But sometimes it is lightning, faulty power lines or arson that cause fires to start.
Elsewhere, poorly adapted fire prevention techniques have led to a buildup of flammable vegetation.
And metropolises, like California, tend to bite into forested areas that are naturally more prone to fires.
– Pollution –
Scientists continue to discover new effects.
Fires change the weather: they modify the winds, throw soot aloft and can cause lightning.
They can generate prodigious quantities of CO2 and even affect the atmosphere.
Canadian wildfires of 2023 released more carbon in five months than Russia emitted from fossil fuels in a year, NASA scientists calculated, even if some was reabsorbed by trees .
In 2023, scientists showed that a chemical reaction from smoke released by massive fires in Australia widened the ozone hole by 10% in 2020.
Fires sometimes have unsuspected consequences.
-One study showed that ash from fires in Australia landed in the ocean thousands of miles away, triggering plankton blooms that absorbed the extra CO2, at least temporarily.
These ashes can travel far. Joan Llort, of the Barcelona Supercomputing Center, who led this study, also says that some of it landed on the ice cap, with the effect of making it melt more quickly: he describes a “regime change” in the Arctic.
– Soot residue –
In the winter of 2021 in Colorado, Christine Wiedinmyer still had to figure out how to decontaminate homes blackened by smoke – a topical issue for the tens of thousands of Los Angeles residents in evacuation zones.
“A lot of pretty harmful things escape when a house, a car or electronic devices burn,” says the researcher.
With colleagues, she took samples from the air, soil and houses, before and after cleaning.
His work showed that the most harmful residues were sucked into the walls, where they can remain for days or months.
To decontaminate effectively, his scientific advice is simple: wash walls and floors with soap and water.
