Indonesia's Underground Peat Fires Surge as El Niño Strengthens

Indonesia's underground peat fires are surging under a strengthening El Niño and severe drought, raising fears of another destructive fire season like those that have periodically choked the region in thick smoke. Unlike ordinary blazes, tropical peatland fires can smoulder slowly and out of sight for months once carbon-rich wetland soils dry out enough to ignite, making them extremely hard to extinguish and especially damaging to air quality.

By one estimate, peat fires release three times more fine particulate matter than other tropical forest fires, along with five times more sulfur dioxide, three times more organic carbon, and twice as much methane and carbon monoxide. Fine particulate matter consists of tiny airborne particles that can travel deep into the lungs, making heavy peat smoke a serious health concern. NASA's Aqua satellite, using its Moderate Resolution Imaging Spectroradiometer (MODIS) instrument, captured an image of the region on September 1 showing widespread fire activity.

Indonesia holds about 36% of the world's tropical peatlands, landscapes that normally store large amounts of water but can turn into highly flammable fuel during severe drought. Its most severe recent fire seasons have occurred during El Niño years, especially 1997 and 2015; in August, NOAA assessed El Niño as present and strengthening, coinciding with a positive Indian Ocean Dipole, another climate pattern that suppresses rainfall around the Indian Ocean.

"Indonesia is only about three weeks into its fire season, but we're seeing fire activity track sharply upward, similar to 2015," said Robert Field, a Columbia University researcher who developed the Global Fire Weather Database. After burning for more than three months in 2015, Indonesia's fires released 1.75 billion tons of greenhouse gas equivalents, more than Japan emits in a year; by September 2, this year's fires, roughly a month old, had already released about 10% as much. Field said once flames move underground, "they just won't stop" until rains arrive in October or November.

The country's meteorological agency said about 90% of Indonesia received little to no rain in early August, and Indonesia's Ministry of Forestry fire-monitoring platform recorded 946 hotspots on August 31 using satellite data. But satellites have limits: thick clouds and smoke can block their view, and underground peat fires can be nearly invisible from above, so "the worst smoke events, paradoxically, can be the hardest to observe from space," said Mark Cochrane, an ecologist at the University of Maryland Center for Environmental Science.