Stubble Burning In Punjab: Is It Declining, Or Are Farmers Outwitting Satellites?

Stubble burning, a widespread practice in some of India’s agrarian regions, especially Punjab and Haryana, has been an enduring environmental challenge.

Traditionally done to quickly clear fields after harvest, it causes a significant spike in air pollution, particularly in Delhi and the Indo-Gangetic Plain.

With satellite monitoring becoming a primary tool to track and curb such environmental threats, new evidence suggests that farmers may be finding ways to evade satellite surveillance. Experts now argue that shifts in the timing of stubble burning may be a strategic attempt by farmers to bypass detection.

Decrease in Fire Count: Real or Misleading?

According to recent government data, the number of farm fires in Punjab has fallen sharply from nearly 79,000 in 2021 to around 32,000 in 2023. Haryana also shows a substantial decrease from about 11,000 to roughly 3,300.

These figures, based on satellite imagery, indicate a significant reduction in stubble burning. The Commission for Air Quality Management (CAQM) has lauded Punjab for reducing stubble burning incidents by 71 per cent compared to previous years.

However, scientists are raising concerns about whether this reported drop in fire counts accurately reflects the reality on the ground.

The satellite data in question primarily comes from NASA’s Suomi NPP and Aqua satellites, which pass over the region around 10:30 am and 1:30 pm. Researchers argue that this data might be missing numerous fires.

Dr. Hiren Jethva, a senior research scientist at NASA Goddard Space Flight Center, took to X (formerly Twitter), to explain how official fire counts overlook many farm fires ignited later in the day. Satellite observations at these specific times may not account for fires started in the late afternoon, post-satellite overpass, raising doubts about whether actual stubble burning incidents have declined.

Increased Aerosol Loading: A Contradictory Signal

Despite reports of lower fire counts, aerosol loading—indicative of pollutants like carbonaceous smoke emitted from stubble burning—remains consistent or even higher compared to previous years. Aerosol data is gathered through satellites that monitor the particulate matter in the atmosphere. Dr. Jethva notes that the steady aerosol presence contradicts the purported decline in stubble burning. This mismatch suggests that the fire activity, rather than decreasing, may only be escaping detection.

Dr. Piyush Bharadwaj, an air quality scientist with the Center for Study of Science, Technology, and Policy (CSTEP), in a conversation with Health Policy Watch (HPW) supported this hypothesis. Bharadwaj mentions that the actual air quality in Delhi, a primary area impacted by the smoke from Punjab’s fields, has shown no clear improvement, despite the reported reduction in farm fires.

According to his group’s atmospheric modeling data, pollution levels haven’t improved significantly over the past five years, suggesting that factors other than satellite-detected fire counts may be influencing the seasonal pollution patterns.

Exploiting Satellite Limitations

The theory that farmers might be intentionally burning crops after the satellite overpasses is further supported by data from a South Korean geostationary satellite, GEO-KOMSAT 2A. Unlike polar-orbiting satellites that only capture images of a region once or twice a day, the geostationary satellite can continuously monitor a specific region, providing images every few minutes.

On November 1, 2024, images from this satellite showed minimal fire activity at 1:30 pm, aligning with NASA’s overpass, but significantly more fires were visible just a few hours later at 4:20 pm. The shortwave-infrared signals, sensitive to heat sources like fires, confirmed a surge in fire activity during the late afternoon hours.

The hypothesis is further supported by Dr. Jethva’s analysis of time-lapse images from GEO-KOMSAT A2 on October 29. These images showed dense smoke clouds forming post-4 pm, implying that farmers may indeed be deliberately timing fires to avoid detection by the NASA satellites. Dr. Bharadwaj adds that the MODIS sensors on NASA’s polar-orbiting satellites have a pixel resolution of 1 sq km, meaning smaller fires may go undetected, potentially skewing the fire count data.

The Broader Implications

If farmers are indeed adjusting their practices to avoid detection, the implications are profound. The data reported by government agencies might not provide a full picture, which in turn affects policy decisions aimed at mitigating air pollution.

The reliance on satellite data for assessing environmental health is essential, but this situation highlights its limitations. Researchers like Dr. Bharadwaj stress that a nuanced approach, combining different satellite sources and possibly ground-based monitoring, is crucial for obtaining an accurate assessment of stubble burning practices.

Smog towers and air quality alerts are immediate fixes, but the larger issue remains the extensive crop residue burning that contributes to poor air quality across the Indo-Gangetic Plain.

Additionally, a geostationary higher-frequency monitoring satellite, like that from GEO-KOMSAT, could provide more precise data. This would allow authorities to better assess whether stubble burning is truly on the decline or merely shifting to avoid detection.