Why Chile's wildfires are spreading faster and burning hotter

BOGOTA, Colombia — Chile is reeling from one of its most serious wildfire emergencies in years.

Deadly flames sweeping across central and southern parts of the South American country have turned large swaths of forest and towns to ash, killed at least 20 people, forced tens of thousands from their homes and left families sifting through charred debris.

Fire scientists say the blazes are being driven not only by extreme heat, drought and wind, but also by how human-shaped landscapes interact with changing climates — a lethal mix that makes fires harder to control.

The fires began around mid-January in the Biobio and Nuble regions, roughly 500 kilometers (300 miles) south of the capital, Santiago. Within days, deaths were reported, more than 50,000 residents had evacuated and firefighters were battling more than a dozen active blazes. The government declared a state of catastrophe — a rare emergency designation allowing for military coordination in firefighting efforts.

The fires have razed forests, farmland and hundreds of homes. In towns such as Penco and Lirquen, families confronted scenes of destruction — roofs collapsed, vehicles melted into twisted frames and community buildings reduced to rubble.

Scale and speed of fires

What distinguishes Chile's current fire season isn't an unusual surge in the number of fires, but the amount of land they are burning.

Castillo said Chile is ''almost tripling the amount of affected area,'' even though the number of fires so far is ''within normal margins, even below average.'' That means fewer ignitions are causing far greater damage — a pattern increasingly seen in extreme wildfire seasons around the world.

''This is a huge challenge for firefighters,'' Virginia Iglesias, director of Earth Lab at the University of Colorado Boulder and a fire scientist and statistician, told The Associated Press.

Iglesias said that the emergency involves fires of different sizes, often advancing toward communities at once.

Heat, drought and wind

Chile is emerging from more than a decade of severe drought, leaving vegetation unusually dry. High summer temperatures and strong, shifting winds have further increased the risk.

''Wind leans the flames over and transfers more heat in the direction of the wind. It also oxygenates the fire, so the fires combust more fuel more quickly raising the intensity.''

Iglesias described wildfire risk as a simple ''recipe'' with three ingredients: ignition, fuel and dry conditions. While fires have long been part of Chile's ecosystems, she said, human activity has altered all three elements.

''Those winds are very erratic and very intense,'' she said, adding that this affects not just how large fires become, but ''how fast it's going to move across the landscape.''

Alejandro Miranda, a researcher at Chile's Center for Climate and Resilience Research, said wildfire behavior depends on several interacting factors: ignition, climate conditions, topography and the amount and continuity of burnable vegetation.

Chile's prolonged drought — now more than a decade long — has dried forests and plantations alike, Miranda said, creating conditions that favor rapid fire spread. He said that recent extreme fire seasons, including those in 2017 and 2023, coincided with record high temperatures and rainfall deficits of more than 30% below historical averages.

Why plantations burn differently

Large areas of central and southern Chile are dominated by industrial pine and eucalyptus plantations, grown for timber and pulp. Fire experts say these landscapes play a major role in how fires behave once they start.

''Plantations facilitate the rapid spread of fire,'' Castillo said.

Miranda said that plantations tend to have a high fuel load, large continuous areas of similar-aged trees and abundant dead vegetation on the ground. When plantations aren't actively managed, branches beneath the canopy can create a vertical ''ladder,'' allowing flames to climb into treetops and generate high-intensity crown fires.

Cochrane said that pine and eucalyptus ''are very flammable and will build up more fuels over time,'' and that these fires often send burning embers far ahead of the main blaze.

Castillo said those wind-blown embers can ignite new fires behind containment lines, making suppression extremely difficult, especially in steep terrain and strong winds.

Native forests, by contrast, tend to be more diverse and, in many areas, more humid, which can slow fire spread.

Causes and environmental impact

Nearly all wildfires in Chile are caused by human activity, whether intentional or through negligence, experts said. Iglesias said that humans add ignitions through power lines, recreation and infrastructure, and that human-caused ignitions can extend the fire season, because they aren't limited to lightning or storms.

The environmental impacts extend well beyond burned trees. Iglesias said smoke degrades air quality and poses serious health risks, especially for vulnerable populations, often far from the flames. After fires, soils can become water-repellent, increasing runoff, floods and landslides — what scientists call ''cascading hazards.'' Sediment can also contaminate rivers and raise the cost of treating drinking water.

What comes next

Looking ahead, Iglesias emphasized that while firefighting is essential, prevention matters more.

She said that 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,'' Iglesias said.

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