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Mega-fires around the world: A literature review
Abstract and Figures
Wildland fires are a disaster phenomenon that can range from an initial attack fire, which can be managed quickly and effectively with minimum losses, to a mega-fire, which can be sometimes unbeatable and can cause major catastrophic situations.
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... Aunado a estos impactos ambientales, los incendios pueden pasar de las áreas forestales a campos agrícolas y pastizales cultivados, o incluso a zonas urbanas, causando daños en la producción agropecuaria, en la infraestructura y en la vivienda. Entre los efectos de mayor calado se tienen que mencionar las afectaciones a la salud humana, tanto por el contacto directo con el fuego, como por el humo que alcanza a personas lejos del lugar donde ocurre el incendio, perjudicando sobre todo el sistema respiratorio [5][6][7][8]. Además, los incendios forestales llevan a la emisión de gases de efecto invernadero, contribuyendo así al cambio climático [9][10]. ...
... Además, el viento juega un papel fundamental en la propagación del fuego [4][5]11]. Con base en esta realización de la importancia de tales factores, se ha desarrollado el Fire Weather Index (FWI), un indicador de las condiciones meteorológicas favorables para los incendios forestales. Este se desarrolló originalmente en Canadá en los años 70 y 80 del siglo XX [12], y se ha venido utilizando alrededor del mundo, por ejemplo, en estudios en Grecia [13], Perú [14] y China [15]. ...
Las condiciones atmosféricas juegan un papel clave en el incremento de la probabilidad de ocurrencia de incendios forestales. En este sentido, a nivel internacional se ha utilizado ampliamente el Fire Weather Index, para determinar el riesgo de incendios relacionado con condiciones ambientales. En el presente trabajo se realiza una comparativa entre dicho índice en el periodo 2015-2020 y los registros de campo de incendios forestales en México de la Comisión Nacional Forestal. Para ello, empleando una aproximación basada en las diferencias normalizadas de ambos conjuntos de datos, se determinan las coincidencias y diferencias espaciales, y se analizan, desde una mirada multidisciplinaria, las posibles causas de dichos patrones. En este análisis se incluyen tanto factores físicos (relacionados con las características ambientales) como la presencia de diferentes ecosistemas con sus regímenes del fuego respectivos y factores sociales (puesto que la mayor parte de incendios en México son causados directamente por actividades antrópicas). Se discute la adaptabilidad del Fire Weather Index para distintas regiones del país, así como la viabilidad de este tipo de índices para el diseño de escenarios del riesgo de incendios forestales en el futuro, y sus implicaciones para el manejo del fuego. También se detallan las limitaciones de esta investigación y de la interpretación de los resultados, dada la dificultad de realizar un análisis de mayor profundidad en un estudio a
nivel nacional.
... In recent years, destructive wildfires and so-called "high-impact mega-fires" have become more common in many parts of the worldoften in forested or shrubland ecosystems in Mediterranean or other temperate climates (Riggan et al., 1994;Krawchuk et al., 2009;Adams 2013). Such fires typically cause significant loss of lives, assets, and infrastructure, in addition to various ecological ramifications (San-Miguel-Ayanz et al., 2013;Williams 2013;Leite et al., 2015). The increasing incidence of these fires has been attributed to elements of global change, such as protracted droughts and extreme fire danger weather conditions associated with global climate change (Kraaij et al., 2013(Kraaij et al., , 2018Nolan et al., 2020); excessive build-up of fuels resulting from extended fire suppression efforts (Keeley et al., 1999;Adams 2013) or from fast-growing, flammable invasive alien plants (IAPs) (Pauchard et al., 2008;le Maitre et al. 2023); or increased ignitions linked to the growing human population and expansion of the wildland-urban interface (Radeloff et al., 2005;Keeley and Syphard 2017). ...
