Toxic Wildfire Haze Spreads Across Southeast Asia as Super El Niño Intensifies

A regional emergency takes shape

A thick blanket of wildfire smoke is spreading from Indonesia across Southeast Asia, exposing millions of people to dangerous air pollution and disrupting schools, transport and daily life. Fires have burned for weeks across Sumatra and Indonesian Borneo, where prolonged drought linked to a powerful El Niño event has left forests, plantations and peatlands highly vulnerable.

Air pollution in some affected areas has reached more than 15 times the World Health Organization guideline. Smoke has crossed the borders of Malaysia, Singapore and the Philippines, with monitoring stations recording unhealthy, very unhealthy or hazardous conditions. The crisis is expected to remain serious while dry weather continues through the peak fire season.

Indonesia’s Health Ministry recorded 50,891 acute respiratory infection cases linked to land and forest fires during July and August. More than 12,000 of those patients were children under five. Health officials and aid agencies have warned that children, older people and those with asthma or other breathing conditions face the greatest risks.

The emergency has also spread into classrooms. More than 1.4 million Indonesian students have moved to remote learning, while about 12,800 schools across Sumatra and Borneo have remained closed as authorities monitor pollution levels.

Why the smoke is reaching neighboring countries

Indonesia’s fires are concentrated mainly in Kalimantan, the Indonesian part of Borneo, and on Sumatra. Seasonal winds can carry smoke across the Malacca Strait and the South China Sea, allowing pollution from individual fire zones to affect communities hundreds of kilometers away.

In Malaysia, Sarawak, which shares the island of Borneo with Indonesia and Brunei, declared an emergency in one district after pollution rose sharply. Nearly 650 schools were ordered to close in the state. The capital, Kuching, was ranked among the world’s most polluted major cities during the worst days of the haze.

Singapore’s National Environment Agency warned that smoke could affect the city state as regional fire activity increased and rainfall remained low. Air quality in the central region reached unhealthy levels. In the Philippines, haze reached parts of Luzon, the Visayas and Mindanao, with Manila and other areas recording very unhealthy or severely unhealthy PM2.5 levels.

PM2.5 refers to microscopic particles less than 2.5 micrometers wide. They can travel deep into the lungs and enter the bloodstream, increasing the risk of breathing problems, heart disease and other serious conditions. Because the particles are so small, ordinary cloth masks provide limited protection. Staying indoors, closing windows and using properly fitted particulate filters are more effective measures when pollution is severe.

El Niño worsens a crisis created by land use

El Niño is a recurring climate pattern involving unusually warm surface waters in the central and eastern Pacific Ocean. Its effects can alter rainfall across much of the world. In Indonesia, a strong El Niño usually brings a longer and drier season, reducing moisture in vegetation and draining wetlands that would normally slow the spread of fire.

Forecasters have described the current event as unusually powerful, with conditions expected to persist into early 2027. Indonesia’s Meteorology, Climatology, and Geophysics Agency has forecast a dry season lasting from July to September, while fire conditions can continue into October if rain remains limited.

El Niño does not start most of the fires by itself. Many blazes are believed to begin through land clearing, including the use of fire to prepare areas for plantations, farms and roads. David Gaveau, founder of the Nusantara Atlas monitoring project, described the relationship in simple terms.

El Niño does not ignite fires. It creates the dry conditions that allow human started fires to escape and become very large.

Environmental groups and researchers have found that fires often return to the same areas, including oil palm and timber concessions. Satellite monitoring recorded more than 210,000 hotspots in Indonesian peatland areas between January and August, while another monitoring platform detected more than 444,200 possible fire sites across the archipelago by early September.

Why peat fires are so difficult to extinguish

Peatlands are wetlands formed from layers of partially decomposed plants. Because these layers accumulate in places where water slows decomposition, peat can store carbon for thousands of years. Some deposits in Kalimantan are more than 20 meters deep and can contain thousands of tonnes of carbon per hectare.

When peatlands are drained for plantations or other development, the material becomes dry and combustible. Fire may spread beneath the surface, sometimes several meters underground, even when flames are no longer visible. A site that appears extinguished can produce smoke again days later.

Dr Nisa Novita, a peatland researcher with Yayasan Konservasi Alam Nusantara, explained why these wetlands are both valuable and dangerous when damaged.

Peatlands are incredibly effective carbon stores because their waterlogged conditions slow decomposition, allowing carbon to accumulate underground for thousands of years. This also means they can become a carbon bomb when they are drained or burned, because that carbon can be rapidly released into the atmosphere.

Fire crews must pump water into the ground, patrol burned areas and watch for new outbreaks. Drying rivers and reservoirs have made that work harder. Andri Susanto, a firefighter with Indonesia’s Manggala Agni service, said crews had gone more than 60 days in some areas without meaningful rain. He also warned that underground embers could reignite after surface flames were controlled.

