Researchers race to predict wildfire behaviour as France’s biggest fire in decades rages

Firefighters on Thursday battled for a third day to contain the biggest wildfire in France since 1949 raging in the southern Aude region, where more than 17,000 hectares (42,000 acres) have been blackened by flames. A 65-year-old woman was found dead in her scorched house and more than a dozen other people have been injured, two of them seriously.

The authorities have mobilised 2,500 firefighters and significant air support to combat the flames.  

The fire continues to spread, fuelled by hot dry weather and strong winds. 

Prime Minister François Bayrou, who visited the area on Wednesday, called the blaze “a catastrophe on an unprecedented scale” and warned that there could be more such disasters in the coming decades as a result of global warming. 

Researchers are trying to better understand wildfires to learn how to prepare for them more effectively. Mélanie Rochoux, a researcher at the European Centre for Research and Advanced Training in Scientific Computing (Cerfacs) in Toulouse, has spent years studying the behaviour of forest fires and how weather and vegetation impact them. She provided some insights into the research currently under way.  

FRANCE 24: The rapid spread of flames in the Aude region seems to have taken authorities by surprise. Are we able to predict how a fire will evolve once it starts?  

Mélanie Rochoux: That is precisely the subject of my work with colleagues from Météo-France (France's national weather monitor) and the University of Corsica. At present, there is no operational tool deployed across France that can predict the behaviour of a fire in advance and determine precisely how it will spread, at what speed and in what direction. 

The answer will depend on meteorological factors – temperature, wind, humidity – and environmental factors, such as the topography of the area and the vegetation.  

Vegetation arranges itself into vertical strata, with a lower layer consisting of ground cover, a middle layer consisting of shrubs and an upper layer at the treetops. 

Anything close to the ground – mainly dead vegetation such as twigs, leaves or pine needles – is particularly sensitive to changes in weather conditions. When the air humidity is low, this vegetation dries out quickly and becomes highly flammable. When a fire starts, it is this vegetation that will help it spread, depending on the wind. 

But in some cases, trees can catch fire and burn all the way to the top, like torches. This is called a "crown fire", which greatly accelerates the spread of the flames. 

In a given geographical area, the specifics of a fire will depend on a combination of these factors. Currently, all our work consists of carrying out simulations to better understand the role of these different factors and modelling scenarios based on data from previous fires.  

However, we are still at the research stage, and we need more data to strengthen our models. In recent weeks, a fire observation campaign has been conducted in the south of France using an aircraft from the CNRS (France's National Centre for Scientific Research) and Météo-France. The aim was to fly over the forest fires, taking multiple readings on their nature, their spread across the ground and the components of the smoke in affected areas. Over the next two years, this aircraft will fly to Spain and Portugal to gather more data on fires in southern Europe as part of the EUBURN research programme (on wildfire risks). 

Read moreAs France battles wildfires, experts call for a rethink of forest management

Is the scale of the fire in the Aude region something that was foreseeable? 

In the Aude region, all the conditions were in place for a large-scale fire: strong winds with gusts of over 50 km/h, high temperatures of over 30°C and very low humidity in a heavily wooded area.

However, the situation was also exacerbated by a wet spring, which promotes the growth of vegetation. This was followed by a very hot and dry June, resulting in severe drought. We therefore ended up with abundant but very dry vegetation – the perfect fuel. 

This explosive combination of heat and drought is what we call “concurrent extreme weather events”. And it's a recipe for large fires. 

Météo France had accurately predicted this in its forest weather forecast. On Tuesday, the Aude department was placed on red alert, meaning a very high fire risk. But it is important to remember that there can be no fire without a spark. In France, nine out of 10 fires are caused by humans. 

Given the scale of the disaster, can we see this as a sign of climate change? 

An attribution study will determine the extent to which climate change made this fire more likely. But what is certain is that with global warming, fires like this are likely to become more frequent. 

As we know, climate change is making extreme events such as heatwaves and droughts more frequent and more intense. The combination of heat and drought that we are seeing in the Aude region is therefore more likely to occur in the future. 

But climate change is also altering the geography of fires. For a long time, fires in France were confined to the Mediterranean region. But increasingly, they can affect any part of the country, as long as the weather conditions are right. We saw this in 2022 with fires in Gironde (in the southwest) but also in Finistère (on the northwestern Atlantic coast) 

Read more‘We’ve lost everything’: Tourists evacuated in France’s Gironde as wildfires rage 

When a wildfire occurs, the current strategy is to act quickly to bring it under control. Does the new reality, with more intense and frequent fires, undermine this policy? 

Firefighters in France try to get to a fire as quickly as possible to bring it under control. So far, this strategy has proven successful. 

But the new reality increases the risk of multiple large fires occurring at once in several places across France, making that strategy difficult. This was one of the things firefighters feared in 2022 during the major fires in the Gironde region. If fires had broken out at the same time across the Mediterranean region, the situation would have been very difficult to manage. 

Technical and logistical resources remain limited and cannot be expanded indefinitely. In the long term, this early-attack strategy could be difficult to apply systematically, especially since fires are not just an issue for France but for Europe.

There is a European solidarity mechanism for fighting fires, but if a major fire breaks out in France at the same time as in Greece or Portugal, we would not be able to benefit as much from these European reinforcements.

With this in mind, would being better able to anticipate fires allow for a better use of resources? 

Better anticipation enables us to better identify which fires to tackle as a priority, for example, by identifying those that are most likely to reach populated areas or escalate into mega-fires. We could then pre-position aerial and human resources according to priority. 

That is why we are seeking to map areas where large fires could develop and plan for how they might evolve during the summer season. Ultimately, we want to be able to say, "If a fire starts here, it will spread there, at this speed, and reach this size." A better understanding of wildfires will enable us to better prepare for them.

This article has been translated from the original in French by David Howley.