... Large forest fires (LFF) are a concern for today's societies and pose a direct threat to the environment, infrastructure, people and the economy (PARENTE; WRIGHT;ROY, 2022). The last decades have witnessed the occurrence of several forest fires, under extreme weather conditions and in locations scattered around the globe, such as in Brazil in 1998, in Portugal in 2003, 2005, 2017, in Greece in 2007, in the United States of America in 2007, 2021(California), in Australia in 2003(Canberra) and 2009(Victoria), in Russia in 2010 or Canada in 2022 (BENTO-GONÇALVES, 2022a;DE LA BARRERA et al., 2018;FERREIRA-LEITE et al., 2015;TEDIM et al., 2013TEDIM et al., , 2020WILLIAMS et al., 2011). ...
In recent decades, in several parts of the world and under extreme weather conditions, we have witnessed the occurrence of numerous large-scale wildfires. This reality has also occurred in Portugal, burning thousands of hectares of forest, destroying infrastructures, and causing the regrettable loss of human lives. In view of this worsening panorama, we proceeded to the cartography of lLarge Forest Fires (LFF) in northwestern Portugal (larger than 100 hectares), in the period from 2001 to 2020, from the analysis of Landsat images and using Machine Learning tools and the Random Forest algorithm, in Google Earth Engine work environment. Based on the results obtained, an attempt is made to understand the LFF context in northwestern Portugal, as well as to analyse its spatial distribution and temporal evolution in the period under analysis. The conclusion is that about 158.741 ha burnt at least once and 40.9% of this area was affected by LFF a second time. The year of 2005 recorded the highest value of burnt area (73,025.1 ha). And the maximum recurrence observed, in the study area, was 7 occurrences, with a maximum recurrence of 6 times. The brush is the type of vegetation, in NUTS Ave, Alto Minho and Tâmega and Sousa, which presents more burnt area in LFF, while in Cávado, it is the forests that present the most extensive area covered by LFF. Thus, in 15 years for the study area, the most significant proportion of burnt vegetation corresponds to brush, being only in 5 years, forests were the class of the larger burnt area. In the current context of global changes and with large forest fires increasing in frequency, extent and intensity, its study and its temporal and spatial understanding are crucial, both at the regional and national scales.
... Humans have increased forest fire risk by augmenting forest fuels through active management (DellaSala et al., 2022a) and by increasing the number and sources of ignition (Balch et al., 2017). The majority of documented megafires globally have been started by humans under extreme fire weather conditions (Ferreira-Leite et al., 2015;Bowman et al., 2017). ...
Several key international policy frameworks involve forests, including the Paris Agreement on Climate Change and the Convention on Biological Diversity (CBD). However, rules and guidelines that treat forest types equally regardless of their ecosystem integrity and risk profiles in terms of forest and carbon loss limit policy effectiveness and can facilitate forest degradation. Here we assess the potential for using a framework of ecosystem integrity to guide policy goals. We review the theory and present a conceptual framework, compare elements of integrity between primary and human-modified forests, and discuss the policy and management implications. We find that primary forests consistently have higher levels of ecosystem integrity and lower risk profiles than human-modified forests. This underscores the need to protect primary forests, develop consistent large-scale data products to identify high-integrity forests, and operationalize a framework of ecosystem integrity. Doing so will optimize long-term carbon storage and the provision of other ecosystem services, and can help guide evolving forest policy at the nexus of the biodiversity and climate crises.
... However, in recent decades, due to climate change and human-caused deforestation and ecosystem degradation, the frequency and intensity of fires has been increasing (Cochrane 2003;Cochrane and Barber 2009;Liu et al., 2010). At the same time, large-scale fires, known as megafires, have been reported in tropical forests (Anivarro et al., 2019;Ferreira-Leite et al., 2015;Fidelis et al., 2018). ...
