Wildland-urban Interface Research Articles

Global expansion of wildland-urban interface intensifies human exposure to wildfire risk in the 21st century.

Rapidly increasing human-nature interactions exacerbate the risk of exposure to wildfires for human society. The wildland-urban interface (WUI) represents the nexus of human-nature interactions, where the risk of exposure to natural hazards such as wildfire is most pronounced. However, quantifying long-term global WUI change and the corresponding driving factors at fine resolution remain challenging. Here, we mapped and analyzed the global WUI at 30-meter resolution in 2000, 2010, and 2020. Our analysis revealed that the global WUI expanded by 35.6% since 2000, reaching 1.93 million square kilometer in 2020. Notably, 85% of this growth occurred between 2010 and 2020. The increase in WUI was primarily driven by the unprecedented expansion of global urbanization, contributing an additional 589,914 square kilometer of WUI. In addition, the number of small fires occurring in WUI areas has increased substantially since 2010. These findings underscore the rising wildfire risk to human society and highlight the urgency of implementing tailored fire management strategies in WUI areas.

The economic and environmental impact of fire preventive strategies in the Mediterranean region

Fire behaviour in the Mediterranean region has been altered by climate change. In the last decade, not only has the occurrence of fires increased but also their virulence. This is primarily due to higher temperatures and the decrease in the rainfall, which have made forest ecosystems less able to withstand fires. It has also been observed that most wildfires are related directly or indirectly with human actions, and they usually occur in wildland-urban interface (WUI) areas. The current research focuses on the economic quantification of the benefits that fire preventive strategies could generate, demonstrating that it is worth it to invest in this kind of measures for both the environment and the society. This study shows the results of a pioneering project, called GUARDIAN, which is applied in a WUI area located at the east of Spain, with the aim of preventing and combating wildfires that could put at risk the life of 15,000 inhabitants while preserving the Natural Park of Túria and La Vallesa (Valencia-Spain). GUARDIAN is a multifaceted project that integrates recycled water, advanced technology, and ecological enhancements to create a more fire-resilient environment while educating and preparing the local community for fire-related challenges. The results of the current research intend to give a value to those benefits of the project that usually have not a market value and are difficult to measure, and due to that fact, they are not usually considered in the cost-benefit analysis. The methodology applied allows to compare in economic terms the environmental benefits of fire preventive measures implemented in the GUARDIAN project with the costs incurred by the measures developed. The environmental area protected by the project results in a value that ranges between €338,035,481 to €485,384,281. Accordingly, the methodology and results of this study are of great interest to public administrations, encouraging the implementation of fire preventive strategies.

How Are Weather and Climate Products and Decision Support Systems Used in Wildland Fire Decision Making in the US Southwest?

Abstract Wildland fire management is a challenging environment in which to utilize scientific information. Despite the robust information system that supports US wildland fire management, recent studies demonstrate that some data/information products and decision support tools available to that community are not being used to their full potential. In the US Southwest the convergence of climate change, past wildland fire policy, and an expanding wildland urban interface has increased pressure on wildland fire managers to use science-based information to improve management outcomes. This tension between the perceived need for more science in fire management and the practical challenges of using science to inform decisions led us to ask two basic questions: 1) How is information about weather and climate used in wildland fire management decision making in the Southwest? 2) How are decision support tools used in Southwest wildland fire management? We found: relatively few sources of weather and climate information are consulted by Southwest wildland fire managers; a small percentage of those sources are used to inform the specific decisions and tasks we asked about; decision support tools are commonly used to justify rather than inform decisions. We further found evidence that suggests that products and tools that are thoughtfully designed to fit within the specific information use environment of wildland fire management—rather than being produced in isolation from that environment—are more likely to be used and therefore have more impact than those that are produced in isolation from that environment.

