"The strong El Niño is making the dry season drier over the fire-prone parts of the country and exacerbating burning — just as we anticipated it would," Field said.

The drought is severe and widespread. Data from the Indonesian meteorological agency showed that about 90 percent of the country received little or no rainfall in early August 2026.

How do these fires burn underground?

Under normal conditions, peat deposits in Kalimantan, Sumatra, and Papua are too wet for fire to move underground. Indonesia contains about 36 percent of the world's tropical peatlands. Severe drought changes the equation dramatically, allowing flames to enter the peat itself and continue smoldering below the surface.

"Surface fires are less of a concern, but when fires get underground, they just won't stop," Field said. "They'll keep burning until the rains come in October or November."

Over the past three decades, these conditions have repeatedly produced long-lasting fires that blanket large areas in smoke for weeks and disrupt the lives of millions of people.

Why can't satellites see the worst fires?

Indonesia relies on NASA and NOAA satellite observations to track active fires in near-real-time. The main instruments are MODIS (Moderate Resolution Imaging Spectroradiometer) aboard the Aqua satellite and VIIRS (Visible Infrared Imaging Radiometer Suite). Indonesia's Ministry of Forestry operates the SiPongi fire-monitoring platform using this data, and the system counted 946 hotspots on August 31, 2026.

But satellite monitoring has serious limitations. MODIS and VIIRS can struggle to detect fires hidden by thick smoke or clouds, burning beneath the forest canopy, or smoldering underground inside peat deposits.

Paradoxically, when Indonesian fires become especially intense, the number of detected fires can actually decline — because the smoke itself blocks the satellites' view.

"The worst smoke events, paradoxically, can be the hardest to observe from space with MODIS and VIIRS," said Mark Cochrane, an ecologist at the University of Maryland Center for Environmental Science who has conducted field research on Indonesian peat fires for nearly a decade.

Why is Indonesia so vulnerable to these fires?

Some of the vulnerability traces back decades. According to Cochrane, extensive construction of irrigation canals and drainage of peat swamps during the 1990s — undertaken in part to create massive rice farms — lowered water tables across wetland areas and made the landscape more combustible. Oil palm plantations and other plantation forestry are also widespread in the region.

After the grim 2015 season, governments and other organizations attempted to reverse some of that damage. Projects have included blocking irrigation canals to restore wetlands, strengthening firefighting capabilities, and stepping up prevention of accidental human ignitions.

"This year will be a real stress test of the measures that were put in place after 2015," said Shi Jun Wee, a University of Maryland graduate student. Wee is part of a team working with NASA and MapBiomas to develop improved methods for spotting understory fires that MODIS and VIIRS may miss, using shortwave infrared observations from Landsat and Sentinel-2 satellites.

What is the smoke doing to daily life?

The effects are already being felt across Indonesia and neighboring countries. Indonesian officials have warned that large portions of the population have been exposed to hazardous smoke. According to news reports, some schools have switched to remote learning, nine national parks have closed, and several flights have been delayed because of heavy smoke.

Cochrane cautioned that attention to the problem tends to spike during major El Niño fire seasons and fade once conditions improve.

"People tend to focus on these fires during an El Niño and then forget about them," Cochrane said. "We need sustained focus, even during the years when they aren't as bad, to solve this. These fires create a tremendous amount of emissions."