National Climate Assessment Calls for Agricultural Adaptation

On June 2, the Environmental Protection Agency (EPA) proposed a nationwide strategy to curb greenhouse gas emissions. The Clean Power Plan aims to reduce carbon emissions from the power sector by 30% below 2005 levels by the year 2030.

Photo courtesy of USDA-NRCS

Governor Brown, who recently called California “the epicenter of climate change,” welcomed the Plan and highlighted the environmental and economic successes of California’s clean energy policies. The Obama administration plan allows for state’s flexibility in developing their programs to meet emission reduction targets, including the potential development of more state cap-and-trade programs. This could bring a renewed push to develop agricultural offset protocols, and allow California’s cap-and-trade program to serve as a model as states move forward.

The Obama administration’s climate change policy announcement came on the heels of the recently-released National Climate Assessment (NCA), which summarizes the current and future impacts of climate change on the United States. The Assessment labels the Southwestern U.S. as an area particularly vulnerable to the effects of climate change, detailing the threats posed by rising CO2 levels, declining water supplies, and warmer temperatures.

Many current and predicted climate change impacts have serious implications for the future of agricultural production in California, highlighting the need for coordinated action to reduce greenhouse gas emissions while boosting the resiliency of agricultural systems.

Here we provide an overview of the recent National Climate Assessment and its implications for California.

Invasive Plants Thrive in Higher CO2 Levels

Rising levels of atmospheric CO2 will increase the range for certain invasive plants that threaten agricultural productivity, according to the Assessment. The yellow star-thistle (Centaurea solstitialis) currently costs California farmers $17 million in control efforts and $75 million in water losses, and is predicted to thrive with increased CO2, a result of rising temperatures. As future atmospheric conditions will stimulate weed growth, scientists expect a decrease in efficacy and increased application of the mostly widely used herbicide in the U.S., glyphosate (RoundUp), which is increasingly found in our environment and now with new concerns about its potential contamination of breast milk.

Less Water and Warmer Weather Threaten Productivity

Unsurprisingly, reduced snowpack and streamflow pose serious threats to California agriculture. The National Assessment reminds us that during the 2006-2009 California drought, groundwater storage in the Central Valley decreased by an amount similar to the entire storage capacity of Lake Mead–the largest reservoir in the country.

Meanwhile, the greater occurrence of dry days and hot nights will influence management decisions and may decrease agricultural productivity. Dry days reduce crop and livestock productivity and increase evaporation, while hot nights also interfere with the pollination process that is critical in the development of fruits, fibers, and grains.

Increased Temperature Reduces Winter Chilling Period

Climate change will extend California’s frost-free season in future years. Although farmers may alter planting times to take advantage of this phenomenon, the Assessment predicts that reduced winter chilling will be a serious challenge for California agriculture. Fruit trees, nut trees, and grapevines may be under the greatest threat: extended frost-free seasons and increased heat will accelerate crop ripening and maturity, reduce yields, and increase agricultural water consumption.  In addition to the high water requirements of these crops, their sales depend largely on cosmetic appearance, making their market value particularly vulnerable to drought and weather fluctuations.

Conclusions and Adaptation Options

Although the National Climate Assessment’s analysis presents a sobering picture for California agriculture under climate change, it also discusses adaptation strategies to mitigate climate risk.

Some strategies U.S. farmers have used to cope with climate changes include: changing crop varieties, increasing the use of pesticides, and taking advantage of technological innovations. Often these practices deal with the immediate impacts of climate change, without considering long-term sustainability. The Assessment notes that farming practices typically associated with sustainable agriculture increase the resiliency of the system to the impacts of climate change. Examples of these sustainable practices include diversifying crop rotations, integrating livestock with cropping systems, improving soil quality, and minimizing off-farm pollution.

The California Central Valley’s climate adaptation plan was praised in the Assessment as a promising approach to managing climate risk. Attention was given to its agricultural adaptation strategy, which integrates changes in crop mix, irrigation methods, fertilization practices, tillage, and land management.

California’s statewide approach to mitigating climate risk also emphasizes the importance of strengthening agricultural resilience to climate change. However, California lacks a statewide agricultural adaptation strategy that integrates multiple methods of mitigating climate risk. CalCAN calls for California’s adaptation strategy to include innovative technical assistance to farmers, whole-farm conservation planning, outreach to small and mid-scale producers, and on-farm renewable energy production. We highlight the resiliency benefits of various sustainable agricultural practices, such as soil building, water stewardship strategies, and biodiversification.

As the nation aims to meet the new carbon emissions reduction goals, other states will look to California’s cap-and-trade system as a model for creating their own carbon markets. CalCAN advocates that climate policies take a whole-farm approach, ensure transparency and accountability within the marketplace, and empower small and mid-scale producers.

For a more in-depth discussion of the National Climate Assessment’s key findings, check out the Union of Concerned Scientists’ webinar series.

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