Agriculture is a $9 billion industry in Arizona, but it is vulnerable to the increased heat and drought likely to accompany climate change, says a federally commissioned report.

Agriculture, a $9 billion industry in Arizona, is vulnerable to the increased heat and drought that's likely to accompany continued climate change, said a new federally commissioned report.

"Farmers are renowned for adapting to yearly changes in the weather, but climate change in the Southwest could happen faster and more extensively than farmers' ability to adapt," said the report.

A warmer, drier climate is projected to accelerate current trends toward transferring agricultural water to growing urban areas and could shift some crop production northward, the report said. In some rural communities, reduced crop yields from higher temperatures and scarce water will displace jobs, the new report said.

The warning came from a chapter on the Southwest in the new National Climate Assessment report, written by a panel of scientists convened by the federal government.

Three experts - a researcher who co-authored the study, a Yuma farming official and a University of Arizona researcher in the lettuce-rich Yuma area - predicted farmers would "think out of the box" to adapt to climate change.

"Arizona farmers know about heat stress, about heat and drought down there," said Reagan Waskom, director of the Colorado Water Institute, a co-author of the new report's Southwest chapter. "I believe the Colorado River Basin overall will be ag-heavy for a long time and that agriculture will adapt. But some crops will move north, and a lot of what you'll see is changes in planting dates and genetics."

Overall, "the Southwest is the hottest and driest region in the U.S., where the availability of water has defined its landscapes, history of human settlement and modern economy," the report said.

"Climate changes pose challenges for an already parched region that is expected to get hotter and, in its southern half, significantly drier."

The report focused on high-value specialty crops, including lettuce and other leafy vegetables, fruits and nuts. The Yuma area has a $3 billion agricultural economy and 250,000 acres under cultivation. The Southwest produces more than half the nation's high-value specialty crops.

Other specialty crops grown near Yuma include mushrooms, cauliflower, spinach, pears, peaches, citrus and dates. Typically, most salad greens sold nationally during the winter come from the Yuma area.

Except for Colorado, 92 percent of the Southwest's cropland is irrigated, and agriculture accounts for 79 percent of the region's water use. In Arizona, farmers use about 70 percent of all water. Yuma County farmers and the city of Yuma plan to divert about 1.23 million acre-feet from the Colorado River in 2013. That's nearly half of Arizona's share of the Colorado.

Drought and extreme weather affect fruit and vegetable market values more than those of other crops because produce contains a lot of water and sales depend on appearance, the new report said. Together, a longer frost-free season, less-frequent cold snaps and more-frequent heat waves accelerate ripening of crops; reduce yields of corn, tree fruit and wine grapes; stress livestock; and raise water use, the report said.

Jon Dinsmore, a farm manager and spokesman for the Yuma County Farm Bureau, said farmers there are concerned about climate change, but added it's hard to be too worried about it when they have today's crops to think about.

"We used to think day to day, but now we plan our growing seasons in advance and think about water availability," said Dinsmore. "Really, all we can do is farm our ground with the resources we have. Every year, our resources are diminishing."

But crop production remains steady, he said.

"In the old days, it seemed that just about everything was flood irrigation, but over the last 15 to 20 years, there's more and more sprinkler irrigation that's more conservative and precise. We learn to think out of the box."

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Kurt Nolte, director of the University of Arizona's agricultural research center in Yuma County, predicted that while drip irrigation's use in that area is minimal now, it could increase.

"The challenge that specialty crops will be faced with is adapting their varieties and cultural practices to the environment that is coming our way," he said. "It's hard to tell if we are going to be able to deal with that."

Genetic changes in crops can help farmers adapt by breeding them to be more heat-, drought- and salt-tolerant, he said. While farmers have bred crops for yield and quality for a long time, they may need to move toward breeding stress-tolerant crops, said Waskom, the new report's co-author.

But one concern raised by many studies is the impact on crops of "more energetic" storm systems that bring hail, winds and hard rains, he said.

"While a cow may accept shriveled-up sweet corn, the housewife in the supermarket does not," Waskom said.

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Contact reporter Tony Davis at or 806-7746.