Effects of accelerated wildfire on future fire regimes and implications for the United States federal fire policy
Alan A. Ager, USDA Forest Service, Rocky Mountain Research Station, Missoula Fire Sciences Laboratory
Ana M. G. Barros, Oregon State University, College of Forestry, Forest Ecosystems and Society
Haiganoush K. Preisler, USDA Forest Service, Pacific Southwest Research Station
Michelle A. Day, Oregon State University, College of Forestry, Forest Ecosystems and Society
Thomas A. Spies, USDA Forest Service, Pacific Northwest Research Station
John D. Bailey, Oregon State University, College of Forestry, Forest Engineering, Resources and Management
John P. Bolte, Oregon State University, College of Agricultural Sciences, Biological and Ecological Engineering
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Wildland fire suppression practices in the western United States are being widely scrutinized by policymakers and scientists as costs escalate and large fires increasingly affect social and ecological values. One potential solution is to change current fire suppression tactics to intentionally increase the area burned under conditions when risks are acceptable to managers and fires can be used to achieve long-term restoration goals in fire adapted forests. We conducted experiments with the Envision landscape model to simulate increased levels of wildfire over a 50-year period on a 1.2 million ha landscape in the eastern Cascades of Oregon, USA. We hypothesized that at some level of burned area fuels would limit the growth of new fires, and fire effects on the composition and structure of forests would eventually reduce future fire intensity and severity. We found that doubling current rates of wildfire resulted in detectable feedbacks in area burned and fire intensity. Area burned in a given simulation year was reduced about 18% per unit area burned in the prior five years averaged across all scenarios. The reduction in area burned was accompanied by substantially lower fire severity, and vegetation shifted to open forest and grass-shrub conditions at the expense of old growth habitat. Negative fire feedbacks were slightly moderated by longer-term positive feedbacks, in which the effect of prior area burned diminished during the simulation. We discuss trade-offs between managing fuels with wildfire versus prescribed fire and mechanical fuel treatments from a social and policy standpoint. The study provides a useful modeling framework to consider the potential value of fire feedbacks as part of overall land management strategies to build fire resilient landscapes and reduce wildfire risk to communities in the western U.S. The results are also relevant to prior climate-wildfire studies that did not consider fire feedbacks in projections of future wildfire activity.
Envision; forest landscape disturbance modeling; forest restoration; wildfire feedbacks; wildfire simulation; wildfire suppression policy
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