Indonesia Peat Fires Choke Region as Ancient Carbon Burns

Peat fires burning across Indonesia have filled the air over parts of Southeast Asia with smoke so thick that pollution readings have climbed to more than 65 times the level the World Health Organization considers safe to breathe over a single day.

In haze-affected areas, concentrations of fine particulate matter known as PM2.5 have routinely passed 500 micrograms per cubic metre, and have reached 1,000 in places, according to an analysis published by The Conversation. The World Health Organization sets its 24-hour guideline at 15 micrograms per cubic metre. The United States Environmental Protection Agency classes air at those levels as hazardous, and breathing it raises the risk of heart attack, stroke and respiratory illness.

The smoke has drifted beyond Indonesia at times, blanketing neighbouring Malaysia, Brunei, southern Thailand and Singapore, and the crisis is still unfolding. A historically intense El Niño has parched the archipelago, and forecasters expect it to strengthen further before the year ends.

People in parts of Indonesia are now breathing air that may be the most polluted on Earth, turning a seasonal hazard into a public health emergency.

Why the fires took hold

Weather alone did not create the crisis. Lowland tropical forests growing on peat soils once resisted fire because the ground stayed wet. Decades of drainage for agriculture, forest clearance and fragmentation have dried that ground and stripped away much of its natural resistance, even in untouched forest near degraded land. The drought brought by El Niño has now made it far easier for fires to start and spread.

Fire is widely used in the region to prepare farmland, clear low vegetation and burn household waste. Set during a drought, those fires can ignite drained peat soil and escape into surrounding land. Unlike a surface blaze, a blaze in peat burns downward into the ground and can smoulder for weeks or months, which makes it hard to put out once it takes hold.

Carbon stored for centuries goes up in smoke

The deeper cost lies underground. Peat holds organic matter locked away for hundreds of years, and burning it sends that carbon into the air permanently, since land converted to farming will not regrow the forest that stored it. Indonesia's fires this year have released an estimated 175 million metric tons of carbon, according to the analysis, equal to three-quarters of the country's annual fossil-fuel carbon dioxide emissions and more than the combined annual fossil-fuel and industrial emissions of the United Kingdom and France.

Satellite analysis has counted more than one hundred and twenty thousand fire hotspot detections across Indonesia so far in 2026. That is fewer than in 2015, another El Niño year, but seven times as many as in 2025. The scale marks a setback after years of progress, when improved fire management and efforts to rewet drained peatland had pushed regional fire activity down.

Detection is improving, but prevention lags

Counting the fires remains difficult, because satellites struggle to pick up the lower temperatures of smouldering peat. New detection technology could help authorities find fires sooner and respond faster, provided the data reaches the people who need it quickly. In many areas, though, the lasting fix is to restore drained peatland so it is less likely to burn at all, and Indonesia is setting up a national peatland and mangrove management agency with that task. Rewetting drained peatland, one of the measures behind the earlier decline, works by keeping the soil damp enough to resist ignition. Indonesia's earlier progress shows the approach can work: fire activity had been falling before this year's El Niño interrupted the trend.

The human toll reaches beyond the region. Globally, exposure to wildfire smoke contributes to a million or more premature deaths each year, including almost one in 10 deaths of children under five. The smoke also adds to the heat-trapping gases in the atmosphere, which the World Meteorological Organization reported had reached record levels last year. For now, the immediate outlook in Indonesia remains bleak, with underground fires resisting suppression and the dry spell expected to run to the end of the year. Reducing the risk of the next disaster will depend on restoring and protecting peatland with renewed effort, as part of a wider climate emergency.