A new study suggests Canada's boreal forest may be releasing more greenhouse gases than it absorbs.
The study -- by Tom Gower of the University of Wisconsin -- will be published tomorrow in the journal Nature.
Gower studied a one million-square-kilometre stretch of forest around Thompson, Manitoba, focusing on how carbon moved between the forest and the atmosphere.
He used computer modelling and forestry records to suggest how that cycle has changed since the 1950s.
He says this forest has gone from a carbon sink to a carbon source, meaning it's now contributing to the amount of carbon dioxide in the atmosphere.
Trees absorb carbon dioxide as they grow and release it when they burn or decompose.
Gower says the cause of the change is a rise in the number of forest fires.
Many climate change models say the phenomenon can lead to an increase in forest fires because it creates hotter and drier conditions.
