One is a boy of 15, who threw a burning cigarette into a wood near Bordeaux. Another is a 36-year-old man who set a paper bag of rubbish on fire in bushes near Perpignan. A third is a 50-year-old woman accused of lighting 17 fires south of La Rochelle.

According to the French interior ministry, since the start of a summer in which a record 115,000 hectares of forest, scrub and heathland have gone up in flames, 514 people – including 198 minors – have been arrested on suspicion of starting wildfires.

Who are they, and what motivates them? Experts say arson is an under-studied field in France. It remains, according to Thierry Toutin, a criminology researcher with the national police, “a mysterious crime, often hard for people to understand”.

The summer of wildfires has turned the spotlight in France on the question of what – and who – is causing them. Photograph: Steph Picture/VHP/AFP/Getty Images

Two hundred years ago, under Napoleon, deliberately starting a wildfire in France was a crime so grave it carried an automatic death penalty by guillotine. These days, sentences start at 10 years in jail and a €150,000 fine, rising to 15 years if protected forests or reserves burn, and life if someone is killed.

Arsonists have “many different profiles”, Toutin said in an essay for The Conversation. Several French departments have set up dedicated arson groups uniting police, forestry board experts and local services to help identify, find and prosecute them, he said, but still: “These are often crimes that are unsolved, or don’t lead to convictions, because the fire has destroyed the evidence.”

France’s official statistics classify wildfires by their cause: natural, such as lightning; accidental (say, a vehicle fire or electrical fault); involuntary professional (sparks from a machine); involuntary individual (a cigarette or barbecue) – and voluntary.

In practice, as a government PSA has repeated all summer on radio, TV and online, nine out of 10 fires are caused by human activity, with roughly two-thirds classed as involuntary (which, if negligence is proven, carries a jail term of one to five years).

That means fully one-third of wildfires in France each year are set deliberately, with the intention of doing harm. In 2025, the last year for which full figures are available, deliberate acts of arson were the biggest single cause of forest fires in France, accounting for 29.4% of blazes.

Among those convicted this summer are a 27-year-old man diagnosed with autism and schizophrenia who set fire to a letter to his late daughter in tinder-dry vegetation near Béziers. He was sentenced to four years of detention and treatment.

Perpignan court last week sentenced a 51-year-old man to five years in prison for lighting four fires in July and August. In Les Sables d’Olonnes, a volunteer firefighter – reported to police by his superiors – was handed a three-year suspended sentence.

In Lyon, a 29-year-old man with a police record for theft, trafficking and domestic violence was convicted of setting a fire that destroyed more than a hectare of land, took 71 firefighters to extinguish and forced the evacuation of 150 people.

Among those convicted of arson this summer is a volunteer firefighter. Photograph: Emma Da Silva/AP

Those convicted of negligence include a motorist who lit a fire to alert emergency services after he broke down (six months, suspended) and two restaurant owners in the south-west who defied a red fire alert to light a charcoal grill and set off fireworks.

An early analysis based on police reports and obtained by Le Figaro showed 97.5 % of arson suspects arrested this year have been men, aged on average 32.5, with 28.7% under 18. More than 95% were French citizens. Of a relatively small sample of 80 suspects, 37 were unemployed.

Exactly what drove them to act is often much harder to establish. In principle, criminologists identify four main categories of motivation. Some arson attacks are carried out in the context of a conflict: a dispute with a neighbour; criminal rivalry between gangs; revenge against someone or something.

Other arsonists may act for financial gain, such as a false insurance claim, or out of ideological or political conviction. The remainder display some kind of pathology, often psychological – including a small number of genuine pyromaniacs.

“Arsonists may be after money, or revenge, or be trying to cover up a crime. They may be under the influence of alcohol or other substances,” said Laurent Layet, a psychiatrist. “A pyromaniac’s sole objective is to set fire to something.”

Pyromaniacs “have difficulty organising their personalities”, Layet told France Inter radio. “They are often impulsive, and they have trouble controlling their emotions. Often, they are quite isolated socially.”

Classified as an impulse-control disorder, pyromania is characterised by “a fascination with fire, by a mounting tension before the act, and then a feeling of pleasure or relief immediately afterwards”, he said. But pyromaniacs are typically organised, aware of the consequences of their acts, and considered criminally responsible.

In all, a record 115,000 hectares of forest, heath and scrubland have gone up in flames so far this year. Photograph: Romain Perrocheau/AFP/Getty Images

They also represent barely 5% of the people who deliberately set fires. Another equally small group are firefighters – mostly volunteers, very rarely professionals – who deliberately set fires for the glory that comes from extinguishing them.

Over the years, France’s departmental fire services have set up filtering mechanisms to detect such personalities during the recruitment process, including psychological tests. They acknowledge that each year, some slip through the net.

But the motivation of most people who deliberately light wildfires is rarely quite so clearcut. For many, it boils down to an ill-defined “act of defiance – to confront the system, and get pleasure from destroying other people’s property”, said Johanna Rozenblum, a clinical psychologist who works with the fire service.

A strikingly large proportion of the arsonists she had dealt with had “marked antisocial profiles”, Rozenblum said. And in the case of minors, adolescent impulsiveness and frustration combine with “immaturity and internal revolt” to prevent them fully realising the devastating scale of the damage they risk doing.