Low-intensity fires mitigate the risk of high-intensity wildfires in California's forests

Integrating flora, fauna, and indigenous practices into spatial optimization for prescribed burning

Climate change has intensified wildfire activity, necessitating a shift towards sustainable fire management strategies that embrace the concept of fire coexistence. Fire coexistence recognizes the role of fire as a natural ecological process and integrates the adaptations of flora (e.g., fire-resistant bark, regenerative capacity), fauna (e.g., fuel reduction through grazing, creation of natural firebreaks), and traditional land management practices (e.g., controlled burns, agricultural firebreaks) that enable ecosystems to persist with fire. These "coexistence factors" are crucial for effective prescribed burning, ensuring minimal disruption to fire-adapted species and maximizing long-term ecosystem resilience. While prescribed burning is a recognized management tool, a comprehensive framework for spatially integrating these coexistence factors into regional-scale planning is lacking. This study addresses this gap by developing a novel approach that spatially optimizes prescribed burning by integrating fire risk and coexistence capacity. Applying this approach to the Jialing River watershed (China), a fire-prone mountainous region, we use machine learning and deep learning to predict fire risk and identify areas with high coexistence potential. Zonation 5 is then employed for spatial prioritization. Results reveal a significant spatial correlation between fire risk and coexistence capacity, with high-value clusters concentrated in the central and southern parts of the study area, particularly around the Jialing River and forested regions. Specifically, 4% of the study area in the central and southern regions (value > 0.679) was classified as very high fire risk, while the top 10% of the area exhibited high coexistence capacity (value > 0.9). Based on Zonation 5 optimization, 5% of fire-prone forests with high coexistence capacity were identified as priority areas for prescribed burning, concentrated primarily in eastern Beibei. This integrated approach offers valuable guidance for policymakers, land planners, and stakeholders in sustainably managing fire hazards in similar mountainous regions globally.

Wildfire Smoke, the Clean Air Act, and the Exceptional Events Rule: Implications and Policy Alternatives

In recent years, increasing wildfire activity in the western US and Canada has driven declining air quality in some regions of the US. Under EPA's Exceptional Events Rule, states are allowed to exempt daily pollution monitor readings impacted by wildfire smoke from determinations of compliance with Clean Air Act air quality standards. As a result, wildfire smoke is leading to a growing divergence between actual and regulatory air quality. This paper reviews treatment of wildfire smoke under the Clean Air Act and the Exceptional Events Rule. It presents quantitative evidence on the effect of the rule on fulfillment of air quality standards, and an analysis of the degree to which smoke that currently leads to air quality violations is driven by out-of-state fires and fires on federal lands. We suggest a modification to the Exceptional Events Rule under which wildfire emissions would be excluded from air quality regulations only if states adopt government-defined best fire management policies, and we discuss the legal and practical feasibility of such a change.

The Trade-offs between Wildfires and Prescribed Fires: A Case Study for 2016 Gatlinburg Wildfires

Prescribed burning is an effective land management tool that provides a range of benefits, including ecosystem restoration and wildfire risk reduction. However, prescribed fires, just like wildfires, introduce smoke that degrades air quality. Furthermore, while prescribed fires help manage wildfire risk, they do not eliminate the possibility of wildfires. It is therefore important to also evaluate fire and smoke impacts from wildfires that may occur after a prescribed burn. In this study, we developed a framework for understanding the air quality and health related trade-offs between wildfires and prescribed fires by simulating a set of counterfactual scenarios including wildfires, prescribed fires, and postprescribed burn wildfires. We applied this framework to the case of the Gatlinburg wildfire and found that emissions from prescribed burns and subsequent wildfire were slightly lower than those from the wildfire itself. This reduction resulted in lower daily average concentrations and exposures of PM2.5, O3, and NO2. Even considering the possibility of a postprescribed burn wildfire, prescribed fires reduced population-weighted daily average PM2.5, daily maximum 8-h average O3, and 1-h maximum NO2 concentrations. In Sevier County, Tennessee where the wildfire occurred, these reductions reached 5.28 μg/m3, 0.18 ppb, and 1.68 ppb, respectively. The prescribed fires also reduced the person-days smoke exposures from the wildfire. Our results suggest that although prescribed fires cannot eliminate the air quality impacts of wildfires, they can greatly reduce smoke exposure in downwind areas distant from the burn sites.

Foundations and Future Directions for Causal Inference in Ecological Research

Ecology often seeks to answer causal questions, and while ecologists have a rich history of experimental approaches, novel observational data streams and the need to apply insights across naturally occurring conditions pose opportunities and challenges. Other fields have developed causal inference approaches that can enhance and expand our ability to answer ecological causal questions using observational or experimental data. However, the lack of comprehensive resources applying causal inference to ecological settings and jargon from multiple disciplines creates barriers. We introduce approaches for causal inference, discussing the main frameworks for counterfactual causal inference, how causal inference differs from other research aims and key challenges; the application of causal inference in experimental and quasi-experimental study designs; appropriate interpretation of the results of causal inference approaches given their assumptions and biases; foundational papers; and the data requirements and trade-offs between internal and external validity posed by different designs. We highlight that these designs generally prioritise internal validity over generalisability. Finally, we identify opportunities and considerations for ecologists to further integrate causal inference with synthesis science and meta-analysis and expand the spatiotemporal scales at which causal inference is possible. We advocate for ecology as a field to collectively define best practices for causal inference.

