Background: In the European boreal forest, the structure of the forest floor (e.g. depth, mass) and of the vascular understory plants (e.g. height, mass) are fundamental drivers for fire behavior. Typically, quantitative assessment of this require time-consuming destructive sampling. Methods: Using novel techniques and destructively sampled fuel data from a large number of plots, we devised and calibrated a non-destructive method for quantifying surface fuel depth and load in upland forests in the European boreal region. The depth of the potentially flammable moss/litter layer was measured using a simple penetrometer, applying a force of 15 N to the forest floor. Penetrometer depths were compared to density profiles and post-fire consumption of organic soil layers. Based on parallel destructively sampled data from nearly 200 plots, the dry mass of flammable moss/litter and that of understory dwarf-shrubs were determined based on penetrometer depth and the surface coverage and height of dwarf-shrubs, respectively. Results: In parallel measurements of pre-fire penetrometer depth and post-flame-passage depth-of-burn during experimental fires in boreal forest, the two were virtually identical, showing that the penetrometer can indeed delineate the fuel potentially available for the flaming front, under sufficiently dry conditions. Using high-resolution density measurements across a gradient of forest floor depths, we found that the penetrometer depth matched the depth at which bulk density reached c. 30 kg m−3, which was identical to the transition layer between moss/litter and the much denser humus below. Penetrometer depth was converted to moss/litter dry mass using a power law function (r2 = 0.53). Dry mass of live surface fuels for three dwarf-shrubs, that are near ubiquitous in European boreal forest, was estimated based on the product of visually assessed cover (proportion of the sample area) and height (second order polynomials, r2 > 0.88). Conclusions: Our method allows for rapid assessment of surface fuels and should, with site-specific calibration, be applicable to other boreal forest ecosystems. A process time in the field of between one and two minutes per plot greatly facilitates large-scale fuel sampling

Wildfire risk at the Wildland–Urban Interface (WUI) emerges through everyday landscape features; features cut across areas of responsibility and impact on diverse land-uses. In Sweden, wildfire hazard is shaped primarily by human activity and rapidly drying vegetation, yet public awareness remains low in part due to the historical rarity of large fires. Recent extreme fire events in 2014 and 2018 have however exposed a growing vulnerability, particularly within dispersed settlements embedded in forested terrain. In this paper we examine perceptions of wildfire mitigation and adaptation through three scenario-based workshops conducted in Oskarshamn, Sundsvall, and Gothenburg. The scenario narratives, grounded in real fire events, were used to facilitate discussion, draw out local knowledge, and examine assumptions of fire risk, responsibility, and mitigation actions. Analysis of the workshop discussions has been structured around five mitigation strategies: vegetation management, structure and garden hardening, community hardening, education, and enforcement and incentives. The analysis reveals both shared concerns and need to recognise context across regions. Participants emphasized the importance of vegetation management, diversified forest structure, improved building and garden practices, and place-specific education, while highlighting persistent challenges linked to unclear responsibilities, economic constraints, and limited regulatory support. Our study demonstrates the usefulness of scenario workshops for collective learning and realising local capacities, for living with fire risk in the Swedish WUI

