Vulnerable Central Valley is on the front lines of climate change

UC Merced researchers release alarming report on climate change’s impact on San Joaquin Valley communities, agriculture

MERCED – California’s Central Valley is on the front lines of climate change, according to a recent report by its own University of California.

In early January, a team of UC Merced and affiliated researchers released the Fourth Regional Climate Change Assessment, illustrating the biggest problems — and possible solutions — facing California’s vast and diverse biomes and communities, from the coasts to the mountains and forests to deserts.

“The San Joaquin [Valley] is uniquely at the heart of California and this first-of-its-kind regional assessment of climate change impacts shows the unique challenges faced by the region, including access to safe drinking water and dependence on vulnerable water supply for agricultural production,” said report co-author and Associate Dean for Research Professor Joshua Viers. “It also demonstrates the capacity of UC Merced researchers to shed new light on these issues and propose meaningful solutions for our region to better prepare for extreme climate events and build more resilient communities.”

The latest San Joaquin Valley regional assessment was published online on Jan. 6 by the California Energy Commission and California Natural Resources Agency. Solicited by the state and coordinated by lead author and UC Merced alum and postdoctoral researcher Angel Santiago Fernandez-Bou, the report includes faculty experts in wildfire, water and climate change — professors Viers, LeRoy Westerling and Josué Medellín-Azuara. These faculty members advised and conducted a graduate class to start the development of the report. Other authors include researchers from the Union of Concerned Scientists, Fresno State and Saint Louis University. The report will be used by the state of California, nonprofit organizations and the general public to gather the most up-to-date science and information on climate change at the regional level.

The San Joaquin Valley already has one of the most challenging environmental and socioeconomic conditions in California: millions of residents have water insecurity and the worst air quality in the United States; the ecosystems are the most degraded in the state; and the main economic engine, agriculture, is continuously at risk to maintain its productivity due to water scarcity. Climate change is aggravating these conditions and threatening the already diminished quality of life and economic livelihood of the San Joaquin Valley.

Researchers point out climate change’s exacerbating effects on familiar Valley experiences: extreme heat, prolonged multi-year drought, with 20% less overall rainfall than normal during the growing season, poor air quality from fire and particulates, and stress or collapse of critical infrastructures such as canals, roads and bridges. The report states Tulare County’s annual average minimum and maximum temperatures increased 1 degree from 1961-1990 but are projected to quadruple by 2050 and possibly rise by 8 degrees before the end of the 21st Century. Annual rainfall is expected to maintain current levels but warmer temperatures mean a “50% decline in snowpack, 13% more precipitation during extreme events, more frequent very dry (+4% to 10%) and very wet years (+34% to 57%) towards the end of the century” Valley wide. That will mean surface water reservoirs will fill up sooner, creating flood concerns, release less water in the summer and fall, causing supply shortages, and increase the use of groundwater in an already overdrafted basin.

On a bright note, the report says there will be less Tule fog descending on the Valley floor. Fog frequency has decreased by 75% since 1980. Unfortunately, the fog is necessary to achieve chilling hours for fruit trees to yield the sweetness desired by commercial markets.

The team identified major climate-linked negative impacts for communities, agriculture, ecosystems and infrastructure that will affect most aspects of life in the San Joaquin Valley. The key findings of the report illustrate the complex nature of climate change impacts on a water-limited area.

Increasing temperatures have a drying effect by evaporating more water, and warmer weather also means many storms will be warmer and wetter and more concentrated in fewer months during the winter. Valley water resources will swing between flooding events and prolonged droughts with increased groundwater pumping.

Dry soils, forests and communities will fuel the severity and extent of wildfires, as well as lengthening fire season, impacting air quality for many months.

The report also speaks to the capacity to adapt current practices and resources to manage climate change. Some promising mitigation and adaptation strategies include improving flood management to serve ecosystems and replenishing groundwater aquifers when water is available. The wide adoption of carbon-neutral technologies and electrification of vehicles will contribute to better air quality, say the authors.