Lack of understanding the negative and positive effects of wildfires poses a challenge to the restoration and management of tropical ecosystems. Although fire can have negative impacts on tropical forests, it is known that many tropical savanna and woodland species are adapted to fire. The objective of this study was to determine the resilience of tree species to wildfire in a seasonally dry region of eastern lowland Bolivia. The study was carried out in four tropical dry Chiquitano ecosystems (Abayoy, Cerrado, Chiquitano dry forest, and sub-humid forest), in the department of Santa Cruz, 7-18 months after wildfires occurred in October 2019. At 45 sampling points, in both burned and unburned areas, we established 50-m x 5-m transects to determine tree species composition, number of individuals, resprout types, survival, diameter, and height of individuals that were ≥1 cm diameter at breast height (DBH). We calculated the percentages of surviving and dead stems by resprout categories and used logistic regression to determine the probability of survival and probability of resprouting as a function of pre-burn size. In the four ecosystems, 35-71% of the individuals sampled survived (crown and basal resprouting) after fire, while an additional 18-59% of individuals had only basal resprouting. Tree mortality (no reprouts) ranged from 5-11%. In burned areas, larger-diameter trees had a greater probability of survival. In contrast, the smaller-diameter trees had a higher probability of resprouting from the base. In conclusion, the Chiquitano tropical dry ecosystems have a high resilience to wildfire in terms of survival and resprouting. Resprouting strategy appears to be an important survival mechanism in trees, especially small trees, and must be considered in the passive restoration of burned forests.
Understanding the complex dynamical interactions that occur during the evolution of a wildland fire still remains a challenge within the research community. Processes such as entrainment, the incident wind field, the interaction between neighboring updrafts, among other processes, motivates the need for more intensive measurement campaigns to determine the mechanisms responsible for the processes observed as wildland fire updrafts evolve. A recent opportunity to examine processes associated with wildland fires was made possible with a Doppler lidar (DL) mounted on a Twin Otter aircraft to measure horizontal and vertical winds during the 2019 Fire Influence on Regional‐to‐Global Environments and Air Quality campaign. Using the data collected, a technique was developed to isolate updrafts over designated hotspots with the intention of statistically analyzing the updraft samples as well as assessing specific cases that underscore the complex dynamical interactions generated by wildland fire behavior. Strong evidence in support of statistically derived relationships between the updraft characteristics and downdraft extrema at the flanks of updrafts are shown using methods developed herein. In addition to the influence of entrainment/detrainment on the updraft structure are features such as updraft displacement and interacting updrafts that could only be resolved by a high along‐ and cross‐beam resolution DL. Lastly, it was found that a high degree of symmetry between profiles to the left and right of core updrafts was preserved for most of the cases, which validates some of the assumptions typically used in idealized updraft formulations.
A safe separation distance (SSD) needs to be considered during firefighting activities (fire suppression or people evacuation) against wildfires. The SSD is of critical interest for both humans and assets located in the wildland-urban interfaces (WUI). In most cases, the safety zone models and guidelines assume a flat terrain and only radiant heating. Nevertheless, injuries or damage do not result exclusively from radiant heating. Indeed, convection must be also considered as a significant contribution of heat transfer, particularly in the presence of the combined effects of sloping terrain and a high wind velocity. In this work, a critical case study is considered for the village of Sari-Solenzara in Corsica (France). This site location was selected by the operational staff since high-intensity fire spread is likely to occur in the WUI during wind-blown conditions. This study was carried out for 4 m high shrubland, a sloping terrain of 12° and a wind speed of 16.6 m/s. The numerical simulations were performed using a fully physical fire model, namely, FireStar2D, to investigate a case of fire spreading, which is thought to be representative of most high wildfire risk situations in Corsica. This study is based on the evaluation of the total (radiative and convective) heat flux received by two types of targets (human bodies and buildings) located ahead of the fire front. The results obtained revealed that the radiation was the dominant heat transfer mode in the evaluation of the SSD. In addition, the predictions were consistent with the criterion established by the operational experts, which assumes that in Corsica, a minimum SSD of 50 m is required to keep an equipped firefighter without injury in a fuelbreak named ZAL. This numerical work also provides correlations relating the total heat flux to the SSD.
