"Fruit and nut farmers around the globe are in jeopardy of seeing a dramatic drop in crop yields as climate change reduces the periodic chilly conditions that are vital to cultivating certain kinds of trees, scientists have found. Researchers at the University of California, Berkeley, and the University of Washington, in a study published this month by the journal PLoS ONE, say fruit and nut trees in California, China, Australia and the southeastern United States are especially vulnerable. The study looked at the likely effect of warming on "safe winter chill" periods that are important for walnuts, pistachios, apricots, plums and most peaches and nectarines. Apples, cherries and pears are also at risk. For farmers of these popular crops, the research pointed to a troubling future. Such tree crops rely on cool temperatures for cultivation during winter months, especially in temperate zones like California, which supports an annual $8.7 billion fruit and nut industry on 1.2 million hectares of orchards. If temperatures rise as anticipated throughout the century, the study predicts a decrease of safe chilly periods of 50 to 75 percent by midcentury and 90 to 100 percent by 2100. "If winter chill decline occurs due to climate change, production constraints are likely to exceed those typically reported, because many trees might not even come close to fulfilling their chilling requirements," the study explains. "In such cases, complete crop failures may frequently occur ... rendering many orchard operations uneconomical."...One complication faced by the farmers is the relatively long planning timeline needed to plant trees that often live for several decades or more. Farmers of crops like corn, wheat or cotton might be better able to adapt to warming because they can shift planting annually. "Tree crop growers will be much more vulnerable to the long- and medium-term effects of climate change than growers of annual crops," the study says."