European spring grassfire danger in a changing climate

Wildfires constitute a frequent example of climate change impact. Fire‑prone weather has increased across much of the world and contributes to a global rise of wildfire disasters. Changing drought patterns affect Mediterranean regions (California, Chile, South Africa) while boreal forests are drying more rapidly during warm summer days.In southern Europe, large and intense fires occur during high summer causing fatalities and affect buildings and ecosystems. In other (north and east) more mesic parts of Europe, smaller early‑spring fires are most numerous. For Scandinavia, these are the fires that cause the greatest damage to people and buildings.In eastern and northern Europe, cold winter weather leads to senescence of grasses and herbs. As sunlight and temperatures rise in dry spring air, this highly flammable litter dries quickly and can spread flames much faster than typically observed for forest fires. However, the grass‑fire season lasts only a few weeks until fresh green grass, with highmoisture content, emerges through the litter. Thus, grasses become flammable indifferent weather conditions than forests, and their seasons are often separated in time.While the impact of climate change to increasing forest fire danger is well established, changes of grassfire risks are not yet studied. An expected increase of dry and warm early‑summer weather would typically increase spread rates, and reduced snow cover expose more litter, thus enabling fire for dry conditions. By contrast, shorter snow seasons and warmer winters accelerates green-up which impedes fire spread potential. Reduced solar radiation and changes in dry winds, cloudiness, and precipitation patterns are also important factors whose influence on grassfire risk remains uncertain.Here we calculate rate of spread in spring grasslands using the Swedish grass fire danger model. Using two scenarios with five independent climate models each,grassfire risks in ten European regions are assessed towards the end of this century in terms of (i) the number of risk days and (ii) each season’s maximum spread rate.The results show that in all non-mountainous regions both the number of risk days and the season’s maximum risk peak are projected to decrease. Under RCP8.5, maximum spread rates decrease by roughly 10% across most lowland regions between the reference period (2006-2035) to the 30-years period (2071-2100). The number of risk days also decrease with 11% to 35%, depending on region, with the greatest reductions occur in places where the largest proportion of snow days is expected to disappear. Faster onset of grass growth shifts the combustible season into less dry weather. In these cases, increased temperatures actually lead to lower flammability through a phenological shift.The Scandes exhibit only small changes while both the Alps and the Carpathians display increasing numbers of risk days. Spatial variability across the mountain regions is large and, in contrast to the lowlands, the areas with the greatest snow loss also show the largest increase in risk days. This trend is driven by more fire‑prone (dry and windy) weather during the early winter months, when grassfire risk rises by increasingly exposed litter layer before the onset of green-up. 

The winter wildfire at Nes in Ørland, February 2026 - Overview of weather drivers and factors limiting building damage The wildfire in Ørland, Norway, started on February 7th 2026, and burned over 200 ha during the night, threatening about 18 buildings, of which one ignited. A long snow-free period of dry katabatic winds from the Scandes mountains dried out the dormant vegetation just as a surge in strong winds occurred during the evening of February 7th. Fire danger, in terms of Initial Spread Index (ISI), was classified as very extreme just after ignition, leading to rapid flame spread. Vegetation comprised open heathland dominated by heather, crowberry, and moss, interspersed with small groves of birch and conifers. Surface fuels (particularly heather) were highly flammable, and firebrands bridged fuel gaps with spot ignitions over 200 meters. A building was destroyed, but several measures prevented the ignition of dwellings and other buildings. Flame contact and firebrand vulnerability was reduced by active measures such as pre-wetting, suppression of fires and fire breaks, and passive preventive measures such as vegetation management, tidy gardens and well-maintained buildings with non-combustible foundations or surrounding gravel. 

This report summarizes current research on physical, social, and ecological

vulnerability to wildfires in the boreal but highly managed landscapes of Sweden.

The literature shows that most human injuries and most building ignitions occur

during small, building-adjacent spring grassfires, and that physical vulnerability can be

reduced by creating defensible space between buildings and flammable vegetation.

Existing literature on social vulnerability suggests that rural residents, older adults, and

individuals engaging in traditional fire use are disproportionately affected. However

little is known about how different societal groups anticipate, respond to, and recover

from fire events in Sweden.

In terms of ecological vulnerability, Swedish boreal forests exhibit moderate

susceptibility and high recovery capacity in comparison to global ecosystems, owing to

long evolutionary adaptation to fire and rapid post-fire regeneration by broadleaved

pioneer species. The forest landscape is on the other hand threatened by a century-long

fire deficit, decreasing the occurrence of mixed and sparse pine forests in favor of dense

spruce stands.

In summary, the structure of settlements and gardens, the societal structure as well as

the highly exploited and managed forest landscape makes it difficult to apply

relationships and conclusions drawn from other regions directly to a Swedish context.

It is important to reflect how the specifics of this region play out in terms of all aspects

of wildfire vulnerability.

