Forest fire danger extremes in Europe under climate change: variability and uncertainty

Forests cover over a third of the total land area of Europe. In recent years, large forest fires have repeatedly affected Europe, in particular the Mediterranean countries. Fire danger is influenced by weather in the short term, and by climate when considering longer time intervals. In this work, the emphasis is on the direct influence on fire danger of weather and climate. For climate analysis at the continental scale, a daily high-emission scenario (RCP 8.5) was considered up to the end of the century, and a mitigation scenario that limits global warming to 2 °C was also assessed. To estimate fire danger, the Canadian Fire Weather Index (FWI) system was used. FWI provides a uniform numerical rating of relative fire potential, by combining the information from daily local temperature, wind speed, relative humidity, and precipitation values. The FWI is standardised to consider a reference fuel behaviour irrespective of other factors. It is thus well suited to support harmonised comparisons, to highlight the role of the varying climate in the component of fire danger that is driven by weather. RESULTS. Around the Mediterranean region, climate change will reduce fuel moisture levels from present values, increasing the weather-driven danger of forest fires. Furthermore, areas exhibiting low moisture will extend further northwards from the Mediterranean, and the current area of high fuel moisture surrounding the Alps will decrease in size. Projected declines in moisture for Mediterranean countries are smaller with mitigation that limits global warming to 2 °C, but a worsening is still predicted compared with present. There is a clear north-south pattern of deep fuel moisture variability across Europe in both climate change scenarios. Areas at moderate danger from forest fires are pushed north to central Europe by climate change. Relatively little change is expected in weather-driven fire danger across northern Europe. However, mountain systems show a fast pace of change. ADAPTATION OPTIONS. Key strategies to be considered may include vegetation management to reduce the likelihood of severe fires, as well as fuel treatments to mitigate fire hazard in dry forests. These measures should be adapted to the different forest ecosystems and conditions. Limited, preliminary knowledge covers specific but essential aspects. Evidence suggests that some areas protected for biodiversity conservation may be affected less by forest fires than unprotected areas, despite containing more combustible material. Specific typologies of old-growth forests may be associated with lower fire severity than densely stocked even-aged young stands, and some tree plantations might be more subject to severe fire compared with multi-aged forests. Particular ecosystems and vegetation associations may be better adapted for post-fire recovery, as long as the interval between fires is not too short. Therefore, deepening the understanding of resistance, resilience and habitat suitability of mixtures of forest tree species is recommended. Human activity (accidental, negligent or deliberate) is one of the most common causes of fire. For this reason, the main causes of fire should be minimized, which includes analysing the social and economic factors that lead people to start fires, increasing awareness of the danger, encouraging good behaviour and sanctioning offenders. LIMITATIONS. Bias correction of climate projections is known to be a potential noticeable source of uncertainty in the predicted bioclimatic anomalies to which vegetation is sensitive. In particular, the analysis of fire danger under climate change scenarios may be critically affected by climatic modelling uncertainty. This work did not explicitly model adaptation scenarios for forest fire danger because ecosystem resilience to fire is uneven and its assessment relies on factors that are difficult to model numerically. Furthermore, a component of the proposed climate-based characterization of future wildfire potential impacts may be linked to the current distribution of population, land cover and use in Europe. The future distribution of these factors is likely to be different from now.JRC.E.1-Disaster Risk Managemen

Stability of Atmospheric Flow and Low-Level Jets Influencing Forest Fire Behaviour - An EFFIS Report

