Scientists from China’s Sun Yat-sen University jointly with their colleagues from the Environmental Pulse Institute and George Mason University have conducted a large-scale study that, for the first time ever, assessed how multiple types of air pollution affect agricultural yields in India. In the past, studies of this kind looked into individual pollutants; this study examined the combined effects of ground-level ozone, fine particulate matter (PM2.5) and nitrogen compounds deposited from the atmosphere during the combustion of coal, oil and gas, as well as the impacts made by this combination of pollutants on rice, corn and soybean yields.
In the course of the analysis, the researchers combined satellite data, climate models and India’s agricultural statistics for the years 2001–2017. The analysis is based on a structural equation model, a method that makes it possible to outline various factors and understand which ones play a key role, taking into account temperatures, precipitation and CO₂ concentrations.
The study focused on the Kharif season, the period of summer rains when staple crops are grown. All data was reviewed at the same scale: the scientists divided the area into small plots of approximately 5 km by 5 km and calculated the parameters for each plot using the same method.
They found that pollutants affect plants in different ways.
Ozone turned out to be the most aggressive factor: it damages leaf tissue, interferes with photosynthesis and disrupts stomatal function. As a result, the plant absorbs carbon less efficiently and loses yield. On average, the impact of ozone reduced yield by about 5.6%. Fine particulate matter has a different effect: it reduces the amount of sunlight reaching plants, thereby limiting photosynthesis. Its contribution to yield loss is estimated at about 3.4%. Meanwhile, nitrogen acts as a fertilizer in moderate amounts and can even increase crop yields by an average of some 4.8%. However, this effect reverses with excess nitrogen: soil becomes acidic, the nutrient balance is disrupted, and its positive impact disappears.
The key takeaway has to do with how these factors interact. It appears that their combined effects do not add up directly: at high pollution levels, they partially absorb one another’s impacts. This means that the total damage is lower than the simple sum of the individual impacts. Nevertheless, the overall balance remains negative.
The impact varies greatly depending on the region. The most noticeable decline in crop yields was recorded in the Indo-Gangetic Plain, one of the country’s main agricultural regions. There, rice and corn yields declined by about 6.3% and 5.2%, respectively. The effect is less pronounced in southern regions: rice losses amount to about 0.8%, whereas corn even shows an increase of approximately 2.2% in some cases.
The practical implication of this study is that air pollution is directly linked to food production. This means that the choice of energy sources and the energy mix have a direct impact not only on the environment and health but also on agriculture. Efforts to reduce emissions in the energy sector (for instance, by switching to cleaner energy sources or improving power generation efficiency) could also serve as a tool for supporting food security.
