Zombie fires: how Arctic wildfires that come back to life are ravaging forests

Blazes that smoulder in the permafrost, only to reignite, are extending fire season though winter, leaving vegetation struggling to recoverIn May 2023, a lightning strike hit the forest in Donnie Creek, British Columbia, and the trees started to burn. It was early in the year for a wildfire, but a dry autumn and warm spring had turned the forest into a tinderbox, and the flames spread rapidly. By mid-June, the fire had become one of largest in the province’s history, burning through an area of boreal forest nearly twice the size of central London. That year, more of Canada burned than ever before.The return of cold and snow at the close of the year typically signal the end of the wildfire season. But this time, the fire did not stop. Instead, it smouldered in the soil underground, insulated from the freezing conditions by the snowpack. The next spring, it reemerged as a “zombie fire” that continued to burn until August 2024. By then, more than 600,000 hectares (1.5m acres) had been des