How El Nino fuelled South-east Asia’s worst haze episodes across decades

By the Editorial Team · Friday, October 23, 2026

Severe haze caused by extensive forest fires in Indonesia linked to slash-and-burn farming has led to unhealthy air quality across Southeast Asia in 2026, disrupting daily life and causing widespread respiratory illnesses. This crisis, the worst in over a decade, underscores the persistent challenge of controlling illegal land clearing and the need for stronger regional cooperation to prevent recurring transboundary pollution.

Southeast Asia has experienced multiple severe haze episodes over the past several decades, with many coinciding with strong El Niño events that bring hotter and drier conditions to the region. Notably, major haze crises occurred in 1982, 1997, 2015, and most recently in 2026, all linked to intensified forest fires in Indonesia.

The recurring blazes primarily result from slash-and-burn agricultural methods, widely used by farmers to clear land despite being illegal in Indonesia. This practice remains prevalent due to its lower cost compared to mechanized clearing.

The current 2026 haze crisis is considered the worst in more than a decade. Forest fires in Indonesia have generated thick smoke detected as far as the Philippines, with Metro Manila experiencing acutely unhealthy air quality levels in late August and early September. The haze has severely affected Malaysia and Indonesia as well, leading to school closures and flight disruptions. Indonesia’s Health Ministry reported over 283,000 acute respiratory infection cases in affected areas from August 18 to October 13.

In Indonesia’s Kalimantan region, the fires produced apocalyptic orange skies, while NASA satellite imagery revealed elevated carbon monoxide concentrations blanketing much of Southeast Asia. Singapore, too, experienced a significant decline in air quality, registering 18 consecutive days of unhealthy air from early October. On October 18, Singapore’s Pollutant Standards Index (PSI) peaked at 230 in the western region, placing it in the very unhealthy range. Conditions improved around October 22 but satellite data indicated the fires persisted in Sumatra and Kalimantan.

Public frustration over government response led to protests in several parts of Indonesia, with demonstrators demanding stronger firefighting measures, stricter enforcement against responsible companies, and greater protection for affected communities. Singapore has issued legal notices under its Transboundary Haze Pollution Act to ten companies, seeking details on their fire prevention and suppression strategies.

The 2015 haze episode remains the most severe on record, exacerbated by a powerful El Niño event dubbed "Godzilla". Research from Harvard University estimated it caused approximately 100,000 premature deaths across Indonesia, Malaysia, and Singapore. The economic toll was significant, with Indonesia’s losses estimated at 221 trillion rupiah (S$15.6 billion) and Singapore’s economic costs around S$1.83 billion according to one study. During that crisis, Singapore schools closed as PSI levels exceeded 300, reaching hazardous levels.

Scientific analyses found that the 2015 fires released more carbon than the entire European Union, emitting roughly 11.3 million tonnes of carbon daily during peak months. The haze also disrupted transportation and tourism, affected wildlife, and resulted in over 40,000 hospitalizations for respiratory and related conditions across the region. The crisis’s broader economic, social, and environmental impacts were estimated at more than US$9 billion, affecting Brunei, Indonesia, Malaysia, the Philippines, Singapore, and Thailand.

The severity of the 1997 episode prompted ASEAN member states to sign the ASEAN Agreement on Transboundary Haze Pollution in 2002, establishing commitments to prevent and control land and forest fires.

Looking further back, the 1982-1983 Great Fire of Borneo marked the first documented large-scale haze event in the latter part of the 20th century, with over five million hectares burned across the island, including East Kalimantan. At that time, Singapore did not employ the Pollutant Standards Index (PSI), which was only introduced in the 1990s. Research indicates haze pollution was not officially recognized as a significant health risk in Singapore until the PSI system was adopted in 1994.

Collectively, these episodes highlight the recurring environmental and public health challenges posed by forest fires in Indonesia, intensified by climatic shifts associated with El Niño, and underscore ongoing regional efforts to address the transboundary haze issue.

This article was reported by synthesizing coverage from multiple independent news outlets to present a balanced, unbiased account. Read about our editorial standards. Spotted an error? Let us know.