SINCE the mid-1980s, when Indonesia first began to clear its bountiful forests on an industrial scale in favour of lucrative palm-oil plantations, “haze” has become an almost annual occurrence in South-East Asia. The cheapest way to clear logged woodland is to burn it, producing an acrid cloud of foul white smoke that, carried by the wind, can cover hundreds, or even thousands, of square miles.

The intervening decades have seen the passage of numerous national and international regulations to stop the fires, but all, it seems, to no avail. The past two weeks have seen some of the worst smog ever, taking a severe toll not only on peoples’ lungs, throats and tempers, but also on diplomatic relations and Indonesia’s attempts to improve its environmental image. Worse still, despite the outcry, it is hard to see how matters are going to improve over the next few years.

Most of the burning, which starts every dry season, is concentrated this year in Riau province on the east coast of Sumatra. Indonesia is the world’s biggest palm-oil producer and Riau its most productive province. Sadly for Singapore and Malaysia, it lies just across the Strait of Malacca from them. From June 16th Singapore and large parts of Malaysia were smothered in smog from this year’s fires.

In Singapore the pollution was the worst ever, pummelling the previous records set in 1997, when the haze affected six countries and perhaps 70m people. Then, the Pollutants Standard Index PSI in Singapore, a measure of air quality, hit a panic-inducing 226, defined as “very unhealthy”. On June 19th, by contrast the day of the satellite picture above, the PSI climbed to over 300, defined as “hazardous”, before peaking at 401 on June 21st. The government issued face masks and almost everyone took its advice to stay indoors. Malaysia declared a state of emergency in parts of its southern state of Johor when the Air Pollution Index, only slightly different from Singapore’s PSI, exceeded 500; it reached 750 on June 23rd. Kuala Lumpur, the capital, and coastal cities were also badly affected, as was Riau province itself, where hundreds were evacuated.

continue reading South-East Asia’s smog: Unspontaneous combustion | The Economist.