Reduced Air Pollution Leads to Higher Crop Yields

A new study, led by Stanford University, has revealed how removing a common air pollutant could lead to significant gains in crop yields.

Nitrogen oxides impact crop productivity

The research, published in Science Advances, is the first to use satellite images to reveal how nitrogen oxides (also referred to as NOx), gases found in industrial emissions and car exhausts, impact crop productivity. The findings could have important implications for increasing agricultural output and analyzing the mitigation costs for combating climate change.

“Nitrogen oxides are invisible to humans, but new satellites have been able to map them with incredibly high precision,” Professor David Lobell, the study’s lead author and director of Stanford’s Center on Food Security and the Environment said in an interview with Stanford News” Since we can also measure crop production from space, this opened up the chance to rapidly improve our knowledge of how these gases affect agriculture in different regions.”

A widely emitted pollutant

Scientists have long understood nitrogen oxides’ potential to damage crop cells directly, as well indirectly impact them through their role as precursors to the formation of ozone, itself an airborne toxin known to reduce crop yields. However, little is known about NOx’ impacts on agricultural productivity. The lack of overlap between air monitoring stations and agricultural areas, coupled with the confounding effects of different pollutants, has limited past research.

To overcome these limitations, Lobell and colleagues utilized satellite measures of crop greenness in combination with nitrogen dioxide levels over the period 2018–2020. Although invisible to the human eye, nitrogen dioxide has a distinct interaction with ultraviolet light. This method enabled the team to take satellite measurements of the gas at far higher spatial and temporal resolution compared to any other air pollutant. As nitrogen dioxide is the primary form of NOx, it can be used as a good measure of total NOx concentration.

Quoted in a news release, study co-author Jennifer Burney, associate professor of environmental science at the University of California, San Diego, said, “In addition to being more easily measured than other pollutants, nitrogen dioxide has the nice feature of being a primary pollutant, meaning it is directly emitted rather than formed in the atmosphere. That means relating emissions to impacts is much more straightforward than for other pollutants.”

What impact will this have on crops?

Utilizing this data, the researchers calculated that a reduction in NOx emissions of around 50% in each region would improve yields by approximately 25% for winter crops and 15% for summer crops in China.

In Western Europe, yields were estimated to improve nearly 10% for both winter and summer crops. Crop yields in India were calculated to increase by roughly eight percent for summer crops and six percent for winter crops. North and South America were generally shown to have the lowest levels of NOx exposures.
Overall, the study highlighted that effects appeared most negative in the seasons and locations where NOx likely drives ozone formation.

How to reduce NOx

Speaking to Stanford News, Burney said, “The actions you would take to reduce NOx, such as vehicle electrification, overlap closely with the types of energy transformations needed to slow climate change and improve local air quality for human health.” She added that the “main take home” from the study is that the consequences of these actions could be beneficial for agriculture, easing the issues associated with food supply for a growing population.

In fact, previous research by Lobell and Burney estimated that reductions in ozone, particulate matter, nitrogen dioxide and sulfur dioxide over the period 1999–2019 contributed to an approximate increase in US corn and soybean yield of around 20%. This equates to approximately $5 billion per year. 

Future research exploring pollutant impact on crop yields

Looking to the future, the researchers say that their analysis could utilize other satellite observations to better understand nitrogen dioxide’s effects on crops’ varying degrees of sensitivity to the gas throughout the growing season. This may lead to more detailed examination of other pollutants as well as meteorological variables, such as drought and heat, all of which could help to explain why nitrogen dioxide affects crops differently across different regions, years, and seasons.

Reference: Lobell David B., Di Tommaso Stefania, Burney Jennifer A. Globally ubiquitous negative effects of nitrogen dioxide on crop growth. Sci Adv. 8(22):eabm9909. doi: 10.1126/sciadv.abm9909.

This article is a rework of a press release issued by Stanford University. Material has been edited for length and content.