Particulate Matter Production from Prescribed Burns in the Chicagoland Area

Prescribed burns are a land management tool currently used to aid in fire mitigation and to promote desired plant species and reduce undesired species, which are often invasive species. Currently, there is a public stigma surrounding the negative effects of prescribed burns, which impacts their use near residential areas. There are also particular challenges of conducting prescribed burns in urban and suburban areas. A better understanding of these relatively small-scale prescribed burns and their impact on atmospheric chemistry and air quality can allow for better communication with the public about their positive impacts, as well as for the acknowledgement and quantification of their drawbacks. This study considers the particulate matter concentrations proximate to prescribed fires being conducted in the greater Chicago metropolitan area. We deployed low-cost sensors in the spring and fall of 2022 at four sites. Concentrations of particulate matter exceeded accepted human health exposure limits at locations that burn crews would experience, but levels quickly returned to baseline after the high-intensity phase of the burn. With the ever-expanding wildland–urban interface and increased efforts in ecological restoration, understanding the particulate matter emissions of prescribed fires conducted near populated areas can provide more data regarding air quality impacts. These impacts should be weighed against the ecological benefits of prescribed burns and potential air quality impacts from uncontrolled burns from ecosystems that are not treated with prescribed burns. Measuring air quality impacts can also inform fire management practices with the goal of reducing future emissions. With the very present effects of climate change, understanding baselines regarding prescribed fires can better equip future research and fire professionals in fighting fire with fire.

Integrating an urban fire model into an operational wildland fire model to simulate one dimensional wildland–urban interface fires: a parametric study

Background Wildland fires that occur near communities, in the wildland–urban interface (WUI), can inflict significant damage to urban structures. Although computational models are vital in wildfires, they often focus solely on wildland landscapes. Aim We conducted a computational study to investigate WUI fire spread, encompassing both urban and wildland landscapes. Methods We developed a 1D landscape-scale semi-physical model by integrating a semi-physical urban fire spread model into an Eulerian level set model of wildfire. The model includes ignition and spread through radiation, direct flame contact and ember deposition. Key results Through a parametric study, we compare the relative change of spread rate from various structural properties and landscape layouts represented by model parameters, highlighting the significant impact of fire-resistant structure materials over surface treatments. Layout configurations play a pivotal role in fire spread, with isolated islands of combustibles effective in reducing spread rate, aligning with existing mitigation strategies. Conclusion Despite using a 1D domain and limitations on spatial and temporal variability, our model provides insights into underlying phenomena observed in WUI fires and their mitigation. It offers early-stage development of strategies for managing structure materials and landscape layouts. Implications Our model and findings provide insights into WUI fire dynamics, paving the way for advanced mitigation strategies.

Molecular Characterization and Photoreactivity of Organic Aerosols Formed from Pyrolysis of Urban Materials during Fires at the Wildland-Urban Interface.

Fires at the wildland-urban interface (WUI) are increasing in magnitude and frequency, emitting organic aerosol (OA) with unknown composition and atmospheric impacts. In this study, we investigated the chemical composition of OA produced through the 600 °C pyrolysis of ten urban materials in nitrogen, which were subsequently aged under UV light for 2 h. The analysis utilized ultrahigh-performance liquid chromatography (UHPLC) separation, coupled with a photodiode array (PDA) detector and a high-resolution mass spectrometer (HRMS) for molecular characterization. Hierarchical clustering analysis demonstrated that lumber-derived OA was the most diverse and distinct in composition. Unaged and aged OA (for each urban material) did not significantly differ in chemical identities. Potential aromatic brown carbon (BrC) chromophores (based on their degree of unsaturation) constituted 13-42% of all assigned compounds. PDA chromatograms revealed multiple BrC chromophoric species that were either enhanced or degraded as a result of UV aging, providing insights into specific BrC chromophores responsible for photobleaching and photoenhancement of the overall absorption coefficient. Thirty-six BrC chromophores were identified across the ten OA types, and their structures were confirmed using reference standards. Components of plasticizers and resins, such as phthalic and terephthalic acids, were structurally confirmed in the samples. We present potential species for WUI fires as components of resins, epoxies, dyes, and adhesives commonly used in manufacturing urban materials. Photolysis did not significantly impact the chemical composition of OA emitted from the burning of specific WUI materials.

