Indonesia’s hidden underground fires are spreading beneath the world’s largest tropical peatlands as El Niño drought and a drying Indian Ocean push the 2026 season toward catastrophe.
Tropical peatland fires don’t behave like ordinary wildfires. They sink underground, smolder for weeks without visible flame, and resist every attempt to smother them — burning until rain finally arrives months later.
By September 1, 2026, NASA’s Aqua satellite was already capturing what that looks like from orbit: a darkening Indonesian archipelago, its skies thickening with smoke barely three weeks into fire season. The thermal signatures spreading across Kalimantan and Sumatra were tracking a trajectory that researchers recognized — one last seen at this pace in 2015, the worst fire year in Indonesia’s modern record.
Why peatland fires are in a class of their own
Not all fires are equal. Peatland fires occupy a category of their own — slower, harder to fight, and far more polluting than surface blazes.
Peat is deep, carbon-rich organic soil that accumulates in wetlands over thousands of years. When it dries out, it becomes fuel that burns underground, beyond the reach of water hoses and firebreaks. Once a fire sinks below the surface, it smolders continuously at low temperatures with no practical way to extinguish it. It simply burns until seasonal rains arrive, often months later.
The pollution output is staggering. Peat fires generate roughly three times more fine particulate matter than other tropical forest fires, five times more sulfur dioxide, three times more organic carbon, and twice as much methane and carbon monoxide. You can’t manage an underground peat fire the way you’d manage a surface fire.
Indonesia holds approximately 36 percent of the world’s tropical peatlands across Kalimantan, Sumatra, and Papua. That concentration makes the country uniquely exposed every time drought conditions arrive.
El Niño returns — and so does the drought
The climate conditions driving the 2026 season are familiar and deeply concerning. NOAA assessed El Niño as present and strengthening in August 2026 — a pattern that typically cuts rainfall sharply across Indonesia. Layered on top of that drying effect is a positive phase of the Indian Ocean Dipole, the same combination of climate forces that made 1997 and 2015 the most destructive fire years in Indonesia’s modern record.
The data on the ground matches that history. About 90 percent of Indonesia received little to no rainfall in early August 2026, according to the Indonesian meteorological agency. In drought conditions, the natural protection peatlands normally provide disappears entirely.
Robert Field, a Columbia University researcher who developed the Global Fire Weather Database, put it plainly: fire activity in 2026 is already tracking sharply upward on a trajectory similar to 2015. The strong El Niño is making the dry season drier across the most fire-prone parts of the country — exactly what researchers anticipated.
In 2015, Indonesia’s fires burned for more than three months and released 1.75 billion tons of greenhouse gas equivalents — more than Japan emits in an entire year. That benchmark now looms over the 2026 season.
What NASA satellites are — and aren’t — seeing
From orbit, the scale of the problem is visible. NASA’s Aqua satellite captured widespread fire detections across Indonesia on September 1, 2026, and Indonesia’s government-run SiPongi platform — drawing on MODIS and VIIRS sensors from NASA and NOAA — tallied 946 hotspots on August 31 alone.
Satellite data tells only part of the story, though. Thick smoke, heavy cloud cover, and underground burning all limit what those sensors can actually detect. Mark Cochrane, an ecologist at the University of Maryland who has conducted field research on Indonesian peat fires for nearly a decade, noted the paradox directly: when fires become most intense, the hotspot count recorded by sensors can actually drop.
That detection gap matters enormously for emergency response and emissions tracking. A University of Maryland team, partnering with NASA and MapBiomas, is developing new algorithms that draw on shortwave infrared observations from Landsat and Sentinel-2 satellites to catch understory fires that current sensors miss entirely.
A legacy of drainage — and the effort to reverse it
The vulnerability of Indonesia’s peatlands didn’t emerge naturally. It was largely engineered.
Large-scale canal construction and peat swamp drainage in the 1990s permanently lowered the water table across vast wetland areas, making the landscape far more flammable. Oil palm and plantation forestry then expanded across these fire-prone regions, adding further pressure to an already stressed system.
After the catastrophic 2015 season, governments and organizations pushed back — damming some irrigation canals, launching wetland restoration projects, expanding firefighting capacity, and working to reduce accidental ignitions. Whether those interventions were enough is now being tested in real time. Shi Jun Wee, a University of Maryland graduate student working on the new satellite detection algorithms, described 2026 plainly: “This year will be a real stress test of the measures that were put in place after 2015.”
Smoke already disrupting millions — with months still ahead
The human cost of the 2026 season is already mounting. Indonesian officials have warned that large portions of the population face hazardous smoke levels. Schools have shifted to remote learning, nine national parks have temporarily closed, and flights have been delayed across smoke-choked regions.
As of early September, 2026 fires had released roughly 10 percent of the greenhouse gas emissions produced by the entire 2015 season — and peak fire months still lie ahead.
Cochrane warned against the pattern of intense attention during El Niño years followed by collective forgetting once conditions ease. “We need sustained focus, even during the years when they aren’t as bad, to solve this,” he said. The coming weeks will reveal how much the post-2015 interventions have actually changed the trajectory — and whether the tools now in place are equal to conditions that, right now, look uncomfortably like a repeat of the worst year on record.
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