OTTAWA, February 23, 2017 – New research from scientists at the University of Ottawa, five partner universities and the Government of the Northwest Territories shows climate change is causing extensive lake expansion and landscape flooding in the southern Northwest Territories, affecting the protected 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 suggested 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,” says co-lead author Dr. Jennifer Korosi, an assistant professor in the Department of Geography at York University, who completed the work while a Banting Post-Doctoral Fellow at the University of Ottawa.

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 the lake surface nearly doubled over that period. The expansion of water on the landscape is disproportionately flooding essential bison habitat by inundating sedge meadows that were prevalent 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 Dr. Michael Pisaric, professor of geography at Brock University. Bison movements, caused by habitat changes, have led to a higher risk of collisions between bison and vehicles on the highway in recent years.

The study relied on information preserved in a dated core of sediment taken from the largest lake in the area to track lake surface changes over the last few centuries, before satellite imagery became available. Sediment cores record the history of changes to the lake and its surrounding area, based on the analysis of materials deposited over time at the lake bottom. The team recorded increases in chemical markers that are produced exclusively by land plants, tracking inundation of the surrounding landscape over the last ~20 years that is unprecedented in more than 200 years of history in the area.

“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” says Dr. Joshua Thienpont, co-lead author on the study, and a postdoctoral fellow at the University of Ottawa. Thienpont notes there are various mechanisms by which lakes can expand or decline with 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,” explains Dr. 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 and tuberculosis as well as forest fires.”

Read the study in Nature Communications.

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
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 inquiries:
Amélie Ferron-Craig
Media Relations Officer
University of Ottawa
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aferronc@uOttawa.ca