Searching for Wood Bison Habitat
Much of the habitat in northern Alberta that once supported wood bison is gone.
Their prime foraging areas are mostly either converted to farmland or inundated with trees.
Researchers at the University of Calgary conclude that with the landscape in its present condition, wood bison can't approach their historical abundance.
This close relative of plains bison once numbered around 170,000 throughout western Canada's boreal forests. Wood bison nearly became extinct in the mid-1900s. Free-ranging herds not infected with diseases had grown to 4200 animals by 2006.
A major constraint on the wood bison population in northern Alberta is the extent of wet meadows. Wetlands offer the richest-quality forage, in the form of sedges and grasses, which are essential for sustaining wood bison during winter.
Summer bison habitat has also been lost. Suppression of wildfires allows forest cover to expand, and trees now dominate upland habitat that was once meadows suitable for grazing. Understory plants provide little nutrition and boreal forests don't produce enough forage for bison to subsist on.
Logging these forests does improve growth, but not quality, of bison fodder. Clearcuts in aspen-dominated uplands produce more palatable vegetation than do forests for the first 25 years after harvesting. Cleared lands are at their best during the first eight years, when four hectares could support a cow and calf for a month. These sites still don't yield enough sedges and grasses, though, to maintain wood bison over winter.
M. Jacqueline Redburn, Wayne L Strong and C. Cormack Gates. 2008. Suitability of boreal mixedwood clearcuts as wood bison (Bison bison athabascae) foraging habitat in north-central Alberta, Canada. Forest Ecology and Management.
Wayne L. Strong and C. Cormack Gates. 2008. Wood bison population recovery and forage availability in northwestern Canada. Journal of Environmental Management.
Environment Canada. 2006. Species at Risk. Wood Bison. Ottawa, Ontario.