A Greenpeace study released Thursday says cutting down trees in the boreal forest is exacerbating climate change by releasing stores of greenhouse gases trapped in soil and vegetation.
It also found that logging makes the forest more susceptible to insect outbreaks and wildfires which, if widespread, could cause a spike in greenhouse-gas emissions - the so-called "carbon bomb."
And the report says a warmer climate melts permafrost, releasing methane, a greenhouse gas 21 times more potent than carbon dioxide.
"The idea is that if the current trends continue ... what could happen is a sudden and massive release of greenhouse gases from the forest caused by a rapid outbreak of forest or peat fires," said Greenpeace's Christy Gerguson.
Canada's boreal forest stores 186 billion tonnes of carbon dioxide, the report says - about 27 times the world's yearly fossil-fuel emissions.
About 80 per cent of the carbon is stored in the soil as dead organic matter. The rest is stored in the forest's evergreen trees, moss and peat.
Older, untouched parts of the forest tend to store about three times more carbon than younger trees planted to replace logged ones, Gerguson said.
The boreal forest cuts a swath from Canada's Far North down to British Columbia and all the way across to the east coast. Most of the untouched parts of the boreal forest are located in the northern parts of Saskatchewan, Manitoba, Ontario and Quebec.
The federal government's national forestry database shows about 900,000 hectares boreal forest are logged each year.
There's some debate, however, about how much carbon is actually released through logging.
The Greenpeace report, a collaboration with University of Toronto researchers, says logging removes about 36 million tonnes of above-ground carbon annually.
That would be more yearly carbon emissions than all the passenger vehicles in Canada combined, according to an Environment Canada report on greenhouse gas sources.
But Natural Resources Canada released a report last year saying the bulk of carbon from logged trees stays in the forest after they're cut down, and the rest stays in logs that are taken to mills.
The Natural Resources report acknowledges that disturbing the soil during harvesting can release carbon dioxide, but generally "forest management practices do not result in substantial emissions."
A spokeswoman for Natural Resources Minister Gary Lunn did not respond to requests for comment.
Gerguson says forests continue emitting carbon up to 10 years after they've been logged as their remnants decompose and decay.
In some cases, she says, those emissions outpace the amount of carbon absorbed by young trees planted to replace the logged ones.
"Research is starting to show that the boreal forest is tipping from being a overall carbon sink to an overall carbon source," Gerguson said.
Greenpeace isn't suggesting Canada halt all logging of the boreal forest, she said. The group wants the untouched parts of the forest kept that way.
The head of the Forest Products Association of Canada agrees.
Avrim Lazar says the association, which represents wood, pulp and paper producers, has agreed there should be no logging in the untouched parts of the forest without adequate planning.
But he says stopping all logging is unrealistic.
"Shutting down logging of the boreal will create a huge market opportunity for the deforesters and the illegal loggers, and will have the perverse impact of trashing the boreal to increase climate change," Lazar said.
"But if people aren't buying it from Canadian places, they're just going to buy it from somewhere else. If you stop harvesting from the boreal, are people going to stop paper or wood? There's no evidence of that."
© 2008 The Canadian Press