Los megaincendios se refieren a igniciones forestales de gran magnitud con marcados impactos ambientales y socioeconómicos. El presente artículo investiga la dinámica espacial y temporal de la ocurrencia de megaincendios y sus causas y efectos en las últimas dos décadas en México, donde este fenómeno ha sido poco explorado. Mediante un sistema de información geográfica y las bases de datos del Global Fire Atlas y de la Comisión Nacional Forestal se analizó la distribución espacial de la ocurrencia y superficie afectada; mientras que los impactos socioeconómicos se identificaron a partir de la revisión de fuentes hemerográficas. Los resultados demuestran que incendios de más de 500 ha y 1000 ha son frecuentes en casi todo el país, pero los eventos de más de 10 000 hectáreas son escasos y se concentran principalmente en los estados del norte. El número de megaincendios en México es mínimo en comparación con el total de incendios registrados a escala nacional. Sin embargo, abarcan gran parte de la superficie afectada, 45.8% según los datos de la Comisión Nacional Forestal y 58% según el Global Fire Atlas para los incendios en superficies mayores a 500 ha. La causa directa en la mayoría de los casos es de origen antropogénica, aunque existe una porción importante de megaincendios que resultaron de causas naturales, sobre todo en el norte del país. Con respecto a los efectos socioeconómicos estos fenómenos también abarcan un porcentaje significativo de los costos y daños generados.
This work reports on a theoretical and experimental study on the role of fire retardant treatments on the discontinuous ignition of wildland fuels. The effect of the concentration of fire retardant in the solution applied to the vegetation is as expected to increase the ignition delay time. We found that the fire retardant modifies the fuel bed effective thermophysical properties, delaying the thermal response of the specimen when subjected to an incident heat flux. Nevertheless, the critical heat flux remains unaltered within the experimental error. We followed a proven approach based on the thermal ignition theory and testing which however has not been previously employed to study fire retardants on wildland fuels. To carry this out, we performed experiments on the I-FIT apparatus, which yields repeatable results and controlled boundary conditions. The theoretical model shows a good agreement with the experimental results, delivering simple expressions for pencil-and-paper calculations of the ignition delay time and analytical tools to evaluate effective fuel properties. These results will help CONAF and other forest services around the world to gain insight on the optimal concentrations and delivery methods for these types of products during wildfire response.
Comparison of long‐term environmental monitoring data show that in August and September 2002 heavy metal (Cu, Pb and Zn) concentrations increased in Lithuanian rivers. Resent investigation has indicated that increase of heavy metals (Cu, Pb and Zn) by 60–81 % in all the rivers that are subject to the State River Monitoring and could be correlative with land fires. Fires of forests and peat bogs have outspread all over Lithuania in the summer and the first half of autumn of 2002. This paper attempts to prove an assumption that these fires could have caused a significant increase of heavy metal concentrations in the water of Lithuanian rivers in August 2002. It also means that land fires should be evaluated as an environmental risk factor with a serious impact on the state of aquatic environment and must be taken into account in calculations of environmental damage.
Wildfires are an important agent in driving ecosystem function by altering vegetation structure and geomorphic processes.
In recent decades, the number of wildfires and the total area burned has increased around the world, causing changes to natural
regimes. In this study, we compared south- and north-facing slopes, their vegetation structure and dynamics, and the sediment
yield generated in areas burned a number of times at the Carmel Mountain ridge in northern Israel. Our underlying hypothesis
was that repeated and frequent fires significantly alter eco-geomorphic processes, including prolonged periods of soil erosion
and delayed recovery of tree species. We tested whether these phenomenon are characterized by different rates on opposing
aspects. To study the long-term changes of the vegetation we analyzed a 21-year (1985–2006) chrono-sequence of satellite images,
in areas burned once, twice, or three times. Additionally, we estimated vegetation structure and cover at high resolutions
in monitoring plots following a fire in 2005 in areas burned once or twice during the last two decades. To evaluate the long-term
dynamics of the system, specific transition probabilities among the vegetation types, as a function of the number of times
each site was burned, were used to construct Markov-based transition matrices. Additionally, runoff and sediment have been
collected after precipitation events from the plots. The satellite image classifications revealed changes in the composition
of tree, shrub, and herbaceous vegetation cover following wildfire events. Satellite image analyses suggest that recurring
fires within short-time intervals may significantly alter the long-term structure of the vegetation communities, and may eliminate
woody vegetation from the landscape (both trees and shrubs). Consequently, this results in the establishment and dominance
of herbaceous vegetation communities. Similar trends were observed in the high-resolution monitoring plots. Sediment yields
differed significantly in areas burned twice on south-facing slopes, compared to lower values obtained in areas burned once,
or located on north-facing slopes. Thus, we demonstrate that repeated fires may dramatically alter long-term trajectories
of Mediterranean-type vegetation communities and ecosystems. This pattern, in turn, may have significant implications for
the associated geo-morphological processes, especially runoff and erosion, and should be of particular concern given recent
changes of fire regimes.
