Civic groups are urging the agro industry to take action against smog problems in the North.
It is too easy to blame the smog problem on locals looking for produce in forests when the real cause lies with agro-giants, they say.
"It's not fair to point your finger at the locals seeking food in the forest as the cause of the smog," said Witoon Lianchamroon, director of the Thai Network on Community Rights and Biodiversity (Bio Thai), speaking at a seminar at Chulalongkorn University on Wednesday.
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He was responding to executives of the Charoen Pokphand Group (CP), the largest Thailand-based agro business, who said the heavy smog in the North was mainly caused by locals burning forest land to seek produce, especially in Nan province.
Mr Witoon also claimed records by the Department of National Parks, Wildlife and Plant Conservation which suggest local people caused the smog were inaccurate.
According to the records, of about 50,000 rai of forest land burned last year, about 46% was burned by people seeking produce in the forest.
He said space in forests for local people to seek produce is falling as many parts of the mountains in Nan province have been bulldozed to grow corn feed for agro businesses.
Pointing to the relationship between the corn price and the smog problem, Mr Witoon said the smog became a national issue only in 2007 after the corn price increased from about five baht a kilogramme to seven baht/kg.
The number of hotspots caused by forest fires reached over 25,000 in 2012 when the price rose to over nine baht/kg. Hotspots dropped to about 23,000 in 2013 when the corn feed price fell by one baht/kg. Farmers grow corn feed on about 3.5 million rai of land in Thailand, he added.
Research by Sal Forest Co Ltd, a sustainable business accelerator company, has also found a link between haze and farmers growing corn feed. It found corn feed farming in steep areas in Nan has caused health and environmental problems.
Based on a satellite map, the research showed the corn feed farming area in Nan's Nam Yao, Auan and Muab watershed areas increased by 109% between 2002 and 2013. About 60% of the farm areas, or 35,440 rai, encroached on forest lands.
Sarinee Achavanuntakul, managing director of knowledge development at Sal Forest, said the research found constant expansion of corn feed farming had caused flood risks, heavy use of chemicals and smog as farmers burned fields to clear the land. This had led to respiratory problems among locals, she said.
She said farmers thought they had no choice but to grow corn feed due to their lack of bargaining power with the agro giants. "These companies can't deny that corn feed is a part of the supply chain. They must work together with others to make it sustainable,'' she said.