Monday, July 6, 2009

Four-Legged Pedestrians?

As I prepare for a significantly longer essay on the introduction of complete streets into the American landscape, I wanted to include a few images of a quiet but growing concern among planners and civil engineers: biofragmentation through the construction of roads. In his book Road Ecology, Richard T. T. Forman estimates that 1,000,000 animals are killed every day from collisions with cars. (This doesn’t include the countless insects who succumb to our windshields.) While some countries in Europe have been trying to reduce animal fatalities through wildlife crossings for several decades, they remain a relatively recent development in North America. Perhaps the best known are the underpasses for Interstate 75 in Florida, which engineers have designed specifically to prevent car collisions with the Florida panther, one of the most endangered large mammals on the continent. As many people know, the deer that are abundant in many parts of the continent can be particularly hazardous, causing significant damage to the car and injuries or death to the passengers within. They are among the most frequent mammals to cause collisions, because of their tendency to graze on food along the periphery of a road—a bitter irony, because much of this roadside food has been disposed by humans, thrown from the windows of their cars.

Below is a busy stretch of the Concord Turnpike in the Town of Concord, Massachusetts, which features four subtly introduced box culverts that serve as wildlife underpasses.

The tunnel pictured below does not target any particular specie, but is part of a general effort to reduce collisions between cars and animals; as the photo proves, the tunnel is clearly large enough for a human to pass through. Also critical is the earthen floor, which helps create a more seamless habitat for a traveling animal than an abiotic strip of cement.

The Sudbury Valley Trustees have installed cameras to monitor the success of the tunnels; their website confirms that they do enjoy use from mammals (and even a few birds) of various sizes.

The Town of Concord, formerly home to Transcendentalist writers Thoreau and Emerson, has a history of strong environmental stewardship, and my suspicion is that the population largely embraced the introduction of such an infrastructure improvement, whereas in other locations it might arouse remonstrations as a frivolous use of taxpayer dollars. However, the town’s Natural Resource Commission apparently partnered with the state highway department to include these box culverts during a broader infrastructural upgrade, in which the Commonwealth installed retaining walls and median dividers, while integrating the wildlife underpasses into the overall design process. This appears to me to be a politically savvy move, because it could mitigate most of the fallout among taxpayers that would take place if the Commonwealth introduced the wildlife improvements as a separate highway project on its own terms. These box culverts most likely cost slightly less as well, since they were part of a larger improvement and did not demand any demolition or structural alterations on their own terms.

In all likelihood these projects will become more prevalent in the United States with each passing year; I believe New Jersey has a few wildlife overpasses, which serve much the same function as a pedestrian bridge but are usually much wider and again covered with an earthen floor. If other jurisdictions adopt the Concord approach and integrate the design with broader street improvements, these wildlife crossings could ascend among the public perception from a luxury to a desirable safety feature that protects both humans and animals.


Nici said...

Public perception unfortunately that is all these wildlife underpasses have to offer. One look at the picture of the tunnel and all I saw was a death trap. Well that’s what I saw looking from a prey animal’s point of view. A prey animal’s first instinct when threatened is flight. The tunnel even with the dirt floor is long and narrow and has only two ways to escape. Think of it this way, if you knew somebody was after you, would you feel comfortable going down that tunnel without any protection? I went to the web cam and there is series of pictures that prove this point of a fox catching a mouse in the tunnel. It was relatively easy for the fox as the mouse had no cover and could not out run the fox. The website does confirm that animals use the tunnel but it’s the type of animal that is important to notice. Roughly 70% of the animals “caught on tape” are prey animals, coyotes, red foxes, mink, grey foxes, fishers, etc. Prey animals are at the top of the “food pyramid” in an ecosystem so percentage wise they should be at most 20% of the four legged pedestrians using the underpass. So now that there is a large concentration of predators using the underpass the prey animals (deer, rabbits, squirrels) are going to avoid the area. The web cam clearly shows that the deer are rarely using the tunnel. While no one wants to see a fox or coyote hit by a car, the main benefit of these tunnels would be to reroute the deer as they cause the most damage to vehicles. I would assume that a study of insurance claims in the area verses insurance claims in areas without underpasses would show the cost of the tunnel has a minimal ROI. The reason why the Florida underpasses are successful is because they are designed to be used by a top predator, at the top of the food chain you go where ever you want.

