“Unsurpassed” fires are ravaging California, Oregon and the state of Washington. A virulence of fires that is partly due to the consequences of global warming, but also linked to many other factors, human or not.
Dozens of fires are raging in California, where ten people have already been killed. Oregon was forced to evacuate 500,000 people, or more than 10% of the population, and fires spread to the state of Washington, far north of the west coast of the United States. the impressive images of the orange sky above San Francisco, where firefighters in recent days have been working to catch the flames and protect the population.
A reality that can also be quantified: since the beginning of June, more than 12000 km² of land went up in smoke. “The extent of the burned areas is unmatched, while it is only halfway through the California fire season,” Dominique Morvan told France24, from the CNRS research group “Feux” and affiliated with the University of Aix-Marseille. “Six of the fires that broke out [depuis juin, NDLR] is already among the twenty most powerful fires that California has encountered in its history, “adds Jean-Baptiste Filippi, director of the CNRS FireCaster program at the University of Corsica, contacted by France24.
It is this spread of fire that nothing seems to be able to stop and the spread of eruptions along the west coast that make these fires extraordinary events in the region’s recent history. Out of the ordinary perhaps, but not unexpectedly. It’s an explosive cocktail that struck the three states in the American West. “The repeated droughts in recent years have weakened the forests,” says Dominique Morvan.
In addition, “the warmer winter seasons have exposed the vegetation to water stress, that is, it has not had time to make the necessary water reserve to meet calmer. Fire season,” specifies Anthony Collin, also a member of the CNRS “Feux” research group and specialist on fire modeling, contacted by France 24.
These abnormally high temperatures in winter have also “made it possible for insects that generally disappear during this period to continue to attack trees”, emphasizes Dominique Morvan.
But that is just the background to the drama. This year, in mid-August, California experienced a period of very hot weather along with “many dry storms, that is, with strong electrical activity, but without water reaching the ground,” explains Jean-Baptiste Filippi. Weather phenomena that served as so many triggers for the fires.
In a way, this is partly due to chance, as these dry thunderstorms may have fallen off the coast of California or in areas with less dry vegetation, states the head of the FireCaster program. But man is not absolved of responsibility in this matter, for the global warming, for which he is partly responsible, “increases the frequency of these extreme weather events and therefore also the risk of them causing fires,” explains Jean-Baptiste Filippi.
Even the Covid-19 epidemic plays a role
The rapid spread of fires is partly due to the fact that the temperature drops slightly during the night, which “is a new phenomenon 2020”, emphasizes the Vox website. “In the past, when night fell, temperatures dropped sharply, allowing humidity to rise, giving firefighters a window to better control flames that have become less strong,” explains Matthew Hurteau, a specialist in global warming effects on forest ecosystems. at the University of New Mexico, interviewed by Vox.
But that is not the only factor. California is also building more and more in high-risk areas and at the forest edge. “The increase in rents in the city center has in recent years driven a growing number of people to settle in the wilderness areas where fires are more common,” states Vox. When fires break out, “firefighters’ action focuses primarily on these populated areas to protect the population,” explains Jean-Baptiste Filippi. But because of this, firefighters are forced to let the fires spread into the wilderness where they quickly gain strength.
There is also a snowball effect with the fires this year. The fires quickly reached “regions that are rarely affected, such as Washington State, and where vegetation may have accumulated over the years, providing new fuel for the flames,” said Dominique Morvan, of the CNRS.
Even the Covid-19 epidemic has contributed to the current situation. “In California, authorities often call in prisoners serving short sentences to help control fires. But this year, they have been released to avoid overcrowded situations that facilitate the spread of the virus in prison.” explains Dominique Morvan. “These prisoners had been helping the California fires for decades, but not this time, depriving firefighters of crucial help.” confirms the New York Times.
It is this accumulation of factors – between the underlying trends linked to global warming and the particular characteristics of the US west coast – that explains why the region is burning so much this year. And it’s not over. “The fire season is generally intensifying around November due to the strong easterly winds that are coming,” reminds Jean-Baptiste Filippi. It remains to be seen what effect the summer fires will have on the coming “high season”. On the one hand, a large part of the vegetation, the natural fuel for fires, has already been consumed, but on the other hand, states Jean-Baptiste Filippi, “the firefighters have already accumulated a lot of fatigue”. A struggle that would then be very unequal.