Date of this Version
Joint Fire Science Program Final Project Report for (JFSP Project # 06-3-3-11)
The fire situation in the United States is well documented with a growing prevalence of larger and more intense fires that have increasingly severe consequences for affected ecosystems and human health and well being. Increasingly, fuels management has been put forth and implemented as part of an integral strategy for limiting extreme fire behavior, reducing the area affected by wildfire and minimizing the economic and ecological costs of fires. Communities and land management agencies are now treating millions of acres of wildland fuels annually and an ever-increasing number of wildfires are burning treated lands. Although the scientific premises of various fuels treatments are well established, their actual performance and combined effectiveness on landscapes have been difficult to assess at the national level. Wildland fire managers and policy makers require specific guidance about the effectiveness of various treatments types, ages (time since treatment), sizes, spatial configurations and their placement on the landscape to support strategic decisions about fuel management policy, planning, implementation and maintenance. To address this, here we provide preliminary assessments of the site level effectiveness on fire severity of many thousands of fuels treatments that were involved in 651 wildfires and detailed landscape-level assessment of the combined effects of 3,489 fuels treatments on the probabilistic spread of 85 large wildfires using >3,000 FARSITE wildfire simulations based on LANDFIRE datasets and ancillary fuels treatment and weather information. The methods for both the assessment of local treatment-related severity (Wimberly et al. 2009) and the stochastic modeling of fire spread (Cochrane et al. 2012) have been established in the peer-reviewed literature, and the project’s research also has resulted in four completed masters theses (Arnold 2009, Pabst 2010, Moran 2011, Timilsina 2011). Important findings from the research include quantifiable differences in the performance of treatment types (thinning, prescribed burning with or without thinning, mastication) within different ecoprovinces across the country. Although most treatment types are being tried to varying degree in most regions, it is clear that certain treatments function well while others work poorly, if at all, but the optimal choices differ by region. We provide management recommendations for regional optimization of fuels treatment selection. This information should help in the development of region-specific land management plans and also provide preliminary life cycle estimation for the performance over time of different treatment types. Using the stochastic modeling studies, we show that fuels treatments act to both increase and decrease burning risk across different portions of landscapes in all wildfires. In general, thinning leads to increased surface rates of spread due to exposure and greater cover of light fuels, while treatments also act to reduce long distance spread via spotting through their tendency to limit or prevent crowning of fires (Cochrane et al. 2012). The net effect of all treatments for the 56 wildfires with statistically significant changes in treatment-related fire extents averaged a 7% reduction in burned area. However, this simple average is an inappropriate measure, as it masks a near dichotomy between wildfires experiencing significant reductions and those with significant increases in area burned due to treatments. In wildfires that had significantly reduced burned area, the average decrease in size was 25%, while wildfires that were significantly increased expanded by an average of 28%. In wildfires significantly decreased in size, for every hectare burned because of the fuels treatments, just over 18 hectares were prevented from burning. Conversely, for significantly increased wildfires, every hectare of fire prevention resulted in nearly 7 hectares of additional burning because of the fuels treatments. We provide suggestions for future research to better understand and implement these findings.
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