Centering and uplifting youth voice in planning for a more resilient climate future in rural Colorado: a case study of a student resilience team asking for change

Rural communities are increasingly facing challenges from climate-related natural hazards such as drought, wildfire, and flood. These cascading hazards threaten social, emotional, physical, and economic well-being, and pose unique challenges to rural areas which may already struggle to find enough resources. Yet, rural areas are rich in social capital, creativity, and resilience, and future leaders are learning how to build agency and increase their community’s resilience in school settings. Students in Estes Park, Colorado, have experienced major climate-fueled hazards in their lifetimes, surviving the floods in 2013 and the East Troublesome and Cameron Peak wildfires in 2020. At Estes Park Middle School, the Environmental Resilience Team (ERT) is an afterschool group of students who are actively participating in promoting public awareness, mitigation, and policy-making to increase resilience to natural hazards. Supported by the Hazard, Education, Awareness, and Resilience Task Force (HEART Force) Program, a comprehensive curriculum that immerses students in the study of their community’s resilience to floods and fires, in conjunction with the Earth Force Environmental Civic Action resources, students and educators gained the tools needed to spearhead community discussions on resilience, all while striving to mitigate and minimize future risks. In this paper, we tell the story of the Environmental Resilience Team’s campaign to pass statewide legislation to implement Wildland Urban Interface (WUI) Building Codes in high-risk areas. Students visited the Colorado State Capitol, met with their State Senator and Governor to lobby for the passage of the bill. This initiative builds upon years of action projects, including service projects to mitigate fire risk in vulnerable populations within the mountain town of Estes Park and build community education and awareness through the distribution of “go-bags” to community members. By including youth voice in public decision-making and planning for climate resilience, community leaders and policymakers can develop more holistic plans that include multigenerational input. This research is part of a broader study across implementations of HEART Force in several classrooms that showed that the HEART Force program helped students develop a sense of agency and grow in their understanding of community resilience.

Coexisting with Venomous Snakes

Urban landscapes are expanding, increasing the wildland-urban interface and leading to more frequent wildlife-human conflict. This publication discusses how to reduce conflict venomous snakes. We first discuss the ecological benefits of these species and then provide suggestions on how to limit conflicts with them. The overarching goal of this publication is to increase the likelihood of coexistence between humans and venomous snakes.

Characterizing firebrands and their kinematics during lofting

Spot fires pose a major risk and add to the already complex physics, which makes fire spread so hard to predict, especially in the wildland urban interface. Firebrands can not only cross fuel breaks and thwart other suppression efforts but also directly damage infrastructure and block evacuation routes. Transport models and computational fluid dynamics tools often make simplifications when predicting spot fire risk, but there is a relative lack of experimental data to validate such parameterizations. To this end, we present a field experiment performed at the University of California Berkeley Blodgett Research Forest in California where we recorded the flame and firebrands emanating from a nighttime hand-drawn pile fire using high-frequency imaging. We used image-processing to characterize the fire intensity and turbulence as well as particle tracking velocimetry to measure ejected firebrand kinematics as they are lofted by the plume. We further collected embers that settled around the fire at varying distances and measured their size, shape, density, and settling distributions. We also examine existing physics-based time-averaged models of firebrand lofting and note discrepancies between such models, often used due to their speed and simplicity, and our experimental observations. Finally, we discuss some implications our observations could have on future modeling efforts by considering the time-dependent fire dynamics, intermittency in the plume turbulence, and in the firebrand generation rate. To the best of our knowledge, these are the first in situ observations of firebrand generation and lofting from representative fuels, addressing a major source of data gap and uncertainty in the wildland fire literature.

