Are roads the biggest driver of ecological destruction?

edition 66: an interview with Ben Goldfarb

Dec 29, 2023

Re-posted as a podcast episode here.

Ben Goldfarb investigates road ecology in his latest book, Crossings.

From major highways to remote backcountry trails, from Brazil’s giant anteaters to caribou migrations in the Arctic, he has traveled far and wide to document a global problem that has unraveled over the past century and a half.

We talked about the history of roads, wildlife’s winners and losers, how would you change things with a time machine, peak roadkill, and conservation journalism.

We spoke in December 2023.

Ryan: What did the best pre-industrial roads look like? What old roads would you visit in a time machine?

Ben: I would want to go back and see what the animal trails that crisscrossed the continent looked like.

That's where a lot of our contemporary roads came from. They were animal trails, often created by bison, which migrated in these enormous herds, that became native footpaths that became wagon roads and then gravel roads and eventually interstate highways.

I would love to see those pre-colonial animal tracks crisscrossing the continent and, really, the world. It's not just the U.S. where animal trails became road networks; that was true of elephants in Africa.

I would love to see those giant bison paths that laid the groundwork for the interstate highway system.

Ryan: Where is that most obvious?

Ben: In Missouri and Tennessee, the Natchez Parkway was originally a trail that bison created to a salt lick: a naturally occurring mineral lick that animals regularly visited to get nutrients. These big herds created really consistent, predictable game trails across the landscape.

One chapter of the book deals with road salt, which we apply in enormous quantities, on highways as a deicing agent. It's ironic that historically animal trails made pathways to salt licks. The highway followed the salt. And now the salt follows the highway as we apply huge volumes of this stuff as a deicer.

Ryan: In your travels, was there a place that gave you a glimpse into the past as to how much of a problem mud used to be?

Ben: I'm glad you picked up on that. That's a big part of what made roads so transformative, especially for wildlife, as we figured out how to pave these objects. First with mud, gravel, clay, and other low tech surfaces, and eventually with asphalt, which permitted the speeds that turned road killings into an enormous ecological crisis.

You can see vestiges of old dirt roads, especially in our national forests and public land. In U. S. national forests we have close to 400,000 miles of road. The vast majority of those are dirt roads, old logging roads, and ATV trails, an enormous network of unpaved roads.

I've driven thousands of miles on those over the years, visiting high lakes and trailheads and fire towers. Some are pretty treacherous.

You get crumbling cliff faces where a dirt road is eroding off into the abyss and incredibly muddy spots where you're constantly at risk of getting stuck. If anybody wants a sense of late 19th century roads, the forest service road network, which was mostly built starting in the 1920s, is a good place to start.

Ryan: If you were sent back in a time machine with the goal to slow down the spread of roads, what would your plan be?

Ben: Thinking about what really creates the explosion in cars, there are a few factors. First, a lot of it is Henry Ford. Cheap mass production techniques democratized the personal automobile and made it famously affordable to his own workers.

Originally cars were sort of these upper-crust machines that Vanderbilt strove around in, and the cheap Model T is a lot of what lead to the exponential growth of car ownership.

And the desire for recreation. The explosion of cars isn't necessarily that cars are so useful. Certainly they did have utility. But really they were kind of liberating. In the late 19th century, nobody ever heard of a vacation. The idea that you would leave your town to go somewhere to enjoy the countryside. That was basically unheard of unless you were the ultra wealthy.

A big part of why cars became so popular is they were liberating and allowed people to go see the countryside and travel a bit.

How do you prevent that growth?

Cars very deliberately overthrew more traditional methods of transportation, like the streetcar. That would be one point of attack. If you wanted to prevent the total automobilization of the United States, preserve the transit options that prevailed before cars took over.

The other important point is we have so many redundant roads. Maybe we could have prevented that at one point in human history. You can get to literally anywhere in our country, not only by road, but by many different roads.

Vast spider webs of redundant roads cover the continent.

Vast spider webs of redundant roads cover the continent. If we could have prevented some of that redundancy, we could have avoided a lot of ecologically harmful road construction.

Ryan: Do you get the impression that animals that are alive today have better cognitive models of roads than, say, a random sample from 200 years ago or 2,000 years ago?

Ben: It really depends on the species. There are animals that are incredibly adaptive and flexible and clearly know what roads are and how to navigate them.

In the book I talked about the famous urban coyotes in Chicago who look both ways and use crosswalks at the appropriate lights. They're incredibly well road-adapted.

There are famous crows in Japan who use cars to crack nuts. They'll place a nut in an intersection at a red light, and wait for a car to drive over it, and then scurry out and grab the nut meat.

So there are animals that have incredibly sophisticated cognitive models of roads, as you put it. But there are also animals that are not as adaptive and flexible and creative.

