Wildlife Crossings: Creature Comforts, Reinforced with Concrete

Traveling along I-78 through northern New Jersey, about twelve miles west of Newark, drivers experience a reprieve from the endless array of New York suburbs as they speed through the Watchung Reservation.


On a map, it looks like this:


But, despite the fact that it's fundamentally a forest preserve, the infrastructure is a bit more sophisticated than one might expect. Notice the thick retaining wall on the right side (the south side of the interstate):



But more interesting is the overpass in the distance. As one gets closer, it becomes obvious it's not the typical country road's overpass.


Look at all the plant growth. It's hard to tell if there's even a road up there. And it's not the only one. Travel a quarter mile further to the east, and there's another scruffy looking bridge, again with a retaining wall on the right.


Getting closer, it's obvious the bridge isn't just landscaped; it has trees growing on it.


Is this just a method of aestheticizing the roadway for motorists, so that those driving on the overpass can't even tell that there's a major interstate highway passing underneath them? What sort of road is this? Let's check that Google Map again.

Here's Street View at that first (more westerly) overpass, and here's the equivalent location: the site of the gray circle in the center of the map.


The roadway crossing over I-78 doesn't even show up. Why not? Because it doesn't exist. There's no road.

This website offers a clue of what it looks like for the visitor on the bridge.

It's a viaduct for voles--if voles even live in Northern New Jersey. Alliteration aside, it's for deer, raccoons, skunks, foxes, maybe even some bears--whatever animal seeks to migrate from the northern portion of the Watchung Reservation to the southern, across I-78. Essentially it's an infrastructural acknowledgement that this busy thoroughfare carves a disruptive and dangerous swath through significant wildlife habitat. It's a ped bridge for quadrupeds, and the dense plant growth helps to mimic the habitat to naturalize the experience, steering the animals at a safe crossing, as opposed to the likely lethal alternatives that comprise the remainder of the I-78 path through Watchung.

Such wildlife crossings are rare in the United States. I've written about one that served as an underpass to protect animals from a busy highway in Concord, Massachusetts. Ostensibly the Everglades have some similar tunnels to guard against the potential extinction of its cherished subspecies, the Florida panther. But few people are cognizant of these accommodations: my guess is only a fraction of the hundreds of thousands of motorists who pass under these two bridges in Watchung even know that there's something special about them.

In a country notorious for well-voiced opposition to government spending on pet projects (pun intended), wildlife crossings will seem to most constituents like a waste of money. They are relatively common in Europe, but we can count on our hands the instances you might find them in the US. Without extensive research, it's hard to estimate exactly how much these two bridges at Watchung Reservation would cost. Though they obviously require no repaving, the topsoil requires a sizable road bed to support all those plants, and it's possible the load-bearing capacity needs to be greater than one that typically carries cars. And, as the trees on the bridge mature, their root systems could easily compromise the strength of the concrete that holds the bridge together. All this to save the lives of white-tailed deer, a species not remotely threatened in northern New Jersey (or most of the rest of the country, for that matter).

From what I can tell, these bridges emerged in the mid-1980s as a response to environmental activists, who protested vocally how the path of I-78 would cut cleanly through the Reservation, a 2,000-acre preserve surrounded by heavy suburbanization. To fend off criticism that this path only exacerbates habitat fragmentation, the New Jersey Department of Transportation agreed to fund the two wildlife bridges. Thirty years later, skepticism prevails: does it really help retain habitat? Would evidence that animals use the bridges serve as sufficient proof that they appreciate them? Can animals ever appreciate anything?

At the very least, the intensive investment to build these bridges may have mitigated one other common occurrence: the collision of high-speed cars with various species of animals (particularly ungulates like deer). It is possible that the bridges have saved millions of dollars in vehicular damage (and possibly some human lives) by diverting deer away from the road. If someone were to conduct a cost-benefit analysis, I'd imagine these would be two of the largest variables. At the same time, what would be the point? The infrastructure is in place and the primary users don't add much to the bridge's wear and tear. Wildlife bridges may actually be much lower maintenance than conventional vehicular overpasses. A true assessment of the bridges' value may only arrive when one or both are in serious need of repair--another thirty years from now.

Regardless of one's opinion on the merits of these two bridges, the New Jersey DOT and its federal partner the FHA may have found a perfect compromise just a bit further to the east, where there's yet another eco-sensitive overpass. When gazing at it from the westbound direction, it doesn't look that different from the others through the Google Street View, but this time, as the map itself indicates, it's an actual, usable road. Here's what it looks like once you're crossing over I-78 on Glenside Avenue:


And when peering over one side of the bridge, the growth is so thick that you can hardly see the cars zipping along the freeway below you:


In this case, it's a combination of a wildlife/vehicular crossing, accommodating both in equal measure--and a chain-link fence separating, to keep the deer from meandering onto the path of motorists, while a second, outer chain-link fence (visible from the Google Street View) protects the animals from plunging off the bridge to their imminent deaths on I-78--if they would ever do such a thing. Regardless of whether we see more of these devices in the future, at least New Jerseyans get a 3.5-mile stretch of highway almost completely free of roadkill. And maybe a few more intact car grills too.

This article originally appeared in the author's personal blog, American Dirt. All photos taken by the author.