California produces more than a third of the vegetables and three quarters of the fruits and nuts in the United States. But water constraints are leaving more and more fields unplanted, or “fallowed,” particularly in the state’s famed farming hub, the Central Valley.
In a study published in Communications Earth and Environment, researchers showed that these fallowed agricultural lands are producing a different problem: dust storms, which can cause road accidents and health problems and can have far-reaching environmental impacts. Using remote sensing methods, the team found that 88% of anthropogenic dust events in the state, such as dust storms, come from fallowed farmland.
California’s frequent droughts could mean a rise in fallowed farmland. In 2014, the state passed the Sustainable Groundwater Management Act (SGMA), a policy aimed at ensuring the sustainability of groundwater resources. A report by the Public Policy Institute of California suggested that to meet the SGMA’s demands, farmers may need to fallow hundreds of thousands of additional acres, potentially worsening dust events.
Tracking Down Agricultural Dust
Dust can come from both natural sources, such as wind blowing across a desert, and anthropogenic sources, such as when transportation, construction, or agricultural activities kick up particles. Previous studies identified agriculture as a significant source of human-generated dust, but study author Adeyemi Adebiyi and his colleagues wanted to narrow down which agricultural practices produced the most.
“If you stop irrigating the land, it becomes dry, and we’re already in a dry climate. It’s easy for it to become a new dust source.”
Fallowed land was a logical culprit. “If you stop irrigating the land, it becomes dry, and we’re already in a dry climate,” said Adebiyi, an atmospheric scientist at the University of California, Merced. “It’s easy for it to become a new dust source.”
The researchers started by pinpointing fallowed land across California between 2008 and 2022 using U.S. Department of Agriculture datasets. The data showed that 77% of the state’s fallowed land was in the Central Valley.
The team then examined NASA satellite images of atmospheric aerosols, identifying which aerosols were dust particles on the basis of the way they scatter light. When they overlaid the regions that regularly experienced dust events with the agricultural data, they saw that dust events were tightly associated with fallowed fields.
The problem appears to be getting worse. Between 2008 and 2022, both the area of fallowed land and corresponding dust levels have increased: In this period, the amount of dust in the atmosphere over the Central Valley grew by about 36% per decade.
Having grown up in California and spent the first decade of his career studying dust in the Central Valley, Thomas Gill, an Earth scientist at the University of Texas at El Paso who wasn’t involved in the study, has long worried that land use changes could lead to dust issues. “This study by Adebiyi et al., unfortunately, shows that my worries have been coming true,” he said.
“These fallowed land locations are emblematic of the properties you would normally see in a typical desert-type location.”
Daniel Tong, an atmospheric scientist at George Mason University who also wasn’t involved in the study, agreed that the work provides some much-needed conclusive data on the connection between land use and dust levels. “This is a very useful study,” he said.
Adebiyi’s team used additional remote sensing data to determine that compared with nearby nonfallowed land, fallowed fields have lower soil moisture and are about 4.2°C hotter. Combined with a lack of vegetation, these factors work together to make such areas more prone to wind erosion. “These fallowed land locations are emblematic of the properties you would normally see in a typical desert-type location,” Adebiyi said.
Far-Reaching Effects
The dust from fallowed fields has wide-reaching consequences. “California is already the state with the largest number of fatalities caused by dust storms,” said Tong, who authored a 2023 study about windblown dust fatalities in the United States. One concern, he said, is that more dust storms could increase road accidents. Dust also contributes to respiratory problems and cardiovascular disease and carries the Coccidioides fungus, which causes the dangerous infection valley fever. Cases of valley fever increased by 800% in California between 2000 and 2018.
“There’s also been a great population increase in the Central Valley,” Gill said. “So not only do you have more particulate matter, but you have more people living there who are vulnerable to its effects.”
Fallowed fields and the dust they produce may also work counter to the groundwater management goals of the SGMA. The Central Valley dust blows east into the Sierra Nevada Mountains, where it speeds snowmelt, a significant reservoir of water for the state. The researchers also found that the heat concentrated in fallowed fields can spread out to nearby fields, causing surrounding crops to need more water. “It’s a double whammy,” Adebiyi said.
He noted the importance of preventing fields from becoming completely bare while still conserving water. One strategy is to plant native, drought-resistant plants that protect the soil from wind erosion without needing much irrigation.
The researchers are now conducting similar studies on the connection between fallowed lands and dust in other agricultural states, such as Kansas, Montana, and Washington. Their findings suggest that addressing dust problems will become increasingly important nationwide.
“The implications are beyond California,” Adebiyi said. “They’re across the United States.”
—Andrew Chapman (@andrewchapman.bsky.social), Science Writer
Citation: Chapman, A. (2025), Fallowed fields are fueling California’s dust problem,
Eos, 106, https://doi.org/10.1029/2025EO250223. Published on 13 June 2025.
Text © 2025. The authors.
CC BY-NC-ND 3.0Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.
