Resources At Risk: A Forest Fire-Based Hazard/Risk Assessment

• Published in: Integrated Assessment of Ecosystem Health pp. 271 - 284
• Main Authors: Burton, Timothy A., Dethe, Deirdre M., Erickson, John R., Frost, Joseph P., Morelan, Lynette Z., Rush, William R., Thornton, John L., Weiland, Cydney A., Neuenschwander, Leon F.
• Format: Book Chapter
• Language: English
• Published: CRC Press 2000
• Edition: 1
• Subjects: Hazard Rating; Bull Trout; Risk Assessment Links; fire regime; Ponderosa Pine Forest; Fire Ignition; Fire Sensitive Specie; LANDSAT Satellite Imagery; Chinook Salmon; Amplitude Time Series; Mixed Conifer Stand; late-successional habitat; California Black Oak; Cover Types; DCA Axis; RAPD Pattern; Proportional Analysis; Fog Collector; Sedimentation Potential; Forested Vegetation; sedimentation; Ponderosa Pine; Idaho Batholith; Altered Fire Regimes; Pole Sized Trees; Grand Fir; historical range of variability
• ISBN: 1566704537; 9781566704533
• DOI: 10.1201/9780429104404-15

On the 2.6-million-acre Boise National Forest (NF) in southwestern Idaho, wildfires have burned nearly 50% of the ponderosa pine forest over the last nine years. Much of this forest has burned with uncharacteristic intensity. The historic fire regime — one marked by nonlethal surface fires that removed dense understories of saplings or pole-sized trees and increased nutrient availability — has changed. The altered fire regime now results in severe, stand-replacing fires that kill large areas of forest and return them to grass- and shrub-dominated landscapes. Preliminary analysis 272 shows the remaining ponderosa pine on the Boise NF could be fragmented, with only isolated patches remaining, within the next 20 years by severe, stand-replacing wildfire. In partnership with the University of Idaho, the Boise NF has developed a Geographic Information System (GIS)-based “hazard/risk assessment” model that estimates where the forest ecosystems are most at risk to severe, large wildfires burning in conditions outside the historical range of variability (HRV) and evaluates important resources at risk to these fires. The hazard/risk assessment links five submodels. When the submodels are linked, the assessment estimates where severe, large wildfires burning in conditions outside HRV would severely deplete late-successional habitat needed by old-growth-dependent and other wildlife species, accelerate naturally high levels of erosion and sedimentation, and increase the likelihood that identified fish populations will not persist. The hazard/risk assessment is most appropriately used to approximate the relative size and extent of the fire-based ecosystem problem on the forest— the result of excluding fire from fire-adapted ponderosa pine ecosystems. It is intended to “nest” between the large-scale analysis undertaken as part of the Upper Columbia River Basin assessment and the site-specific evaluation performed for landscape- and project-level analysis. The assessment estimates on a relative, forestwide basis where forest ecosystems are most at risk to severe, large wildfires burning in conditions outside the historical range of variability (HRV) and evaluates important resources at risk to these fires. The hazard/risk assessment links five submodels — forested vegetation outside HRV, fire ignition, wildlife habitat persistence, watershed hazard, and fisheries condition. A scale was then used to express relative risk of fire ignition on a 1 to 5 scales. The hazard/risk assessment represents an important addition to the “analysis toolbox” available to land managers. The assessment’s use of Geographic Information System (GIS) as the ''modeling medium” is particularly appropriate in examining landscape conditions because GIS can analyze large amounts of data and sophisticated relationships across extensive areas. The hazard/risk assessment may then support the adjustment in the Boise National Forest’s management course needed to incorporate different types of timber harvest and more extensive use of prescribed fire than traditionally undertaken.