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How will climate change affect the location, frequency,
and intensity of fire in the boreal forest of the Northern Hemisphere?
Because the occurrence and behavior of fires are governed by weather,
and therefore climate, global circulation models (GCMs), are used
in order to answer this question. Several different GCMs were run
to obtain information about the climate conditions in the Canadian
boreal zone in an atmosphere containing from 500 to 600 parts per
million carbon dioxide (roughly the concentration of carbon dioxide
in the atmosphere in the next 50-100 years). In general, the results
from many separate model runs indicate that temperatures will be three
to four degrees Celsius warmer throughout the region, with precipitation
increasing in the eastern half of the Canadian boreal zone. These
results were then fed into fire models, which take into account climate
and weather data, vegetation characteristics, ecosystem dynamics,
the hydrologic cycle, soil characteristics, wind, etc. The fire models
give us a general picture of the fire regimes in an atmospheric of
doubled carbon dioxide. |
Temperature change in degrees Celsius for a doubling of CO2
http://www.climatechange.gc.ca/english/climate_change/maps.asp
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Models of future fire indicate that the eastern and western portions of Canada's boreal zone will experience divergent fire behavior under changing climate. In both areas, however, the existing fire regime shifted rapidly in response to climate warming and changes in precipitation (4). Because of the increase in precipitation in the east, fire frequency and intensity is projected to decline in this area. In the western half of the boreal zone, however, fire will become both more common and more intense; this change is driven by increasing mean temperatures and the associated lengthening of the growing season. From this point on, all discussion will address changes to the fire regime in the western portion of the Canadian boreal forest. Overall, fire will become more widespread and more intense as climate warms. The fire season will increase by approximately 28 days, extending into March and September, and a greater portion of the land area will be under extreme fire danger during this time (5). Rising mean temperatures will also drive an increase in available biomass fuels (through both increased plant growth and stronger drying of organic detritus) and more frequent lightning strikes, resulting in an increase of fire ignitions of over 40 % (4, 5). The total area of land burned in western Canada will increase by over 75% (4,5). Additionally, larger stores of available fuel will cause fires to burn more intensely, reaching deeper below the surface layer. As fires are able to burn deeper into the soil profile, they will be able to oxidize more and more of the boreal zone's vast pool of stored organic soil carbon (6,8). |
http://fire.cfs.nrcan.gc.ca/research/climate_change/factsheets/factsheet1_e.htm
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