Health effects are mounting

Residents in Indonesia have described thick smoke that enters homes even when doors and windows are shut. Rizma Nur Fatimah, a 19 year old teaching assistant in South Kalimantan, said visibility in her classroom became so poor that people could not see their own feet. She said residents had grown used to annual haze, yet this season felt worse.

In nearby Pengayuan village, a mother said her three year old daughter developed a cough, sore throat and runny nose. At a clinic in Pontianak, physician Muhammad Arief Tri Hapsoro reported patients arriving with coughs, shortness of breath, sore throats, fever, diarrhea and vomiting. He said the number of patients was roughly double the previous year’s level.

Malaysia has reported rising cases of asthma and conjunctivitis. The country’s Health Ministry said asthma cases increased by 259 percent in the final week of August, while upper respiratory infections rose by 124 percent in one week. In the Philippines, residents reported itchy eyes, sore throats and headaches even in places more than 800 kilometers from the main fire zones.

Children are particularly vulnerable because their lungs and immune systems are still developing, and they breathe more air relative to their body size than adults. Repeated exposure can affect lung growth and worsen asthma. School closures reduce exposure, yet remote learning can be difficult for families without reliable internet, electricity or a quiet place to study.

Save the Children has distributed 8,500 masks to children and families in three districts of Kalimantan. Regional Director Arshad Malik said the smoke crisis was also a child rights issue because it was affecting health, education and emotional wellbeing.

Schools, water supplies and wildlife face disruption

The haze has created problems beyond breathing. In Palembang, South Sumatra, online classes were ordered for more than 250,000 students at 1,030 schools. Officials said the decision would be reviewed as air quality changed and asked teachers to avoid placing excessive demands on children during remote learning.

In Pontianak, families have queued for treated water after household supplies ran dry. Some residents collect rainwater, yet dust from the smoke settled on roofs and turned the water black. Months without rain have also placed pressure on farmers, firefighters and communities living near the burned areas.

Wildlife has suffered as fires move through rainforest and plantation landscapes. Firefighters have found dead snakes and pangolins, while an orangutan rescued from an oil palm plantation in West Kalimantan later died, reportedly after inhaling smoke. Borneo is home to many rare species, including orangutans whose habitat has already been reduced by logging, plantations and road construction.

A familiar disaster with a larger warning

Indonesia has faced major fire and haze seasons for decades. Much of the current land use pattern was established during the Suharto era, when extensive rainforest and peatlands were opened for logging, plantations and development. The practice of using fire for land clearing can be inexpensive, yet it becomes extremely dangerous when peat is drained and weather conditions turn dry.

The 2015 fire season remains the most recent benchmark. Government figures said about 2.6 million hectares burned between June and October that year, 24 people died, and millions across Southeast Asia were exposed to smoke for weeks. Fires also spread during El Niño years in 2019 and 2023, although the damage was less extensive than in 2015.

Professor Bambang Hero Saharjo, a forest fire forensics expert at Institut Pertanian Bogor University, said last year’s fires burned about 359,000 hectares without El Niño conditions. He has warned that the current season could burn between 10 million and 11 million hectares if the dry weather and fires intensify, a figure comparable to the worst seasons of the late 1990s.

Other estimates have placed the area already burned this year between more than 200,000 hectares and nearly 300,000 hectares, depending on the period and method used. The different figures reflect the difficulty of measuring fires across remote peatlands and plantations, as well as the fact that the season is still continuing.

Governments increase firefighting and monitoring

Indonesia has expanded firefighting operations and received aircraft and other assistance from countries including Japan, the United States, Russia, Australia, Canada and Ukraine. Authorities have also investigated suspected cases of deliberate burning. Seventy two people were arrested in August on suspicion of starting forest fires, according to regional reports.

Forestry Minister Raja Juli Antoni said the country was entering the most difficult period of the season as September brought the peak of dry conditions.

Our problems are not over. September is the peak of El Niño. September is the main fight for us.

Malaysia has considered cloud seeding in Sarawak, although the method requires suitable clouds and enough moisture. It cannot create rain from a clear, exceptionally dry sky. The ASEAN Specialised Meteorological Centre has activated its highest alert for transboundary haze in southern Southeast Asia, while agencies are tracking hotspots, wind direction, rainfall and PM2.5 readings.

Government enforcement will remain central because weather alone does not explain where fires begin. Protecting peatlands, restoring water levels, monitoring plantation concessions and prosecuting illegal burning can reduce the chance that small fires become a regional disaster. Cross border coordination is also needed because smoke does not stop at national boundaries.

The Bottom Line

• Wildfires in Sumatra and Indonesian Borneo are sending hazardous haze into Malaysia, Singapore and the Philippines.
• A powerful El Niño is creating unusually dry conditions, while land clearing and drained peatlands are helping fires spread.
• Indonesia recorded more than 50,000 fire related respiratory infection cases in July and August.
• More than 1.4 million students have shifted to remote learning, with about 12,800 schools closed in affected areas.
• Peat fires can burn underground and release large stores of ancient carbon into the atmosphere.
• Firefighting, health protection and regional cooperation are being expanded as dry conditions continue.