Eco-warming called pervasive threat to key cold water fish in northern Ontario


TORONTO — Gradual warming due to climate change posts the most pervasive threat to a vital economic and cultural resource in one of the world’s last intact ecosystems: the fish that live in the icy waters of northern Ontario, new conservation research suggests.

In a recent report on their findings, researchers found warmer waters would make species such as brook trout, walleye, lake whitefish, and lake sturgeon more vulnerable to other threats such as habitat loss and fragmentation of watersheds and streams.

“As in many other places, the freshwater habitats of northern Ontario face a variety of threats, both natural and as a result of human activities,” according to the study from Wildlife Conservation Society Canada. “The largest single threat is climate change, which is occurring more rapidly in the north compared to the rest of Ontario.”

Ontario’s Far North contains some of the world’s largest undammed rivers. It is home to thousands of lakes and the largest wetland complex in North America. Its freshwater ecosystems support at least 50 species of fish, making it the largest area of high fish biodiversity in Canada, according to the report.

At the same time, its remoteness and sparse population — although home to about 40 Indigenous communities — has made it understudied even as the provincial government attempts to foster development, particularly in the mineral-rich area known as the Ring of Fire.

In an effort to fill in some of the knowledge gaps, the study is based on computer-assisted projections of what would happen to fish populations over the next 50 years in a region covering about 440,000 square kilometres based on high and low-development scenarios — admittedly “rough” models that nevertheless perform “remarkably well,” the researchers say.

“This is really ground-breaking work in many ways, both in its focus on culturally important fish … and the development of new modelling approaches with fisheries experts from across North America,” said Cheryl Chetkiewicz, a conservation scientist and one of the researchers.

A huge problem, the report concludes, is the short-term piecemeal approach to planning that fails to take into account the cumulative impacts of environmental stressors due to development when combined with climate change. Continuing down this path, Chetkiewicz said, could have “devastating consequences” for both fish and people in the region.

According to the study, climate change will exacerbate potential problems caused by fishing, industrial forestry, mining and mineral exploration, hydroelectric development, and new infrastructure such as roads and transmission lines.

Study modelling predicts substantial warming in the Far North over the next 50 years — putting walleye, lake sturgeon, lake whitefish, and brook trout at risk.

“All four species exhibited increased risk over the simulation period,” the study finds. “Overall, climate change was the most influential driver of risk to freshwater fish, followed by hydroelectric dams. Climate change consistently exacerbated the effects of land use and natural disturbance changes.”

The study makes several recommendations aimed at mitigating negative impacts on the fish without shutting down development in the region. Key among them is to assess those impacts over time and in combination — based on solid empirical data.

“While we cannot be absolutely certain about future conditions, we can examine plausible scenarios based on current information and informed assumptions,” the study states. “This allows potential environmental impacts to be understood and evaluated today with a focus on risk management — before options for land-use management and conservation have been foreclosed.”

Other recommendations include prioritizing areas for freshwater fish research and protection, and the need for a regional and strategic approach to assessing the impact of hydroelectric development.

Colin Perkel, The Canadian Press


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