Inside the experimental world of animal infrastructure

But Banff’s wildlife crossings, like most, suffer from a kind of horseless carriage syndrome, their design surrounded by existing infrastructure. Tunnels are often slightly-adapted culverts, (usually concrete) tubes that carry water down roads. And overpasses are usually bulk borrowed from roadways તેઓ they’re built as if they were carrying the weight of an 18-wheeler and then “top-dressed” with foliage, Lister says.

Structural concept of structure

Andrew Merritt

This model of scattering of experiments is beginning to be reconsidered. One is the Wallis Annenburg Wildlife Crossing, a $ 90 million wildlife bridge under construction north of Los Angeles. Designed by architect Robert Rock, it avoids the sloping arch of old bridges in favor of a huge flat extension that requires only one pillar to support it between the mountains and on the highway, which is passed daily by an estimated 300,000 cars. Renee Kalahan, executive director of ARC Solutions, says it is “Poster Child for Innovation”, a group that is researching how to build better wildlife bridges. “It’s literally designed for species ranging from mountain lions to mule deer to deer to rats,” says Calahan. “They’re designing it completely down – literally, in terms of the soil, the microcirculation layer, to make sure the soil itself has a network of fungi that can support the native vegetation.”

There are a lot of unknown things right from the start of construction, no matter how the different species will react to the sheer volume of vehicles passing underneath. The National Park Service will monitor activities on the bridge as well as the DNA profiles of animals on both sides of the freeway. Many people are watching to see what will happen to the population of this area of ​​mountain lions. Over time, breeding has led to genetic disorders such as tail tail kink in domestic cats. The agency predicted that the population would become extinct in decades without crossing.

Across the U.S., the 350 million infrastructure bill is far less than would be necessary to address the divisions created by the country’s 4 million miles of public roads. But there are a handful of innovations that can tip cost-benefit analysis by allowing crossings to be built at low cost or in places where it was not possible before.

Currently animal bridges are built only where there is protected land on both sides of the road, as the general cost of building a concrete bridge will be difficult to justify in a place where one can develop in a few years. The lightweight, inexpensive, modular system can be used in places where futures are less secure, Huiser explains: “If nearby lands become unsuitable for wildlife, we isolate them and you can move them.”

One candidate material for such a modular system is precast concrete. There is also excitement about fiber-reinforced polymer (FRP), a less dense material than concrete made from structural fibers set in resin. The FRP has been used to build foot and bike bridges in Europe and a quick and easy wildlife bridge in Rhenen, south of Gooi in the Netherlands. Currently the Federal Highway Administration does not allow its use in traffic infrastructure in the U.S., but the demand for change is growing. “These are barriers that are primarily about policy and governance. They are not about science and they are not about technology, “says Lister.

“They know the last thing anyone wants is for a big creation, with a lot of publicity, to be built – and then it doesn’t work.”

Daryl Jones

Designers like Lister and innovators like Kalahan are advocates of building wildlife bridges across the country. Road ecologists and wildlife scientists, on the other hand, are more cautious. “They are hypersensitive because they know that the last thing anyone wants is a huge structure, with a lot of publicity, built – and then it doesn’t work. Because everyone will come out of the woodwork and say, ‘Look “It’s a waste of time! Absolute nonsense!” Says Jones.

But even today the cautious types want to see more built. Although we haven’t done enough research to get all the answers, it would be dangerous to take it as a sign that we should stop, says Heiser. He calls such excessive caution a “type II error” – a false negative. In this time of mass extinction, it looks like the house is on fire and our solution so far has been to fire a few water pistols at it. It would be a mistake to conclude that there is no water.


Despite the challenges at Ede and elsewhere, Van der Grift says the answer lies in learning while building. We still need to invest in the actual work of tagging, installing trail cams and DNA testing and long-term population monitoring, he emphasizes. But we should build more crossings first – and the evidence we have so far says to make it bigger and bolder. “You have to understand that you almost can’t do too much,” he says. “Do what you think is necessary, study it and then, nine times out of 10, you’ll see, ‘Oh, I should have done more.’ But there is no point in waiting until you understand that. ”

Matthew Ponsford is a London-based freelance reporter,

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