This week, we’re joined by author Ben Goldfarb to talk about his book, Crossings: How Road Ecology is Shaping the Future of Our Planet (Norton). We discuss how roads cut off ecosystems, wildlife crossings, and animal mobility at different scales.
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Jeff Wood: How important are deer to this discussion?
Ben Goldfarb: Really starting in the 1950s and early '60s, deer really made the intersection of roads and wildlife a prominent national issue. It’s interesting to go back into some of the early roadkill studies, which started in the 1920s. And all of these biologists are sort of driving around and their Packards and Model Ts and they’re counting ground squirrels and woodpeckers and garter snakes, all of these different species. But none of those early wildlife biologists ever documented any white-tailed deer. And the reason is that there just weren’t really many deer to be hit at that point. We think of deer as these incredible ubiquitous animals, but you know, we hunted them almost to extinction by the end of the 19th century.
So in sort of the first half of the 20th century, there really weren’t many deer on the landscape, but by the 1950s, deer populations were recovering — and that really coincides with the construction of the interstate highway system. Americans are driving farther and faster than ever before, and suddenly there’s this big, relatively common 150-pound mammal blundering into their way and crossing highways and causing all of these collisions. And today, deer are the most dangerous wild animal in the country, responsible for between 200 and 400 driver deaths every year.
And, you know, in deer vehicle collisions, of course, it’s not the deer’s fault, right? It’s the car obviously that has made the deer so dangerous. But, you know, it is interesting to think that in the early 1900s, back when people were only hitting snakes and squirrels and turtles, the discipline of Road Ecology really was the fringe concern of a few naturalists who were considered a little bit kooky. Then once deer proliferate and driver safety becomes a big problem, you know, suddenly all of these wildlife biologists and transportation departments are suddenly concerned. So the issue, you know, wasn’t necessarily how cars endangered wildlife, it was how wildlife endangered cars somewhat perversely.
Road Ecology wouldn’t be nearly as robust as it is today if it weren’t for the recovery of white-tailed deer and all of the deer-vehicle collisions that ensued.
Jeff Wood: So then this leads to some sorts of solutions and trial and errors and figuring out ways to keep the deer from maybe crossing when they still wanted to cross?
Ben Goldfarb: That’s right — you see all of these solutions being tried. I mean, of course the deer sign, right? That’s the first thing that every transportation department sort of falls back on the classic yellow diamond with the leaping black silhouette of the buck. And those are totally useless, right? And there’s, you know, plenty of research showing that, you know, the drivers just habituate to those things and ignore them. Nobody slows down when they see a "Deer Crossing" sign, they’re basically visual pollution at this point, right? So most of the early strategies like signs and reflectors and deer whistles, you know, those, all, all of that stuff doesn’t, doesn’t really work.
But by the 1970s, transportation departments in states like Wyoming and Colorado and Utah, start building these wildlife crossings and passageways for deer and elk and antelope and other kind of migratory species of big game moving around the American West. And over time, it really becomes clear that that’s the most effective solution to this problem of wildlife-vehicle collisions and the loss of these migration routes. If you give animals a chance to cross the road separated from the surface of the highway itself, they take advantage of those opportunities. Roadside fences are a big part of that to guide the animals to the crossings.
Today, the wildlife crossing is really the best tool in our toolbox for dealing with the problems that roads create — or at least some of the problems.
Jeff Wood: They cost a fair amount of money, so it's important to do the math so that highway agencies would know that it'll offset that cost because it will save many human lives and car fenders. But ultimately, it doesn’t seem like it’s always necessarily a positive thought for the animals. It’s more like, "What can we do for ourselves?"
Ben Goldfarb: You’re exactly right. The great thing about these wildlife crossings is that they do tend to pay for themselves. The average deer-vehicle collision cost society more than $9,000 in vehicle repairs and hospital bills and tow trucks and insurance costs and so on, right? These are really expensive incidents. And if you can build a structure that prevents 50 of them a year, some of these wildlife crossings have done, those structures pay for themselves really, quickly. So there’s often some initial sticker shock when you say, "We’re gonna spend $5 million on helping elk across the highway?!" That seems kind of crazy. And then, you know, you realize that these structures are actually pretty thrifty in a sense.
But the focus on savings has been somewhat myopic. There are lots of animals out there like frogs and turtles and all those reptiles and amphibians especially, you know, that are some of the most road-endangered animals on the planet. And yet nobody’s ever totaled their car hitting a spotted salamander, right? So we tend not to build crossings for those animals. For now, this is definitely focused on mitigating those large dangerous animals that threaten us. We’ve mostly ignored the smaller critters for which roadkill might be a conservation crisis, but is not a public safety problem.
