El Niño does not destroy quickly. It degrades slowly, drying out tropical forests over months until a single escaped management fire can tear through understory that evolved without flame. In September 2026, that process arrived in the central and eastern Amazon, and NASA scientists say the worst is still coming. Satellites detected sharp increases in fire activity and smoke from forests surrounding Manaus and Santarém to the mouth of the Amazon River. On October 12, MODIS imagery captured smoke streaming from fires on both sides of the Amazon. Manaus — a city of more than 2 million — recorded PM2.5 levels above 135 micrograms per cubic meter, its second-worst air quality rating. Schools closed. Children's sports leagues were canceled. Daily life in the largest city in the Brazilian Amazon ground to a halt. The mechanism is well-documented and maddeningly repetitive. Douglas Morton of NASA Goddard and colleagues mapped a "cascade" of tropical fire following El Niño in a 2017 Nature Climate Change study: drought and peat fires first hit Indonesia, then the central Amazon, then the northern Amazon, then the southern Amazon. The 2026 El Niño is running the same playbook. Indonesia has been burning since August, with hundreds of homes razed in October. Now the second domino has fallen. Morton expects fires to shift north into Roraima, northern Pará, Amapá, Venezuela, Guyana, and Suriname in November and December, with a final wave in the southern Amazon around August–September 2027. What makes 2026 worse than a simple repeat is cumulative degradation. Many of the same forests that burned in 2015 and 2023 are burning again. Earlier fires partially charred trees, degraded the canopy, and left the remaining forest more susceptible to intense burning. The ecological damage compounds: most Amazon species are not adapted to fire, and each cycle pushes degraded forest closer to a transition state from which recovery becomes improbable. The fires are almost entirely human-caused. Lightning ignites less than 1 percent of fires in the Brazilian Amazon. The current blazes began as management fires — clearing shrubs from pastures or crops from fields — that escaped into a landscape where Manaus rainfall was 95 percent below normal in August and 60 percent below normal in September. Analysis by Shane Coffield at the University of Maryland identifies 50 to 70 uncontrolled fires in the Santarém region alone, with an estimated 40 percent more fires than official FIRMS data products capture, because dense smoke, clouds, and canopy cover block satellite infrared sensors. Coffield's work, part of a NASA Earth Action project, mines VIIRS data for fires that fall below official detection thresholds and shares locations with MapBiomas, a multi-institutional network that maps fires and land-use change. This represents a genuine capability improvement — extending the observational floor so that lower-intensity understory fires become visible to responders. But the structural problem is upstream: the fires are set by people in a landscape where institutional controls on burning are either absent or unenforced during drought. Morton expects fires around Santarém and Manaus to continue until the rainy season arrives in December 2026 or January 2027. For the regions still ahead in the cascade — northern and southern Amazon — there is lead time. Whether that lead time translates into reduced burning depends entirely on governance decisions that the fire cascade pattern has accurately predicted, and that have repeatedly failed to materialize, for over a decade.
