Crystal A. Kolden’s research while affiliated with University of California, Merced and other places
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The most destructive and deadly wildfires in US history were also fast. Using satellite data, we analyzed the daily growth rates of more than 60,000 fires from 2001 to 2020 across the contiguous US. Nearly half of the ecoregions experienced destructive fast fires that grew more than 1620 hectares in 1 day. These fires accounted for 78% of structures destroyed and 61% of suppression costs ($18.9 billion). From 2001 to 2020, the average peak daily growth rate for these fires more than doubled (+249% relative to 2001) in the Western US. Nearly 3 million structures were within 4 kilometers of a fast fire during this period across the US. Given recent devastating wildfires, understanding fast fires is crucial for improving firefighting strategies and community preparedness.
Climate change increases fire-favorable weather in forests, but fire trends are also affected by multiple other controlling factors that are difficult to untangle. We use machine learning to systematically group forest ecoregions into 12 global forest pyromes, with each showing distinct sensitivities to climatic, human, and vegetation controls. This delineation revealed that rapidly increasing forest fire emissions in extratropical pyromes, linked to climate change, offset declining emissions in tropical pyromes during 2001 to 2023. Annual emissions tripled in one extratropical pyrome due to increases in fire-favorable weather, compounded by increased forest cover and productivity. This contributed to a 60% increase in forest fire carbon emissions from forest ecoregions globally. Our results highlight the increasing vulnerability of forests and their carbon stocks to fire disturbance under climate change.
Climate change is forcing societies to contend with increasingly fire-prone ecosystems. Yet, despite evidence of more extreme fire seasons, evidence is lacking globally for trends in wildfires with socially and economically disastrous effects. Using a systematic dataset, we analyse the distribution, trends, and climatic conditions connected with the most lethal and costly wildfire disasters from 1980-2023. Disastrous wildfires occurred globally but were disproportionately concentrated in the Mediterranean and Temperate Conifer Forest biomes, and in populated regions that experience intense fire. The frequency of disastrous wildfires increased sharply from 2015, with 43% of the 200 most damaging events occurring in the last 10 years. Major disasters coincided with extreme climatic conditions, and such conditions significantly increased from 1980-2023, highlighting the urgent need to adapt to a more fire-prone world.
Climate change contributes to the increased frequency and intensity of wildfires globally, with significant impacts on society and the environment. However, our understanding of the global distribution of extreme fires remains skewed, primarily influenced by media coverage and regionalised research efforts. This inaugural State of Wildfires report systematically analyses fire activity worldwide, identifying extreme events from the March 2023–February 2024 fire season. We assess the causes, predictability, and attribution of these events to climate change and land use and forecast future risks under different climate scenarios. During the 2023–2024 fire season, 3.9×106 km² burned globally, slightly below the average of previous seasons, but fire carbon (C) emissions were 16 % above average, totalling 2.4 Pg C. Global fire C emissions were increased by record emissions in Canadian boreal forests (over 9 times the average) and reduced by low emissions from African savannahs. Notable events included record-breaking fire extent and emissions in Canada, the largest recorded wildfire in the European Union (Greece), drought-driven fires in western Amazonia and northern parts of South America, and deadly fires in Hawaii (100 deaths) and Chile (131 deaths). Over 232 000 people were evacuated in Canada alone, highlighting the severity of human impact. Our analyses revealed that multiple drivers were needed to cause areas of extreme fire activity. In Canada and Greece, a combination of high fire weather and an abundance of dry fuels increased the probability of fires, whereas burned area anomalies were weaker in regions with lower fuel loads and higher direct suppression, particularly in Canada. Fire weather prediction in Canada showed a mild anomalous signal 1 to 2 months in advance, whereas events in Greece and Amazonia had shorter predictability horizons. Attribution analyses indicated that modelled anomalies in burned area were up to 40 %, 18 %, and 50 % higher due to climate change in Canada, Greece, and western Amazonia during the 2023–2024 fire season, respectively. Meanwhile, the probability of extreme fire seasons of these magnitudes has increased significantly due to anthropogenic climate change, with a 2.9–3.6-fold increase in likelihood of high fire weather in Canada and a 20.0–28.5-fold increase in Amazonia. By the end of the century, events of similar magnitude to 2023 in Canada are projected to occur 6.3–10.8 times more frequently under a medium–high emission scenario (SSP370). This report represents our first annual effort to catalogue extreme wildfire events, explain their occurrence, and predict future risks. By consolidating state-of-the-art wildfire science and delivering key insights relevant to policymakers, disaster management services, firefighting agencies, and land managers, we aim to enhance society's resilience to wildfires and promote advances in preparedness, mitigation, and adaptation. New datasets presented in this work are available from 10.5281/zenodo.11400539 (Jones et al., 2024) and 10.5281/zenodo.11420742 (Kelley et al., 2024a).
