Contemporary wildfires increasingly differ from those firefighters faced just a few decades ago. In many parts of the world – from the Iberian Peninsula to Australia – we are witnessing a new wildfire dynamic that not only exceeds the technical capacity to extinguish them but also challenges the very foundations of our understanding of fire behaviour. A new kind of fire has emerged: sixth-generation wildfires.
As society, landscapes, and the climate change, so too does the nature of wildfires. The concept of big fires generations, developed by Catalan fire analysts, is an attempt to bring order to these changes. Each successive generation describes a new type of fire – more difficult, more complex, and requiring a different tactical and organizational approach. This classification system helps us understand how environmental and societal developments influence the evolution of wildfires. It was born out of necessity and shaped by the experience of Catalonia – a region that has grappled with frequent and often catastrophic fires for decades. Today, its framework is becoming a point of reference for other parts of the world as universal patterns of fire development intersect with increasingly similar challenges.
🔥 First-generation wildfires are a direct result of rural abandonment and the decline of traditional land use practices such as agriculture, grazing, and forest management. Over time, meadows and former farmlands became overgrown with grasses, shrubs, and young trees, forming a flammable layer of vegetation. The absence of natural breaks in this vegetation increased fuel continuity, making it easier for fire to spread rapidly and uncontrollably across the area. These fires typically have moderate intensity and usually cover between 1,000 and 5,000 hectares. Firest generation fires develop in areas where dry biomass has accumulated over a period of 2 to 15 years. While they can be contained using local resources, hand tools, water lines, and traditional firefighting techniques, they still require a well-coordinated response. They are not extremely difficult to extinguish, but they clearly signal that transformed, abandoned landscapes can foster escalating fire risks. In response to such fires, the first specialized forest firefighting crews were established, along with the development of basic wildfire prevention infrastructure. These fires can be prevented by restoring “mosaic landscape” – a spatially and functionally diverse environment that naturally slows down the spread of fire. To make suppression of these fires possible, linear infrastructure must be developed to improve access to these neglected and overgrown areas.
🔥 Second-generation wildfires occur in landscapes that have been left unused and unmanaged for decades, leading to an intense accumulation of fuel. Over a period of 10 to 30 years, flammable biomass – fuel load of shrubs, young trees, and dry undergrowth – builds up, creating an environment in which fire spreads rapidly and aggressively. The structure and continuity of the fuel generate a fast-moving fire front that hampers response efforts. These fires easily breach firebreaks, produce ember spotting, and often spiral out of control. Traditional suppression methods such as hand tools, water lines, or fire engines prove insufficient. Increasingly, helicopters, aircraft, and rapid mobilization of forces from outside the operational area are required. This type of wildfire typically affects areas ranging from 5,000 to 10,000 hectares. The phenomenon is further exacerbated by the so-called „fire suppression paradox”: the more effectively smaller fires are extinguished, the less fuel is naturally burned. As a result, dry biomass continues to accumulate until ignition occurs at a scale beyond the capacity of fire protection systems. It’s a vicious cycle – short-term suppression success increases the likelihood of large, hard-to-control fires in the future. To mitigate the scale of the threat, early warning systems, automatic alerts, information points, and educational campaigns are being implemented. A key preventive measure is active fuel reduction: mechanical removal of biomass, controlled burning, and restoring land use by people and animals.
🔥 Third-generation wildfires mark a turning point in the evolution of fire events. They occur in forests that have gone 30 to 50 years without active management – no thinning, no removal of deadwood, and no maintenance of forest structure – or have been placed under passive protection. This leads to massive fuel accumulation and the development of continuous “ladder fuels” connecting surface vegetation all the way to the treetops. In such vegetation structure, intense crown fires erupt. These are accompanied by strong convection columns, air turbulence, and numerous firebrands that can rapidly ignite new fires over distances of many kilometers. The extent of these wildfires often exceeds 10,000 hectares and can sometimes surpass 20,000 hectares. Under such conditions, direct suppression becomes impossible – the fire’s intensity and behavior exceed the limits of standard firefighting methods. When a fire’s intensity surpasses the so-called „fire suppression threshold”, even a massive increase in resources has no meaningful effect on its behavior – the energy released during combustion makes effective intervention impossible. This kind of tipping point typically occurs in forests where the fuel load exceeds 10 tons of dry biomass per hectare. At this stage, tactical and operational fire management becomes essential. Rather than fighting the fire head-on, the priority shifts to anticipating its development, identifying “windows of opportunity,” and using natural or artificial barriers to contain it. Controlled burning (backburning) is increasingly used as a suppression method, along with strategic planning, risk analysis, and advanced fire behavior modeling. Preventing third-generation wildfires requires long-term care for resilient forest structure. Key actions include reducing fuel continuity by diversifying stand age and species composition, thinning and pruning, removing deadwood, and creating forest zones with reduced fire risk.
