Between 2002 and 2016, the fire count in Punjab’s fields increased by 60%, a study that has drawn a link between rising paddy productivity and stubble burning in the state suggests.
According to the study, ‘Connecting Crop Productivity, Residue Fires, and Air Quality over Northern India’, published in the journal Nature, rice production in Punjab increased by 25% and vegetation index by 21% between 2002 and 2016. Crop residue is estimated to be 1.5 to 2.25 times the quantity of the crop.
The rise in fire counts led to an increase in aerosol loading by nearly 43%, which are fine particles suspended in the air that cause air quality to deteriorate and aid formation of haze and smog, over not just Delhi but the Indo-Gangetic plain, the study said. It also noted a 60% spike in the concentration of ground-level particulate matter of 2.5 micrometres over Delhi post-monsoon.
Since the first week of November, the combined impact of a change in wind direction, dip in temperature and crop residue burning has plunged Delhi’s air quality to the ‘severe’ and ‘very poor’ categories. The Delhi government has blamed the practice of crop residue burning, while experts pointed out that Delhi’s high basal pollution level is also part of the problem.
“A robust relationship between vegetation index, which is a proxy for crop productivity, and post-harvest accumulated fire activity, a precursor of poor air quality, allows the prediction of intensity of crop fire season and the resulting degradation of air quality in advance,” the study stated.
The study has been carried out by researchers from US-based institutes including Universities Space Research Association, NASA Goddard Space Flight Centre, Columbia University, Environmental Defence Fund and Science Systems and Applications.
As per sources in the Punjab Pollution Control Board, a change in the pattern of sowing paddy is also why the effects of farm fires are felt more now than before 2009. “In 2009, the Punjab Preservation of Subsoil Water Act was passed, which mandated that paddy be sown only after May 15 to save groundwater. Sowing would earlier happen in April. Now, stubble burning coincides with the change in wind direction to northwesterly, and the smoke is carried towards Delhi,” said an official who did not want to be named.
The study also noted that between 7,000 and 16,000 premature deaths and 6 million asthma attacks per year have been attributed to the observed PM 2.5 levels in Delhi, which on an average ranges between 87 and 123. The standard is 60 µg/m3.