Those crops, accustomed to the cooler edges of California's climate, are showing declining yields, according to the USDA's National Agricultural Statistics Serv-ice. That could mean higher prices for consumers as the supply shrinks. This summer's record droughts in the Midwest prompted the USDA to predict a rise in prices driven by devastated yields for corn and soybeans, the primary food for chicken and cattle nationwide.
If California's water crisis persists, seasonal vegetables and fruits also will be dramatically affected. Some already are.
Much of the southern Central Valley is a patchwork of fallow fields, according to Gayle Holman with the Westlands Water District in Fresno. Thousands of acres that once grew onions, tomatoes, melons and other crops have been set aside by farmers who no longer can obtain, or afford, water, a scarcity, scientists say, that is caused by the dramatic shifts in the timing of rainfall in the state.
Like just about everything having to do with climate change, the consequences unfold like a sequence of trapdoors. First, there's the temperature, a jagged progression over the past decade of unusual highs and lows occurring at times of the year that can debilitate growing crops.
Then there's water. California's water sources are caught in a bind: More water is needed at a time when less water is delivered into the canals carrying it from the north to the agricultural regions in the south.
A precipitous drop in snowfall has led to declining water runoff in the San Joaquin and Sacramento rivers in the spring and summer months, when it's central to irrigation in the valley. Over the past century, the state Department of Water Resources has measured a steady 10 percent decline in runoff from April to July. In recent years, however, the rate has accelerated to as much as 20 percent.
Farmers in the valley generally blame the drop-off in water on the 2007 state Supreme Court decision affirming the need for water to preserve Pacific smelt and other endangered species.
A study by the Public Policy Institute of California, however, concludes that the roughly 300,000 acre-feet of water diverted to comply with the Endangered Species Act constitutes no more than 20 percent of the reduced water flow to the valley.
Rather, the overall pool of water is shrinking.
"The water that used to exist is now coming earlier in the year," said Francis Chung, chief of the Modeling Support Branch for the Department of Water Resources. "So there's less water to distribute (to the valley) during the summer."
Another growing problem has been rising sea levels associated with climate change. The San Francisco Bay, according to a recent National Academies of Sciences assessment, is projected to rise by as much as 18 inches, and potentially triple that by the end of the century. Those inches translate into waves of new salt sources lapping into the Sacramento-San Joaquin Delta.
Less water channeled into the delta from the Sierra means less available fresh water to dilute the onrush of salt, which has been pushing steadily eastward.
A study by the University of California at Davis estimates that if salinity continues to rise at the current rate, the financial costs to the Central Valley could be huge by 2030: as much as $1 billion to $1.5 billion a year in decreased agricultural activity, amounting to some 27,000 to 53,000 jobs lost.
Daniel Cozad, executive director of the Central Valley Salinity Coalition, a group of local farmers, businessmen and government officials, said some farmers in the western valley are being forced to adapt by switching from crops that are salt sensitive such as strawberries and avocados to less sensitive -- and less profitable -- crops such as alfalfa and wheat.
"Unfortunately," Cozad said, "the higher the value of the crop, the more sensitive it is to salt."
This story was produced by the nonprofit Center for Investigative Reporting, the country's largest investigative reporting team, in collaboration with KQED public radio. For more, go to www.cironline.org. Mark Schapiro can be reached at firstname.lastname@example.org.