🔥 Fourth-generation wildfires occur at the intersection of forested areas and human settlements, in what is known as the Wildland-Urban Interface (WUI). This is the point at which a second- or third-generation fire stops being a purely environmental issue and begins to pose a direct threat to people, their homes, and infrastructure. When there are no breaks in fuel continuity – from the forest, through backyard vegetation, gardens, hedges, and all the way to fire-prone buildings – it’s no longer just trees that burn, but also vehicles, power lines, houses and entire neighborhoods. As we know fourth-generation fires can even consume parts of large cities… In such situations, firefighters lose the ability to conduct active suppression. The fire moves too fast, shifts direction unpredictably, and its intensity exceeds the limits of direct attack. The priority becomes protecting lives, selectively defending critical infrastructure, and evacuating residents. There are not enough resources to save everything – choices must be made about what to protect first. Response becomes defensive, carried out under time pressure and in highly chaotic conditions. As cities expand toward shrubs and forested areas, the threat increases. Today, it’s no longer just about protecting forests from fire, but about protecting society from large, high-intensity fires spreading through poorly prepared suburbs. Preventing fourth-generation wildfires requires better spatial planning: establishing buffer zones, using fire-resistant building materials, adapting the species composition of urban green spaces, reducing fuel around structures, and educating residents. Only a properly prepared wildland-urban interface stands a chance of surviving contact with a large fourth-generation wildfire.
🔥 Fifth-generation wildfires are the result of multiple fourth-generation fires occurring simultaneously. They erupt in many areas at once – both in forests and wildland-urban interface zones. Fire ceases to be a local event and becomes a landscape-scale phenomenon, affecting entire regions, provinces, and sometimes even countries. Under such conditions, there is not enough personnel, equipment, or water. Emergency services operate at the edge of their capacity, and traditional command models fail. Operational chaos ensues, and decisions must be made not for individual fires, but based on their interrelations. Sometimes this means abandoning one operation to save something more critical elsewhere. Instead of trying to extinguish every fire, a strategy of limited intervention is used where possible – allowing fire to burn accumulated fuel in valleys, on inaccessible slopes, or in remote forests, as long as it does not threaten people. Firefighting resources are directed where they can save lives or infrastructure. This approach is not just a choice, but often a necessity – with limited resources and a growing number of simultaneous fires, it is impossible to be everywhere at once. That is why fire management becomes the art of prioritization. Preventing fires of this generation requires a long-term strategy – smart spatial planning, reducing fuel buildup in the landscape, creating large buffer zones, and strengthening local resilience. Communities must be prepared not only for evacuation but also for living in a world where fire is an inherent part of reality. The emergence of fifth-generation fires forces a paradigm shift – instead of the motto “fight with fire,” the prevailing approach is increasingly to learn to “live with fire”. This is especially true for regions that experience seasonal, intense wildfires almost every year and can no longer count on full control over the element. Until 2017, this was believed to be the worst possible generation.
