Smoke over two million people
Satellite observations picked up a sharp increase in fires and smoke across the central and eastern Amazon beginning in September. The activity appeared in NASA's Fire Information for Resource Management System, the Global Fire Emissions Database and NASA Worldview.
The affected area runs from the forests around Manaus and Santarem, two major commercial and transport hubs in Brazil, east towards the mouth of the Amazon River. On October 12, the MODIS instrument on NASA's Aqua satellite captured images of large smoke plumes rising on both sides of the river.
Thick smoke covered Manaus, home to more than two million people. Officials reported fine particle pollution above 135 micrograms per cubic metre, placing the city in the second-worst category of a regional air quality index. Schools shut, public events were cancelled and children's sports leagues suspended activities.
A cascade, not a single disaster
Douglas Morton, an Earth system scientist at NASA's Goddard Space Flight Center, describes the pattern as a cascade of tropical fires driven by rainfall disruption linked to El Nino. It usually starts near the equator, where drought helps ignite peat fires in Indonesia. As dry conditions spread, fire activity intensifies in the central and eastern Amazon.
Indonesia has already had months of drought, smoke and destructive fires since August. In October, wildfires destroyed hundreds of homes while dense smoke covered entire islands on most days. Morton said the Amazon is now the second domino in the sequence.
Why the worst may be ahead
The pattern is not new. After the 2015-2016 El Nino, Morton worked with researchers from the University of California, Irvine, Vrije Universiteit Amsterdam and the University of Maryland on a 2017 study of how tropical fires follow shifting rainfall. A similar sequence appeared in 2023.
Researchers warn that the current surge may be only one stage of a longer season, with fire risk extending into 2027 if drought persists. Forests already weakened by earlier burns hold less moisture and recover more slowly, which makes each subsequent fire season harder to contain.
For cities in the region, the immediate problem is air quality and the cost of closing schools and businesses. For the forest, the concern is that repeated burning converts dense rainforest into drier, more flammable scrub, shifting the landscape toward a state that burns more easily every year.