Fallowed agricultural lands dominate anthropogenic dust sources in California.

Abstract

Air pollution remains a major problem in many parts of California, significantly impacting public health and regional climate. However, the contribution of anthropogenic dust particles from agricultural sources, among the major pollutants, in California's semi-arid Central Valley region remains largely unclear. Here, we used the Cropland Data Layer from the US Department of Agriculture to identify crop types and land cover and leveraged satellite-derived estimates of major anthropogenic dust events between 2008 and 2022 over California. We identified fallowed land – an unplanted agricultural land parcel – as a key anthropogenic dust source in California. Specifically, we find that the Central Valley region accounts for about 77% of total fallowed land areas in California, where they are associated with about 88% of major anthropogenic dust events. We also find that regions with higher coverage of fallowed lands are expanding, increasing anthropogenic dust activities over the period considered. Additionally, these anthropogenic dust activities are sensitive to the dryness levels over the fallowed lands, with potential cumulative effects on downstream dust burden during prolonged multi-year drought conditions. Overall, our results have important implications for public health, including possible increased risk for Valley fever, a fungal respiratory infection caused by inhalation of soil-dwelling infectious spores, and on regional climate, such as increases in extreme precipitation and snowmelt over the Central Valley and the Sierra Nevada.