NASA’s MODIS (Moderate Resolution Imaging Spectroradiometer) sensor aboard the Aqua satellite captured dense gray smoke rising from numerous fires on the island of Borneo on September 1, 2026. The red dots on the map show the pixels where the sensor and algorithm detected thermal anomalies indicating fire; a single fire can generate multiple detections. Most of the fires are seen in the southern part of the island.
Tropical peatland fires moving through dried wetland soils burn at low temperatures, often underground and across extensive peat deposits. As a result, they spread slowly, are difficult to extinguish and produce heavy pollution. According to one estimate, peat fires release three times more fine particulate matter, five times more sulfur dioxide, three times more organic carbon, and twice as much methane and carbon monoxide as other tropical forest fires.
In Indonesia, which is home to approximately 36% of the world’s tropical peatlands, these fires are a recurring problem. During periods of drought, the fires can lead to smoke blankets lasting for weeks. According to NOAA, El Niño, which was present and strengthening in August, is reducing rainfall together with the positive phase of the Indian Ocean Dipole.
Robert Field, a researcher at Columbia University, said fire activity was increasing rapidly, in a pattern similar to 2015. In 2015, the fires released 1.75 billion tons of greenhouse gas equivalent; as of September 2, the 2026 fires had reached approximately 10% of that amount.
Why it matters
This development shows that the fires consist of more than flames visible only on the surface; peat burning progressing underground makes firefighting efforts more difficult and leads to intense pollutant emissions. While this characteristic explains why the smoke can persist for long periods and affect wide areas, it also increases pressure on air quality. Climate conditions associated with declining rainfall provide a critical framework for understanding the recurrence of fires during dry periods and smoke blankets lasting for weeks. The comparison with 2015, meanwhile, shows that the issue is not merely a local fire event and must also be monitored in terms of greenhouse gas emissions. For this reason, satellite data make it possible to assess drought, pollution and emissions together, beyond merely identifying fire hotspots.