SINGAPORE: When haze descends on Southeast Asia, attention focuses on respiratory illnesses, school closures, disrupted flights and poor visibility. Far less attention is paid to another population continuously exposed to polluted air: crops. Haze is only the visible symptom of a broader air-quality problem that includes particulate matter, ground-level ozone and nitrogen oxides. These pollutants can affect crop growth, yield and quality, making air pollution a food security issue, not just a public health concern.

Plants exchange gases through tiny holes called stomata on leaves and depend on sunlight for photosynthesis. Poor air quality can reduce photosynthesis, growth, yields and crop quality. Particulate matter may also carry contaminants that accumulate in plants, especially in vegetables grown near urban and industrial areas. Severe haze also reduces sunlight. During the 1997 Indonesian forest fires, reduced solar radiation affected photosynthesis, which then shrank output of rice, fruits, vegetables and perennial crops.

The 2026 haze episodes underline this risk. During the December 2025 to May 2026 dry season, ASEAN reported widespread transboundary smoke across the Mekong sub-region, particularly in eastern Myanmar, northern Thailand, Laos and Vietnam. In southern ASEAN, hotspot counts in the first half of 2026 were about 86 per cent higher than in the same period of 2025.

By Sep 30, 2026, the main active haze problem had shifted to maritime Southeast Asia, with Kalimantan and Sumatra becoming critical source areas of smoke, affecting parts of Malaysia, Singapore and Borneo, and even the Philippines. LARGE AGRICULTURAL AREAS EXPOSED TO POLLUTANTS The exposed agricultural areas can be substantially larger than the fire-affected areas because smoke travels hundreds of kilometres. ASEAN has about 126 million hectares (ha) of farmed land. An indicative estimate by this author suggests approximately 50 to 70 million ha of cropland - roughly 40 to 55 per cent of Southeast Asia’s farmland - may have been potentially exposed to significant haze during the major 2026 northern and southern episodes.

This estimate combines the 2026 haze footprints released by the ASEAN Specialised Meteorological Centre (ASMC) with the Food and Agricultural Organisation’s (FAO) cropland statistics. It is an estimate of exposure, not of crop loss. ASEAN still lacks scientific assessments of the impact of haze on agricultural productivity.

Haze is not the only atmospheric threat. Ground-level ozone is also another invisible pollutant that has been described as a hidden cause of crop quantity and quality losses.

Ozone has long been a concern for agriculture. US estimates show that ozone reduced maize yield by 3.5 per cent and soybean by 6.1 per cent across 40 years (1981–2021). In 1984 alone, estimated losses for American agriculture ranged between USD$2 to 3 billion. Crop sensitivity varies between rice, soybean, beans, peanuts and horticultural crops. Research in Vietnam has documented effects on rice and peanut cultivars. Even small yield reductions matter when multiplied across millions of hectares.

ASEAN traditionally treats haze as a transboundary environmental problem. The Second Haze-Free Roadmap 2023–2030, ASEAN Peatland Management Strategy 2023-2030 and ASEAN Investment Framework for Haze-Free Sustainable Land Management could potentially support action leading to haze-free agriculture and commodity sectors.

However, the ASEAN Food, Agriculture and Forestry Sectoral Plan 2026–2030 fails to connect air quality directly with agricultural productivity, output loss and food security. This missing link is increasingly consequential. POLICY IMPLICATIONS Priority should be given to the following five actions.

First, government and private entities in ASEAN member states (AMS) need to monitor agricultural exposure by integrating crop maps with observations of fire, ozone, and PM2.5 (which disperses widely).

Second, research is needed to quantify losses through field experiments and long-term monitoring of major crops.

Third, AMS’ environment and agriculture agencies should integrate air-quality warnings into digital agriculture using satellites, low-cost sensors, farm weather stations and crop models.

Fourth, public and private entities should intensify their efforts in breeding and managing crops for tolerance to ozone and particulate pollution alongside drought, heat, flood and salinity.

Fifth, governments need to enforce policies to reduce agriculture’s own contribution to haze pollution by promoting economically attractive alternatives to open residue burning - such as residue incorporation, composting, biochar, animal feed and productive biomass use.

The climatic trends in the final quarter of 2026 and going into early 2027 warrant close attention to agriculture. El Nino conditions, the southern ASEAN dry season, below-normal rainfall in parts of archipelagic Southeast Asia and elevated fire activity can reinforce one another into a polycrisis.

Monitoring operations should prioritise crops of economic and food security importance, namely rice, maize, cassava, soybean, vegetables, fruits, coffee, cocoa, rubber and oil palm. Implementing agricultural policy in the current conditions of flux and uncertainty requires evidence on the amount of haze or ozone, and the relationship between these pollutants and crop yield and other responses.

These relationships must be localised to Southeast Asia because crop sensitivity, pollution mixtures, climate, and production systems differ from those in other regions where most existing evidence was developed.

Agriculture depends on healthy soil, water, climate and biodiversity. Clean air should be recognised as another essential natural resource integral to agricultural policy. The critical question is no longer whether polluted air can damage crops; the science shows that it can. ASEAN now needs to quantify how many tonnes of its crops are being lost due to air pollution. This is increasingly becoming an existential question as prolonged haze episodes with the super El Niño season darken the horizon.

Paul Teng is a Visiting Senior Fellow in the Climate Change in Southeast Asia Programme of ISEAS – Yusof Ishak Institute. He is also Senior Consultant of NIE International, Nanyang Technological University Singapore. This piece first appeared on ISEAS - Yusof Ishak Institute’s blog, Fulcrum.