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Science points to a need for wider wildlife corridors in Bow Valley proposal

Y2Y is challenging the Province of Alberta and the Town of Canmore to accept a scientifically defensible wildlife corridor when making decisions on development in the Bow Valley.

MEDIA RELEASE: March 14, 2017

The Yellowstone to Yukon Conservation Initiative (Y2Y) is challenging the Province of Alberta and the Town of Canmore to accept a scientifically defensible wildlife corridor when making decisions on development in the Bow Valley.

The group has released a composite map of the Three Sisters area to show where its data and that of Three Sisters Mountain Village significantly differs.

“The vision we are advancing for the Three Sisters lands ensures long-term viability of the wildlife movement corridor there,” says Stephen Legault, program director for Y2Y.  

“Large mammals in the Bow Valley spend 95 per cent of their time travelling on relatively flat terrain on slopes less than 25 degrees,” says Dr. Hilary Young, an ecologist and Alberta program coordinator for Y2Y.

“From time to time, they travel over steep terrain to find food, but numerous studies by biologists show they prefer flatter areas. Determining where the 25-degree slope line is in a valley as hilly and irregular as the Bow is part of the challenge for everybody addressing the issues facing Three Sisters,” she says.

Working with a Geographic Information System specialist, Y2Y used high-resolution mapping data to highlight all of the lands in Southern Canmore with a 25-degree slope or steeper. Rules were developed for determining how to deal with the numerous steep and discontinuous slopes that animals generally avoid in the valley.

“For example,” says Young, “We knew the line had to be relatively straight. Years of research show while animals will zig-zag their way across the landscape, the most effective wildlife corridors are generally straight. Most importantly, we wanted to ensure the corridor was functional for the species that will use it. When establishing this line, it is important to err on the side of being conservative.”

Once Y2Y determined where the 25-degree slope line was, it transposed its line on top of one created by Three Sisters Mountain Village (TSMV) for their development proposal.

“There’s a big difference,” says Legault. “Our slope line is lower in the valley and considers features on the landscape our research shows would hinder wildlife movement.”

Finally, Y2Y has drawn a 450-metre buffer from the 25-degree slope line, which is narrower than what local corridor guidelines and experts suggest for a wildlife passage as long as the one at Three Sisters. Because of existing developments and infrastructure, the ideal width of 850 to 1,000-m for this corridor is not possible. However, even with 450-m width, Legault says the corridor proposed by Three Sisters Mountain Village is not feasible for wildlife because TSMV’s line is well above the actual 25 degree slope.

“Much of TSMV’s development proposal falls in the areas where wildlife prefer to move, putting the success of wide-ranging species like elk and grizzly bears at risk. This doesn’t mean that Three Sisters Mountain Village can’t develop. What it does mean is that they need to go back to the drawing board and use the best science available to come up with an entirely new plan,” he says. 

When combined with other proposed developments at Dead Man’s Flats and Silvertip Resort, Legault says the Three Sisters Mountain Village proposal could significantly impact wildlife connectivity in the Bow Valley.

“That has international implications for the biological diversity of the Rocky Mountains,” he says.

Y2Y has sent a letter to the provincial Minister of the Environment and Parks, Shannon Phillips, asking that no approvals be granted for Three Sisters or Silvertip Resort until a cumulative impacts assessment is completed for all major development in the Bow Valley.

Legault says Y2Y has shared their data files and methodology to the Province of Alberta to aid in the upcoming decision on the Three Sisters Wildlife Corridor, expected by April 20.

For further comment:

Stephen Legault, Yellowstone to Yukon Conservation Initiative program director for Crown, Alberta and Northwest Territories
403-688-2964 | stephen@y2y.net

Hilary Young, Yellowstone to Yukon Conservation Initiative Alberta program coordinator
403-609-2666 ext. 104 | hilary@y2y.net

Graphics:

This map shows the difference between the 25 degree slope line calculated by Three Sisters Mountain Village, shown in magenta, and the line calculated by Y2Y shown in blue. The red markings indicate slopes more than 25 degrees. This is an overlay map on top of TSMV's as their data has not been shared publicly. Courtesy: Yellowstone to Yukon Conservation Initiative 

Background:
See below for detailed information on the need for a 25-degree slope and the methodology used by Y2Y to determine its line.