🔥 Sixth-generation wildfires are extremely dangerous phenomena closely linked to the climate crisis. These are megafires of such immense intensity that they alter the dynamics of the upper layers of the atmosphere and generate winds that are extremely difficult to model, making their behavior impossible to predict. They impact atmospheric stability and create their own weather phenomena – including pyrocumulonimbus clouds, firestorms, and lightning strikes that ignite new fire outbreaks tens of kilometers away. Their development is completely unpredictable, fire behavior is no longer determined by traditional factors such as topography or wind, but evolves according to its own dynamics, creating conditions that current scientific models are unable to accurately forecast. These fires exceed operational capacities – they cannot be extinguished or effectively controlled until atmospheric conditions themselves weaken the force of the element. The only possible response is to try to mitigate their effects and protect people and critical infrastructure. Sixth-generation wildfires do not fit into conventional frameworks of firefighting. They can only be brought under control once the weather changes. Faced with such extreme threats, daily operations must be based on uncertainty matrices and dynamic scenario forecasting. Sixth-generation fires are not just a challenge for firefighters, they represent a global security issue that demands a new approach to risk management, spatial planning, public education, and international cooperation among firefighters and researchers. To confront the scale of the challenge posed by this new scenario, we must accept that some processes associated with pyroconvection are not yet fully understood. New research should focus on investigating and understanding this complex effect of fire-atmosphere interaction.
Let this sixth generation be the last, and may scientists not have to update the list in a few years, because it is difficult to even imagine the threats a seventh generation of wildfires could bring.
| Generation | Period | Area | Description | Operational Challenges | Mitigation Measures / Response |
| 1st – Fuel Continuity | 1950s–1960s | 1,000–5,000 ha | Abandonment of traditional land use (agriculture, grazing, forestry). Creation of a continuous, highly flammable fuel layer. | Difficult terrain access, need to coordinate local forces. | Development of linear infrastructure (roads, water points), restoration of mosaic landscapes, reintroduction of traditional land use. |
| 2nd – Fuel Accumulation, High Speed | 1970s–1980s | 5,000–10,000 ha | Long-term accumulation of dry biomass. Suppression paradox: successful extinguishing of small fires increases the risk of large ones. | Traditional methods ineffective, rapid fire spread, need for aerial support. | Early warning systems, controlled burns, mechanical fuel removal, land use restoration. |
| 3rd – Neglected Forests, Crown Fires | 1990s | 10,000–20,000 ha | Lack of forest management leads to crown fires—intense and difficult to control. | Suppression threshold exceeded, strong convection columns, multiple spot fires. | Tactical fire management, use of “windows of opportunity,” diversified forest structure, creation of forest buffer zones. |
| 4th – Wildland-Urban Interface (WUI) | Since 2000 | >1,000 ha (plus infrastructure) | Fires directly threatening people and infrastructure. No barriers between forest and development. | Operational chaos, need for evacuation, insufficient resources to protect all assets. | Spatial planning (protective zones), fire-resistant building materials, firebreaks, community education, evacuation strategies. |
| 5th – Simultaneity of Fires | Since 2000 | Cumulative across many sites | Simultaneous fourth-generation fires in multiple locations. Fire becomes a regional phenomenon. | System overload, insufficient resources, collapse of command structures, need to prioritize. | Limited intervention strategy, regional and scenario-based management, national resource mobilization, building community resilience. |
| 6th – Extreme Fire Phenomena (Pyrocumulus) | Since 2017 | Megafires >10,000 ha, Gigafires >100,000 ha, Terafires >1 million ha | Megafires linked to the climate crisis. Generation of their own weather phenomena (e.g. pyrocumulonimbus, firestorms). | Complete unpredictability, unreliable models, autonomous fire dynamics, no effective intervention until weather conditions change. | New forecasting models, research on pyroconvection, population protection strategies, international cooperation, planning under uncertainty. |
Understanding wildfires through the lens of generations allows us to view the phenomenon from a broader perspective – not only as an operational issue, but as a consequence of social, climatic, and spatial transformations. As the climate and landscape structures change, more and more countries are experiencing fires that were once considered exceptional. These fires are now becoming the new norm. Our planet is undergoing a profound transformation of its fire regime. This calls for a shift in how we manage land, conduct spatial planning, and educate the public. It also requires recognizing fire as a natural landscape phenomenon, something that can and should be managed, not merely fought. The emergence of sixth-generation wildfires shows that we have crossed a threshold beyond which traditional response strategies are no longer sufficient. We must learn to live with fire. We have to plan for its presence, mitigate its impacts, and strengthen the resilience of our communities. This is a challenge not only for firefighters, but for society as a whole, which must shift from reaction to prevention, from fighting fire to coexisting with it.
