Issue 56
August 11, 2005

Weather Trivia

 You Asked us

Environment Canada's knowledgeable specialists answer questions about wildlife, air pollution, water, weather, climate change and other aspects of the environment.

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How many tonnes of greenhouse gases are created by a forest fire per hectare?  Jeff Morrice, Calgary, Alberta

Direct carbon emissions are a product of combusted fuel during a fire. From an average fire in Canada, 1.3 kilograms (kg) per square metre of carbon is released to the atmosphere. This is equivalent to 13 000 kg (13 tonnes) of carbon per hectare. Fires release carbon dioxide (CO₂), carbon monoxide (CO), methane (CH₄), nitrogen oxides and other particulate matter, but 80 to 90 per cent of the carbon released becomes carbon dioxide. On average in Canada, 2.6 million hectares of land are burned each year, releasing 34 million tonnes of carbon dioxide.

Although fossil fuel burning is the biggest contributor to increasing atmospheric greenhouse gases, emissions from a forest burning is also a major source of greenhouse gases. Emissions from such fires represent about 18 per cent of current Canadian carbon dioxide emissions.

Post-fire effects can cause additional losses of carbon and changes to the forest sink condition. Carbon sinks, areas where more carbon is stored than released, help stabilize atmospheric carbon dioxide through natural absorption and storage. Forests play an important role in this process. When forests burn, carbon sinks burn as well, so carbon dioxide does not get stored by the forest and is released into the atmosphere. Decomposing organic material left in the wake of the fire also releases carbon dioxide.

However, fire plays an important role in most forest ecosystems in Canada, helping to maintain the health and diversity of a forest.