Why does the forest carbon balance fluctuate so much?
The fluctuation in the sink–source carbon balance of Canada’s managed forest from 1990 to 2005 (see question above) was closely associated with the area annually burned. In extreme fire years, like 1995, direct emissions from wildfires in the managed forest have represented up to 45% of Canada’s total greenhouse gas emissions. In Canada, wildfires started by natural phenomena such as lightning are responsible for about 85% of the area burned in the total forest (managed plus unmanaged forest). As well, since 1999, the mountain pine beetle infestation in western Canada has been increasing emissions as trees are killed and begin to decay. Harvesting had a fairly steady impact on the managed forest carbon balance; throughout most of the 1990–2005 period, the area harvested each year remained fairly stable.