The increasing severity of wildfires poses significant challenges through the release of greenhouse gases and other harmful gases and particles. Although field measurements exist, there is a lack of systematic data collection to understand the influence of moisture content on the particle and gas emissions of boreal fuels, particularly for European boreal forest fuels. This study investigates the influence of moisture content and fuel type on flaming combustion emission characteristics of surface fuels collected from two Swedish forest types, which share key characteristics with fire-prone forests across the European boreal. The results are based on bench-scale controlled combustion conditions in a cone calorimeter, where gaseous and particle emissions were measured using Fourier Transform Infrared spectroscopy and an Electrical Low-Pressure Impactor, respectively. Moisture content of the fuels only insignificantly affected combustion efficiency, with higher moisture content leading to increased emissions of incomplete combustion products (CO, CH4 and NH3). Thus, although moisture affects the amount of fine fuel consumed in a wildfire, it is not significant for the emissions factors during the flaming combustion. The combustion of mosses was instead significantly less efficient than that of litter for all moisture contents. Average emission factors highlighted clear differences between fuel types, with mosses producing higher CO (87 ± 20 g/kg) and lower CO2 (1350 ± 220 g/kg) compared to litter (47 ± 12 g/kg and 1620 ± 81 g/kg, respectively). Particle emissions were strongly dependent on fuel type with (Formula presented.) of 29 ± 12 g/kg for mosses compared to 98 ± 15 g/kg for Pinus sylvestris needles and twigs

Retrospective analyses of fire danger typically use reanalysed data, but its relation to observed fire danger is not well researched. Here we use daily weather observations to calculate fire danger for nine weather stations in Sweden, spanning 1100 km N–S, for the period 1951–2020, making it among the longest series of observed fire danger to date. All sites except the northernmost one exhibited increasing seasonal FWI-metrics over the period and linear trends were statistically significant for three sites. On average, annual peak 7-day moving-average FWI increased by 18% over 70 years. Increasing trends were mostly driven by higher noon-temperature and not by altered precipitation patterns. Further, observed fire danger differed substantially from that based on ERA5 reanalysis data. For FWI > 5, reanalysis FWI-values were on average 25% lower than corresponding observational values. The strength of reanalysis data is to form gridded data using single assimilation schemes against homogeneous model fits and it is not designed to fully represent actual point scale weather. While reanalysis data enables comprehensive geographical analyses, this study shows how it also underestimates peak fire weather in northern Europe. We recommend checking extreme-value bias against point observations in future studies.

Wildfire damage to the built environment and people is typically understood through case studies of high-impact events, or from incident databases where the smallest wildfires are not always accounted for. We analyzed an exhaustive database of 131 040 reported fire service wildfire dispatches (1996–2022) in Sweden. There were on average per year 126 wildfires that threatened buildings, 22 that ignited buildings, 17.6 that injured people and 1.1 that led to a fatality. The analysis showed that building ignitions, human injuries as well as fatalities in this region were caused primarily by relatively small fires (90th percentile <10 ha) and that they occurred predominantly in the spring season. Untended grass litter near buildings constituted a much higher fire threat to the built environment than did forest vegetation, even when fire danger was relatively low. The source of the ignitions was 99 % anthropogenic and mostly connected with intentional fire use such as burning grass litter or garden debris. Our study highlights the need for improved fire statistics to cover the full extent of threats to life and property from wildfires. Further, it suggests that the potential for harm reduction through improved wildfire knowledge among the rural population should be large.

This article aims to delineate the wildland–urban interface in the sparsely populated, limited-resourced Scandinavian peninsula (excluding Finland). Common WUI mapping assumptions and how different thresholds capture the reality of building ignition from wildfire in this region are evaluated. We show that dedicated fuel maps capture areas at risk slightly better than vegetation maps, although the choice of map per se is less important than the selected limit for possible ember transport. The commonly used 6.17 buildings/km2 threshold for building density fails to capture most wildfire incidents that have led to building ignition.