This summer, France's wildfires burned more land than ever recorded, displaced more people than at any point since World War II, and likely produced the country's first firestorm thundercloud. The smoke from the biggest inferno in nearly 80 years choked Limoges, 125 miles (200km) from the flames, with more toxic dust than Delhi's worst smog day last year.
The blaze outside Bordeaux in late July took weeks to reshape France's relationship with fire, but the conditions were centuries in the making. In the 18th century, the coastal wetlands of south-western France were so swampy that shepherds used stilts. A 1857 decree by Napoleon III forced landowners to drain the marsh and plant maritime pines, creating Europe's largest human-made forest - now an economic engine employing 30,000 people.
It's also a firefighter's nightmare. The pines, 90% of the Landes forest, hold resin that burns like petrol, needles that carpet the ground with flammable material, and cones that whiz like grenades, spreading flames across breaks that should act as barriers. Without broad-leafed species that retain moisture, the dense monoculture burns with fury.
That happened in 1949, when a saw mill blaze burned 50,000 hectares, killing 82 people - mostly volunteer firefighters. It remains Europe's deadliest wildfire.
Firefighting has improved, but disaster potential has grown. Humanity has added 1.85tn tonnes of planet-baking carbon since 1857, warming Europe by 2.4C and increasing hot, dry extremes. A wet winter helped plants grow, then heatwaves dried them, creating fuel. By mid-July, record temperatures and record-low soil moisture set the stage for the Gironde inferno.
On 22 July, after three weeks of 30C heat, smoke rose near Saumos, 20 miles west of Bordeaux. Workers for Enedis, a utility company, reported sparking a fire with a faulty machine; the Bordeaux prosecutor is investigating. Enedis declined to comment. Most wildfires are human-caused; French police have arrested nearly 500 people on suspicion of arson, about 70% deliberate.
Once started, weather and geography dictate the outcome. The fire engulfed hundreds of hectares in hours, reached La Porge (losing 1 in 10 homes), and within 24 hours pushed to Cap Ferret, nine miles away. The area had been flattened by a 1999 storm and replanted uniformly, creating continuous fuel. Firefighters rejected local recommendations for controlled burns, and residents claim resources were diverted to wealthier Cap Ferret. The fire service denies this. Bruno Lafon of the regional prevention service said the combination of drought, heat, and wind made spread hard to stop: "The men did what they could, though more planes from the beginning would have helped." Only seven of 12 water-bombing planes were available due to maintenance.
Evacuations began on 22 July with 100 residents, rising to 10,000 overnight and nearly 220,000 days later. Across France and Spain, orders covered 300,000 people - unprecedented in peacetime Europe. No one died directly from the Gironde fire, though four firefighters died in separate blazes.
Among evacuees was Hervé Jactel, a forest scientist at INRAE, who lost a 20-year experiment on tree diversity. He said the fire was no surprise: "Everything was in place to increase the risk of a very large fire - not only climate, but the amount and homogeneity of fuel."
Scientists suspect extreme energy created a pyrocumulonimbus cloud - a fire-breathing dragon that spits lightning and embers. But the true danger was pollutants. Wildfire smoke causes 1.5 million deaths yearly worldwide. Smoke choked Bordeaux, then Angoulême and Limoges, with soot levels rivaling Delhi.
Firefighters halted the blaze at 42,000 hectares by late July, but "zombie fires" smoulder underground. Scientists fear bark beetles and invasive pine nematode, which block sap flow, will worsen recovery. Future threats loom: fire weather will intensify, and burned area in Europe could rise 39% even in best-case scenarios, or nearly triple in worst-case. Experts urge rapid emissions cuts and land management like diversifying tree species.