Clean air is a key component of America's impressive agricultural output. Farmers can do little to reduce it. According to a Stanford study, pollution reductions between 1999-2019 contributed to approximately 20 percent of the rise in soybean and corn yields during that time -- a sum worth around $5 billion annually.This week's Environmental Research Letters analysis revealed that four important air pollutants were particularly harmful to crops. They accounted for an average loss in soybean and corn production of around 5 percent over the course of the study period. These findings can inform policy and technology changes that will benefit American agriculture. They also highlight the importance of reducing pollution in other countries."Air pollution impacts were difficult to measure in the past because farmers can live 10 miles apart and have very different air quality. We were able to measure very fine patterns and decode the roles of different pollutants by using satellites," David Lobell, the Gloria and Richard Kushel Director at the Center on Food Security and the Environment, said.Satellites have the ability to show pollution impacts on a scale that is not possible with other methods, according to this research. This power could prove to be even more valuable in countries that have less access or yield data.The air is what you breatheAlthough scientists have known for a long time that high levels of air pollution are toxic to plants, they don't know how much it is affecting farmers' yields at present. It is still not known what the impact of pollution on agriculture in general and individual pollutants on agricultural yields.AdvertisementLobell and Jennifer Burney, an associate professor of environment science at the University of California San Diego, focused their study on nine states (Illinois. Indiana. Iowa. Michigan. Minnesota. Missouri. Ohio. South Dakota.) That region produces approximately two-thirds of the nation's soybean and maize output.Ozone is formed when nitrogen and hydrocarbons react with heat and sunlight. Particulate matter is a large amount of dust, dirt and smoke. Sulfur dioxide and nitrogen dioxide are gases that are released into the atmosphere by burning fossil fuels in power plants and other industrial facilities.Burney explained that this was a difficult problem to solve because historically, our measurements of different types and levels of air pollutants have not been spatially correlated at the required resolution. "With high spatial resolution data we were able to look at crop yields in proximity to both pollutant emission sources and pollution monitors. This revealed evidence of different levels of adverse effects from different pollutants.Lobell and Burney extended the analysis back to 1990 when Congress passed Clean Air Act Amendments. This resulted in significant improvements in air quality across the country. Researchers looked at air pollution data from hundreds if not thousands of monitoring stations in the region, federal data about power plant emissions, satellite data of nitrogen dioxide around power plants, crop yield data derived from federal surveys and satellite imagery, along with weather data to account to changing growing season conditions that could explain variations in crop yield.Surprising resultsLobell and Burney were surprised by what they discovered. They discovered that each of the four pollutants had a negative effect on soybean and corn yields. Additionally, there was a clear increase in yields the further away the crops were from power plants. They were able to decode the effects of each pollutant using unique spatial patterns that they discovered. This was a breakthrough in comparison to previous studies.Researchers estimated that the total yield loss from these four pollutants was 5.8 percent in maize and 3.89% for soybean over the last 20 years. As the air became cleaner, these losses decreased over time. The reduction in air pollution led to an estimated 4 per cent increase in corn yields, and 3 percent in soybean yields. These increases equal 19 percent of the overall corn yield gains over the same period and 23 percent of the overall soybean yield gains.Lobell stated that "we already know that Clean Air Act resultedin trillions of dollars in benefits in terms human health, so these billions in agricultural benefits are just icing on top." It's only a fraction of the benefits that clear air has provided, but it has played a significant role in our ability to keep agricultural productivity up.NASA and the National Science Foundation funded this research.
