In the summers, the sky is completely black when Raúl Cruz arrives at this cane field in the Imperial Valley to begin his day. Cut, clean and tie the crop, and take precautions at dawn. It’s hard work, but it’s also hard to start at 4:00 in the morning, although you know it’s the safest thing to do when the temperatures in this desert of California They usually exceed 100 degrees Fahrenheit.
“We just have to do it because we need to beat the heat,” said Cruz, who has worked here for 15 years. They finish work at 9:00 or 10:00 in the morning to avoid the risk of heatstroke, he added, but when the heat starts to increase around 8:00 in the morning, “mentally it is stressful.”
The warm climate that makes this region of Southern California an agricultural powerhouse also makes it dangerous for farm workers, who are increasingly vulnerable to rising temperatures due to greenhouse gas emissions from burning coal. oil and natural gas.
Researchers at San Diego State University (SDSU) are trying to understand the consequences of heat stress on the health of agricultural workers and where the heat is most extreme in this rural environment. They hope their findings will lead to a better understanding of rural heat islands.to identify gaps in research and help develop interventions that better protect them from climate change.
“Workers could potentially be dying or having serious problems,” said Nicolás Lopez-Galvez, project leader and associate professor at the SDSU School of Public Health. “It is better to start acting as soon as possible.”
1/7 | Devastating scene: dead corals in Puerto Rico due to extreme heat and bleaching. Restored staghorn coral (“Acropora palmata”) colonies completely bleached and recently killed during the 2024 mass bleaching event. Extreme temperatures can kill corals exposed to temperatures above their tolerance level for prolonged periods. This species is protected under the federal Endangered Species Act. – Supplied: Edwin Hernández Delgado
Understanding thermal stress
Since the beginning of the 20th century, temperatures in California have risen nearly 3 degrees Fahrenheit (°F), according to state and federal data. Warming has accelerated, and seven of the last eight years — through 2024 — were the hottest on record in the state. While all areas of the state have warmed, Southern California is warming about twice as fast as the north.
Ana Solorio, an organizer with the farmworker advocacy group Líderes Campesinas, who collaborates with researchers, remembers feeling “stifled” in the summer heat of the Coachella Valley when she was a farmworker.
“With the humidity, it felt very ugly,” said Solorio, who has lived in Imperial Valley — as the El Centro metropolitan area is known — for more than 30 years. The heat was so intense that he did not return for another season, preferring the cooler months of the lettuce harvest in Imperial Valley during the winter.
“This can cause a lot of damage to your health,” he stressed.
Researchers try to understand how farmworker heat stress may vary across cropsthe season and the number of breaks they take.
For the past two years, they have collected annual data from about 300 farmworkers. Body sensors measure things like internal body temperature and heart rate while you work. Elsewhere on the fields, environmental monitors measure temperature, humidity, wind speed, solar angle and daytime cloud cover, also known as the wet bulb globe temperature (WBGT index), considered the best metric for understanding the thermal stress.
Using satellite imagery along with historical and current globe and wet bulb temperature data, researchers map areas of extreme heat, particularly in the Imperial Valley and Coachella Valley. Researchers find that ground-level crops can expose workers to higher levels of heat compared to tree crops, for example, but it also depends on harvest months.
In summers, farm workers who prepare fields for planting or help maintain irrigation systems are also more exposed.
He heat Rural can vary depending on factors such as tree cover, proximity to a body of water, and empty fields, which can be hotter.
“This creates a kind of island where people could live or work with heat stress that is higher compared to other places,” Lopez-Galvez added.
Extreme heat in main agricultural regions
Bounded on the east by the Colorado River, on the northwest by Salton Lake, and on the south by MexicoImperial Valley is home to hundreds of thousands of hectares of farmland and produces billions of dollars in agricultural production. It grows two-thirds of the winter vegetables consumed nationally and provides thousands of jobs. Between 2023 and 2024 alone, about 17,579 migrant and seasonal farmworkers worked in Imperial County, according to the state.
And it’s also extremely hot. In any given year, there are about 123 days with temperatures above 95°F, often exceeding 110°F in August and early Septemberaccording to calculations by Sagar Parajuli, a research scientist and associate professor in the School of Geography at SDSU. The county has one of the largest Latino populations and the highest number of heat-related illnesses among workers than anywhere else in the state.
What researchers hope to find
Some of their data analyzes have already been published.
One study found that irrigating crop fields in Imperial Valley reduced globe and wet bulb temperatures on summer days, thanks to the cooling effect of water evaporation. However, on summer nights the opposite occurred: irrigation increased globe and wet bulb temperatures as humidity increased. Irrigation also raised heat in urban areas and in fallow areas near crop fields due to moisture transport.
“It is concerning because a high nighttime temperature restricts farmworkers’ ability to cool down,” said Parajuli, the study’s lead author. “So they can’t recover from the heat stress they might be accumulating during the day.”
Due to this research, The authors were able to recommend how often farmworkers should take breaks to protect themselves from heat stress.based on the frequency with which globe and wet bulb temperatures exceed safety thresholds in different seasons and work shifts. While California has heat regulations, it does not strictly enforce them, he added.
“We realized that farm workers do not have enough breaks, and that there are also no clear policy guidelines in terms of heat-related break breaks,” he explained.
Lopez-Galvez said they plan to continue their research in California’s Central Valley and hope to expand it to Yuma, Arizonaand other parts of the southwestern United States.