Haze, by definition, is a term normally denoting a naturally occurring climatic condition in which visibility is affected; for instance, the phrase “heat haze”. In Southeast Asia the term is rather euphemistically used to refer to the smoke emitted from land and forest fires, both natural and man-made, that visibly persists in the atmosphere. Haze is described as transboundary when the smoke travels across political boundaries and remains in the airspace of neighbouring countries.

The first reported incidence of transboundary haze in Southeast Asia was in 1982. Almost forty years later, the region continues to suffer from almost annual haze episodes, the most severe being during the years 1994, 1997–98 (which remains the region's worst haze episode in history), 2005, 2013, 2015, and most recently in 2019. Indeed, the situation seems to be getting worse: while previous severe episodes were largely confined to the southern Southeast Asian subregion, recent years have seen serious incidences in the northern (Mekong) subregion as well.

What can explain the persistence of transboundary haze in Southeast Asia? Why has the region not been able to act to effectively mitigate the issue in light of its well-known negative health, environmental and economic effects (see “Here's How Much the Haze Costs Us”, p. 58 of this collection)? This collection argues that transboundary haze is not only a physical problem linked to fire but also a political one with complex socioeconomic and diplomatic considerations.

Regional Responses: ASEAN and Haze Cooperation

The fires that cause haze in the southern Southeast Asian region are mainly located in Indonesia and to a lesser extent Malaysia. Fires in the Mekong subregion occur mainly at the Golden Triangle border areas of Thailand, Laos and Myanmar. To date, transboundary haze has, at one time or another and in varying levels of severity, affected all ten member states of the Association of Southeast Asian Nations (ASEAN).

With causes and effects squarely rooted within the region, the haze is a uniquely ASEAN problem. The association first acknowledged that haze was a regional concern in 1985, and this was soon followed by many agreements for regional cooperation to mitigate the issue, as summarized in the timeline below:

1985 The Agreement on the Conservation of Nature and Natural Resources specifically referred to air pollution and “transboundary environmental effects”.