Water-Enhancing Gels Exhibiting Heat-Activated Formation of Silica Aerogels for Protection of Critical Infrastructure During Catastrophic Wildfire.

A promising strategy to address the pressing challenges with wildfire, particularly in the wildland-urban interface (WUI), involves developing new approaches for preventing and controlling wildfire within wildlands. Among sprayable fire-retardant materials, water-enhancing gels have emerged as exceptionally effective for protecting civil infrastructure. They possess favorable wetting and viscoelastic properties that reduce the likelihood of ignition, maintaining strong adherence to a wide array of surfaces after application. Although current water-enhancing hydrogels effectively maintain surface wetness by creating a barricade, they rapidly desiccate and lose efficacy under high heat and wind typical of wildfire conditions. To address this limitation, unique biomimetic hydrogel materials from sustainable cellulosic polymers crosslinked by colloidal silica particles are developed that exhibit ideal viscoelastic properties and facile manufacturing. Under heat activation, the hydrogel transitions into a highly porous and thermally insulative silica aerogel coating in situ, providing a robust protective layer against ignition of substrates, even when the hydrogel fire suppressant becomes completely desiccated. By confirming the mechanical properties, substrate adherence, and enhanced substrate protection against fire, these heat-activatable biomimetic hydrogels emerge as promising candidates for next-generation water-enhancing fire suppressants. These advancements have the potential to dramatically improve the ability to protect homes and critical infrastructure during wildfire.

Urban design and wildfire engineering at the wildland-urban interface: a review of international urban planning and building requirements

It has been almost a decade since Gonzalez-Mathiesen and March (2014) completed their international analysis that identified 9 design features for wildfire risk reduction via urban planning. Despite their recommendations and subsequent global attempts to enhance and improve resilience from an urban design perspective, wildfires1 remain one of the costliest hazards globally, both from a financial and a human perspective. This continued devastation raises the question as to whether urban design and wildfire engineering practices have either been adopted or changed since Gonzalez-Mathiesen and March (2014). To consider this, this paper presents a review and comparison of contemporary international wildland-urban-interface-related urban design legislation, policy and frameworks. Inconsistent approaches to addressing wildfire-related risk, and at times competing standards required between planning and building approaches were identified. These only serve to further reduce the potential effectiveness of measures intended to improve wildfire resilience at the national and international scales. Future work should focus on establishing evidence-based performance standards that emphasise the practical application of the findings of the best available current research to be incorporated into planning and construction. At the same time, it may be necessary to review policy approaches to clearly align key definitions of tolerable risk as well as provide clarification about how performance standards can be demonstrated.

Urban forest cover and ecosystem service response to fire varies across California communities

Urban fires that result from wildfires are an emerging, extreme event affecting communities and urban forests globally. However, much of the fire effects on urban ecosystems literature is primarily focused on Wildland-Urban Interface (WUI) areas, correlates of building loss, risk mitigation, and wildland vegetation and fuels. Three recent urban fires in California USA provided an opportunity to explore these effects on urban forests: the 2017 Tubbs (Santa Rosa) and Thomas (Ventura) and the 2018 Camp fire that burned Paradise. Accordingly, we analyzed pre- and post-fire neighborhood level urban tree cover (nUTC) change over 5 years using Sentinel and LiDAR data (10m resolution). Then, we explored the effects of fire severity on changes in several regulating ecosystem services (e.g., carbon, air pollution, stormwater). Findings from the Rapid Assessment of Vegetation Condition after Wildfire severity processes and other geospatial datasets show that fire effects were patchy with fire severity within neighborhoods ranging from unburned to extreme. We found that ~5 years after the fires, and relative to adjacent non-fire affected neighborhoods, Ventura and Santa Rosa’s nUTC is recovering to pre-fire levels while Paradise’s nUTC is being consistently lost over time. Ventura and Santa Rosa had 20-25% of their fire affected area outside established WUI boundaries. However, local-scale urban tree cover and ecosystem service supply are lagged, and recovery time depends on the surrounding biome and socio-ecological context. In inland, higher elevation communities – like Paradise – the recovery of nUTC and the associated ecosystem services might materialize over a much longer timeframe. Our study provides a roadmap to assess the response of urban wildfire-affected tree cover and ecosystem services across space and time. It is also one of the first assessments of fire effects on urban ecosystems and communities outside of WUI boundaries that are now experiencing increased threat from wildfires globally.

