Wildlife Corridors in the Bow Valley River Valley in Alberta

Excerpts from:

Paquet, P.C., Gibeau, M.L., Herrero, S., Jorgenson, J., and J. Green. 1994. Wildlife corridors in the Bow River Valley, Alberta: A strategy for maintaining well-distributed, viable populations of wildlife. A report to the Bow River Valley Corridor Task Force. 38pp.

The Effects of Roads, Highways, and Railways

(Larger gif: 125K) The Trans-Canada Highway and Canadian Pacific Railway roughly parallel the Bow River through the study area. Both are major transcontinental transportation routes with large traffic volumes (Woods 1991). There are approximately 212 km of additional roads within the Bow River Valley. During 1983-87, 26 km of the easternmost section of the highway within Banff National Park were fenced on either side with 2.4 m high, ungulate-proof fencing. Underpasses and bridges provide ungulates opportunities to cross the fenced highway at 12 locations. However, both the Trans- Canada Highway and Canadian Pacific Railway continue to be significant causes of wildlife mortality (Woods 1991, Gibeau 1993, Paquet 1993) in the Bow River Valley.

There is general acceptance that road density is one key predictive variable that can be used to estimate the effects of disturbance and habitat fragmentation (Diamondback 1990, Mattson et al. 1987). Although the literature varies with regard to the amount of displacement and other impacts, there is irrefutable evidence that roads and the disturbances associated with roads reduce habitat effectiveness resulting in reduced fitness and increased risk of mortality (Diamondback 1990). Briefly, roads (and railways) fragment wildlife habitat, reducing the capability of habitat to provide security from humans. This results in animals avoiding or underutilizing the fragmented areas or being exposed to elevated risk of mortality; thereby reducing habitat effectiveness for meeting the biological requirements of wildlife. Moreover, habitat fragmentation may precipitate population decline and extinction by dividing an existing widespread population into 2 or more subpopulations, each in a restricted area. Fences may exacerbate the problem by preventing the natural movement of species over their home range (Primack 1993).

Wildllife in the Bow River Valley - The Current Situation

"You can't depend on your judgment when your imagination is out of focus" (Mark Twain ca. 1890)

What is the Conservation Problem?

Alteration of the environment is disrupting natural processes and displacing endemic species. Ecological integrity has been significantly compromised by human induced changes, which have upset the structure and function of the system (Cowan 1947, Kansas et al. 1989, Woods 1991, Gibeau 1993a, 1993b, Purves et al. 1992, White et al. 1992, Paquet 1993) [Ecological integrity exists where the structure and function of an ecosystem are unimpaired by stress induced by human activity and are likely to persist. State of the Parks Report 1990]. Of the terrestrial mammals for which information is available all have been adversely affected by human activities.

Since 1952, grizzly bears, wolves, cougars, lynx, wolverines, otter, and moose (Alces alces), have been effectively displaced or eliminated from the Bow River Valley. The elk population, although still substantial in size, has been severely perturbed and is generally considered to be in social disarray (Woods 1991, Banff National Park Elk Workshop notes, Paquet et al. in prep). The long term viability of the black bear (U. americanus) population is tenuous (Kansas et al. 1989) and the mortality rate of adult coyotes (C. latrans) exceeds that of exploited populations in unprotected areas (Gibeau 1993a).


What Are The Effects of Human Activities?

At present, the encroachment of human disturbance represents the single largest threat to sustaining wildlife populations in the Bow River Valley. Disturbances include extractive resource exploitation (e.g. mining, forestry), development of transportation and utility corridors, air and water pollution, residential development, recreational facilities, and rapidly expanding recreational use. The most significant and pernicious threats to wildlife are the combined effects of direct habitat loss and alteration, and increased sensory disturbance and subsequent habitat alienation associated with the establishment of permanent facilities and development of the supporting infrastructure [We note that for some species the additive mortality resulting from illegal killing, management actions, accidental deaths, and legal hunting is probably not sustainable. The question of sustainability is a topic that has generated considerable debate. In the face of uncertainty we believe management must be conservative until the issue is satisfactorily resolved].

These developments and associated human activities are resulting in the fragmentation of the landscape into disjunct and isolated patches of habitat (Kansas et al. 1989, NRCB 1992; McCallum and Paquet 1992; Canadian Parks Service 1992; Gibeau 1993b; Paquet 1993, Herrero in press), occluding essential regional dispersal corridors (Fig. 2) (CPS 1992, Boyd et al. 1994), and creating impediments to inter- and intra-territorial movements of animals (Paquet 1993, Herrero in press). Owing to the lack of coordinated regional planning, these losses and impacts are incrementally eroding the ecological processes and components necessary to sustain biodiversity.

Effects of fragmentation on regional populations of ungulates such as elk, bighorn sheep and carnivores (black bear, grizzly bear, wolf, cougar wolverine and lynx) have been exacerbated by increasing conflicts between wildlife and humans. Habituation of elk and bighorn sheep to humans and human developments has resulted in the need for increased management of wildlife in the vicinity of the Banff and Canmore townsites. Conflicts between large carnivores and recreational users or residents and the subsequent removal of "problem" animals has resulted in mortality sinks, which may be having significant effects on regional populations of these species (UMA Engineering 1991; McLellan 1993). Highways and railways are direct and increasingly important causes of wildlife mortality (Nette and Jorgenson 1989, Paquet 1993, Gibeau 1993a). For example, Nette and Jorgenson (1989) estimated that predation and highway mortality on the Trans Canada Highway between the East Park Gates and Deadman's Flats were removing all or more than the annual recruitment of elk in the vicinity. These barriers also interrupt, filter, or redirect wildlife movements. In most cases, the permanence of these facilities has foreclosed future opportunities for restoration (Fig. 3).

For further information contact Paul Paquet at: ppaquet@sasknet.sk.ca