Perspectives on carbon emissions from Canadian forest fires

How much carbon is released from Canadian forest fires? A recent analysis indicates that Canadian forest fires have released an average of 27 Mt (1012 g) of carbon annually over the past four decades (Amiro et al. 2001a). These emissions are caused by direct combustion. About an equal additional amount of carbon may also be lost through decomposition of fire-killed vegetation and a temporary decrease in the forest sink, although this amount is not well quantified. The carbon emissions were calculated based on the size of each fire, the dates over which it burned, and the fuel consumed based on the Canadian Forest Fire Behavior Prediction System (Forestry Canada 1992). The estimates are a product of the Canadian large-fire database, a geographically referenced data set of all fires greater than 200 ha in area, which includes information on the size of each fire and the start date (Stocks et al. 2002). The emissions vary widely among years ranging from 3 to 115 Mt carbon per year (Fig. 1). This is largely caused by the wide interannual variability in area burned, which ranged from 0.3 to 7.5 million ha/year. Across the country, an average of 1.3 kg of carbon is lost per m2 of burned area, but this varies from about 1 to 2 kg C/m2 on average among different ecozones.