July 22, 2009 -- California's famously fertile Central Valley -- home to a $9 billion industry that provides much of the United States' supply of fruit and nut crops -- may be teetering on the edge of a climate-induced disaster, according to a new study.
A team lead by Eike Luedeling of University of California, Davis used a computer simulation of past and future climates in the 400-mile long valley to predict what impact future, human-induced global warming could have on fruit and nut tree farmers.
Fruit trees need cold winter weather almost as much as they need warm summer sunshine. If it doesn't get cold enough, trees stay dormant later into the spring, and flower erratically. As a result fruit crops may not be fully matured at harvest time, or there may be nothing to pick at all.
Compared to 1950, the team found cool winter weather had already decreased 30 percent by 2000. If human emissions of greenhouse gases continues to grow unabated until the end of the 21st century, a worst-case scenario, chill may decline as much as 80 percent.
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Under such conditions, as much as three quarters of the valley may be rendered unsuitable for the production of peaches, walnuts, plums, apricots, pistachios and nectarines -- some of the Central Valley's most lucrative crops. Cherries, apples, and pears are even more sensitive. They could be severely damaged, or even disappear from the valley as early as 2050.
"This is going to have a very significant effect on many crops," Luedeling told Discovery News, scientists wrote in research published yesterday in the journal PloS ONE."It will be very tough for orchard farmers to adjust. For some tree species, they may have to think about planting something else."
Almonds and pomegranates will be least effected, as they require less cold weather than other crops. But the team predicts that almost all of the nearly 40,000 fruit and nut orchards in the region will suffer some damage. The economic losses, while difficult to predict, could be high.
"A lot of the fruit that we love and that's healthy for us only grows in California," David Baldocchi of the University of California, Berkeley said. "As people try to eat healthier and healthier, we may find the things we want to eat might be going away."
Baldocchi, who grew up on a farm in the Central Valley and whose cousin is a cherry farmer, said farmers are already being forced to contend with warmer winters are already impacting crops.
"My cousin complains about how it's costing him all this money because he has to spray hormones on his trees to get them to break dormancy," he said. Such technological measures may work for a while, he said, but eventually the warming will become to great.
"The bottom line is we need to reduce our carbon emissions," he said. "This is just a symptom of a larger, global problem."
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