More Like this

1. Examining the existing definitions of wildland‐urban interface for California

   https://doi.org/10.1002/ecs2.4306  

   Kumar, Mukesh ; Li, Shu ; Nguyen, Phu ; Banerjee, Tirtha ( December 2022 , Ecosphere)

   Past studies reported a drastic growth in the wildland–urban interface (WUI), the location where man‐made structures meet or overlap wildland vegetation. Fighting fire is difficult in the WUI due to the combination of wildland and structural fuels, and therefore, WUI areas are characterized by frequent damage and loss of structures from wildfires. Recent wildland fire policy has targeted fire prevention, evacuation planning, fuel treatment, and home hardening in WUI areas. Therefore, it is important to understand the occurrence of wildfire events relative to the location of the WUI. In this work, we have reported the occurrences of wildfires with respect to the WUI and quantified how much of the WUI is on complex topography in California, which intensifies fire behavior and complicates fire suppression. We have additionally analyzed the relative importance of WUI‐related parameters, such as housing density, vegetation density, and distance to wildfires, as well as topographic factors, such as slope, elevation, aspect, and surface roughness, on the occurrence of large and small wildfires and the burned area of large wildfires near the WUI. We found that a very small percentage of wildfire ignition points and large wildfire‐burned areas (>400 ha or 1000 acres) were located in the WUI areas. A small percentage of large wildfires were encountered in WUI (3%), and the WUI area accounted for only 4% of the area burned, which increased to 5% and 56%, respectively, outside WUI (5‐km buffer from WUI). Similarly, 66% of fires ignited outside WUI, whereas only 3.6% ignited within WUI. Results from this study have implications for fuel management and infrastructure hardening, as well as for fire suppression and community response.

    

   more » « less
2. Wildfire Risk in the Complex Terrain of the Santa Barbara Wildland–Urban Interface during Extreme Winds

   https://doi.org/10.3390/fire5050138  

   Zigner, Katelyn ; Carvalho, Leila M. ; Jones, Charles ; Benoit, John ; Duine, Gert-Jan ; Roberts, Dar ; Fujioka, Francis ; Moritz, Max ; Elmquist, Nic ; Hazard, Rob ( October 2022 , Fire)

   Each year, wildfires ravage the western U.S. and change the lives of millions of inhabitants. Situated in southern California, coastal Santa Barbara has witnessed devastating wildfires in the past decade, with nearly all ignitions started by humans. Therefore, estimating the risk imposed by unplanned ignitions in this fire-prone region will further increase resilience toward wildfires. Currently, a fire-risk map does not exist in this region. The main objective of this study is to provide a spatial analysis of regions at high risk of fast wildfire spread, particularly in the first two hours, considering varying scenarios of ignition locations and atmospheric conditions. To achieve this goal, multiple wildfire simulations were conducted using the FARSITE fire spread model with three ignition modeling methods and three wind scenarios. The first ignition method considers ignitions randomly distributed in 500 m buffers around previously observed ignition sites. Since these ignitions are mainly clustered around roads and trails, the second method considers a 50 m buffer around this built infrastructure, with ignition points randomly sampled from within this buffer. The third method assumes a Euclidean distance decay of ignition probability around roads and trails up to 1000 m, where the probability of selection linearly decreases further from the transportation paths. The ignition modeling methods were then employed in wildfire simulations with varying wind scenarios representing the climatological wind pattern and strong, downslope wind events. A large number of modeled ignitions were located near the major-exit highway running north–south (HWY 154), resulting in more simulated wildfires burning in that region. This could impact evacuation route planning and resource allocation under climatological wind conditions. The simulated fire areas were smaller, and the wildfires did not spread far from the ignition locations. In contrast, wildfires ignited during strong, northerly winds quickly spread into the wildland–urban interface (WUI) toward suburban and urban areas.

    

   more » « less
3. Effects of plant hydraulic traits on the flammability of live fine canopy fuels

   https://doi.org/10.1111/1365-2435.13771  

   Scarff, Fiona R. ; Lenz, Tanja ; Richards, Anna E. ; Zanne, Amy E. ; Wright, Ian J. ; Westoby, Mark ; McCulloh, ed., Katherine ( February 2021 , Functional Ecology)

   Plant species vary in how they regulate moisture and this has implications for their flammability during wildfires. We explored how fuel moisture is shaped by variation within five hydraulic traits: saturated moisture content, cell wall rigidity, cell solute potential, symplastic water fraction and tissue capacitance.

