How 2015 Indonesian forest fires choked Southeast Asia for months

Nature · Published 30 September 2026 Swipe more like this →

In short: In 2015, a massive air pollution crisis blanketed Southeast Asia, caused by slash-and-burn farming on Indonesian peatlands. Exacerbated by El Niño, the haze triggered states of emergency, closed thousands of schools, and forced millions to breathe hazardous air. This environmental disaster sparked international tension and unprecedented legal action across the region.

The 2015 haze was driven by the clearing of land for palm oil and timber plantations. Companies and farmers frequently use fire as an inexpensive method to remove vegetation, often ignoring regulations that require burning on concrete beds to prevent spread. Because much of the fire occurred on highly combustible, carbon-dense peatland in Sumatra and Kalimantan, the blazes were exceptionally difficult to contain. The severity of the crisis was amplified by the El Niño phenomenon, which created unusually dry conditions that allowed fires to proliferate rapidly across the region.

The impact was widespread, affecting countries including Singapore, Malaysia, Thailand, Vietnam, and the Philippines. In Indonesia, the crisis led to a state of emergency in six provinces, with air quality indices reaching extreme, record-breaking levels. Millions of people suffered from respiratory illnesses, and the economic toll was immense, with the Indonesian government estimating mitigation costs as high as US$35 billion. The haze disrupted daily life, forcing school closures for millions of students and causing the cancellation of major sporting events like the Kuala Lumpur Marathon.

The crisis prompted a shift in regional diplomacy and accountability. Singapore, which suffered its most serious haze episode to date, utilized its Transboundary Haze Pollution Act to pursue legal action against companies suspected of contributing to the smoke. Indonesia eventually faced international pressure to address the fires, leading to efforts like cloud seeding and the construction of retention basins to re-wet peatlands. Despite these measures, the 2015 event remains a stark example of the environmental and health consequences of industrial land-clearing practices in the region, with NASA suggesting it may have been the worst haze crisis ever recorded.

The environmental cost was staggering, with the Global Fire Emissions Database reporting that the fires generated approximately 600 million tonnes of greenhouse gases. This output was comparable to Germany's total annual emissions. While heavy rains in late October 2015 finally provided relief, the event left a lasting legacy, highlighting the difficulty of managing transboundary pollution when economic interests and environmental protection collide.

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