Keywordsrepeated fires–Mediterranean ecosystem–vegetation dynamics–remote sensing–Markov model–soil erosion
In May 2003, severe forest fires in southeast Russia resulted in smoke plumes extending widely across the Northern Hemisphere. This study combines satellite data from a variety of platforms (Moderate Resolution Imaging Spectroradiometer (MODIS), Sea-viewing Wide Field-of-view Sensor (SeaWiFS), Earth Probe Total Ozone Mapping Spectrometer (TOMS) and Global Ozone Monitoring Experiment (GOME)) and vertical aerosol profiles derived with Raman lidar measurements with results from a Lagrangian particle dispersion model to understand the transport processes that led to the large haze plumes observed over North America and Europe. The satellite images provided a unique opportunity for validating model simulations of tropospheric transport on a truly hemispheric scale. Transport of the smoke occurred in two directions: Smoke travelling northwestwards towards Scandinavia was lifted over the Urals and arrived over the Norwegian Sea. Smoke travelling eastwards to the Okhotsk Sea was also lifted, it then crossed the Bering Sea to Alaska from where it proceeded to Canada and was later even observed over Scandinavia and Eastern Europe on its way back to Russia. This is perhaps the first time that air pollution was observed to circle the entire globe. The total transport time was about 17 days. We compared transport model simulations using meteorological analysis data from both the European Centre for Medium-Range Weather Forecast (ECMWF) and the National Center for Environmental Prediction (NCEP) in order to find out how well this event could be simulated using these two datasets. Although differences between the two simulations are found on small scales, both agree remarkably well with each other and with the observations on large scales. On the basis of the available observations, it cannot be decided which simulation was more realistic.
Les incendies de forêt affectent de grandes surfaces et causent d'importants dommages qui peuvent avoir de lourdes conséquences écologiques, sociales et économiques. Plus de 50 000 feux brûlent environ 500 000 hectares de végétation chaque année dans les pays du bassin méditerranéen européen (JRC, 2006; Lampin-Maillet, 2008). Les interfaces habitat-forêt sont directement concernées par ces incendies : 90% des départs de feux sont liés à l'activité humaine en Europe Méditerranéenne (Eufirelab, 2004), et chaque année de nombreux morts sont à déplorer à cause de ces incendies de forêt, notamment parmi les habitants des interfaces habitat-forêt. Dans le contexte d'une forte pression d'urbanisation et d'une accumulation de biomasse combustible, les interfaces habitat-forêt représentent une véritable préoccupation pour la gestion du risque d'incendie (Davis, 1990; Velez, 1997; Cohen, 2000), particulièrement au regard des deux composantes du risque : l'aléa en terme de départs de feu causés par les activités humaines, et la vulnérabilité, en termes de surfaces brûlées menaçant les zones habitées et aussi de dégâts sur les habitations (Hardy, 2005; Jappiot et al, 2009). La thèse, qui relève des sciences de la géographie et de la cyndinique, montre toute la pertinence de l'utilisation de l'objet géographique « interface » dans le contexte de l'évaluation du risque d'incendie. Cet objet « interface » a été appliqué dans la thèse au cas particulier de l'interface habitat-forêt. Après avoir défini, caractérisé et cartographié l'interface habitat-forêt, la thèse a alors examiné la valorisation possible de cette entrée par l'interface habitat-forêt dans le cadre d'une démarche d'analyse spatiale et de cartographie du risque d'incendie sur le territoire. Ainsi l'interface habitat-forêt a été définie de façon précise dans le contexte du risque d'incendie. Une typologie d'interfaces a été créée, fondée sur la combinaison de deux critères jugés pertinents pour le risque d'incendie, traduisant des caractères prégnants des milieux humain, avec la