This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Right now, people in parts of Indonesia are inhaling what may be the most polluted atmosphere on Earth. As the historically large 2026 El Niño intensifies, parts of Southeast Asia have been plunged into an air quality crisis of catastrophic proportions.
Smoke from fires has driven concentrations of dangerous and tiny particulate matter, known as PM2.5, to extreme levels—creating a public health emergency threatening millions of lives. The World Health Organization (WHO) stipulates a maximum breathable "safe limit" of 15 micrograms per cubic meter of PM2.5 across a 24-hour average. In haze-affected parts of Indonesia, this year's concentrations have routinely exceeded 500 micrograms, and even 1,000 in places—that's more than 65 times the WHO maximum.
This is not the kind of polluted air you might find on a smoggy day in most parts of the world—it is a toxic atmosphere considered by the U.S. Environmental Protection Agency to be "hazardous." The delayed effects of breathing such air include increased risk of heart attack, stroke and a host of respiratory illnesses. The catalyst for this year's crisis is a collision between meteorological events and decades of changes to Indonesia's landscape.
The historically intense El Niño has brought a punishing dry spell across the archipelago, leaving the landscape parched. But the weather is only the match; land management practices provide the fuel. Historically, lowland tropical forests growing on peat soils were naturally resistant to fire because of their moist conditions.
However, deforestation for agriculture, forest fragmentation and peatland drainage have drastically altered the landscape and increased its flammability. The effects can extend beyond the areas directly cleared or drained: even untouched forest close to degraded areas will have lost some of its natural fire resistance. The El Niño–driven drought has supercharged these changes, making it easier for fires to take hold and spread.
Fire is widely used across the region to help prepare land for agriculture, clear low-lying vegetation or to burn household waste. Yet, when fires are set during a drought, they can ignite the drained peatland soil and escape into the surrounding landscape. A peat fire does not simply flame and pass; it also smolders downward into the ground, sometimes burning for weeks or months.
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