Climate change contributes to the increased frequency and intensity of wildfires globally, with significant impacts on society and the environment. However, our understanding of the global distribution of extreme fires remains skewed, primarily influenced by media coverage and regionalised research efforts. This inaugural State of Wildfires report systematically analyses fire activity worldwide, identifying extreme events from the March 2023-February 2024 fire season. We assess the causes, predictability, and attribution of these events to climate change and land use and forecast future risks under different climate scenarios. During the 2023-2024 fire season, 3.9 × 10 6 km 2 burned globally, slightly below the average of previous seasons, but fire carbon (C) emissions were 16 % above average, totalling 2.4 Pg C. Global fire C emissions were increased by record emissions in Canadian boreal forests (over 9 times the average) and reduced by low emissions from African savannahs. Notable events included record-breaking fire extent and emissions in Canada, the largest recorded wildfire in the European Union (Greece), drought-driven fires in western Amazonia and northern parts of South America, and deadly fires in Hawaii (100 deaths) and Chile (131 deaths). Over 232 000 people were evacuated Earth Syst. Sci. Data, 16, 3601-3685, 2024 https://doi.
Climate change is increasing the frequency and intensity of wildfires globally, with significant impacts on society and the environment. However, our understanding of the global distribution of extreme fires remains skewed, primarily influenced by media coverage and regional research concentration. This inaugural State of Wildfires report systematically analyses fire activity worldwide, identifying extreme events from the March 2023–February 2024 fire season. We assess the causes, predictability, and attribution of these events to climate change and land use, and forecast future risks under different climate scenarios. During the 2023–24 fire season, 3.9 million km2 burned globally, slightly below the average of previous seasons, but fire carbon (C) emissions were 16 % above average, totaling 2.4 Pg C. This was driven by record emissions in Canadian boreal forests (over 9 times the average) and dampened by reduced activity in African savannahs. Notable events included record-breaking wildfire extent and emissions in Canada, the largest recorded wildfire in the European Union (Greece), drought-driven fires in western Amazonia and northern parts of South America, and deadly fires in Hawai’i (100 deaths) and Chile (131 deaths). Over 232,000 people were evacuated in Canada alone, highlighting the severity of human impact. Our analyses revealed that multiple drivers were needed to cause areas of extreme fire activity. In Canada and Greece a combination of high fire weather and an abundance of dry fuels increased the probability of fires by 4.5-fold and 1.9–4.1-fold, respectively, whereas fuel load and direct human suppression often modulated areas with anomalous burned area. The fire season in Canada was predictable three months in advance based on the fire weather index, whereas events in Greece and Amazonia had shorter predictability horizons. Formal attribution analyses indicated that the probability of extreme events has increased significantly due to anthropogenic climate change, with a 2.9–3.6-fold increase in likelihood of high fire weather in Canada and a 20.0–28.5-fold increase in Amazonia. By the end of the century, events of similar magnitude are projected to occur 2.22–9.58 times more frequently in Canada under high emission scenarios. Without mitigation, regions like Western Amazonia could see up to a 2.9-fold increase in extreme fire events. For the 2024–25 fire season, seasonal forecasts highlight moderate positive anomalies in fire weather for parts of western Canada and South America, but no clear signal for extreme anomalies is present in the forecast. This report represents our first annual effort to catalogue extreme wildfire events, explain their occurrence, and predict future risks. By consolidating state-of-the-art wildfire science and delivering key insights relevant to policymakers, disaster management services, firefighting agencies, and land managers, we aim to enhance society’s resilience to wildfires and promote advances in preparedness, mitigation, and adaptation.
Wildfires are increasing in duration and intensity across the United States' Pacific West region, resulting in heightened particulate matter from smoke in the atmosphere. Levels of peak particulate matter are concurrent to peak visitor attendance at National Parks, given seasonal alignment with summer vacation travel and heightened forest fire conditions. Particulate matter threatens visitor health and safety and contributes to poor visibility and a deteriorated visitor experience. To assess visitation response to diminished air quality, we utilized wildfire-generated particulate matter (PM2.5) data in conjunction with monthly attendance records for three ecoregions containing eight national parks in Washington, Oregon, and California from 2009 to 2019. We analyzed daily PM2.5 levels from data gridded at the 10 km scale for National Park Service units by Level III forest ecoregions within the National Park Service's Pacific West Unit. Data were then compared to normalized monthly visitation trends for each of the ecoregions using two statistical methods Kendall's Tau and Analysis of Variance (ANOVA) with post-hoc Tukey tests. Results demonstrate that attendance at these national parks does not decrease in response to increased PM2.5 levels. Instead, we see several statistically significant increases in attendance across these ecoregions during periods of reduced air quality. Of 115 shifts between air quality categories during the busy season of July to September, there are no significant decreases in attendance as air quality worsens. These findings suggest that visitors are willing to tolerate reduced air quality compared to other factors such as temperature or precipitation. Given that park units within each ecoregion feature diverse historical contexts, varied built environments, and unique ecological systems, our discussion specifically addresses managerial concerns associated with maintained high levels of visitation during suboptimal, and potentially dangerous, conditions. There is substantial need for specific, scalable approaches to mitigate adverse health and experiential impacts as visitors are exposed to increased risks during a range of exertional activities associated with diverse settings.