I'm not sure that a spotted salamander today has any better sense of what a road is than a spotted salamander 200 years ago, which is why you see such a high amphibian roadkill rate. These are incredibly ancient, and maybe objectively not all that intelligent, animals who blithely walk into traffic on their way to breeding ponds.

They don't have much sense of the road being a deadly force. So, it really depends on the species you're talking about.

Ryan: In my city I see a lot of geese, and it seems like they do well to fly over traffic and drop into feeding areas. Did you come across any studies on geese?

Ben: One story I did hear from a few different people is that they love new growth. New grass is where you always see them, like soccer fields. And often after roadsides are replanted, or after mowing, they'll end up colonizing roadsides.

And they do get hit. Of course flying is helpful, but lots of birds get hit by cars, something like 300 million a year, and especially geese. These big bodied birds take a little while to achieve liftoff, and they're definitely at risk. That goes for lots of different birds.

Of the winners, the animals who have benefited from road construction, scavenging raptors come to mind. Golden eagles, bald eagles, turkey vultures, black vultures all do pretty well along roadsides eating carrion.

You've got lots of barn owls who hunt along grassy roadsides which tend to have lots of mice. Red tailed hawks. Lots of scavenging and predatory birds have learned to use these landscapes, but they're dangerous places.

If you're a golden eagle who's feeding on a deer for 20 minutes by the side of the road, and you attempt to achieve liftoff, it takes a while to get going. Just like a Canada goose. You're vulnerable to be hit.

So these roads can turn into ecological traps. They have resources to offer that lure animals in, and in some cases wildlife can benefit, but living alongside the road is a really dangerous place to be.

Ryan: In addition to the danger of a collision, there's also road noise, which you have a chapter about. It sounds like forest birds are especially impacted. What are the consequences of road noise for birds, and could you maybe speak about the foraging-vigilance trade-off?

Ben: That section of the book comes from this really ingenious and famous study called the "phantom road experiment"1. It was conducted a few years ago by researchers in Idaho.

They recorded the noise of traffic and played it through speakers on this roadless forest in Idaho. What they found was lots of birds avoided that area, and the birds who did stick around were in more spotty condition than other birds.

The hypothesis there is if you're a migratory bird, flying enormous distances, you have to be feeding constantly to maintain your body weight and energy levels. Normally they're constantly eating beetles and berries and other foods. But, if you're living in this swath of road noise, you have to constantly be alert to predators.

Ordinarily you could hear predators coming. Maybe you'd hear a hawk's wings or you'd hear the bobcat creeping through the underbrush. But if those subtle noises of approaching predators are drowned out by all of the road noise, you’ve got to look for predators instead of listening for them. Every minute that you, as a bird, are looking around for predators is a minute when you're not feeding, which is why birds who were exposed to the phantom road were in a worse body condition. They couldn't feed as much because they were constantly searching for predators.

Noise is really a form of habitat loss.

That's something we forget about sometimes, that noise is really a form of habitat loss.

If you're a bird who has to constantly look for predators because you're living near a noisy roadside, maybe that's not a place that you can live. Or if you're a predator, imagine an owl who has to listen for the sound of a mouse chewing in the leaf litter. If the sound of your prey is drowned out by engines and tires, that's not a place that you can hunt.

The road itself might only be 50 or 100 feet from shoulder to shoulder, yet this noise pollution billows away, in some cases, a couple of miles from the roadside. It casts this enormous shadow and changes the lives of all of the critters who live near it.

Ryan: During the pandemic, restaurants reclaimed parts of city streets for outdoor dining. It was a reminder of how much public space we surrender to cars. Do you think that experience will effect infrastructure policy?

Ben: Outdoor curbside cafes have replaced what was formerly parking, and people love that stuff. So it stuck around after the pandemic.

A lot of bike lanes were put in cities. Paris, Rome, and London aggressively added bike lanes and reduced car capacity. A lot of those changes have stuck around. There are cities from Cincinnati to Tampa, cities you wouldn't necessarily think of as being great mobility leaders, who closed traffic on certain streets and turned areas into pedestrian plazas, and those stuck around too.

Some of the changes that we saw during Covid have proved durable. But I think that largely our society is pretty similar as it was in 2019. Traffic rates remain mostly unchanged.

Lots of little changes, but we didn't see dramatic changes in how people get around. So I don't think we overhauled society and transportation exactly.

Ryan: What do you think is the best thing that's happened in road ecology? Was it when 2% of forest service roads were permanently closed?

Ben: I don't know if there's a singular great thing that happened. This rule that you mentioned was created by the forest service under Mike Dombeck, which protected a lot of areas from rebuilding.

That was a big deal. Back to the wilderness. In 1964 this giant piece of legislation protected enormous swaths of roadless wilderness on public lands all over the country. Certainly that was transformative.

