The 2002 fire season was one of the biggest of the past half-century. By the end of the year, fires had burned across 7.2 million acres, costing over $1 billion to fight. Almost uniformly, the fires of 2002 were characterized as catastrophic, but in fact, each fire was unique in character, offering individual lessons for the future. The following fact sheet is one of five analyses prepared by The Wilderness Society to better understand the causes and consequences of major 2002 wildfires.
Quick Facts
Location: Southwest Colorado. 5 miles north and northeast of Durango, CO.
Cause: Human.
Area: 73,391 acres.
Structures lost: 83.
Ownership: 94% San Juan National Forest (including portions of the Weminuche Wilderness. Landscape: The burned area is steep, ranging from river valley to subalpine, with a wide variety of forest cover types. Suppression Cost: $39.9 million approximately. |
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The Missionary Ridge Fire began on June 9, 2002, apparently from a carelessly discarded cigarette. The fire burned through Gambel oak, ponderosa pine, mixed conifer, aspen, and spruce-fir cover types mostly on National Forest System lands, though some Bureau of Land Management, Bureau of Reclamation, Colorado State, and private lands were also burned. On June 25, 2002, on the opposite side of the Animas Valley, the Valley fire began, eventually adding 439 acres of ponderosa pine on private lands to the Complex’s total.
Fire behavior, spread rates, and burn intensity associated with the Missionary Ridge Complex were the result of a complex interaction of factors. Extremely dry fuels resulting from long-term drought conditions and dense forests with high ladder fuels combined with topography and unstable atmospheric conditions to allow a surface fire to quickly turn into a plume-dominated blaze.
Rapid spread of the fire was largely influenced by weather and drought conditions
The fires occurred at the height of a record drought in southwestern Colorado, resulting from low winter snowpack and only 1.3 inches of precipitation since the beginning of the year. Fuel moisture and relative humidity were among the lowest ever recorded. Fire control operations did not make significant progress until fire behavior and spread moderated with cooler and more humid weather.
Large portions of the burn received some form of logging or other fuel treatment in the past
A large portion of the lower elevation ponderosa pine stands, much of which is private property, was heavily cut near the turn of the 20th century. Approximately 11,000 acres of the fire occurred on National Forest System lands approved as suitable for wood fiber production in the San Juan National Forest Land and Resources Management Plan. Much of this "suitable base" acreage has received past harvest and reforestation treatments, including clearcutting of spruce-fir and aspen forests, planting of lodgepole pine and Engelmann spruce in many of the spruce-fir clearcuts, and intermediate cutting in spruce-fir and mixed conifer stands. Many acres outside the present suitable base also received similar treatments, including prescribed burning of Gambel oak stands to improve forage for big game.
The effect of the fire on vegetation was highly variable
Different forest types naturally burn with different characteristic frequencies and intensities, or "fire regimes." The vegetation of the Missionary Ridge fire can be classified into five fire regimes according to the following scheme:
I: Low severity (non-lethal) with less than 35 years between fires (Ponderosa Pine, Warm-dry Mixed Conifer).
II: Stand replacing (lethal) with less than 35 years between fires (Mountain Grassland)
III: Mixed severity (patchy mortality) with fires every 35-200 years (Mountain Shrubland, Pinyon-Juniper Woodland)
IV: Stand replacing with fires every 35-200 years (Aspen, Cool-moist Mixed Conifer)
V: Stand replacing with more than 200 years between fires (Spruce-Fir)
Because of the variability in elevation and topography across the Missionary Ridge landscape, the vegetation within the fire was diverse, as was the effect of the fire on the vegetation. In a post-fire evaluation of the effect on vegetation, the Forest Service found that nine different vegetation types had experienced a mixture of high, moderate, low, or no effects as a result of the fire (Table 1).1
VEGETATION | FIRE
REGIME | HIGH
SEVERITY | MODERATE
SEVERITY | LOW
SEVERITY | UNBURNED | TOTAL |
Ponderosa Pine | I | 5.3% | 5.6% | 4.8% | 1.1% | 16.7% |
Warm-dry Mixed Conifer | I | 6.2% | 4.8% | 5.3% | 1.4% | 17.7% |
Mountain Grassland | II | 0.1% | 0.7% | 1.0% | 0.7% | 2.5% |
Pinyon-Juniper | III | 0.1% | 0.1% | 0.0% | 0.0% | 0.3% |
Mountain Shrubland | III | 0.8% | 1.7% | 0.5% | 0.1% | 3.2% |
Aspen | IV | 3.8% | 4.4% | 5.4% | 8.0% | 21.5% |
Cool-moist Mixed Conifer | IV | 6.5% | 5.7% | 9.6% | 5.1% | 26.9% |
Spruce-Fir | V | 1.4% | 1.4% | 4.3% | 3.8% | 11.0% |
Riparian | Variable | 0.0% | 0.0% | 0.1% | 0.1% | 0.2% |
| | 24.2% | 24.4% | 31.1% | 20.3% | 100.0% |
It can be seen from Table 1 that much of what burned with high or moderate severity was in vegetation types that naturally burn with high severity (e.g. Aspen, Cool-moist Mixed Conifer, Spruce-Fir) where high severity fire would not be expected to cause ecological damage. Ecological concern is justified only on the 21.9 percent of the fire where Ponderosa Pine and Warm-dry Mixed Conifer burned with uncharacteristic high or moderate severity.
For More Information
Footnotes
- Missionary Ridge Complex BAER report (http://www.fs.fed.us/r2/sanjuan/bulletin_board/baerreport.htm)
