Heat waves, droughts and floods are climate trends that will force California farmers to change some practices — including what they grow — to continue producing yields that historically have fed people nationwide, a new study by the University of California says.

Researchers reviewed 89 studies on California climate trends and impacts on the state’s diverse agriculture industry to predict how the industry must adjust through the end of the 21st century.

“Understanding climate change and how it is impacting agriculture can help us develop relevant adaptation strategies and enhance agricultural resilience to climate risks,” said Tapan Pathak, the lead author on the paper, which was published in Agronomy.

About half the fruit and nuts consumed by people in the U.S. are grown in California, including almonds, pistachios, walnuts, grapes, citrus, kiwi, and more. Yet the state makes up 1.2 percent of the nation’s farmland, some of which produces crops grown nowhere else in the country. Agriculture in this state is a $50 billion industry.

And in Fresno County, agriculture was a $6 billion industry, according to 2016 numbers, the latest available. Almonds and grapes are the top commodities, accounting for nearly 400,000 acres of land.

Make no mistake, Pathak said, the climate directly impacts crops, and farmers know it.

“The agricultural community recognizes the changes we are experiencing and impacts we may face,” he said. “It is important to engage agricultural stakeholders in climate adaptation discussions, understanding their needs, what they may already be doing to adapt, and any barriers to climate change adaptations.”

Warming temperatures will make it difficult for most of the Central Valley to grow crops such as apricots, kiwis, peaches, nectarines, plums and walnuts. By the end of the century, only 23-46 percent of the Valley will be suitable for those crops, the study found.

This is caused by the drop in winter chill hours that many fruit and nut trees require.

Wine grape yields throughout the state are predicted to decrease by 10 percent by the end of the century as well from higher nighttime temperatures.

Researchers suggest growers switch to crops that don’t rely as much on winter chill and alternate planting and harvesting seasons.

The milder winters and warmer temperatures also will create a better habitat for pests, and the paper recommends adopting pest-resilient crop varieties.

Joel Nelsen, president of California Citrus Mutual, a nonprofit that advocates for citrus growers, said that’s easier said than done for farmers who grow permanent crops like citrus, stone fruit, grapes and nuts.

“In an industry like ours, it’s a 20 year project,” he said.

Ryan Jacobsen, the Fresno County Farm Bureau executive director, said while climate may influence what is grown in the San Joaquin Valley, the market demand and consumer habits ultimately dictate what farmers grow.

“As we’ve seen crop patterns change and be influenced by changing diets throughout the country and world, we’ve seen lots of new varieties and rootstocks that have allowed us to do things we didn’t think was possible even 20 years ago,” he said.

“It goes without saying that farmers and ranchers work hand-in-hand with mother nature,” Jacobsen said. “We rely upon what’s given to us.”

That includes water. The study found a 50 percent increase in the number of severe droughts expected in the state by the end of the century. The snowpack, which Jacobsen referred to as the “state’s largest reservoir,” will decrease by 65 percent and melt earlier, resulting in winter floods and decreased water supplies for irrigation.

The study recommends farmers reduce irrigation seasons, grow crops that develop quicker and maximize water through drip and sprinkler irrigation systems.

The study also suggests increasing water storage in dams and reservoirs.

Valley farmers have been lobbying state lawmakers to do just that for years with the Temperance Flat Dam proposal, which received a zero score from the California Water Commission on the cost-benefit ratio earlier this year, shocking and disappointing proponents.

One of the researchers who contributed to the study, Daniele Zaccaria with UC Davis’ Department of Land, Air and Water Resources, acknowledged that constructing water infrastructure in California is highly controversial.

“Before considering the construction of new water infrastructures, it would be highly advisable to appraise the cost-effectiveness and social acceptability of alternative options, such as improved operation and management of existing surface reservoirs, and increasing artificial groundwater recharge,” he said.

Nelsen said he hopes studies such as this one will help policymakers see agriculture’s place in the broader picture of the state’s future.

“I would hope that people in the state’s public policy arena would begin to appreciate that they need to connect the dots,” he said. “As we become a society that’s information rich, we’re narrowly focused and knowledge poor. ... It’s too easy to focus on a single dot.”