Greenhouse gases from boreal forests a threat

Warming temperatures could see trees rot instead of becoming peat

OTTAWA — The immense forests of Canada’s north, relied on as a natural way to soak up greenhouse gases, are threatening to become major emitters of these gases instead.

Canada has told the world for years that our forests help soak up carbon dioxide and store carbon. The argument is that this cancels out some emissions from our cars, homes and industries.

But this is already shifting in the boreal forests, covering three million square kilometres from Newfoundland to the Yukon.

A wide-ranging review of climate change in these forests says that dead trees will rot as the temperature rises instead of being stored as peat, releasing carbon dioxide and methane. Both are greenhouse gases. As well, a greater number of forest fires will release carbon dioxide.

“Large C (carbon) stocks have accumulated in the boreal because decomposition is limited by cold temperatures and often anoxic (low-oxygen) environments. Increases in temperatures and disturbance rates could result in a large net C source during the remainder of this century and beyond,” says the paper from Natural Resources Canada.

While not a sure bet, the shift is seen as having a strong chance, and would affect world levels of carbon dioxide.

This conclusion is just one element in five sweeping new studies of how climate change affects Canada’s three million square kilometres of boreal forest. Nine more are still to be published.

All come from Natural Resources Canada. Rather than presenting new research, they summarize the most current information available about boreal forests in Canada and elsewhere.

They are printed in Environmental Reviews, a science journal published in Ottawa by NRC Research Press.

Editor John Smol says these are “consequences of global warming that people often don’t think about, and these are all in our back yard.”

Smol said the package of reviews provides a picture of the boreal region that Parliament and forest managers will need to understand. The overview forecasts a rise of 2 C by 2050, and 4.5 C by 2100.