Uneven change

Climate change does not affect all Californians equally. Those without sufficient resources — economic, infrastructure and frontline communities in general — will be disproportionally hit. Air quality and human health impacts due to climate change are more pronounced in rural disadvantaged communities of the San Joaquin Valley than in the rest of California. These populations, predominantly low-income Hispanic communities, are more likely to experience more heat-related deaths and illnesses, deteriorating air and water quality, and general lower quality of life and decreased potential for livelihoods.

The San Joaquin Valley has some of the lowest environmental quality and socioeconomic conditions statewide (OEHHA, 2017). The region hosts a much higher proportion of disadvantaged communities than the rest of California, as 55% of the population in the San Joaquin Valley lives in 413 census tracts classified as disadvantaged. These communities are predominantly Latino, migrant workers, and lower income people.

Vulnerable populations and disadvantaged communities will suffer disproportionally more from the impacts of climate change since they have less capacity to adapt. The lack of curbs, gutters and sidewalks makes them more susceptible to floods. The lack of reliable, potable water supplies makes them more vulnerable to droughts. Without more diversified job options, farmworkers will be the most affected by the fallowing of acreage and mechanization of harvesting in an area with historically double-digit unemployment. But if they keep working the fields, they are more likely to suffer warming nights, which increase anxiety and heart problems, and dirtier air, which exposes them to asthma, Valley fever, and smoke inhalation due to wildfires.

The key solution from the UC Merced authors is focusing on at-risk communities and the capacity to change the situation for multiple benefits. One promising adaptation opportunity that can bring environmental justice and new economic development to frontline communities is repurposing land surrounding rural disadvantaged communities into green areas, aquifer recharge projects, wildlife corridors, cleaner industry, solar panels, and other clean socioeconomic opportunities. This approach has the potential of creating wealth for the communities, for all the involved stakeholders, and for the state.

“Emergency management and health services require proper investments and adequate planning in underserved frontline communities. The San Joaquin Valley report highlights what investments will help us all adapt to climate change,” Fernandez-Bou said. “The agricultural identity of the Valley can become an important asset for mitigation and adaptation strategies, and to promote environmental and socioeconomic justice — if some regenerative-agriculture practices are incentivized with adequate policies.”

Agricultural change

Agriculture employs 16% of Valley residents, accounts for a quarter of all revenue produced in the Valley and uses about 89% of all water in the Valley. In addition to more extreme cycles of flood and drought, warmer winters means more insects and pests. Changes in cropping patterns with climate change will have effects on labor demand for agriculture. Most valuable commodities including fruits, nuts, and vegetables concentrate roughly 85% of the labor and gross revenues in crop agriculture. Thus, employment effects from these shifts remain largely uncertain.

Fewer winter chill hours will affect many of the productive orchards throughout the Valley and foothills, and all agricultural production will be affected by water availability, increased evaporative demands and extreme heat. Reduced crop yields and changes in timing of cropping systems may affect the regional economy and employment.

“Some of the most economically valuable commodities are threatened by some early climate change effects,” the Climate Change Assessment says.

The report suggests farmers may have to use biomass instead of traditional fertilizers to promote rich soil, switch to more drought-resistant, less water-intensive crops, installing overhead irrigation to maintain chill hours and adding shade trees for livestock on pastures.

Management of aquifer recharge projects are the most promising way to expand the current water storage, allowing water to be safely captured from the more frequent extreme storms and the more intense snow melting. The researchers said soil storage is at least ten times more effective than surface storage, and dams may not be able to hold all the water released during peak flows and extreme events. Adequate soil storage will also reduce the impacts of droughts and can contribute to preventing land subsidence.

Some intensive agricultural practices and unplanned development in the Valley may also exacerbate negative impacts of climate change, furthering habitat loss for native species and the establishment of invasive species.

“Multi-benefit and inclusive approaches to strategically repurpose land in the San Joaquin Valley and increasing climate resilience are worth pursuing to ensure a habitable and thriving area,” Medellín-Azuara said. “But agriculture, communities and ecosystems in the San Joaquin Valley can coexist sustainably if the state’s plans are comprehensive and include mitigation and adaptation.”

The more that it is done soon to reduce emissions of heat-trapping gasses going into the atmosphere, the less negative climate change impacts the San Joaquin Valley will experience in the future.

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