Southeast Asian haze

Southeast Asian haze is a fire-related large-scale air pollution problem that occurs regularly. These haze events have caused adverse health and economic impact on Brunei Darussalam, Indonesia, Malaysia, Singapore, and to a lesser degree, the Philippines and Thailand. The problem flares up every dry season, in varying degrees. Transboundary haze in Southeast Asia has been recorded since 1972.

The haze is largely caused by illegal agricultural fires due to industrial-scale slash-and-burn practices in Indonesia, especially from the provinces of South Sumatra and Riau in Indonesia's Sumatra island, and Kalimantan on Indonesian Borneo. Burned land can be sold at a higher price illegally, and eventually used for activities including oil palm and pulpwood production. Burning is also cheaper and faster compared to cutting and clearing using excavators or other machines.

Most haze events have resulted from smoke from fires that occurred on peatlands in Sumatra and the Kalimantan region of Borneo island.

Undisturbed humid tropical forests are considered to be very resistant to fire, experiencing rare fires only during extraordinary dry periods.

A study published in 2005 concluded that there is no single dominant cause of fire in a particular site and there are wide differences in the causes of fires in different sites. The study identified the following direct and indirect causes of fire:

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