in the Canadian
Rockies
Bears and
Habitat
Bears and
Roads
Bears and
Science
Mitigation: Reducing the Impacts of
Roads and Railways on Bears
Bears and
Roads
Attempts to reduce the negative effects of roads and railways on bears and other wildlife can be broadly grouped into two categories: structural mitigation and other types of mitigation. Examples of structural mitigation include the use of specially designed, strategically located crossing-structures intended to provide wildlife with access to habitats on either side of busy roadways, and road alignments that minimize destruction of quality habitat. Other types of mitigation that are not directly related to physical structures include managing human-use levels around important wildlife crossing areas, and educating people as to proper behaviour when viewing wildlife along roads or railways. Evaluating the efficacy of these measures, and identifying additional or improved approaches to mitigation is an important focus of current research in the Canadian Rockies.
Structural mitigation
The majority of road mitigation structures that have
been employed in the Canadian Rockies are along the Trans-Canada Highway
(TCH) through Banff National Park. Portions of the highway were twinned
(expanded from 2 lanes to 4) in several phases between the mid-1980s and
1997. The intention is to twin the remaining 2 lane portions through Banff
and Yoho National Parks in the near future.
What mitigation structures are in
place?
In order to reduce the number of animals
killed in collisions, a 2.4m fence was erected along either side of the
45km highway corridor. A variety of different types of gates and
cattleguards were also installed along the fence/highway corridor to allow
pedestrian and vehicle access through the fence, while at the same time
preventing wildlife from getting into the corridor. The fencing along one
recently completed 18km segment of the highway was partially buried in an
attempt to prevent animals from tunneling under.
While the fence has positive effect of reducing road-related mortality, it also can act as a barrier to large mammal movement, thereby contributing to habitat fragmentation. To increase permeability (i.e., “crossability”) and habitat connectivity across the highway, a series of 22 wildlife underpasses and 2 overpasses have been installed along the fenced section of the highway. (Clevenger and Waltho 2000)
How effective are the fence and
crossing structures?
Measuring the effectiveness
of these mitigation structures is a complex task because:
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judging success must take into account both the goal of reducing road-related mortality and the goal of maintaining habitat connectivity.
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managers and scientists may have different criteria for evaluating effectiveness. For example, with respect to maintaining connectivity, a conservation geneticist might define success with one grizzly bear passing per grizzly bear generation (11-13 years) while a conservation biologist would expect more use. There is no magic number.
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animals need time to learn to find the crossing structures and to incorporate them into their movement patterns. Individual animals need more than a few months to adapt to these structures and populations need even more time – possibly even decades.
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answering some of the complex ecological questions around roads and long-lived wildlife, like bears, may require research timeframes of up to 10-15 years.
(Clevenger 2001)
Given these factors, what can be said at this point about how effective the fencing and crossing structures are? The following research results highlight some of the successes and challenges to date and give insight into the factors that influence effectiveness.
MORTALITY
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between 1981-2000, 73% of all black bears killed on the TCH in Banff National Park occurred on unfenced, unmitigated sections of the highway. There were no recorded grizzly bear kills. (Clevenger 2001)
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black bears’ ability to climb the fence reduces its effectiveness in preventing black bear-vehicle collisions. Parks Canada is testing several designs to modify the existing fence so as to minimize the potential for bears (and cougars) to get into the highway corridor.
MAINTAINING CONNECTIVITY
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in just over four years, black bears made 502 passes through the crossing structures and grizzly bears made 30. Adult female grizzly bears have made little use of the structures, though recent use of one underpass by an adult female is encouraging.
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the low use of crossing structures by adult female grizzlies is largely a function of the fact that very few adult females’ home ranges include areas in the immediate vicinity of the twinned, mitigated sections of the TCH. If adult female grizzlies tend not to use habitats near the highway, how will they discover and learn to use the crossing structures?
(Clevenger 1999 and Gibeau 2000)
Clevenger and Waltho analysed structural, landscape and human activity factors that influence the effectiveness of underpasses in Banff based on crossing data collected between January 1995 and July 1998. Conducting their analysis at three scales of ecological resolution (species, groups of species [carnivores and ungulates] and all large mammals combined), they found a common thread: human influence consistently ranked high as a significant factor influencing underpass use by wildlife. These results led them to conclude that “the best designed and landscaped underpasses may be ineffective if human activity [in and around them] is not controlled.” 3
Selected recommendations for improvement
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to reduce the ability of black bears to climb over the fence: test steel fencing posts rather than the existing wood posts (Serrouya 1999)
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to increase grizzly bear use of habitats adjacent to the Trans-Canada Highway (TCH), and therefore, increase the opportunities for them to use crossing structures: reduce total human access density (roads and trails) adjacent to the TCH by controlling the timing and volume of human use (Gibeau 2000)
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to encourage increased use of crossing structures by bears and other species: manage human activity near crossing structures by relocating foot trails, restricting human use of the underpasses and continuing to monitor human and wildlife use of them (Clevenger and Waltho 2000)
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to maximize the effectiveness of crossing structures to be incorporated into future highway expansion projects: conduct ongoing detailed research that identifies important crossing locations (for bears and for other species) and determines the spatial and temporal characteristics associated with their use. (Gibeau 2000 and Percy 2000)
Other types of
mitigation
Non-structural efforts to mitigate the impacts of roads and railways on
bears tend to focus on three areas: removal of attractants, education
and human-use management. This section highlights some of the methods that
have been recommended and/or employed within and outside of
the Mountain National Parks.
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Parks Canada has been working with the Canadian Pacific Railway (CPR) to clean up major grain spills when they occur, and to clean up grain that is chronically leaking onto the tracks from many aging rail cars. To address the latter issue, the CPR has purchased a special truck that vacuums grain from the tracks. While this represents a start, chronic grain leakage continues to pose a significant problem for bears and other species, and progress on the issue of repairing/replacing leaky cars is slow.
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the CPR and Parks Canada have also worked together towards prompt reporting of train-killed ungulates so that carcasses can be removed from the tracks before bears and other wildlife are attracted to feed on them.
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replacing existing highway and railway right-of-way vegetation with species that are less palatable to bears has been recommended as a means of reducing their attraction to these areas. (Munro 1999)
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parks and protected areas, provincial governments, private industry and others work to educate visitors to the Canadian Rockies about roadside habituation and bear-viewing etiquette. The Living With Wildlife and Partners in Life programs are two examples.
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scientists, government and industry have worked together to decommission, close or otherwise limit use of roads when they are no longer needed by industry. Because road access has a significant impact on bear mortality, efforts to step-up road-closures have been recommended. (Benn 1998 and McLellan and Shackleton 1988)
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in 1998 Banff National Park began implementation of a voluntary, night-time closure of a portion of the 1A Highway (a secondary highway which parallels the Trans- Canada Highway) in the spring. This measure is intended to protect use of high quality spring habitat for bears and other wildlife that is adjacent to the 1A. The rate of compliance with this voluntary closure is not yet known.
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grizzly bear mortality researcher Bryon Benn recommended the creation of “No Hunting Zones adjacent to parks and high human use areas, and along driveable roads to reduce the killing of habituated grizzlies by hunters and other people with guns who encounter these bears at close range.” (Benn 1998)