Bangkok: Chiang Mai air is generally clean, but this year’s annual smog from mid-February to mid-April has been so bad there have been days when it has had the most poisonous city air in the world. Due to the continued absence of effective government intervention to tackle the smog a loose group of academics, doctors and students, many from Chiang Mai University (CMU), has been trying to address the problem for the last few years.
Burning in the northern Thai countryside and beyond creates the smog. Dr Poon Thiengburanathum from CMU’s School of Public Policy has been tracking the burning since 2012. He said approximately 60% to 70% of it happens in forested areas while 30% to 40% is in agricultural areas – but over the past seven years, burning has decreased in Thailand but increased in neighboring Shan State in Myanmar, and Laos.
Dr Poon explained that previously most farmers in the mountains were subsistence farmers so they did relatively little burning, but about 15 years ago they started to farm commercially and increased the amount they grew and burned. This coincided with an increase in demand for corn to feed cattle by large industrial food producers such as CP Foods who guaranteed to buy all the corn farmers could produce, so many started growing it.
Unfortunately, the easiest and cheapest way of disposing of the corn waste left after harvest is to burn it. Due to public pressure, there has been a reduction in the number of new corn farms being set up in northern Thailand, though Dr Poon said there is a possibility that corn production has just shifted into Shan State, which could account for increased burning there.
The smog problem is exacerbated because Chiang Mai lies in a bowl surrounded by mountains and at this time of year there is little wind and a climate inversion that traps smog near the ground under a layer of warmer air.