The following is a brief summary of a new University of California report, Beyond the Haze, which highlights the implications of climate change and increasing dust emissions for agricultural communities in California, as well as the ways in which farmers can reduce dust emissions through healthy soils practices. 

Causes of Increasing Dust Emissions

When arid, open landscapes with fine particulate matter experience strong winds, windblown-erosion, or dust, is emitted. While dust and dust storms occur naturally in certain areas, the frequency and intensity of dust emissions and storms in California and the southwestern US have increased dramatically as a result of increased human development and activities since the arrival of settlers in the 19th century. For example, lake records in the Rocky Mountains show that dust emissions were 500% higher in the past two centuries than any other era in the last 5,000 years, despite the fact that the 19th and 20th centuries were relatively wet periods. 

Human activity increases dust emission through two mechanisms: changes to land cover and use and changes to the climate. Environmental engineering projects that divert water for urban development and agriculture have contributed to the drying-up of lakebeds such as the Salton Sea and Owens Valley-Mono Basin, two major sources of dust in the state. Some common agricultural practices, particularly practices that leave fields dry and uncovered, generate significant dust emissions in California. The fallowing of hundreds of thousands of acres in the San Joaquin Valley to achieve groundwater sustainability under the  Sustainable Groundwater Management Act is expected to increase dust in the area. 

Climate change is expected to increase dust storms in California because “dust emissions are affected by environmental drivers, such as precipitation, soil moisture, surface temperature, and surface winds, which are projected to change as the planet continues to warm.” The increasing intensity and frequency of wildfires associated with climate change reduces vegetation which acts as a wind block, and can leave the soil physically and chemically altered in ways that decrease absorption capacity. Finally, unprecedented drought since the beginning of the 21st century in California and the entire southwestern US has increased aridity, decreased soil moisture content, and has already resulted in a 240% increase in dust emissions. 

Dust Impacts on Agricultural Production & Water Supply

Agriculture in California is affected by dust emissions in various ways. Dust storms can physically damage plants and harm livestock. Both dust suspended in the air and deposited directly on leaves reduces the photosynthetic capabilities of plants. Dust deposition in the Sierra Nevada also reduces agriculture’s water supply by increasing solar absorption and accelerating snowmelt. Accelerated snowmelt reduces the natural storage of winter precipitation as snowpack, which reduces surface water availability and distribution during the dry summer months.

Dust Impacts on Health of Rural and Farmworker Communities 

Dust emissions can have negative impacts for human health. Epidemiological studies link dust exposure to increased rates of respiratory illness and cardiovascular disease. Dust from agricultural areas can carry chemicals like neurotoxic pesticides, which can accumulate in the body and affect neurological development and immune function. In California, inhaling dust containing the fungi coccidioides can cause Valley Fever. Although most symptomatic cases of Valley Fever resolve, symptoms can last for months. Five to 10% of cases develop chronic pulmonary disease and, most severely, 1-4% of infections spread beyond the lungs and can damage the nervous and skeletal systems. Rates of Valley Fever are on the rise in California, and additional regions are expected to become endemic with climate change. 

Dust exposure and impacts to human wellbeing are unequally distributed across California. Low-income communities, communities with higher Latino populations, and communities with higher proportions of undocumented people are more likely to live and work near sources of dust like playas and fallow farmland. In the San Joaquin Valley, “Hmong and Latino [populations] make up a large percentage of field workers… These populations tend to fall into the lowest wealth bracket with little to no access to healthcare, thus representing those with the least availability and opportunity to seek medical care, and the most exposed to [Valley Fever]…” To mitigate the impacts of dust exposure, the report suggests increasing forecasting capabilities and outreach in rural communities.

Healthy Soils Practices Can Reduce Dust Emissions

As many farmers in our network can attest, many of the practices that mitigate dust and soil erosion on farms have other agronomic benefits and build overall resilience. Healthy soils practices like cover cropping and compost application increase soil organic matter and water-holding capacity while physically covering the soil and reducing erosion. Hedgerows and windbreaks block wind from creating dust, while providing habitat for pollinators and wildlife. Organic agriculture reduces potential harms of dust by preventing the application of toxic chemicals into soil, which can be spread in dust to farm workers and nearby communities. Reduced tillage can reduce dust by as much as 85%, and technological innovations like off-ground almond harvesters reduce dust emissions while allowing farmers to cover crop and graze, simultaneously boosting soil health, reducing fertilizer costs, and mitigating erosion.

The state of California has been successfully incentivizing farmers to adopt and sustain many of these practices through the Healthy Soils Program (HSP) since 2017. A recent program evaluation found that  HSP participants planned to maintain 71% of funded practices and planned to expand 64% of funded practices. While we often discuss the benefits of this program and the practices it funds in terms of their agronomic and climate benefits, we appreciate the ways in which the new University of California dust report draws attention to some of the lesser known public health and water supply benefits of healthy soils practices, as well as the urgency to continue supporting farmers in adopting those practices. 

If you’d like to learn more about this issue and potential solutions, we encourage you to read the full report and visit the new UC Dust website.