A review of optimization and decision models of prescribed burning for wildfire management

Prescribed burning is an essential forest management tool that requires strategic planning to effectively address its multidimensional impacts, particularly given the influence of global climate change on fire behavior. Despite the inherent complexity in planning prescribed burns, limited efforts have been made to comprehensively identify the critical elements necessary for formulating effective models. In this work, we present a systematic review of the literature on optimization and decision models for prescribed burning, analyzing 471 academic papers published in the last 25 years. Our study identifies four main types of models: spatial-allocation, spatial-extent, temporal-only, and spatial-temporal. We observe a growing number of studies on modeling prescribed burning, primarily due to the expansion in spatial-allocation and spatial-temporal models. There is also an increase in complexity as the models consider more elements affecting prescribed burning effectiveness. We identify the essential components for optimization models, including stakeholders, decision variables, objectives, and influential factors, to enhance model practicality. The review also examines solution techniques, such as integer programming in spatial allocation, stochastic dynamic programming in probabilistic models, and multiobjective programming in balancing trade-offs. These techniques' strengths and limitations are discussed to help researchers adapt methods to specific challenges in prescribed burning optimization. In addition, we investigate general assumptions in the models and challenges in relaxation to enhance practicality. Lastly, we propose future research to develop more comprehensive models incorporating dynamic fire behaviors, stakeholder preferences, and long-term impacts. Enhancing these models' accuracy and applicability will enable decision-makers to better manage wildfire treatment outcomes.

Prescribed burn related increases of population exposure to PM2.5 and O3 pollution in the southeastern US over 2013-2020

Ambient air quality across the southeastern US has improved substantially in recent decades. However, emissions from prescribed burns remain high, which may pose a substantial health threat. We employed a multistage modeling framework to estimate year-round, long-term effects of prescribed burns on air quality and premature deaths. The framework integrates a chemical transport model with a data-fusion approach to estimate 24-h average PM2.5 and maximum daily 8-h averaged O3 (MDA8-O3) concentrations attributable to prescribed burns for the period 2013-2020. The Global Exposure Mortality Model and a log-linear exposure-response function were used to estimate the premature deaths ascribed to long-term prescribed burn PM2.5 and MDA8-O3 exposure in ten southeastern states. Our results indicate that prescribed burns contributed on annual average 0.59 ± 0.20 µg/m3 of PM2.5 (∼10 % of ambient PM2.5) over the ten southeastern states during the study period. On average around 15 % of the state-level ambient PM2.5 concentrations were contributed by prescribed burns in Alabama (0.90 ± 0.15 µg/m3), Florida (0.65 ± 0.19 µg/m3), Georgia (0.91 ± 0.19 µg/m3), Mississippi (0.65 ± 0.10 µg/m3) and South Carolina (0.65 ± 0.09 µg/m3). In the extensive burning season (January-April), daily average contributions to ambient PM2.5 increased up to 22 % in those states. A large part of Alabama and Georgia experiences ≥3.5 µg/m3 prescribed burn PM2.5 over 30 days/year. Additionally, prescribed burns are responsible for an average increase of 0.32 ± 0.12 ppb of MDA8-O3 (0.8 % of ambient MDA8-O3) over the ten southeastern states. The combined effect of prescribed burn PM2.5 exposure, population growth, and increase of baseline mortality over time resulted in a total of 20,416 (95 % confidence interval (CI): 16,562-24,174) excess non-accidental premature deaths in the ten southeastern states, with 25 % of these deaths in Georgia. Prescribed burn MDA8-O3 was responsible for an additional 1,332 (95 % CI: 858-1,803) premature deaths in the ten southeastern states. These findings indicate significant impacts from prescribed burns, suggesting potential benefits of enhanced forest management strategies.

Climate resilience through ecocultural stewardship

The climate crisis has exacerbated many ecological and cultural problems including wildfire and drought vulnerability, biodiversity declines, and social justice and equity. While there are many concepts of social and ecological resilience, the exemplar practices of Indigenous stewardship are recognized in having sustained Indigenous peoples and their countries for millennia and past climate change events. California has been at the crossroads of many of these issues, and the historic and current contributions of Indigenous peoples to addressing these provide an excellent study of ecocultural stewardship and leadership by Indigenous peoples to achieve climate resilience.

Coexisting with wildfire: strengthening collective capacity by changing the status quo

This article is the fuller written version of the invited closing plenary given by the author at the 10th International Fire Ecology and Management Congress. The article provides a consideration of our capacity to cope, care, and coexist in a fiery world from a social and structural point of view. It focuses on privilege as the root cause of a long and troublesome history within the wildfire profession of not valuing all generational knowledge equally, not treating all cultures with the same respect, not embracing diversity and inclusion, and not affording the same status to all disciplines and voices. The article argues that we can strengthen our collective capacity to coexist with wildfire by embracing local and indigenous fire stewardship practices, by enabling workforce diversity and inclusive leadership culture, and by providing sustainable working conditions for wildland firefighters. To do so requires individual and collective noticing of what is wrong, and everyday action steps towards equity.