Google. (n.d.) Lake Highway Around, AB, Canada. Retrieved from https://bit.ly/2KeHuFi
Wildlife crossings are various forms of infrastructure designed to connect animal habitats that have previously been fragmented by roads. They are either tunnels that travel underneath the pavement or fenced bridges that travel over the roadways. In addition to the crossings themselves, fences are built to dissuade animals from attempting to directly cross. The use of wildlife crossings was popularized by Banff National Park which has received global praise for its effectiveness, reducing collision rates by 80%.1 Now, many countries, such as China, Mongolia, Argentina, and the USA, are implementing them to help reduce nonhuman and human injuries, mitigate habitat fragmentation, and prevent genetic isolation of species.
Analysis of wildlife crossings in Banff National park found that the area surrounding the crossing has a strong effect on its use.2 Grizzly bears, elk, and deer were more likely to use crossings that had lots of open space near them. Meanwhile, cougars preferred crossings with lots of cover near the crossings. The open space is key for prey species to escape should they encounter a predator, meanwhile the cover was important for cougars to remain hidden whilst they crossed. As such, it is important for crossings to be variable in their design and environment to serve all species equally.
It is important to note that corridors and wildlife safety measures along highways are used by different species in various ways. For example, Fleury and Brown assert that corridors for large mammals require at least 400 meters distance away from traffic and 800 meters away from pedestrians in addition to a spatial “buffer” of woody brushy areas intermixed with more open spaces. On the other hand, they note that small animals prefer mainly woody and brushy and tend not to cross streams and roadways greater than 30 meters in width. 3 For our analysis and site recommendations, we wanted to take these factors into account in addition to collision incident rates, hillslopes, and land characteristics. As such, forestation and land use were factored into the criteria of our suitability analysis.
As illustrated in the Landsat capture above, the highways in Banff National Park already feature a number of wildlife crossings and anti-AVC safety measures. The four types of crossings are as follows:
Red: Overpasses
Light Blue: Creek Bridges
Green: Culverts
Brown: Bridges
Overpass Crossing – (Highway Wilding. (n.d.) Red Earth Overpass Crossing, Banff, Alberta. Retrieved from https://bit.ly/3r4nwO)
Creek Crossing – (Highway Wilding. (n.d.) Red Earth Creek Crossing, Banff, Alberta. Retrieved from https://bit.ly/2Wq5EP)
Culvert Crossing – (Highway Wilding. (n.d.) Castle Culvert Crossing, Banff, Alberta. Retrieved from https://bit.ly/3h1Un1)
Bridge Crossing – (Highway Wilding. (n.d.) Buffalo Bridge, Banff, Alberta. Retrieved from https://bit.ly/3paBGLX)
It is important to note that each crossing type had various rates of use by different species. Although we didn’t analyze this, if we had better data on species populations in our area we may have used it to decide which crossing types we be proposed. Our statistical analysis found that Deer used crossings the most of any species. However, bridges were mainly used by elk.
Citations
1 Dickie, G. (2017, December 4). As Banff’s famed wildlife overpasses turn 20, the world looks to Canada for conservation inspiration. Canadian Geographic. https://www.canadiangeographic.ca/article/banffs-famed-wildlife-overpasses-turn-20-world-looks-canada-conservation-inspiration
2 Clevenger, A. P. & Waltho, N. (2005). Performance indices to identify attributes of highway crossing structures facilitating movement of large mammals. Biological Conservation, 121(3), 453-464. https://doi.org/10.1016/j.biocon.2004.04.025
3 Fleury, A. M. & Brown, R. D. (1997). A framework for the design of wildlife conservation corridors with specific application to southwestern Ontario. Landscape and Urban planning, 37(3), 163-186. https://doi.org/10.1016/S0169-2046(97)80002-3