The fires in the Amazon, which reaches across nine South American nations, are the result of an extreme drought fueled by climate change, experts said.

The region has been feeling the effects of a natural weather phenomenon known as El Niño, which can worsen dry conditions that were intensified this year by extremely high temperatures.

That has made the rainforest more vulnerable to fast-spreading blazes, said Ane Alencar, the science director at the Amazon Environmental Research Institute in Brazil.

“The climate is leaving forests in South America more flammable,” she said. “It’s creating opportunities for wildfires.”