The Southeast Asian transboundary haze is a recurrent, fire-related air pollution issue in which smoke from burning biomass crosses national borders, degrading air quality and causing adverse health, environmental and economic impacts in several Southeast Asian countries. It has been recorded since 1972, with the 1997 and 2015 events being particularly severe. Haze generally worsens between July and October and during El Niño events.

Causes

The haze is caused primarily by slash-and-burn land clearing. Industrial-scale slash-and-burn practices to clear land for agriculture—particularly for palm oil and pulpwood production—are a major cause. Burning is often cheaper and faster than cutting and clearing with machinery, and fires started for this purpose can spread into forest fires. The high concentration of peat in soil contributes to the haze’s density and high sulphur content. Fires in Indonesia, especially in South Sumatra and Riau in Sumatra and in Kalimantan, are a significant source.

Regional impacts

Haze events occur when air quality reaches hazardous levels due to high concentrations of airborne particulate matter from burning biomass. The 1997 Southeast Asian haze was an international air pollution disaster during the second half of 1997, considered the most severe Southeast Asian haze event of all time, with total costs estimated at US$9 billion, due mainly to health care and disruption of air travel and business activities. During its peak, satellite imagery showed a haze layer covering more than 3,000,000 km², reaching Malaysia, Singapore, Brunei, Thailand and the Philippines, and extending as far as Sri Lanka.

Governance

The ASEAN Agreement on Transboundary Haze Pollution is a legally binding environmental agreement signed in 2002 by ASEAN member states to reduce haze pollution in Southeast Asia. It recognises that transboundary haze pollution resulting from land and/or forest fires should be mitigated through concerted national efforts and international co-operation. As of September 2014, all ten ASEAN countries have ratified the agreement.