"The hardest thing to get people to understand is that you need a series of crossings to increase effectiveness," says DiGiorgio. "They should be regularly spaced along the roadway and tied together by fencing. We need to apply the science in the right way so we don't patchwork our wildlife crossings. In this case, with the investment in one overpass in the right place, you can tie the whole system together."

Peter Kozinski, CDOT's project manager for the I-70 mountain corridor, says the federal earmark funds have allowed the agency to progress deep into preliminary design. Even with the success of vegetated bridges in Banff, the logistics of building one over the interstate at 10,000 feet are daunting. The bridge has to bear not only the weight of enough soil to accommodate evergreens, but a tremendous snow load, too; Vail Pass gets up to 500 inches of snow a year. It has to be properly bermed and shield its users from alarming headlights from traffic below, while not adding to icy conditions on the roadway.

"We want it to be a stellar success," Kozinski says. "But there are still lots of questions out there. For one thing, there isn't any money that's been identified to build this thing."

Biologist Chris Haas has studied wildlife crossings around the state, including this underpass on U.S. 285.
Biologist Chris Haas has studied wildlife crossings around the state, including this underpass on U.S. 285.
After years of lobbying and studies, conservation strategist Monique DiGiorgio sees momentum building for Colorado's wildlife bridge, the first of its kind in the United States.
After years of lobbying and studies, conservation strategist Monique DiGiorgio sees momentum building for Colorado's wildlife bridge, the first of its kind in the United States.

CDOT executive director Russ George, the former head of the Colorado Department of Natural Resources, has been supportive of the idea of improving wildlife crossings — more so, certainly, than his predecessor, Tom Norton, who once complained to a Wall Street Journal reporter that earmark projects like the wildlife bridge were a waste of money and "make my life miserable." But no single entity holds the key to all the federal and state boxes of revenue that finance highway projects, and backers of the bridge know that it's going to take some skillful political maneuvering and public campaigning to get the Vail overpass past the design stage.

DiGiorgio points out that the earmark money came out of a public-lands appropriation; in other words, it didn't take money away from a competing state highway project. It's possible, she suggests, that additional funding could come through other federal grants that wouldn't otherwise be available for state use. "The entire country is underfunded for transportation projects, but that doesn't mean we stop planning," she says. "It's constantly in flux, but projects are slowly getting funded. You never know what opportunities might arise."

Actually, if the crossing advocates have their way, Colorado will be the first state in the nation to boast not one but two wildlife bridges. Another overpass is being studied for the intersection of U.S. 6 and 119, the gateway to Blackhawk. The interchange was rebuilt in 1997 in response to increased traffic to the mountain casinos, but the new design has resulted in an increase in bighorn sheep kills as they try to follow Clear Creek. Engineers are studying the feasibility of an overpass spanning 119 for the sheep, about seventy feet wide, that would cost around $4 million to build.

"It's very much in preliminary design," says Tony DeVito, CDOT's Region One transportation director. "The biggest hurdle is identifying funding."

The cameras used in the citizen monitoring of wildlife on Vail Pass are now positioned across a much longer stretch of the interstate, from Golden to Dotsero. The Center for Native Ecosystems is using them to study how wildlife handle other potential crossings, but with only a few dozen cameras scattered over 120 miles, the information is somewhat fragmentary. The CNE's Bonaker says the group plans to launch a website in the fall that will allow I-70 motorists to report their own wildlife sightings.

A major challenge to the crossing planners is gathering reliable data about how wildlife actually move across the state — and the West. Highways may be the weakest link in most migratory patterns, but they're not the only one. The human population of the western half of the Colorado is expected to double by 2035, bringing more roads, development pressures and barriers.

"You need to think big," says Dave Theobald, a CSU geography professor who was part of the team that studied wildlife crossings and collisions for CDOT. "How are the wolverines going to get down there? Can they make it across this ravine or that river? The piece of going over the highway is needed, but it's not the only thing. You need a complete network of linkages."

Theobald has written extensively on shifting land-use patterns in the West, developing big-picture studies of the "wildlife-urban interface" as well as documenting specific impacts at ground level ("Map to the Future," October 4, 2007). He's currently working on a paper on habitat connectivity across the West but has found little detailed government research or policy on the issue. Yet momentum is building both at a regional and state level, with a western governors' task force and a blue-ribbon panel convened by Governor Bill Ritter both calling for increased protection of essential wildlife corridors.

"More work needs to be done at all levels," Theobald says. "We need to have finer-scale information about some of the critical species. For example, we have a lot of radio-collar telemetry data for lynx in Colorado, but we're not getting a real detailed understanding of how they're moving across the landscape."

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