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Agriculture is at the nexus of global warming pressures in California. Mild weather and fertile soils make California the country's largest agricultural producer. But commercial farming depends on water that may become scarcer, stable weather that may become erratic, and moderate temperatures that are creeping up.
Until recently, most agricultural climate research focused on carbon dioxide. Because plants breathe in carbon dioxide, the thinking goes, elevated levels of the gas actually benefit many crops. But now agricultural scientists also have started considering temperature changes. California fruits such as blueberries and black currants won't flower until they've been in temperatures below 45 degrees for at least 150 hours, and most species require 500 hours or more. Stone fruits such as peaches, apricots, and cherries require anywhere from 200 to 1,500 "chill hours" every year. In Fresno County-an important fruit-growing region-there were about 830 chill hours this year, near the lower threshold of many crops. One study reports this number may go down further, affecting kiwis, walnuts, pistachios, nectarines, plums, apricots, and almonds.
Farmers also worry about the growing number of hot days per year. One of the most sensitive crops to this is the wine grape, which requires warm, moderate summer days and cool nights to produce sugars at an even pace. By 2100, California's moderate summers may pick up too many days above 95 degrees Fahrenheit for many wine grapes, crippling as much as 80 percent of U.S. wine production. Wine contributes $45 billion to California's economy through exports and tourism.
Some scientists speculate that warming ocean tem-peratures also could cause a continuous El Niño effect. El Niño is a pattern of ocean circulation that causes stronger storms in California, more hurricanes in the eastern Pacific, and droughts in parts of Asia every three to seven years.
In addition to having more El Niños, a warmer Pacific also would be higher. Rising ocean levels will put the Sacramento-San Joaquin River Delta at particular risk, because the land has subsided and much of it is now below sea level. The land is protected by an aging system of levees, which is fragile even at current ocean levels. Some 22 million Californians, including those in the Bay Area and Central Valley, get their water from the Delta, and if the ocean were to overwhelm the levees, that water supply would be contaminated with salt.
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viernes, julio 18, 2008
En California el cambio climático podría afectar la producción de arándanos
Es de público conocimiento la cantidad de focos de incendio que se repiten en California este año al igual que el año pasado. En la siguiente nota de California Magazine, los expertos ven con preocupación como variedades como el arándano que necesita determinada cantidad de horas de frío se podría ver perjudicada en la región de continuar esta tendencia climática.
Esto es importante sobretodo para productores argentinos y chilenos que entran con su fruta en las semanas mas tempranas y temen el crecimiento de la oferta californiana sobretodo de los grandes cultivos que se han implantado los últimos años.
a la/s 10:17 a.m.