Presence of asbestos in building materials and soils in postfire areas of Mati, Kineta and Varimbombi in Greece.

The present study was carried out to determine the presence of asbestos in Wildland Urban Interface (WUI) areas of Attica, Greece affected by wildfires between 2018 and 2021. It concerns the first major campaign that took place in Greece. The samples tested in this work were collected from prespecified buildings of the burned area. The samples included different types of building materials such as bricks, wall coatings, insulation plates etc. Soil samples nearby the buildings were also collected to examine dispersion of the fibers. The identification of asbestos was based on the optical properties of the fibrous particles and was performed with stereo microscope and Polarized Light Microscopy according to P401 provided by BOHS (Health and Safety Executive (HSE) 2021). Scanning Electron Microscopy with energy dispersive spectroscopy was also used to validate the presence of asbestos and determine its chemical composition. In this work, 2 different types of asbestos were determined, chrysotile and crocidolite. In some cases, fragments of asbestos containing materials were also detected in the afore-mentioned soil samples indicating dispersion of asbestos containing debris in an area around the burned spots. The presence of asbestos that was identified in this preliminary study could raise concerns to humans in the urban areas. For that reason, a risk assessment for the identified asbestos containing materials (ACMs) was conducted according to the guidelines on management and abatement of ACMs of Health and Safety Authority and the Asbestos: Survey guide, Appendix 4: Material assessment algorithm of Health and Safety Executive (HSE).

A fire safety engineering approach to improving community resilience to the impacts of wildfire

AbstractEach year severe wildfires continue to cause significant destruction resulting in the loss of life, property, critical infrastructure, and the environment. In an effort to increase community preparedness and resilience to wildfire, international jurisdictions have adopted both guiding principles and prescriptive codes that apply to both urban planning and fire engineering design of buildings within the wildland–urban interface. These measures are intended to protect occupants, enhance the survivability of structures from different fire exposure mechanisms, and increase the chances of successful firefighting operations. However, research has identified (i) inconsistent approaches to regulation and governance; (ii) limited research on which urban design and building standards are based; and (iii) misaligned or contradictory urban design and building standards. This not only stifles the use of development proposing suitable performance‐based design that could achieve the required outcomes but can increase administrative burdens and development costs without increasing safety. The aim of this current study is to contribute to addressing identified shortfalls by identifying and distilling the last 23 years of research in the field related to (i) the development of evidence‐based performance requirements, and (ii) the application of effective governance arrangements in order to enhance urban design and wildfire engineering practices. These aims are achieved through a systematic literature review. Ultimately, however, of the 608 initial articles captured in the identification phase of the SLR, not a single article provided insight into the most effective regulatory or governance mechanism, and only three provided criteria suitable for adoption as a performance requirement. While the aims of this study were only partially achieved, it does provide a foundation for the field by way of identifying and distilling the current state of practice.

Wildland-Urban Interface fire exposure of rural settlements: The case of Montesinho Natural Park