   Using pressure–volume curves, we measured these hydraulic traits in twigs and distal shoots (i.e. twigs + leaves) in 62 plant species across four wooded communities in south‐eastern Australia. Moisture content of fine fuels was then estimated for circumstances typical of fire weather. These projections were made assuming that under the hot, dry, windy conditions typical of large wildfires, leaves and fine twigs would function at internal water pressures close to wilting point (i.e. turgor loss point, TLP). The effect of different moisture contents at TLP on ignition time was then modelled using a fully mechanistic, finite element model of biomass ignition based on standard principles of physical chemistry.

   We also measured predawn water potential, an indication of plant access to soil water that is influenced by root architecture. These data were used to model how root traits influence fuel moisture and ignition time.

   Most variation among species in fuel moisture under fire weather conditions arose from differences in saturated moisture content (3.4‐ to 3.6‐fold variation). Twig capacitance was also an important driver of fuel moisture under these weather conditions (1.9‐ to 2.2‐fold variation in moisture content). A suite of other leaf and root traits influencing how much shoots dry out as they approach wilting point each contributed 1.0‐ to 1.6‐fold variation in projected fuel moisture during fire weather. Fuel moisture variation in turn drove variation in flammability by modifying predicted ignition time.

   Two main life‐history types in fire‐prone habitats are obligate seeders and resprouters. There were no significant differences between these species groups in estimated fuel moisture during fire weather, nor in any measured hydraulic traits.

   Live fuel moisture is an important determinant of wildfire activity. Our data show that variation in tissue saturated moisture content among co‐occurring species represents an important ecological store of variation in flammability in the study communities.

   A freePlain Language Summarycan be found within the Supporting Information of this article.

    

   more » « less
4. Assessing the economic trade‐offs between prevention and suppression of forest fires

   https://doi.org/10.1111/nrm.12159  

   Heines, Betsy ; Lenhart, Suzanne ; Sims, Charles ( January 2018 , Natural Resource Modeling)

   The number of large‐scale, high‐severity forest fires occurring in the United States is increasing, as is the cost to suppress these fires. We use a technique developed by William Reed to incorporate the stochasticity of the time of a forest fire into our optimal control problem. Using this optimal control problem, we explore the trade‐offs between prevention management spending and suppression spending, along with the overall economic viability of prevention management spending. Our goal is to determine the optimal prevention management spending rate and the optimal suppression spending, which maximizes the expected value of a forest. We develop a parameter set reflecting the 2011 Las Conchas Fire and numerically solve our optimal control problem. Furthermore, we adapt this problem to simulate a sequence of fires and corresponding controls. Overall, our results support the conclusion that the prevention management efforts offset rising suppression costs and increase the value of a forest.

   Increasing wildfire size and increasing federal suppression costs have prompted investigations into alternative methods to help prevent and manage large wildfires.

   Fire prevention lowers the risk of experiencing large fire events, but investment in fire prevention is risky because its benefits are realized at an unknown time in the future.

   Results illustrate that there are real economic costs associated with using funding directed to fire prevention to fund immediate fire suppression.

   In our work with unknown fire sequences, we observe an 88% reduction in suppression spending on average with fire prevention, and a 55% reduction in spending overall.

    

   more » « less
5. Adapting western North American forests to climate change and wildfires: ten common questions

   https://doi.org/10.1002/eap.2433  

   Prichard, Susan J. ; Hessburg, Paul F. ; Hagmann, R. Keala ; Povak, Nicholas A. ; Dobrowski, Solomon Z. ; Hurteau, Matthew D. ; Kane, Van R. ; Keane, Robert E. ; Kobziar, Leda N. ; Kolden, Crystal A. ; et al ( August 2021 , Ecological Applications)

   null (Ed.)

   We review science-based adaptation strategies for western North American (wNA) forests that include restoring active fire regimes and fostering resilient structure and composition of forested landscapes. As part of the review, we address common questions associated with climate adaptation and realignment treatments that run counter to a broad consensus in the literature. These include: (1) Are the effects of fire exclusion overstated? If so, are treatments unwarranted and even counterproductive? (2) Is forest thinning alone sufficient to mitigate wildfire hazard? (3) Can forest thinning and prescribed burning solve the problem? (4) Should active forest management, including forest thinning, be concentrated in the wildland urban interface (WUI)? (5) Can wildfires on their own do the work of fuel treatments? (6) Is the primary objective of fuel reduction treatments to assist in future firefighting response and containment? (7) Do fuel treatments work under extreme fire weather? (8) Is the scale of the problem too great – can we ever catch up? (9) Will planting more trees mitigate climate change in wNA forests? and (10) Is post-fire management needed or even ecologically justified? 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 successional 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. 

   more » « less