New research from scientists at the University of Ottawa, five partner universities and the Government of the Northwest Territories shows that climate change is causing extensive lake expansion and landscape flooding in the southern Northwest Territories, affecting the core habitat of the Mackenzie wood bison herd. Wood bison are listed as “threatened” under Canada’s Species At Risk Act and the Mackenzie herd plays a key role in efforts to conserve and increase wood bison populations in the Northwest Territories.
“The Mackenzie Bison Sanctuary, on the north shore of Great Slave Lake, is home to an important population of wood bison. Observations over the last decade by local land users and wildlife managers suggest that the lakes of the region have expanded, flooding large areas of sedge meadows. We set out to assess these changes to better understand their impact on bison populations,” said co-lead author Jennifer Korosi, an assistant professor in the Department of Geography at York University who completed the work at the University of Ottawa as a Banting Postdoctoral Fellow.
The team measured the area covered by water in a 10,000 km2 section of the region using satellite images taken between 1986 and 2011. Their findings show that lake surface areas nearly doubled over that period. Moreover, this flooding is disproportionately affecting essential bison habitat by inundating sedge meadows that tend to grow in previously dry lake basins.
“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 in search of forage,” explains co-author Michael Pisaric, a professor of geography at Brock University. These habitat changes have displaced bison herds, increasing the risk of bison-vehicle collisions on highways in recent years.
The study relied on information preserved in a dated sediment core, which was drawn from the largest lake in the area, to track changes in lake surface area over the past few centuries. Scientists use sediment cores, which are a record of the materials deposited on the lake bottom over time, to reveal the history of changes to the lake and its surrounding area. The team noted changes in chemical markers that are produced exclusively by land plants to show that the flooding of the surrounding landscape over the past two decades is unprecedented in over 200 years.
“The results of our study, both from the satellite imagery and lake sediments, point to recent climate change as being the primary driver of lake area expansion in this region,” said Joshua Thienpont, co-lead author of the study and a postdoctoral fellow at the University of Ottawa. Thienpont noted that there are various mechanisms by which lakes can expand or shrink due to climate change across the vast northern landscape, which are currently being studied.
“Our findings clearly indicate that increases in lake size, as a result of climate change, have directly impacted the use of the land by threatened wood bison,” said Jules Blais, co-author and professor of biology and environmental toxicology at the University of Ottawa. “This represents an additional challenge for the conservation of wood bison herds that have also been affected recently by diseases like anthrax.”
Members of the research team
Dr. Jules Blais (University of Ottawa), Dr. Joshua Thienpont (University of Ottawa), Dr. Jennifer Korosi (York University), Dr. Michael Pisaric (Brock University), Dr. John Smol (Queen’s University), Dr. Myrna Simpson, Ms. Jamylynn McDonald (University of Toronto), Mr. Peter deMontigny, Ms. Joelle Perreault (Carleton University), Dr. Steve Kokelj (Northwest Territories Geological Survey), and Dr. Terry Armstrong (Environment and Natural Resources, Government of the Northwest Territories).
Funding for the research was provided by the Cumulative Impact Monitoring Program (Government of the Northwest Territories), the W. Garfield Weston Foundation, and the Natural Sciences and Engineering Research Council of Canada.
Media Relations Officer
University of Ottawa