Coexistence with wildfires has always been part of human life. However, the severity of these events has intensified due to the combined effects of climate change and interventions on the environment. Rural settlements, especially those with heritage values, are vulnerable, leaving their existence under constant threat. Montesinho Natural Park, characterised by many settlements with remarkable vernacular buildings, exemplifies this situation. In response to this challenge and added to the wildfire hazard, it was chosen to apply the Wildland-Urban Interface Index (WUIX) methodology to assess the exposure of the wildland-urban interface (WUI) to wildfires in three of the villages: Aveleda, Montesinho, and Rio de Onor. The WUI represents the boundary between the natural landscape and the community and might serve as a path for the percolation of fire. The study focused on evaluating the evolution of WUI over time for those three villages by taking advantage of the two open data national orthophotos of 2018 and 2021. The initial stage of vegetation recognition was changed to an automated process, relying on a Python script that captures the image for the database, extracts the vegetation, converts, and prepares the files for applying WUIX, and again converts and georeferenced the results for analysis. This approach makes the application a faster, reliable and replicable process. As a result, maps of WUIX affectation were generated, visually and quantitatively pointing to the village of Aveleda as the one with a higher level of exposure. While the results alone cannot support the entire vulnerability assessment of those villages, they serve as a complement to efforts to define proactive measures for safeguarding the rural heritage.

Ignition limits of pine wood building material under the coupling effects of thermal radiation and cross winds

The ignition of timber buildings in the context of wildland-urban interface (WUI) fires has emerged as a significant challenge amidst the backdrop of global climate change. However, to the best knowledge of the authors, little attention was paid to the ignition conditions of wood building materials in WUI fires especially in thermal-fluid coupling environments. This study experimentally investigated the smoldering and flaming ignition characteristics of wood under the coupling effects of thermal radiation and cross winds. Surface temperature, internal temperature, mass loss rates, and time to ignition of wood samples were measured to study their variation with the above factors and the threshold between smoldering and flaming ignition phenomena. The results showed that wood exhibited reduced susceptibility to flaming ignition under low radiant heat flux conditions, and the introduction of cross winds posed more challenges for flaming ignition. In addition, both the critical surface temperature and mass loss rate varied with radiant heat flux and cross-wind speeds, so it was not feasible to determine the occurrence of flaming ignition by any of the two factors directly. This is because the coupling effects of thermal radiation and cross winds would result in a competition between radiant heating and convective cooling on wood surfaces. In light of this fact, two dimensionless quantities, namely Damköhler number and heat transfer ratio, were introduced to distinguish between smoldering and flaming ignitions. Damköhler number was used as an indicator of the potential for gas-phase flaming ignition, while the heat transfer ratio, namely the ratio of convective heat loss to radiant heat flux, was used to measure the net thermal energy received by wood surfaces. It has been demonstrated that the two quantities were effective to distinguish between smoldering and flaming ignitions from the perspectives of gas and solid phases with 20–40 kW/m2 in radiant heat flux and 0–1.0 m/s in cross-wind speed. The data and theories disclosed in this study could help predict the ignition behaviors of timber buildings under thermal-fluid coupling conditions, thus providing useful guidance for WUI fire mitigation and control.

University Population and Wildfire Risk: An Analysis of Perception-Based Variables and Geospatial Differences

This research presents a novel perspective on university students, staff, and faculty and their perception of risk concerning wildfires in the fire-prone US State of Idaho. Past studies have conducted resident surveys in high-risk communities to investigate what factors make homeowners more likely to engage in mitigation activities, increasing communities’ resiliency. Research on a population without property ownership and using the wildland-urban interface (WUI) as activity and recreation spaces is limited. The main hypothesis is that a university population will have different perception and awareness levels in perception-based variables when comparing students to staff/faculty in a traditional survey and geospatial analysis. This study investigates Boise State University’s population’s risk perception using an online survey and interactive spatial assessment to examine differences between associated and geographically allocated risk spaces. Findings from perception mapping, binomial regression, and geostatistical analysis contrast current literature with traditional residents’ surveys. The explorative geostatistical analysis reveals distinct allocation patterns of perceived risk not captured in survey questions. Overall, findings promote a better understanding of where risk and awareness are apparent and suggest that wildfire communication efforts should reach out to all users of the WUI.

