Climate change is making things worse for Canada’s largest land-dwelling mammal, a research team has found.
The wood bison of the Northwest Territories is already on the country’s threatened species list, but more precipitation is forcing the animal into areas that pose dangers to them, says Brock University geographer and research team member Michael Pisaric.
For decades, the wood bison population has been living in the Mackenzie Bison Sanctuary on the western shore of Great Slave Lake in N.W.T. The iconic animal lives off of grass-like plants called sedges, which are common along lake shorelines in the region.
But these sedge meadows are increasingly becoming flooded as the lakes expand “and the bison’s preferred habitat declines,” explains Pisaric, professor in Brock’s Department of Geography and Tourism Studies.
Pisaric was part of a research team led by the University of Ottawa that included the government of N.W.T. and five partner universities, including Brock. They studied satellite images from the 1980s to present and, before that, sediment cores taken from a number of lakes in the area to track lake surface changes over the last few centuries.
The team’s study, “Broad-scale lake expansion and flooding inundates essential wood bison habitat,” was published in the Feb. 23 edition of the journal Nature Communications.
“We found out from satellite data that the total area of the Mackenzie Bison Sanctuary covered in water was about five per cent in the 1980s,” explains Pisaric. “This has increased to over 11 per cent of the land area now.”
While the exact causes of the lake expansion remain uncertain, Pisaric says warmer temperatures bring more precipitation and some permafrost thawing.
Because the bison sanctuary land is so flat, even slight changes in precipitation and flow causes water bodies to grow. He says some lakes in the area have expanded “hundreds of times in size” and are the largest they’ve been in at least 200 years.
“Surveys of the bison population at the same time indicate that, as the lakes have expanded, the Mackenzie herd appears to have abandoned the former core of its range within the protected area of the sanctuary as habitat becomes inundated,” says Pisaric.
The wood bison are moving toward a busy highway that connects Edmonton with Yellowknife. The road is often travelled by large trucks going back and forth from the North’s diamond mines.
“Incidents of collisions have increased,” says Pisaric. “It’s especially dangerous in the fall, when daylight begins to decrease again and there’s no snow cover yet; drivers don’t see the bison until they’re right on top of them.”
The wood bison, found in Alberta, Manitoba, British Columbia, Yukon, and southwestern N.W.T, is a subspecies of the American bison listed as “threatened” under Canada’s Species at Risk Act.
“Disease, cross-breeding with plains bison and habitat loss through human development, agriculture, forestry and petroleum resource development are the main threats faced by Wood Bison,” says the Species at Risk Public Registry.
Pisaric explains that the wood bison living in Mackenzie Bison Sanctuary are “genetically pure,” taken to the sanctuary from a remote location in Wood Buffalo National Park during the 1960s.
“Most of the wood bison that we have in Canada are a cross between the plains bison and wood bison, so they’re not genetically pure,” he says.