What’s behind Chile’s dangerous wildfire season
Chile is reeling from one of its most serious wildfire emergencies in years, as deadly flames swept across central and southern areas and turned forests and towns to ash. The emergency began around mid-January in Chile’s Biobío and Ñuble regions, about 500 kilometers (300 miles) south of Santiago, and within days the fires prompted reported deaths, evacuations of more than 50,000 residents and firefighting efforts against more than a dozen active blazes. The Chilean government declared a state of catastrophe, a rare designation that allows for military coordination in response efforts.
Fire scientists and engineers said what distinguishes the current season is less the number of ignitions and more how much land the fires are burning and how quickly they are spreading. Miguel Castillo, director of the Forest Fire Engineering Laboratory at the University of Chile, said Chile was in “a particularly critical situation that is very far from the usual averages” seen in wildfire seasons, and he added that Chile was “almost tripling the amount of affected area” even as the number of fires was “within normal margins, even below average.” Virginia Iglesias, a fire scientist and statistician who directs Earth Lab at the University of Colorado Boulder, described the challenge for responders as “a huge challenge for firefighters,” including fires of different sizes that often advanced toward communities at once.
Several factors have been cited for the rapid spread, starting with conditions on the ground after years of dryness. Chile is emerging from more than a decade of severe drought, leaving vegetation unusually dry, and high summer temperatures and shifting winds have increased the risk. Mark Cochrane, a fire ecologist at the University of Maryland’s Center for Environmental Science, said, “The hotter and drier things are the more of the fuel becomes available to burn,” explaining that wind can push flames, transfer more heat and oxygenate fires so they combust fuel more quickly and with greater intensity. Iglesias also described wildfire risk as a “recipe” with three ingredients—ignition, fuel and dry conditions—and said human activity has altered all three elements.
Scientists also linked the behavior of this season’s fires to the interaction of climate, ignition patterns and terrain. Alejandro Miranda, a researcher at Chile’s Center for Climate and Resilience Research, said wildfire behavior depends on interacting factors including ignition, climate conditions, topography and the amount and continuity of burnable vegetation. He said Chile’s prolonged drought has dried forests and plantations alike, creating conditions that favor rapid fire spread, and he pointed to earlier extreme fire seasons—including 2017 and 2023—when high temperatures and rainfall deficits of more than 30% below historical averages coincided with destructive fires.
The region’s land-use pattern has become central to how experts say the fires behave once ignitions start. Large areas of central and southern Chile are dominated by industrial pine and eucalyptus plantations grown for timber and pulp, and experts said those landscapes play a major role in fire spread. Castillo said, “Plantations facilitate the rapid spread of fire,” and Miranda said plantations tend to have a high fuel load, large continuous areas of trees of similar ages and abundant dead vegetation on the ground. He said that when plantations are not actively managed, branches beneath can act like a vertical “ladder,” allowing flames to climb into treetops and generate high-intensity crown fires.
Other experts described how plantation fires can also ignite far beyond the main blaze. Cochrane said pine and eucalyptus “are very flammable and will build up more fuels over time,” and he said the fires can send burning embers far ahead of the main fire. He warned that “It isn’t usually the direct fire that ignites homes,” adding, “It is embers landing everywhere.” Castillo also said wind-blown embers can ignite new fires behind containment lines, making suppression particularly difficult in steep terrain and strong winds, while he contrasted this with native forests, which tend to be more diverse and, in many areas, more humid—conditions that can slow fire spread.
In addition to how the fires spread, experts said what starts them matters for how long the emergency lasts. Iglesias said nearly all wildfires in Chile are caused by human activity, whether intentional or through negligence, and she said humans add ignitions through power lines, recreation and infrastructure—ignitions that are not limited to lightning or storms, potentially extending the fire season. She also warned that the effects extend beyond burned trees, saying smoke degrades air quality and poses serious health risks for vulnerable populations, often far from the flames. After fires, experts said soils can become water-repellent, increasing runoff, floods and landslides—described as “cascading hazards”—and sediment can contaminate rivers and raise the cost of treating drinking water.
Miranda said intense burns can permanently alter ecosystems, including through changes in which species can regenerate after the flames, warning that invasive species such as pine can regenerate rapidly and replace native forests, increasing future fire risk. As the emergency response continues, Iglesias emphasized that while firefighting is essential, prevention matters more, saying reducing ignitions, managing fuels, addressing climate change and redesigning communities—including defensible space around homes—are all critical steps. “These are very concrete actions that we can take to reduce the fire problem,” she said.