Forest fire
From BWCAWiki
Forest fires, or wildfires, have played a significant role in the ecosystem of the Boundary Waters Canoe Area Wilderness for thousands of years. Prior to fire suppression efforts in the 20th Century, many parts of the BWCAW experienced stand-replacing fires every 10 to 50 years.
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Conditions
Wild fires usually occur in two distinct seasons in the Boundary Waters region. One begins in May and continues through June when vegetation “greens up.” Summer rainstorms in most years drop enough moisture to keep fire danger low. A second fire season starts with a drying trend in July and continues into October until first snowfall. Large wildfires usually occur in the fall fire season after an extended summer drought.
Some of the largest fires occurred after a very specific weather combination:
- Three to eight months of below-average precipitation
- Above-normal temperatures for at least ten days
- Humidity levels below 30 percent
- Winds of at least 10 to 15 mph
Hudson Bay Highs
Some of Minnesota’s largest fires have occurred in May and June. During that time, a phenomenon called a Hudson Bay High contributes to the high fire potential. A large area of cool, dry air builds up west and southwest of Hudson Bay, including the BWCAW. This air mass stalls over the region and produces many consecutive days of dry weather, which dries out the previous season’s fine fuels. The temperature increases and the stage is set for a fire event.
Catastrophic fire
Under certain conditions, fires tend to spread into the treetops and can move quickly across lakes and waterways. Historically, larger fire events have burned in forest stands containing spruce, balsam fir, aspen, birch, and jack pine. Balsam fir burns intensely, even when green. Several years of spruce budworm infestation prior to the 1999 Fourth of July Blowdown left large areas of dead and dying balsam fir, increasing the amount of fine fuels.
Management
During much of the 20th century, the goal of the Forest Service was complete suppression of all wildfires, often in order to preserve scenic qualities and lumber. This long-term fire suppression led to an increase of fire danger in some areas due to an increase in fuels. With a growing understanding of fire's natural role in forest ecology, the management of forest fires has changed.
Fires that are started by people or that threaten human lives or property continue to be vigorously suppressed, but natural fires that are not a significant hazard may be allowed to burn. This management style is referred to as a Wildland Fire Use, and is designed to reduce the cost of suppression as well to re-introduce natural fire into the ecosystem.
References
- Superior National Forest storm recovery website
- Heinselman, Miron. The Boundary Waters Wilderness Ecosystem, University of Minnesota Press, 1996. ISBN 0816628041
- Wildland Fire Use: An Essential Fire Management Tool (pdf), The Wilderness Society, 2004.
- This article incorporates text from the Superior National Forest storm recovery website, a public domain work of the United States Government.
See also
- Fourth of July Blowdown
- list of historical forest fires in the BWCAW by name
- list of forest fires in the BWCAW by date