structure de l'habitat résidentiel, et naturel, avec la structure de la végétation. Les types d'habitat résidentiel : habitat isolé, diffus, groupé dense et groupé très dense ont été définis en posant des principes de distances entre bâtis et de dénombrement des bâtis. Ils ont également été caractérisés en termes de densité de bâtis, de surfaces à débroussailler et de périmètre à défendre. La structure de la végétation a été traduite en termes de continuité horizontale avec un indice d'agrégation emprunté à l'écologie du paysage. L'indice est fondé sur des cartes de végétation, au format raster, d'une résolution maximale de 10 m avec un rayon de 20 m pour la fenêtre de calcul. Un seuil à 95 % discrimine une agrégation faible (végétation éparse) d'une agrégation forte (végétation continue). La méthode de caractérisation et de cartographie des interfaces habitat-forêt, développée dans la thèse, est applicable sur de grandes surfaces et à une grande échelle dans les départements du sud de la France. Elle a permis pour la première fois en France de quantifier l'importance des interfaces habitat-forêt sur un territoire. Puis la carte des interfaces a contribué à produire une nouvelle carte du territoire, alors compartimenté en espaces dits « interfacés » (types d'interfaces habitat-forêt), et en espaces dits « non interfacés » (espaces bâtis hors interfaces et le reste du territoire). Une première relation, forte, entre les types d'interface habitat-forêt et l'importance des départs de feu et des taux de surfaces brûlées a été mise en évidence. Une méthode d'évaluation du risque d'incendie, innovante, a alors été développée dans la thèse. Elle s'appuie sur une analyse spatiale et statistique du territoire, fondée sur une nouvelle cartographie de types de territoire déduite de la cartographie des interfaces habitat-forêt. L'analyse a consisté à croiser les types de territoire et les caractéristiques environnementales, topographiques et socio-économiques avec l'historique des feux à travers la distribution spatiale des départs de feu, celle des surfaces brûlées et la fréquence de passage des incendies. Elle a permis de mettre en évidence l'importance de certaines variables pour leur contribution positive (interfaces habitat-forêt en habitat isolé, espaces naturels autres que forestiers, garrigue, exposition très chaudes, zones de végétation éparse, densité de chemins) ou négative (interfaces habitat groupé dense et très dense, densité de bâtis et de routes, espaces urbains et agricoles, végétation résineuse) à l'explication de trois indicateurs de risque définis comme densité d'éclosion, densité d'incendie et taux de surfaces brûlées. La modélisation de ces indicateurs a contribué à la construction d'un indice global de risque et à sa cartographie qui permet de déduire facilement, et de manière assez directe, l'information synthétique sur les niveaux de risque à l'échelle du territoire. L'approche par les « interfaces habitat-forêt », intrinsèquement porteuses de l'information synthétique aléa/enjeux/vulnérabilité, a servi de clé d'entrée pour une évaluation directe et globale du risque, fondée sur l'observation et la description des territoires d'une part, et en particulier des interfaces habitat-forêt, et sur une analyse spatiale et statistique de ces territoires. Elle permet également de tirer des enseignements d'une meilleure connaissance du territoire et du risque d'incendie associé en termes de prévention. Elle est particulièrement bien adaptée à la mise en évidence, quantifiée, d'une dynamique de territoire lu à travers les interfaces habitat-forêt. Cette dynamique de territoire peut alors être facilement associée à une dynamique du risque dont l'étude est particulièrement intéressante dans le contexte du changement global : dynamique de végétation, dynamique d'urbanisation. Elle offre des perspectives encourageantes en matière de géogouvernance et développement durable dans le cadre d'une prévention contre le risque d'incendie toujours plus efficace et adaptée.
