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In this study, we used wildfire simulations and building location data to evaluate community wildfire exposure and identify plausible disasters that are not based on typical mean-based statistical approaches. We compared the location and magnitude of simulated disasters to historical disasters (1984–2020) in order to characterize plausible surprises which could inform future wildfire risk reduction planning. Results indicate that nearly half of communities are vulnerable to a future disaster, that the magnitude of plausible disasters exceeds any recent historical events, and that ignitions on private land are most likely to result in very high community exposure. Our methods, in combination with more typical actuarial characterizations, provide a way to support investment in and communication with communities exposed to low-probability, high-consequence wildfires.
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Despite the increasing challenges wildfires are posing around the globe, and the flourishing production of high quality wildfire scientific knowledge, the ability of fire science to impact knowledge on the ground, for people, society, economy, and the environment, in a way that facilitates change in the current wildfire management system has been limited. We believe that one reason for this limited impact is due to the fragmentation of this scientific knowledge. Therefore, we propose a Translational Wildfire Science (TWFS) as a new field of knowledge that captures the comprehensive dynamics of wildfire events, that provides information relevant, useful, and accessible to practitioners and citizens, and that facilitates the transfer of scientific knowledge into practice. The foundations of TWFS, including the main principles, the overarching characteristics, and the approach of a TWFS scientist, are presented. Finally, the next steps to be undertaken to consolidate TWFS as a new scientific field are identified.
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Here, we advance the practice of using satellite-derived maps with four guiding principles designed to increase end user confidence and thereby accessibility of these data for decision-making.
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Sage-grouse increasingly selected areas closer to conifer removals and were 26% more likely to use removal areas each year after removal. Sage-grouse were most likely to select areas where conifer cover had been reduced by ≤10%. The proportion of available locations having a high relative probability of use increased from 5% to 31% between 2011 and 2017 in the treatment area and locations with the lowest relative probability of use decreased from 57% to 21% over the same period. Dynamics in relative probability of use at available locations in the control area were stochastic or stable and did not demonstrate clear temporal trends relative to the treatment area. Targeted conifer removal is an effective tool for increasing usable space for sage-grouse during the breeding season and for restoring landscapes affected by conifer expansion.
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Multivariate analyses and ANOVAs showed that in invasion stages where native shrub and perennial grass and forb communities were replaced by annual grass-dominated communities, the ecosystem lost more soil N and C in wet years. Path analysis showed that high water availability led to higher herbaceous cover in all invasion stages. In stages with native shrubs and perennial grasses, higher perennial grass cover was associated with increased soil C and N, while in annual-dominated stages, higher annual grass cover was associated with losses of soil C and N. Also, soil total C and C:N ratios were more homogeneous in annual-dominated invasion stages as indicated by within-site standard deviations. Loss of native shrubs and perennial grasses and forbs coupled with annual grass invasion may lead to long-term declines in soil N and C and hamper restoration efforts. Restoration strategies that use innovative techniques and novel species to address increasing temperatures and ICV and emphasize maintaining plant community structure—shrubs, grasses, and forbs—will allow sagebrush ecosystems to maintain C sequestration, soil fertility, and soil heterogeneity.
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This report assesses recent forest disturbance in the Western United States and discusses implications for sustainability. Individual chapters focus on fire, drought, insects, disease, invasive plants, and socioeconomic impacts. Disturbance data came from a variety of sources, including the Forest Inventory and Analysis program, Forest Health Protection, and the National Interagency Fire Center. Disturbance trends with the potential to affect forest sustainability include alterations in fire regimes, periods of drought in some parts of the region, and increases in invasive plants, insects, and disease. Climate affects most disturbance processes, particularly drought, fire, and biotic disturbances, and climate change is expected to continue to affect disturbance processes in various ways and degrees.
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Based on our review of the scientific evidence, a range of proactive management actions are justified and necessary to keep pace with changing climatic and wildfire regimes and declining forest heterogeneity after severe wildfires. Science-based adaptation options include the use of managed wildfire, prescribed burning, and coupled mechanical thinning and prescribed burning as is consistent with land management allocations and forest conditions. Although some current models of fire management in wNA are averse to short-term risks and uncertainties, the long-term environmental, social, and cultural consequences of wildfire management primarily grounded in fire suppression are well documented, highlighting an urgency to invest in intentional forest management and restoration of active fire regimes.
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Relative to unburned sites, we found that burned sites had lower stem density and had lower proportions of recently dead trees (for stems ≤47.5 cm dbh) that presumably died during the drought. Differences in recent tree mortality among burned and unburned sites held for both fir (white fir and red fir) and pine (sugar pine and ponderosa pine) species. Unlike earlier results, models of individual tree mortality probability supported an interaction between plot burn status and tree size, suggesting the effect of prescribed fire was limited to small trees. We consider differences with other recent results and discuss potential management implications including trade-offs between large tree mortality following prescribed fire and increased drought resistance.
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This study demonstrates the importance of episodic periods of favorable weather for long-term plant population recovery following disturbance. Management strategies that increase opportunities for seed availability to coincide with favorable weather conditions, such as retaining unburned patches or repeated seeding treatments, can improve restoration outcomes in high-priority areas.
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During the first years after removal of perennial grasses and forbs, there was an increase in soil water availability in spring at 13–30 cm soil depth that was associated with sagebrush establishment, particularly at upper elevations. In subsequent years, sagebrush continued to dominate even though little difference in soil water availability existed between disturbed and undisturbed plots. This indicates that quickly establishing sagebrush preempted resources and reduced perennial herb recovery. Resource preemption after disturbance will likely be a major driver of plant succession in the future as in the past. Species that establish best under future warmer and drier conditions are most likely to dominate after disturbance. A negative correlation (r2 = 0.34) between the standard deviation of annual spring soil water availability and perennial vegetation cover, which helps resist annual grass invasion, supports the hypothesis that greater resource fluctuation is associated with greater plant community invasibility. Current responses to fire and loss of native plant cover across elevational gradients can indicate future responses under a warmer and drier climate.