That action wasn't necessarily taken for wildlife. It was really taken for almost spiritual reasons. Wilderness advocates wanted to protect untrammeled land mostly for their own recreation purposes.

But the creation of our wilderness system was hugely beneficial to animals like grizzly bears, wolverines, lynx, and other species that require large intact habitats.

Construction of wildlife crossings is a big deal as well. Overpasses and underpasses and tunnels, structures that allow animals to safely cross roadways have been built and are being built, on I-25 among many other places.

I think that's had an enormous impact and has really mitigated a lot of very problematic roadkill hotspots out there, especially in the American West, where a lot of these structures have been built.

I'm not sure that there's a singular transformative event in the history of this field. It's more like we've done lots of things that have helped wildlife. But at the same time, I think the trajectory is generally in the wrong direction.

We're protecting roadless places and building wildlife crossings, but we're also building a crapload of new roads all the time, not just in the U.S. but all over.

Traffic rates are going up on existing roads as well, which makes them more of a barrier to animal movement. We're learning that tire particles are a gigantic problem that are killing salmon all over the Northwest.

So we're doing things about the problems that roads create, but the problem continues to get worse. And we're still learning how bad the problem is. Most of the trend lines, unfortunately, are going in the wrong direction.

Ryan: If you close a forest service road, how many years does it take to disappear into the surrounding wilderness?

Ben: One of the big issues with all of those fire service roads is compaction. Decades of logging trucks and ATVs and other vehicles. The soil is incredibly hard and compacted. If all you do is put a gate up, the road doesn’t return to nature for decades. The soil is so hard it's tough for plants to take root.

What it means to do this work well, road closure and decommissioning, is to get back in there with, in some cases, the same heavy machinery that built the road in the first place. Excavators and front loaders and backhoes and tear that road bed up, loosen the soil, create a little bit of micro-topography that plants can take to. Reseeding vegetation. Churn up the road bed and it can be incredibly effective.

I've visited decommissioned roads that were closed in the 1990s and early 2000s, in Idaho and Montana, and you'd have no idea that there'd ever been a road there if you weren't looking for it.

If humans disappeared overnight, even decades later, there would still be signs of highways that were buried under grass. It wouldn't return to just being undifferentiated from the wilderness without actively breaking up the underlying soil.

When it comes to our major interstate highways, even if humans disappeared tomorrow, you can go centuries or millennia and still know that there's been a highway there.

There's a good book called The World Without Us, by Alan Weisman2, that proposes exactly that thought experiment. If we disappear tomorrow, what would happen to all of our infrastructure? I forget exactly what he says about roads, but the paved ones would last for an incredibly long time.

Some grasses pop up through cracks in the asphalt, but we can come back in a few thousand years and you would still see the linear signature of that structure.

Ryan: Do you think peak roadkill was in the past or is it still ahead?

Ben: It's a fascinating question. I thought a lot about this. How much roadkill do we see compared to some of those early road ecologists like Simmons3?

On one hand road kill rates have gone up. Studies show that the proportion of animals, or at least vertebrates, who die by car has increased over time over the last 50 years. If you are a raccoon or opossum or squirrel, you are more likely to be killed by a car now than you were 50 years ago. In that sense I think we're still going towards peak roadkill. Maybe we haven't even hit it yet.

But on the other hand, when it comes to the total number of animals that you see on the road dead, it's kind of fascinating to read some of the old roadkill surveys from people like Simmons in the 1920s and 30s. They were just seeing so many critters. And not just raccoons and squirrels and opossums that we see today, but dozens of red-headed woodpeckers and snapping turtles and all kinds of different animals.

Some of those early roadkill surveys…feel like they were seeing a lot more animals than we are.

I go back and read some of those early roadkill surveys and feel like they were seeing a lot more animals than we are. That could reflect a couple of different things. Maybe it's because there were more animals back then.

Maybe our wildlife populations really have declined. For many species roadkill is part of that. So maybe those early road ecologists were seeing more animals because there were just more animals to be hit by cars back then. So maybe that really was peak roadkill.

I also think it's possible that there are just as many animals being killed today, but we don't see them because we go a lot faster. In the 1920s and 30s, when guys like Simmons were writing, all of these early road ecologists were rolling along at 30 or 40 miles an hour on gravel roads in their Model T's.

Today we're zipping along at 70 or 80 on I-90 in our F250s, and we might see a lot less road kill because we're going so much faster. I always find that striking whenever you walk or bike along the highway, you see so many more dead animals, especially songbirds and rodents and reptiles. The smaller critters that you wouldn't notice inside the cab of an SUV racing along at 70 miles an hour. So I think that's part of it, too. They saw more roadkill because they were closer to the ground and going slower, potentially.

On the topic of conservation journalism

Ryan: What's something you remind yourself of when you're interviewing someone?

