Agriculture overtakes fossil fuels to become largest emitter of sulfur that causes acid rain, finds study
Agriculture appears to have dethroned fossil fuels to become the largest emitter of sulfur, one of the culprits behind acid rains, according to researchers. The finding brings certain farming practices into the spotlight and calls for efforts to work with farmers to tackle the problem at hand.
In farming, sulfur is a crucial ingredient present in fertilizer, fungicide and soil conditioners. It is a necessary nutrient for life on Earth and is also good at fighting pests, Dr Eve-Lyn S Hinckley from the University of Colorado, tells MEA WorldWide (MEAWW). She collaborated with Charles Driscoll, a professor at Syracuse University, to analyze how sulfur is used in agriculture.
"Although sulfur is applied to agricultural lands to improve the production and health of crops, it can have detrimental effects on agricultural soils and downstream waters, similar to what occurred in remote forest landscapes under acid rain," Driscoll explains.
Back in the 1960s and 70s, human-released sulfur and nitrogen in the atmosphere were traced to fossil fuel industries. These chemicals then returned to the ground in the form of acid rains, degrading forests and poisoning aquatic animals. To regulate them, policymakers implemented the Clean Air Act, helping certain parts of the US show early signs of recovery. But the sulfur emission from agriculture has not received attention. Other pollutants such as nitrogen and phosphorus, on the other hand, have been well-studied and regulated.
"Since the 1950s, sulfur as a component of fossil fuel emissions has been the major focus in science and policy. No one has looked comprehensively at the effects of purposeful sulfur applications in agriculture, to determine if they are similar to the effects [acidified soil, for instance] of acid rain," says Hinckley, who is the lead author of the study.
"It seemed like the sulfur story was over," she says. But when the team investigated its applications on crucial crops across the US, they found that it was often used at 4-10 times the amount of sulfur found in acid rain at its maximum, they found. "This analysis suggests that the mass of sulfur applied to agricultural lands in the US is comparable to that from air pollution," Driscoll, the co-author of the study, tells MEAWW.
The team gathered data from across multiple important crops in the US, including corn in the Midwest, sugarcane in Florida, and wine grapes in California. They also analyzed and compared data from the 1980s to the present. They found that the amount of sulfur used in agriculture is shooting up.
"Our analysis is just scratching the surface," Driscoll says, adding that the effects of using sulfur on agricultural lands are poorly understood and needs more investigation. Going forward, Hinckley plans on extensively investigating the health and environmental effects of the chemical. She also hopes to work with farmers and agronomists to figure out ways to optimize sulfur use that reduces negative impacts, without compromising crop yield and quality goals.
An important limitation, according to Hinckley, is that in many places data on the use of sulfur products are not publicly available. "While we were able to get data on sulfur inputs from a number of national and state databases, as well as the peer-reviewed literature, as we move forward, more transparency on sulfur use would help to develop more sustainable management plans." The study is published in Nature Geoscience.