't use them very readily. You know, and then in the 1990s, really, you know, engineers and biologists figured out that deer just needed sort of more open, light-filled, wider underpasses to cross through, you know, structures that seemed a little bit more natural. because, I mean, no human wants to, you know, sort of crawl through a dark dripping, echoey tunnel, right? They're good for genetic connectivity as well, and that's a really important point, too.

You know, you don't want just animals walking through wildlife crossings. You know, you want them breeding on either side of the crossing, and you want to encourage that genetic connectivity in Banff. They showed that very conclusively that grizzly bears were not only crossing those wildlife overpasses, They were mating on either side, and then they were having cubs, and then they were teaching their cubs how to cross, and their cubs became frequent crossers. So I think that's just an incredible lesson as well, is that animals not only learn to use these things, they teach their offspring, and entire populations can become ready users of wildlife crossing structures.

I think that's pretty exciting. And I was going to ask about that, because, I mean, roads are not just cutting off migration or, as you're talking about cutting off population. I mean, they're affecting the very evolution of animals. Can you unpack some of the other ways that roads are changing literally the shape, the size, the populations of wildlife? Yeah. One of my favorite stories in the book, and really one of my favorite stories from all of road science is about, you know, the evolution of cliff swallows in Nebraska. I'm sure, you know, many listeners have seen their little mud nests that they build on the underside. of highway overpasses and bridges.

But, you know, obviously living over an interstate highway is a dangerous place to be, and lots of birds end up roadkill. So this researcher Charles Brown showed over many decades that cliff swallow roadkill is declining over time. And the reason for that is that their wings are becoming shorter. And you can sort of imagine that a long wing on a bird is good for long-distance, fast, straight flying. and a short wing is good for performing tight rolls and turns and pirouettes and, you know, avoiding

predators and avoiding giant 18-wheelerers, you know, barreling under those highway overpasses. So over time, all of that traffic basically weeded out the long-winged swallows from the population and left behind those shorter wing swallows. It's a really fast-acting, very clean-cut case of natural selection and evolution induced by traffic. One other thing that really stood out in the book are insects. Growing up, I remember our windshield being covered in insects. I don't notice that as much anymore. What sort of roller roads playing in in kind of the fate of insects? Yeah, so that's known as the windshield phenomenon. You know, this, the idea that cars are sort of these sampling tools for insect populations, you know, and we know that there is likely this kind of mass insect die-off happening. right now for all kinds of different reasons, and cars reveal that die-off in a lot of ways. And one of the kind of the ironies or tensions of roads is that they kill a lot of insects themselves.

Billions of pollinating insects are killed in North America by cars every year. But, you know, roads are also insect habitat. Those roadside strips of vegetation are some of the last kind of remnant native prairies for species like monarch butterflies or rusty patch bumblebees. So, you know, roads are actually... habitat in their own right, but of course they're also very dangerous habitats. We've talked about overpasses and underpasses, but what are some of the other solutions that you encountered as you were reporting this for ways that we can kind of undo the harm

of roads for wildlife? I mean, certainly, you know, the biggest one is just getting people out of cars, improving transit options, you know, in urban areas and in rural areas as well. You know, I mean, one of the things that I was really conscious of in the book was not shaming individual drivers, right? We're all sort of trapped in this world that you need a car to navigate, and it's not really our fault that we drive. It's really the job of state and federal transportation agencies to kind of remake some of the infrastructure that they created. And, you know, that's starting to happen. In the 2021 Federal Infrastructure Act, you know, there's $350 million for new wildlife

crossings and a billion dollars to replace culverts that are blocking salmon passage. Different states, you know, from Colorado to Oregon to Utah to New Mexico, have recently passed bills of their own or allocated money in state budgets for new wildlife crossings. So, you know, that state and federal progress is starting to happen and as it should. Ben, thank you for taking us on this voyage down America's roads. Thanks for coming along with me. This episode was produced by Rachel Carlson, edited by our managing producer, Rebecca Ramirez, and fact-checked by Anil Oza.

The audio engineer was James Willits. Beth Donovan is our senior director, and Anya Grundman is our senior vice president of programming. I'm Aaron Scott. Thanks as always for listening to Shortwave from NPR.