Ben: I have a friend named Chris Altman, who's a fantastic outdoor and nature writer and journalist I admire a lot. Chris spoke to one of my classes last year, and he said the attitude that he tries to adopt, both in relation to his sources and in his on-page persona, the tone he's going for is “the curious dumb shit”.

I think that's a really good term that I've kind of unconsciously been adopting for many years and Chris kind of gave me a phrase for it.

I always try to project curiosity, interest in the person I'm talking to. I'm there to learn. I'm eager to learn. The dumb shit piece comes in because when you portray yourself as curious but somewhat ignorant, that's when you get the best answers.

If you keep going to interviews thinking that you already know everything, there's this temptation to try to display our knowledge in conversation with our sources. Portraying yourself as curious, but a little bit ignorant, gets your sources opening up and talking, and that's really what you want as a writer

Ryan: This subject would make a good documentary, don't you think? Are you into documentaries?

Ben: One that I just re-watched, so it's kind of top of mind, is a film called Deer 139, that you, as a hunter, would also probably enjoy. It’s about mule deer migration in Wyoming. It's a lovely film that captures the incredible romance and athleticism of ungulate migration, through a personal lens, with strong lead female characters.

I'm not an enormous consumer of documentaries. But if some documentary filmmaker is listening and is like, “road ecology, what a fantastic topic!”, I'm ready to take part.

Ryan: Was there a time where you felt like you suffered for your art?

Ben: I went to a ton of places and talked to a ton of people, and I never really thought about that as suffering.

That is what makes journalism fun. The opportunity to go to fantastic places and meet wonderful, incredibly generous people. It's a surreal thing about journalism that you can reach out to all of these brilliant sources and be like, "hey, can I tag along with you for a few days?" and most of the time they say, “sure", which is such a great privilege.

I found myself in some weird, extreme places, like chasing anteaters on the Brazilian savannah, or helping satellite-collar mule deer in the deserts of Wyoming. I didn't think about it as suffering.

Watching chum salmon spawn in western Washington, the monarch butterfly migration in Minnesota, meeting all these Australian animals who'd been orphaned by cars, like bats and wallabies. One of the things that I like about this book, as its author, is the rich biodiversity that's present in it. The opportunity to spend time with that amazing diversity of animals, for me, was a fun, rewarding project.

Ryan: When you're interviewing someone on location, do you go out with a pen and paper and make notes? Do you rely on an audio recorder or camera?

Ben: Yeah, I've got a tape recorder going. First, there's just nothing like verbatim quotes and dialogue. That stuff is just so valuable.

I don't want to be thinking constantly about scratching down every single word that comes out of my sources. I want to be present in the moment. And I want to keep my hands free.

I take notes about what I'm seeing, what I'm smelling, hearing, and feeling and my own reactions to these experiences, and if all I'm doing is writing down quotes, I'm sort of numb to the world a little bit.

So definitely got a tape recorder going. I've got my pen and paper, and I'm mostly using that to record sensory impressions and thoughts that pop into my head in the moment.

And certainly the camera is important, taking pictures the whole time you're in the field, because those are valuable resources. When you sit down a month later to write about your experience those pictures really help reconstruct the scene.

Ryan: You've talked to a lot of people who pay attention to animals. What do you notice about the common qualities of that group?

Ben: It's a diverse group. One personality trait that comes up again and again is optimism.

If you're going to devote yourself to working with wildlife, you know that wildlife is declining. Animal populations are decreasing. We're in the middle of this biodiversity crisis and extinction event that is human caused, with cars kind of at the center of it in a lot of ways.

Working with wildlife…you basically have to be a fundamentally optimistic person.

If you're going to commit yourself to trying to reverse those trends, you basically have to be a fundamentally optimistic person. You have to believe your work matters and that those negative, discouraging trends are even capable of being reversed. Otherwise, why bother?

People like Beth Pratt4, with the campaign to build a wildlife crossing near Los Angeles over the 101, the busiest freeway on Earth, which disconnects mountain lion populations in Southern California. She spent a decade of her life trying to get this done. Certainly she wouldn't have done that if she didn't think it was possible.

Another great story is Matt Aresco5 in Florida. He moved turtles for years across the highway until finally he was able to convince the Department of Transportation to build an underpass for this turtle population, and effectively saved these turtles. He was out there every single day, picking up turtles and putting them in buckets, and carrying them across four lanes of traffic.

It's people like that who are realistic in all of the challenges that nature faces, but they're also fundamentally positive, optimistic people, who believe that change is possible, and are willing to work incredibly hard to achieve it.

Ryan: That’s a great place to wrap up. Ben Goldfarb, thank you so much for your time. It was a pleasure.

Ben: Thank you.

Ben Goldfarb's latest book is Crossings: How Road Ecology is Shaping the Future of Our Planet. His previous, award-winning book is Eager: The Surprising, Secret Life of Beavers, and Why They Matter.