Nobody is counting what the smoke does to the crops

Haze is counted in closed schools, clinic visits and lost work days. Paul Teng, a plant scientist at Singapore's ISEAS-Yusof Ishak Institute, says it should also be counted in food. Plants take in air through tiny holes in their leaves, called stomata, and they need sunlight to grow. Thick smoke blocks that light and dirties the air going in, and growth slows. The harvest gets smaller and the quality drops, and nobody writes it down. He points back to the Indonesian fires of 1997, when weaker sunlight cut the output of rice, fruit, vegetables and tree crops.

His rough arithmetic is the part worth keeping. ASEAN farms about 126 million hectares. Teng estimates that 50 to 70 million of those hectares sat under heavy haze during this year's worst episodes, so roughly 40 to 55 per cent of the region's farmland. He is careful about what that figure means: it measures exposure, not loss. Southeast Asia still has no scientific estimate of how many tonnes of crops the smoke takes away. By the end of September the worst of it had moved south, with Kalimantan and Sumatra as the main sources, and hotspot counts in the southern half of ASEAN in the first half of 2026 ran about 86 per cent above the same months of 2025.

There is also a pollutant you cannot see. Ground-level ozone, a gas that forms when sunlight reacts with exhaust and smoke, burns leaf tissue. In his Fulcrum commentary Teng cites American data where ozone cut maize yields by 3.5 per cent and soybean by 6.1 per cent over four decades. Small percentages across millions of hectares add up to real tonnes. His complaint lands on the paperwork: ASEAN's farm and forestry plan for 2026 to 2030 never connects air quality to crop output, so the loss has no line of its own.

Why it matters

If you farm in Sumatra or Kalimantan, a poor harvest this year has at least two causes, drought and smoke, and only the drought is being recorded. That decides whether your loss is ever counted when relief money is handed out. For everyone else the bill arrives later, at the market, in rice, chilli and coffee. Watch whether the agriculture ministry starts publishing crop damage figures next to the fire maps, because what is not measured is not paid for.