During the past years, there have been a considerable number of occasions that a forest fire burns with such strong intensity that seems far out of proportion to apparent burning conditions. This proved to be the case for the Sweden fire “blow-up” that took place during 4 August 2014 between Sala and Surahammar municipalities. The fire broke out after an unusual spell of hot, dry summer weather in northern Europe and proved to be the Sweden's largest wildfire in 40 years encompassing an area of ~15,000 hectares. The fire was declared a national emergency. Close investigation of fire weather parameters revealed the existence of an upper-air trough linked to a dissolving warm front on the previous day (3 August) providing low stability values over the fire centroid and the approach of a cold front from southwest further lowering the stability of the atmosphere. But above all, the air dryness and the prevailing of strong surface wind gusts due to a Secondary Low-Level Jet (SLLJ) at 950 hPa accompanied by a short-wave trough most pronounced at 700 hPa (the level of the main LLJ’s kernel of max winds) made ideal conditions for such an extreme event. In such a case, the left entrance area of SLLJ would have allowed an ageostrophic circulation to feed dry air the fire by a direct downward current during the critical hours of 4 August. The time that the SLLJ was crossing and intensifying over and to the east of fire centroid found to be in agreement with the position and movement of the area of maximum instability as defined by the very high (and at times “saturated”) values of Haines Index (HI) being combined with almost “saturated” Fire Weather Index (FWI) values. The HI gives an indication about the potential for a fire "blow­-up” due to low stability values of the atmosphere whereas FWI provides a description of the fire suppression difficulty. It should be noted that a fire blow-­up would lead to erratic/extreme fire behavior. Most of the initial simulations utilising ECMWF instantaneous wind speed values, as driving terms for EFFIS (European Forest Fires Information System) fire evolution models, namely FireSim and FARSITE, were inaccurate due to errors in the intensity and gustiness of true prevailing winds. By introducing model gust factor values (GFs) instead of instantaneous wind speeds (WSs) significant improvement in accuracy was accomplished in all fire evolution simulations. In such distinct unstable environment and under the presence and influence of both LLJ and SLLJ the utilization of model gust factors instead of instantaneous winds found to be more appropriate for simulating fire evolution behavior. Overall, it seems quite important to consider the concept of atmospheric stability, dryness and the presence of LLJs/SLLJs as key elements in the forest fire management system particularly in circumstances conducive to interactions within the PBL (Planetary Boundary Layer).JRC.H.3-Forest Resources and Climat

Wildfires in the Amazon region 2019

Analysis of wildfire trends in the Amazon regionJRC.E.1-Disaster Risk Managemen

Forest Fires in Europe, Middle East and North Africa 2016

Analysis of fire regimes and impacts during the 2016 wildfires season in the region monitored by EFFISJRC.E.1 - Disaster Risk Managemen

Pan-European wildfire risk assessment

Wildfires may result in long-lasting impacts to social, environmental, and economic systems. In a context of changing climate, human activity, and extreme events becoming more frequent, it is crucial to identify spatially the risks posed by wildland fires, to foster better fire management policy tools, and develop mitigation strategies accordingly. However, given the complexity of the problem, scope and methods for wildfire risk assessment (WRA) vary widely among countries leading to different regional/national approaches not always comparable. These uneven approaches understandably focus on the corresponding regions of interest and are affected by the specificities of each country. To integrate currently incompatible approaches, harmonised procedures for wildfire risk assessment are needed at the pan-European scale, enhancing planning and coordination of prevention, preparedness, and cross-border firefighting actions to mitigate the damaging effects of wildfires. The development of a pan-European approach follows from a series of EU regulations requiring the European Commission to have a wide overview of the wildfire risk in Europe, to support the actions of its Member States and to ensure compliance in the implementation of EU regulations related to wildfires. The conceptualization of a European WRA as the combined impact of wildfire hazard on people, ecosystems, and goods exposed in vulnerable areas, explicitly accounts for the multiplicity of risk dimensions and sources of uncertainty.JRC.E.1 - Disaster Risk Managemen

Advance EFFIS report on forest fires in Europe, Middle East and North Africa 2019

This report contains an anticipated annual summary of the fire season of 2019 with an analysis of fire danger and areas mapped in the European Forest Fire Information System (EFFIS). This report precedes that to be published in August/September 2020, which will include detailed reports prepared by countries in the Expert Group on Forest Fires.JRC.E.1-Disaster Risk Managemen

Basic criteria to assess wildfire risk at the pan-European level

This report present basic criteria that could be used for the estimation of wildfire risk at the pan-European level. The report has been elaborated in consultation with the national experts in the Expert Group on Forest Fires. The report represents a first attempt on establishing critical variable that may help in characterizing areas in the pan-European region on the basis of the susceptibility to suffer damages caused by wildfiresJRC.E.1-Disaster Risk Managemen

Advance EFFIS Report on Forest Fires in Europe, Middle East and North Africa 2020

Report on the analysis of Forest Fires in Europe, Middle East and North Africa in 2020JRC.E.1 - Disaster Risk Managemen

Forest Fires in Europe, Middle East and North Africa 2021

This report provides an overview of the evolution and impact of wildfires in Europe, Middle East and North Africa in 2021JRC.E.1 - Disaster Risk Managemen

Advance EFFIS report on Forest Fires in Europe, Middle East and North Africa 2017

This report contains the annual summary of the fire season of 2017 with an analysis of fire danger and areas mapped in the European Forest Fire Information System (EFFIS).JRC.E.1-Disaster Risk Managemen