Why Chile’s wildfires are spreading faster and burning hotter

BOGOTA, Colombia (AP) — Chile is reeling from one of the most serious wildfire emergencies in years.

The deadly flames that swept through the center and south of the South American country reduced large swathes of forests and towns to ashes, killed at least 20 people, forced tens of thousands from their homes and left families rummaging through the charred debris.

Fire experts say the fires are driven not only by extreme heat, drought and wind, but also by the way human-shaped landscapes interact with climate change — a deadly mix that makes fires harder to control.

The fires started around mid-January in the Biobio and Nuble regions, about 500 kilometers south of the capital Santiago. Within days, deaths were reported, more than 50,000 residents were evacuated, and firefighters were battling more than a dozen active fires. The government declared a state of disaster – a rare emergency allowing military coordination of firefighting efforts.

The fires razed forests, agricultural land and hundreds of homes. In towns like Penco and Lirquen, families faced scenes of destruction: roofs collapsed, vehicles melted into twisted frames, and community buildings were reduced to rubble.

Size and speed of fires

What sets Chile’s current fire season apart is not an unusual increase in the number of fires, but the amount of land they are burning.

“We are experiencing a particularly critical situation, very far from the usual averages observed during forest fire seasons,” said Miguel Castillo, director of the Forest Fire Engineering Laboratory at the University of Chile.

Castillo said Chile “has almost tripled the area affected,” although the number of fires so far is “within normal margins, or even below average.” This means fewer fires are causing much greater damage – a trend increasingly seen during extreme wildfire seasons around the world.

“It’s a huge challenge for firefighters,” Virginia Iglesias, director of the Earth Lab at the University of Colorado Boulder and a fire specialist and statistician, told the Associated Press.

Iglesias said the emergency involves fires of varying sizes, often advancing toward communities at the same time.

Heat, drought and wind

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

“The hotter and drier things are, the more fuel there is available to burn,” said Mark Cochrane, a fire ecologist at the University of Maryland Center for Environmental Sciences who studies wildfires globally.

“Wind tilts the flames and transfers more heat in the direction of the wind. It also oxygenates the fire, so fires burn more fuel faster, increasing intensity.”

Iglesias described wildfire risk as a simple “recipe” with three ingredients: ignition, fuel and dry conditions. Although fires have long been a part of Chilean ecosystems, she explained, human activity has changed all three elements.

“These winds are very erratic and very intense,” she said, adding that this affects not only the size of the fires, but also “the speed at which they are going to move across the landscape.”

Alejandro Miranda, a researcher at the Chilean Center for Climate and Resilience Research, said wildfire behavior depends on several interacting factors: inflammation, climatic conditions, topography and the quantity and continuity of burnable vegetation.

Chile’s prolonged drought – now lasting more than a decade – has dried out forests and plantations, Miranda said, creating conditions for fires to spread quickly. He said recent extreme fire seasons, including those in 2017 and 2023, have coincided with record temperatures and rainfall deficits more than 30% below historical averages.

“These conditions are ones that are expected to become more intense in the future,” Miranda said.

Why plantations burn differently

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

“Plantations make it easier for fire to spread quickly,” Castillo said.

Miranda said plantations tend to have a high fuel load, large continuous areas of trees of the same age and abundant dead vegetation on the ground. When plantations are not actively managed, branches below the canopy can create a vertical “ladder,” allowing flames to climb to the treetops and generate high-intensity crown fires.

Cochrane said pine and eucalyptus “are very flammable and accumulate more fuel over time,” and these fires often send out burning embers well in advance of the main fire.

“It’s not usually direct fire that ignites homes,” Cochrane said. “It’s embers landing everywhere.”

Castillo said these wind-blown embers can start new fires behind containment lines, making them extremely difficult to suppress, especially on steep terrain and in strong winds.

In contrast, native forests tend to be more diverse and, in many areas, wetter, which can slow the spread of fires.

Causes and environmental impact

Almost all forest fires in Chile are caused by human activity, whether intentional or negligent, experts say. Iglesias said humans add fires through power lines, recreation and infrastructure, and human-caused fires can extend the fire season because they are not limited to lightning or storms.

The environmental impacts extend far beyond burned trees. Iglesias said the smoke degrades air quality and poses serious health risks, especially for vulnerable populations who are often far from the flames. After a fire, soils can become water-repellent, increasing runoff, flooding and landslides – what scientists call “cascading risks.” Sediment can also contaminate rivers and increase the cost of treating drinking water.

Miranda warned that fires can permanently alter ecosystems. After intense burns, invasive species such as pine can regenerate quickly, replacing native forests and increasing the risk of future fires.

What comes next

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

She said reducing fires, managing fuels, tackling climate change and redesigning communities – including defensible spaces around homes – are all essential steps.

“These are very concrete steps we can take to reduce the fire problem,” Iglesias said.

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