... A country's focus on the study of natural disasters and calamities is closely related to their frequency and intensity, as well as the economic losses they incur. Between 2001 and 2020, the daily peak growth rate of wildfires in the western United States more than doubled, with over three-quarters of the structures destroyed by wildfires being burned in these rapid-fire events [51]. The loss of timber due to wildfires has been increasing throughout the 21st century, primarily occurring in the Pacific Northwest of the United States, as well as in northeastern Russia, southeastern Australia, and Brazil [52]. ...
... Fire is a natural process and a fundamental component of ecosystems (Bond et al 2005). Human activities and climate change have profound impacts on ecosystems, leading to changes in behaviors and impacts of fires (Jones et al 2022(Jones et al , 2024. For example, fire seasons are lengthening globally, and fire weather conditions are becoming more extreme in recent decades (Jolly et al 2015). ...
... Currently, many studies attributed the serious forest fires in Canada during 2023 to the impact of extreme weather [5,6], with the average temperature having increased by approximately 2.2 °C from May to October compared to the average of the past decade [2]. Generally, extreme heat and drought make forest fires more likely to occur, especially under the frequent influence of lightning weather during the summer season in Canada. ...
... To this end, we employ the interferometric synthetic aperture radar (InSAR), which has been widely used and proven effective in detecting permafrostrelated surface deformation from local to regional scales (Liu et al 2014, Michaelides et al 2019, Yanagiya et al 2023. Using InSAR time series analysis, we investigated the post-wildfire permafrost ground deformation around a 2019 fire scar (figure 1) in the lower Mackenzie Valley, in the northern part of Northwest Territories (NWT), where an increasing number and extent of wildfires along with a significant warming trend have been reported (Hu et al 2024, Kolden et al 2024. As shown below, the study site has likely undergone the highest positive-degreedays ever recorded during the five years after the fire (figure 2). ...
... In this study, both unburned and burned tundra of the YKD were annual net C sinks across the three years, with on average 19.5 g C m −2 more taken up in the burned tundra compared to the unburned tundra. When considering that 1680 g C m −2 were lost in the 2015 YKD fire (Moubarak et al 2023), at the current rate of NEE, it would take ∼86 years to recover the C lost from the fire itself, which is slow relative to lower latitude systems (Hudiberg et al 2023). This number is likely much higher when considering compounded effects of fire with permafrost thaw: wildfire can trigger talik development and expansion as well as increase thaw settlement along burned margins (Brown et al 2015, Gibson et al 2018), which can lead to greater respiration from deeper soil layers (Gibson et al 2019). ...
... Despite these considerations and the common tradeoffs among prescribed burning outcomes, decision-makers face the challenging task of managing its use and striking a balance among these outcomes to ensure its suitability for their objectives (Bradford & D'Amato, 2012;Granath et al., 2018;Schollaert et al., 2024). Considering the various strengths, weaknesses, and challenges associated with prescribed burning, the decisionmaking process surrounding its use is inherently complex and multifaceted (Finney, 2005;Scasta et al., 2023;Swain et al., 2023). This process involves strategic, operational, and tactical components (Howard et al., 2020;Martell, 2015). ...
... Similarly, Yadav et al. (2023) found that disadvantaged communities in California, USA, are increasingly affected by wildfires, underscoring the need for equitable wildfire management strategies. Although research (Davies et al. 2018;Lambrou et al. 2023) (Davies et al. 2018;Lambrou et al., 2023) has explored how social and environmental vulnerabilities influence wildfire preparedness and recovery, there remains a pressing need to examine spatial and socio-demographic disparities in public responses to wildfires. This is particularly important given the geographic and social diversity within WUI areas (Meldrum et al. 2018). ...
... the Western US, downslope winds driven by hot inland conditions-such as Santa Ana, Diablo, and others-are associated with numerous historical extreme fire events [16]. These offshore flows have been analyzed as a driver and even predictor of wind-driven fires in the brushy, chaparral ecosystem characteristic of Mediterranean climates like Southern California [17][18][19]. ...
... This suggests that impacts of crown scorch and subsequent reduction in photosynthetically active leaf area are short-lived and that the recovery of NSC stores, at least in the inner bark and new needles, is swift if minimal bud kill occurs and if the crown scorch is not high. This finding aligns with studies that have measured changes in the photosynthetic capacity of live needles post-fire, which sometimes find higher photosynthetic rates after fire (Wallin et al. 2003, Renninger et al. 2013, particularly for trees that sustain moderate levels of crown injury but that survive, possibly to compensate for the lost leaf area (Bryant et al. 2022). However, even with increased photosynthetic rates, large reductions in leaf area due to high crown scorch could likely lead to whole-tree imbalances for NSCs and the inability to meet metabolic demands. ...
... Additionally, during this stage, the decrease in soil temperature limits root activity, affecting water uptake and transport capacity. Furthermore, the decline in xylem conductivity further exacerbates the attenuation of water charge and discharge processes within the plant stem tissue (Ding et al. 2021;Partelli-Feltrin et al. 2023). These combined factors may contribute to a decrease in the rehydration ability of stem tissues, causing a continuous decrease in stem water content until reaching a minimum value the following morning. ...
