For more than a week, Chile has been plagued by hundreds of fires in the regions of Ñuble and Biobío, south of Santiago, which have already ravaged more than 40,000 hectares. The situation could worsen over the next few days, with a new heat wave raising fears of an expansion of these “megafire”.
This phenomenon was still unknown a few years ago, but really took root in the minds of the French last summer with the great fires of Gironde, which burned nearly 30,000 hectares and required around 50,000 preventive evacuations. These extreme events are at the heart of a new exhibition which opens in quay of knowledge From toulouse.
Already presented at the Cité des sciences under the title “Fire”, it has been enriched for Toulouse with an immersive experience on “megafires”, a hot topic and on which we do not yet have a lot of data. .
What are “megafires”?
“The term megafire is a media term. Scientists prefer that of extreme fire events. These are fires that are extreme in terms of their speed, their intensity, the phenomena involved, the magnitude they can have and which we have rarely seen in the past,” says Mélanie Rochoux, researcher at the Center for Fundamental and Applied Research. specialized in numerical modeling and simulation, which works on the theme of forest fires.
Megafires would represent “only” 3% of fires, but would be responsible for more than 50% of the burned surfaces of the planet. Unlike fires, which occur regularly in the heart of summer, these phenomena are more uncontrollable. “It is something that we know but that we do not control, because the very principle of the megafire is that it goes so fast that it very quickly exceeds the operational capacities of the firefighters”, recognizes Sébastien Vergé, the director of the Haute-Garonne departmental fire and rescue service.
“When we think of the Australian fires of 2019-2020, there were multiple fire swings, projections of embers at very great distances which will declare new fires, but also pyroconvection phenomena, these plumes which go to very high altitude and which will cause the fire to create its own local weather dynamics”, continues Mélanie Rochoux.
What are the major contemporary fires?
The phenomena that we saw in Gironde last summer can be classified in the category of megafires. But they are far, in terms of burned areas or impact on populations, from reaching those that have affected the American or Australian continent in recent years. In 2018, in Camp Fire, California, 85 people lost their lives and 19,000 homes were destroyed.
The following year, during the winter of 2019-2020, a real ecological disaster took place in Australia during the fires which claimed the lives of 33 people and ravaged 240,000 km of vegetation. Baptized the “black summer”, this event would be the cause of the death or displacement of 3 billion animals and an amount of damage estimated at 6.5 billion euros. Two years ago, the Pantanal in Brazil was dying, hit by megafires that burned 39,000 km2.
But Europe is far from being outdone. In 2017, the municipality of Pedrogao Grande, in Portugal, experienced an incredibly violent fire, causing the death of 65 people. In the summer of 2018, Latvia and Sweden also experienced megafires. But that year, it was in Greece that the deadliest fire of the last decade took place. At the height of summer, in Attica, 102 people lost their lives.
Phenomena related to climate change
Like the majority of fires, megafires have a human origin, whether accidental or deliberate. Except in certain remote areas where meteorological phenomena such as lightning can be the cause of the spark. But another factor has come into play in recent years.
“The fact that these cases are increasing is indeed linked to climate change: megafires are both the symptoms and the consequences of this climate change”, underlines Mélanie Rochoux.
Extreme heat waves, coupled with significant droughts and strong winds, are the perfect combo for them to thrive. Deforestation also plays a role. According to the IPCC, in the Amazon, it has had a greater impact on the increase in burned areas than global warming itself.
These fires themselves are certainly fueling global warming. “We know that the 2019-2020 Australian fires, among the most extreme on record, can be considered a moderate volcanic eruption in terms of their impacts on the upper atmosphere. The smoke plumes rose so high in the atmosphere that they managed to inject particles into the stratosphere. And once they are there, they can stay there for several months, and that can change the solar radiation and have an impact on the climate. Studies are underway to better understand and quantify this impact,” notes the Cerfacs researcher.
… And which also have an impact on health
These nanoparticles will have an impact on atmospheric pollution, and therefore affect those who breathe them. “After the big fires in Australia, we were able to follow the cloud of nanoparticles that went as far as Latin America. Thousands of kilometers away, people breathed in the nano ashes emitted in Australia, ”recalls Laurent Chicoineau, director of the Quai des Savoirs.
At the heart of the exhibition presented by this place of scientific culture, we can thus learn that at the time of the megafires in Indonesia in 2015, 43 million people suffered from long-term exposure to smoke. It must be said that they emitted 1.5 billion tonnes of CO2, or 5% of annual global emissions. With a direct consequence on human health since it is estimated that up to 100,000 people died prematurely because of these fumes and the poor air quality that ensued.
No more megafires in the future, everywhere
Fires have always marked the summer news in Europe. For a decade, there has been at least one, whether in Portugal, Sweden or Greece. Siberia too, even if we talk about it less, is often affected by megafires.
“There are areas, such as the south-east, which are regularly affected, the Maures massif in the Var, for example, has burned three times in thirty years. These areas will continue to have them and we know, with climate projections, that the risk will intensify. They also show that there are new regions in France where the risk will increase, even if it is subject to significant uncertainties, in particular in the west of France or the center. For example, the forest massif in Sologne, we know that it could be vulnerable with climate change, that it has tree species that are not adapted to fires, ”warns Mélanie Rochoux.
Failing to be able to control them, today scientists are trying to identify, “thanks to the observation of the state of the soil or the drought, the places which are more favorable than others to go up in smoke”, explains Laurent Chicoineau. Before adding that with “remote sensing tools, satellite cartographic analysis, but also artificial intelligence laboratories, researchers are developing programs that will make it possible to predict the occurrence of a megafire or not”.
In the meantime, to avoid them, the best weapon according to the boss of the Haute-Garonne firefighters remains that of prevention. “We must also accentuate all that is clearing of vegetation, because all that is interface of forests and habitats is problematic. This is where we have risks for people’s lives and this mobilizes a lot of firefighters who are not fighting the fire during this time”, assures Sébastien Vergé, who has reinforced specialized training in recent years ” Forest fire “.