Jakarta. Indonesia's worsening peatland fires may be more difficult to track than satellite hotspot data suggests, as some fires smolder underground or remain hidden beneath thick smoke and forest cover while drought grips large parts of the country.

NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) captured thick plumes of smoke from fires across Kalimantan on Sept. 1, as Indonesia entered a fire season intensified by severe dry conditions and a strengthening El Niño.

The challenge is particularly acute in peatlands. Unlike conventional forest fires, peat fires can continue burning beneath the ground, making them difficult to extinguish and detect from space.

"Surface fires are less of a concern, but when fires get underground, they just won't stop," Robert Field, a Columbia University researcher and developer of the Global Fire Weather Database, said in NASA's report. He said such fires can continue burning until heavier rains arrive.

Indonesia's Forestry Ministry has also cautioned that a decline in detected hotspots does not necessarily mean the fire threat has ended. Peat can continue smoldering underground and reignite if affected areas are not repeatedly cooled and rewetted, Forestry Minister Raja Juli Antoni said.

NASA noted that its MODIS and VIIRS satellite sensors can struggle to detect fires through thick smoke and clouds, beneath forest canopies, and underground in peat deposits. As a result, the number of satellite-detected fires can fall even when conditions on the ground remain severe.

Indonesia is home to about 36% of the world's tropical peatlands, making the country particularly vulnerable when prolonged drought dries areas that are normally too wet to burn.

The worsening haze is already disrupting daily life. Schools have moved classes online in Jambi and Pekanbaru, while authorities in Dharmasraya, West Sumatra, closed 268 schools as air quality deteriorated as of Aug. 29.

The government, meanwhile, has stepped up efforts to contain fires across Sumatra and Kalimantan during the severe dry season, including inspecting companies whose concession areas have been affected by blazes.

Fire risks are expected to remain elevated as dry conditions persist. Indonesia's Forestry Minister has warned that suppressing the fires could become more challenging as El Niño reaches its peak, adding pressure to efforts to prevent blazes from spreading across fire-prone peatlands.

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