Research and Publications
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Although previous studies have documented social inequalities in the distribution of wildfires and their adverse impacts, spatial statistical approaches have rarely been applied to examine social vulnerability to wildfire risk. We demonstrate how local indicators of spatial association (LISA) can be implemented to identify census tracts in the US where high wildfire risk and high social vulnerability intersect spatially and key characteristics of social vulnerability in these locations. Tracts are classified into relevant spatial clusters based on bivariate LISA to analyze the relationship between share of properties at risk of wildfire (2022) and the Centers for Disease Control and Prevention (CDC)’s Social Vulnerability Index (2022), the ‘High–High’ cluster representing tracts at the intersection of high wildfire risk and high social vulnerability. High tracts are located mainly in western and southern states, and characterized by disproportionately higher percentages of American Indian and Hispanic individuals and mobile homes. Several socially vulnerable groups are significantly over-represented in areas vulnerable to wildfire risk and should be prioritized for further investigation and mitigation. Bivariate LISA can provide important place-based insights on the intersection of wildfire risk and social vulnerability, and inform spatially precise interventions that address both biophysical and social dimensions of wildfires.
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Rapid surveying provided nuanced, event-based insights into how households perceived individual prescribed fires, particularly related to air quality, risk, and access to information sources. We found that the success of these pilot efforts lay in co-production of survey content and administration with partners responsible for each prescribed fire, allowing administrative flexibility, additional social and planning context, and improved applicability of resultant recommendations. This article provides a template for other researcher-practitioner teams interested in developing social science research focused on rapid surveying, studying individual prescribed fires, or investigating other fire- or forest-related management activities internationally.
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Amid rising wildfire risk, western U.S. states face an urgent need to protect fire-exposed communities. With limited
time and money to act, they must go beyond fire suppression activities and implement proven mitigation measures
with verifiable outcomes.
This paper outlines a risk-based framework guiding states to focus their efforts where they are more likely to see
results: the built environment, particularly existing structures and surrounding vegetation, and electricity infrastructure.
The framework consists of six steps:
- Inventory the universe at risk.
- Establish metrics for quantifying risks and damages.
- Determine the key physical risks to mitigate and the appropriate actions needed to address each of them.
- Assess the cost of mitigations and potential funding sources.
- Secure stakeholder buy-in.
- Create an action plan prioritizing mitigation methods and targets.
State leaders are likely to face many obstacles when pursuing wildfire mitigation, including consumer resistance
to change, misconceptions about risk, and concerns about funding. This framework helps stakeholders anticipate
challenges and mobilize populations to adopt the necessary steps that will reduce wildfire risk, improve insurability,
and lead to sustainable communities.
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Our study demonstrates that invasive annual grasses are rapidly spreading across the study area regardless of prescribed fire. Low severity prescribed fire may not exacerbate the invasion of some annual grasses in forested areas and sagebrush patches where the canopy cover is already open. However, burning in sagebrush patches may have negative effects on important non-forest ecosystems when burning results in the loss of fire-sensitive species. This information can help aid decision making and improve species-specific management and treatment effectiveness in dry forest landscapes.
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Although the modern wildfire crisis is characterized by large, severe wildfires, historical fire regimes also included extensive fires. On an Arizona landscape, the sizes of several historical fires were on par with the largest wildfire on record. Similar historical precedent of large fires is likely true elsewhere in dry conifer forests of western North America. These findings underscore that future wildfire events could be even larger, and likely more severe, as fuels accumulate and the climate grows warmer and drier. Forest restoration aimed at reestablishing characteristic disturbance regimes, including frequent, large, low-severity fires, could be used to assist recovery of these ecosystems resulting from the cumulative fire deficit.
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Contemporary North American wildfires exhibit increasingly erratic intraday burning, posing immediate operational and socioeconomic challenges. Here, we show that climate-driven weakening of day-night (diurnal) weather constraints extends and intensifies burning hours, a key mechanism behind broader fire regime transformations. Analyzing hourly geostationary satellite observations for ~9000 fires (>200 hectares; 2017–2023), we found western mountains and boreal forests experienced the longest active burning hours, with approximately one-third of active days exceeding 12 hours. About 60% of fires reached peak intensity within 24 hours of detection, while 14% of active days peaked at night. On the basis of fire weather, annual potential burning hours were estimated to rise 36% over 1975–2024, with pronounced increases in western regions and spring/fall (48 to 57%). Regions with significant changes gained 26 more potential active days annually and 1.2 additional potential burning hours daily, while extreme days (≥12 or 24 potential burning hours) rose 81 to 233% in fire-prone biomes. Future management requires adaptation to wildfires that increasingly defy diurnal norms.
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Seeding across two years was beneficial as 2021–2022 was warm and dry (less growth) and 2022–2023 was cold and wet (more growth). The perennial seed mix of forbs, grasses, and shrubs used included nine
dryland species. The forbs were most successful, with the best results in the high seeding rate during the cold, wet year. Unexpectedly, the perennial shrubs and grasses hardly germinated. Researchers suspect
perhaps the commercially grown seeds were not adapted to the Reno climate, or there was not enough rainfall. Bethedging like this with high rates of annual seedling, that include different plant groups, and across multiple years, could be helpful for landscapes with unpredictable interannual weather patterns.
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Aspens impede fire spread
- The study found that, as the percentage of aspen cover increased in a burned patch, the daily area burned and maximum linear spread both decreased. This effect increased as the percentage of aspen cover increased. For example, when aspen cover within a daily burn patch was less than 10 percent, the mean burned patch size was 1112 ± 84 ha/day. However, when aspen cover exceeded 25 percent, the mean daily burned patch size averaged 368 ± 43 ha/day. The researchers found similar effects for linear spread.
- These effects remained consistent relative to other vegetation types regardless of weather or climate. So, while particularly dry or windy conditions cause all vegetation types to burn more, aspen stands still burn at a lower rate than conifer stands. Aspens influence fire perimeters
- Aspens were also disproportionally represented at the perimeters of fires—they were 44 percent more abundant in perimeters than burn interiors. While aspen stands will not stop a fire dead in its tracks,
this result indicates that they can alter fire perimeters and potentially help slow fire spread.
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Land managers rely on best available information and relevant research for decision making, but matching the right information to the right questions can sometimes be challenging. To close this gap, when researchers and managers co-produce research from the beginning it is more likely research findings will have practical applications. Recently published work by USDA Forest Service researchers Chris Armatas, Teresa Hollingsworth, and colleagues working at the Aldo Leopold Wilderness Research Institute (ALWRI) in Missoula, Montana, reflects on both the benefits and tradeoffs of using a co-production approach for developing the ALWRI 10-year science agenda intended to help inform management of wilderness areas.
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From this review of fuel treatments and their impact on wildfire behavior, a few key points emerge that help answer the question: how much forest needs to be treated to restore resilience to dry conifer ecosystems?
A. When fuel treatments that combine thinning and prescribed fire cover from 10 to 40% of the landscape, fire behavior is significantly reduced. Research continues to support the ‘rule of thumb’ that an appropriate landscape goal is 20% in fuel treatments.
B. There is a positive and non-linear relationship (with diminishing returns beyond 30-40% of a total landscape) between fuel treatment effectiveness and the area treated, the size of individual treatments, and the spatial scale examined.
C. Treatment longevity varies but lasts about 10-20 years in southwestern dry conifer forests.
D. Landscape factors like vegetation and disturbance history strongly limit fire spread and should be incorporated in the treatment optimization.