Why does the smoke and haze occur?
The smog in northern Thailand is caused by a combination of factors. The burning of land is the main reason. Slash and burn farming techniques have been common over the centuries in the northern region of Thailand as well as neighbouring Burma and Laos. Some years, the smoke from the fires lingers because of climatic conditions. Lower than usual humidity levels, lack of wind and higher than average summer temperatures can all combine to exacerbate the effects of the pollution. Because of the topography of north Thailand, the mountains tend to hem in the smoke which nestles in the valleys below.
Although legislation is in place to punish people who set fires illegally, the reality is that few people are caught or prosecuted. In years where the haze and smoke is severe, the Thai armed forces are drafted in to help put out some of the forest fires. Cloud seeding is also used under the direction of the Royal Rainmaking Project.