Plans for new TCH overpass in the works
Thursday, Feb 01, 2018 06:00 am
A wildlife overpass to help threatened grizzly bears and other wildlife cross the deadly Trans-Canada Highway east of Canmore is closer to reality than ever before.
The news comes at the same time a new study has shown grizzlies need a range of crossing structures to get across highways, and that females consistently require large open span underpasses or overpasses.
While there are no new projects listed in Alberta Transportation’s current three-year capital plan, department officials say they’re in the process of putting out a Request for Proposal for the design of an overpass.
“We are in the process of retaining a consultant to work on design of a wildlife overpass between Lac Des Arcs and Highway 1X,” said Wayne Wood, communications advisor for Alberta Transportation.
In addition, Wood said, a consultant is currently working on the design of an animal detection system for the same area to alert drivers of wildlife along the highway.
“The detection system, while still in its early stages, would be an electronic detection system that could detect wildlife movement, which in turn would trigger a message on nearby signs,” he said.
“What it would look like and how it would work is part of the current study.”
Roads have increasingly fragmented North America’s landscapes over the last 100 years and the Trans-Canada Highway is a barrier to wildlife movement in the Bow Valley.
In a new peer-reviewed study published online in the Wildlife Society Bulletin, researchers examined 17 years of highway crossing structure research in Banff National Park, then they studied the travel patterns of grizzly bears between 1997 and 2014.
Adam Ford, Canada research chair in wildlife restoration ecology at UBC’s Okanagan campus, and Tony Clevenger, renowned road ecologist and Bow Valley scientist, led the work.
The study looked at five different wildlife crossing structure designs distributed across 44 sites along a 100-kilometre stretch of the Trans-Canada in Banff – which began to be used by bears more and more over time.
Tracking and motion-triggered cameras were used to monitor grizzly bear movement, indicating grizzly bears selected larger and more open structures like overpasses and open-span bridges, compared to tunnels and box culverts.
But research clearly indicated a mother bear with cubs opted to use an overpass instead of an underpass in almost every case. Bears not travelling in these family groups used both underpasses and overpasses.
“You can’t just build a tunnel under a highway and expect to conserve bears,” said Ford. “Our work shows that the design of structures used to get bears across the road matters for reconnecting grizzly bear populations.”
Clevenger, an ecologist with WTI-Montana State University’s road ecology program, said overpasses are critical to maintain viability of grizzly bears in the Rocky Mountains given the survival of family groups is coupled with population growth.
“Highway mitigation that does not address the passage needs of breeding females is not highway mitigation,” said Clevenger. “It will not result in mitigating connectivity of breeding females, or long-term viability.”
Previous landscape-scale grizzly bear genetics work by Mike Proctor, one of North America’s most respected bear researchers, showed that highways are an insurmountable barrier to movement of breeding females, even Highway 3 in Crowsnest Pass.
Clevenger said this results in significant genetic structuring of the population.
“Males occasionally cross, but females do not,” he said.
“This is the same pattern of sex-biased dispersal we have seen with wolverines and highways in the Canadian Rockies and others have documented for other wide-ranging, fragmentation-sensitive species, for example, jaguar.”
Bear biologist Mike Sawaya’s genetic analysis of bear hair samples in Banff showed bears were crossing the road to mate with bears on the other side, highlighting the importance of crossing structures.
Clevenger said this new study allowed them to dig a little deeper into what structures females needed, noting little was known about those females that crossed the highway, their age or reproductive status in the previous research.
“In this new paper, we not only show that grizzlies use a variety of structure types frequently, we’ve gone beyond crossing structure selection by a given species and identified the most critical mechanism of demographic and genetic connectivity, that is, how to move breeding females across landscape barriers,” he said.
“In order to ensure that we’ve connected the population genetically and demographically, we’ve got to get breeding females across these highways if they’re going to be viable over the long-term.”
In 2012, a highway mitigation plan was developed for a 39-km stretch of highway between Canmore and Highway 40, where there are only two underpasses with wildlife fencing over a three-km stretch near Dead Man’s Flats.
Clevenger worked on that mitigation plan, which considered wildlife corridor research and highway wildlife mortality data.
“We’re not talking about a bunch of overpasses,” he said. “There’s got to be a range of other structure types that are smaller, but one or two overpasses there are critical, especially with this expanding grizzly bear population.”
Meanwhile, the U.S. Interagency Grizzly Bear Study Team – a cooperative research team that addresses monitoring and research needs for the Greater Yellowstone grizzly bear population – is very interested in Ford’s and Clevenger’s work.
At this point, grizzly bears in the Greater Yellowstone ecosystem have been delisted from the endangered species list; other grizzly bear populations in the Lower 48 remain listed.
While there has been a lot of mitigation for wildlife along U.S. Highway 93 within the Northern Continental Divide ecosystem, there has not been in the areas between that region and Yellowstone, where there are two major interstate highways, I-90 and I-15.
Frank van Manen, the team leader of the Interagency Grizzly Bear Study Team, said the committee’s most recent work was to identify potential movement paths for male grizzlies between the Yellowstone and Northern Continental Divide ecosystems.
“This was particularly relevant for Yellowstone grizzly bears because they have been isolated and, so far, there is no genetic evidence of recent immigration into the Yellowstone population,” he said.
“Because of that, genetic diversity in Yellowstone grizzly bears is lower than other bear populations and successful immigration of a bear from another area would be required to increase genetic diversity,” he added, noting recent genetic research shows genetic diversity of the Yellowstone population has not declined in the last 25 years, and long-term genetic viability remains high.
With the Northern Continental Divide being the closest population, van Manen said the committee wanted to understand how a male bear may travel between the two ecosystems.
He said that’s where Ford’s and Clevenger’s paper comes in.
“It is clear from our work that major highways – for example, interstate and high volume federal highways – may pose a barrier to dispersal movement, said van Manen.
“Mitigating this barrier effect can be very effective and the work done in Canada is very informative in terms of developing an effective mitigation strategy.”