Using Systematic Conservation Planning to Identify Climate Resilient Habitat for Endangered Species Recovery While Retaining Areas of Cultural Importance

The effective management of at-risk species often requires fine-scale actions by natural resource managers. However, balancing these actions with concurrent land uses is challenging, particularly when compounded by the interplay of climate shifts, and escalating wildland–urban interface conflicts. We used spatial prioritization tools designed for biodiversity conservation to help resource managers on the Island of Lānaʻi prioritize mutually exclusive land use objectives: endangered species recovery and subsistence and recreational hunting. We weighed the current and anticipated future distributions of threatened and endangered plant species against the distribution of non-native game mammals to plan for species recovery more effectively. Prioritization results identified multiple footprints that could support recovery of all endangered species targets in climate resilient areas while retaining the majority of existing hunting areas. However, very little native vegetation was retained in conservation footprints without deliberate inclusion, which increased footprint area by 268%. Scenarios which prioritized contiguous conservation areas also dramatically increased conservation footprint area, although these scenarios may reduce associated fencing costs. This work demonstrates how spatial prioritization may guide localized species recovery efforts by supporting long-term conservation planning that addresses anticipated climate-driven increases in conflict between conservation and other land uses, with clear applicability beyond Lānaʻi.

Black carbon and particulate matter concentrations amid central Chile's extreme wildfires

The increase in the frequency and severity of global wildfires has been largely influenced by climate change and land use changes. From February 2 to 6, 2024, central Chile experienced its most devastating wildland-urban interface wildfire in history, severely impacting the Valparaíso region. This catastrophic event, which led to extensive forest destruction, the loss of thousands of homes, and over a hundred human fatalities, directly impacted the area surrounding the campus of Federico Santa María Technical University. In that period, an air quality monitoring campaign was set up on the campus to measure black carbon (BC) and particulate matter (PM) during the wildfire season. The monitoring station was located directly within the smoke plume, allowing for the collection of unprecedented air quality data. Extremely high concentrations of BC at 880 nm were reported during the wildfires, with a daily mean (±σ) of 14.83 ± 19.52 μg m−3. Peak concentrations measured at 880 nm and 375 nm reached 812.89 μg m−3 and 1561.24 μg m−3, respectively. The maximum daily mean BC concentrations at these wavelengths were 55 and 99 times higher, respectively, compared to the pre-event period. The mean Ångström absorbing coefficient during the event was 1.66, indicating biomass burning as the primary BC source, while the maximum BC/PM2.5 ratio (at 375 nm) reached 57 %. From February 2 to 5, 2024, PM concentrations exceeded the Chilean air quality standard by 82 % and 198 % for coarse and fine particles, respectively. These levels are 4.7 and 6.0 times higher than the World Health Organization's recommendations. These elevated concentrations persisted for up to three days after the fire was extinguished.This study provides unique evidence of the rapid deterioration of regional air quality during a wildfire event using in situ measurements, serving as a stark reminder of the far-reaching consequences of a warming climate.

Comparing Ignition of Fuel Beds to Firebrand Showers to Ignition of Fuel Beds by Non-Reacting Heaters

ABSTRACT The combustion of various fuels results in the release of firebrands during wildland-urban interface (WUI) fires. Firebrands represent a hazard, since the release of firebrands may lead to multiple ignitions at locations distant from the original combustion source. A newly developed experimental protocol using a non-reacting heater was used to simulate a firebrand. A direct comparison of this simplified non-reacting heater setup was undertaken to realistic fuel bed ignition to actual firebrand showers. Firebrand showers were generated using a custom experimental setup developed for this investigation. The novelty of this research is a detailed comparison for the first time to fuel bed ignition from non-reacting heaters to actual firebrand showers, for the same fuel bed type. The focus here is on smoldering ignition (SI) of the fuel beds, as this is seen as a complex and least understood aspect of firebrand ignition of actual WUI fires. Results indicate that the overall phenomenology of the ignition process is different between a non-reacting cartridge heater and a shower of firebrands. Complicated smoldering ignition phenomena of fuel beds by firebrand showers cannot be simulated by a simple non-reacting heater.