All this being said, I believe your right that they will become more prevalent in the future. Not because they are cost effective and actually do what they are built to do but because of the publics perception. My background allows me to I look at things differently from the general public. A politian, community leader or teacher will point to the website and show the cute (prey) animals in the tunnel and the general public will ooo and aww, get a warm fuzzy feeling and walk away feeling good about what they have done to protect the environment. I must sound awfully cynical but the uniformed public forcing ineffective actions, decisions, policy whatever you want to call it about the environment, strikes a nerve with me. Hopefully, as time goes by, wildlife underpasses will become more prevalent and society as whole will become more informed and this will lend itself to real effective change and protection for the four legged pedestrian.

AmericanDirt said...

Great observation, Nici, about the tunnels favoring predators. It never occurred to me, though I'm sure that's exactly the sort of question an ecologist would raise. The goal no doubt is to keep the correct balance between predation and prey. While it's true that both predators and prey are victims of vehicle collisions, you are also right that deer are the ones with some of the highest collision rates, particularly because they forage on the side of a road with whatever food humans throw out the car. And it's very possible that deer avoid the tunnels if it makes them particularly vulnerable to predators. But that leads to another complication: are the tunnels trying to save deer and other large animals--often predators--because they are more critical to the ecosystem, or because collisions with them are more likely to cause injury to a car or its passengers? In much of the country, deer suffer from overpopulation so it would seem surprising to argue for infrastructure to protect them from cars, unless it were chiefly in the interest of motorists.

At this point, I think public perception generally does not favor this type of infrastructure. The only exception might be if it is saving a seriously threatened specie like the Florida panther. There's a Youtube clip of a state rep in Michigan going on and on about the pork-barrel spending for a "turtle fence" to protect the critters from passing cars.

Nici said...

I have to disagree with you on one point of your response. I’m not saying it doesn’t occasionally happen but deer are not mainly on the side of the road foraging for human food from cars. That is more of something a carnivore (dog / cat) or an omnivore (raccoon) would do. Deer are feeding by the roadside but on the grass. It is unfortunate that the roads provide the perfect foraging opportunity for the deer. Take a typical interstate in the eastern part of the country; it has grass on the shoulders that are bordered by at tree line. Tree lines are like “deer roads”, deer use the cover of tree lines to move through open spaces. While the forest provides cover and safety, the foraging opportunities are limited. Deer must venture into the open to feed on grasses, but they will stay close to a tree line or some type of cover to use as an escape route. So you can see how appealing roadside foraging would be to a deer. Then add the fact they prefer to feed around dawn and dusk and you have a "perfect storm" for collisions with cars. I have also seen big horn sheep foraging literally off the mountain side along I70 in Colorado. They don’t need the protection of a tree line as their ability to maneuver on cliffs is their protection. They are forced to graze along side roads because just like the forest, the mountain side provides safety but poor foraging opportunities.

I do so love reading "Dirt" as it engages my mind and often changes the way I look at the built environment. I know you are limited with time and resources, but "Dirt" or "Dust" keep writting, as it is appreciated!

AmericanDirt said...

Thanks for your counter-argument, Nici. I see what your saying in regards to omnivores and carnivores, and they probably are most likely to feast on human discards (especially those raccoons). But I'm basing my comment about dear from my limited education on urban ecology, and the arguments are that deer are often willing to eat litter thrown out by humans--that's why so many of them linger near the sides of highways.

However, the bigger reason I mention deer is because people are far more attuned to looking out for them, due to the damage they can cause to a car. They're bigger than most dogs/cats/raccoons and are far more likely to cause damage or deploy an airbag and potentially injure passengers. I know in places like Maine they have moose warning signs, which obviously are much much MUCH bigger than deer. (From what I hear, unless you're in a Hummer, the car is likely to suffer more damage than the moose.) And this is purely my own speculative opinion, but deer are also more likely to get hit because I have a strong suspicion they just aren't as intelligent as dogs/cats/raccoons. But it does seem like we both agree that deer enjoy roadside foraging. Keep in mind what I said about those estimates that 1,000,000 animals perish every day in America due to collisions with cars--and I don't think that includes insects splattering on the windshields!