Indonesian forest fires trigger worst regional haze crisis in a decade

The smoke arrived in early August, and by late month it had turned the sky of Malaysian Borneo the color of old ash. In Kuching, the state capital of Sarawak, the air quality index climbed to 407—well into the hazardous range, where anything above 100 is considered unhealthy. In the nearby town of Serian, closer to the Indonesian border, it hit 408. For the first time in a decade, the region was choking under what would become its worst haze crisis since 2015.

The smoke drifted north from fires burning across Kalimantan, the Indonesian portion of Borneo. Peatland and rainforest were burning—some deliberately set by plantation companies and smallholders clearing ground for palm oil, farming, and pulp production—and the wind carried the toxic plume across the island and beyond, reaching peninsular Malaysia, Brunei, and Singapore. Mia Emylia Hassan, a 33-year-old mother of two in Kuching, watched visibility from her house drop to about a kilometer. "We have not seen blue sky for over a month," she said. The smell of smoke was inescapable, the air so thick it seemed to have weight.

Hassan's 10-month-old daughter had just come home from the hospital after a lung infection when the haze settled in. The child's lungs were still developing, and the toxic air prevented her from healing. She coughed and vomited through August, on medication the entire month. Twice, the family rushed her to the emergency room because she could not breathe. "It's a mini heart attack for us every time," Hassan said. Across Malaysia, the health system was being overwhelmed. During the week of August 23 to 29, asthma cases surged to 1,811, up from 219 the previous week. Conjunctivitis cases rose to 720, from 146. Karen-Michaela Tan, a 52-year-old asthma patient near Kuala Lumpur, found herself wheezing audibly and breathless climbing stairs. She needed two nebuliser treatments back to back, plus a heavy dose of steroids. Even with her house sealed and two air purifiers running continuously, she battled throat scratchiness and nasal dryness.

The impact rippled through daily life. Sarawak cancelled its outdoor Independence Day celebrations on Monday. Schools began closing: on August 20 and 21, nearly 600 schools in and around Kuching shut their doors, keeping some 200,000 primary and secondary students home. On August 28, another 30 schools across Sarawak closed. Youth sports ground to a halt. Yap Kai Jinn, a 31-year-old coach at Square One Football academy in Kuala Lumpur, cancelled all training sessions and matches. "Along with our parents, we decided that it is not healthy; it is not safe for our players to play under these conditions," he said. The regional bloc ASEAN activated its highest alert level—a Level 3 transboundary haze alert—signaling severe cross-border haze risk. Douglas Uggah Embas, Sarawak's deputy premier, warned that any area where readings crossed 500 would be placed under local emergency, with all public and private offices closed except essential services.

The toll in Indonesia itself was far heavier. The country's deputy health minister reported that some 13,500 people were treated for respiratory infections in July and August alone. About 5.5 million people on Borneo and Sumatra had been directly exposed to smoke. Between January and July, fires burned more than 200,000 hectares—an area three times the size of Jakarta—across both islands. Nearly 95,000 hectares burned in July alone. In West Kalimantan, hotspots nearly doubled on a single day, rising to 7,377, with 104 active fires and visibility falling below a kilometer. In Central Kalimantan, readings on the IQAir index reached 780 in Palangkaraya; in Pontianak, West Kalimantan, they hit 593. Indonesian police arrested 72 people suspected of setting recent fires, but the blazes continued to spread.

Scientists warned the region to prepare for a prolonged crisis. El Niño—the naturally occurring weather pattern that shifts winds, air pressure, and rainfall worldwide—was intensifying toward "super" strength, according to Helena Varkkey, a specialist on transboundary haze at Universiti Malaya. In Southeast Asia, she said, this meant "hotter and drier conditions," so "any fires that happen will have a bigger and longer regional impact." Jayaprakash Muralitharan, a Malaysian atmospheric scientist, said the worst was still ahead. The hot weather had started much earlier than usual, El Niño had dried conditions further, and now the peatland itself was extremely dry. Peat fires are stubborn—what appears extinguished on the surface can smoulder underground for weeks and flare up again. Nothing short of sustained rain will soak the soil enough to stop it. "Human intervention now is only a temporary solution," Muralitharan said. "It would go on until end of September or October when the rain comes in." The region was locked into a waiting game, watching the calendar and hoping the monsoon arrived before the fires consumed everything.