The need to determine the 25-degree slope line in the Bow Valley

In Canmore, development and other human activities have taken up most of the valley bottom, leaving large mammal species with few places to feed, rest and travel.

Humans and wildlife love valley bottoms for the same reasons: they’re lush and productive, warm, and easy to travel through. Not surprisingly, studies have shown again and again that large mammals in the Canadian Rocky Mountains prefer to travel on flat terrain (e.g. valley bottoms) or on very shallow slopes.

Generally speaking, the steeper the slope, the less it is used by both carnivores and ungulates. This is not to say that animals can’t or don’t use steeper slopes for movement — some species and individuals are capable of adapting their behaviour and using what is available. But that may come at a cost; it takes a lot of energy to travel across steeper terrain and there is often less food to be acquired on rocky slopes.

To our knowledge, all studies on the use of steep terrain in the Bow Valley conclude that large mammals prefer to travel on slopes under 25 degrees. Studies quantifying habitat use, rather than travel, generally support this finding as well.

      1. The Wind Valley Corridor Study (Alberta Parks, Town of Canmore, and others 2002) on the movement and habitat use of large mammals in and around the Wind Valley across from Dead Man’s Flats avoided including slopes over 25 degrees in their proposed corridors, as “the data indicate[d] [they] were not used extensively by any wildlife species of interest”.
      2. Two unpublished Alberta Parks studies (Percy 2006) found that the majority of cougar and wolf locations occurred on slopes of 25 degrees or less.
      3. An Alberta Parks study in 2006 of the use of steep terrain by grizzly bears in Canmore during both berry and pre-berry seasons found that they use relatively gentle slopes and rarely use slopes over 25 degrees. More than 90% of GPS telemetry locations occurred on slopes under 25 degrees, regardless of the season.
      4. It is well established that wolves in most areas of the Rocky Mountains select low elevations and shallow slopes (Paquet 1993, Duke 2001, Callaghan 2002, Whittington et al. 2005, Hebblewhite and Merrill 2007, Hebblewhite and Merrill 2008, Webb 2009).
      5. The Eastern Bow Valley Wildlife Corridor Study (Alberta Parks 2010) that tracked cougars, wolves and lynx found that 95% of cougar movements occurred on slopes under 30 degrees, and 95% of the movement of other carnivore species occurred on slopes below 25 degrees.
      6. Studies in the Bow Valley indicate that flatter areas are preferred by most wildlife species including deer, elk, coyote and wolf (Duke 2001, Callaghan and Jevons 2001 and 2004, Alberta Parks 2011).
      7. A review of snow tracking databases collected from Banff National Park, Yoho National Park, Kootenay National Park, Kananaskis Country and the Canmore-area that found that on average, 95% of the tracks of the eight large mammal species tracked occurred on slopes of less than 20 degrees (Fauvelle and Ford 2016). 

Because of the volume of evidence against the use of steep slopes by large mammals in the Bow Valley, we aimed to create a slope line that avoids forcing animals to travel over 25-degree slopes when moving through the corridor. Specifically, our slope line: 

  1. Does not cross 25-degree slopes;
  2. Minimizes the number of discontinuous steep slopes within the corridor;
  3. Assumes animals will not travel through a gap between steep slopes that is narrower than 10 metres wide. A number of factors will affect whether an individual will travel through a 10-m gap, including the availability of hiding cover and proximity to human disturbance. Admittedly, although prey species might avoid gaps of this size, predators may not be as reticent;
  4. Does not have any large doglegs — the line is fairly straight;
  5. Follows the base of the mountain. The line forms the south edge of the corridor so that most of its 450-m width is on flat ground.