Of mist and nuts…California remains, despite its current drought, one of the main source

Of mist and nuts…California remains, despite its current drought, one of the main source of fruit, vegetables and nuts for both the US market (95%) and worldwide export. Much of this is grown in the Central Valley, watered by irrigation, pollinated by increasingly uncommon bees, and dependent on a particular kind of winter fog to convince these originally colder clime plants that a winter has occurred. New research suggests that these vital fogs are becoming rarer with climate change, endangering a substantial chunk of the state’s economy.The mists are known as Tule fogs after the grassy wetlands that once covered the valley. They form between November and April, and are caused by cold air sinking into the valley at night from the surrounding mountains, condensing the moisture in the warmer valley air (a process known as radiation fog). They can linger for days along the whole 650km length of the valley, since winds cannot budge the dense air and temperature inversions can often keep them confined in the valley.These fogs are crucial for may fruit and nut trees, giving the plants the impression of a dank, dark and cool European winter. Some trees, such as cherries, almonds and peaches need a dormant period during the winter that needs prolonged coolth to trigger. The rest is vital to their ability to produce buds, flowers and fruit, and its absence results in drastically lowered yields. Recent research at the University of California at Berkeley has shown that these vital fogs have declined dramatically during the last 30 years.The team used both NASA/NOAA satellite data and weather station records to chart the fogs over the last 32 winters, revealing a 46% drop in fog days during the crucial winter season. Variability between seasons is due to whether the year is wetter or drier, but the lowering trend is unmistakeable. Other work underlines this, showing a drop in several hundred hours of temperatures between 0 and 7 degrees Celsius since the 1950’s. The current drought is also preventing their formation, exposing the fruit trees to a variety of mixed stresses.Climate forecasts imply this situation will worsen, eventually threatening the entire current model for Californian agriculture. Fruit developers are trying to breed varieties that can do without a winter, but without much success for now. Only the future will tell exactly where and how the chips are going to fall, but the best educated guesses suggest that threats to crop yields worldwide from a changing climate are considerable, and may already be affecting world politics, such as the food riots in 2008-9 when a series of unfortunate climate events caused huge rises in the prices of a variety of staple grains. Maybe when climate change hits enough people in the wallet, they may finally awaken and take notice of what is going on around them, lets hope it won’t be too late to seek viable solutions to these problems.LozImage credit: CSERC.orgOriginal paper, paywall access: http://onlinelibrary.wiley.com/doi/10.1002/2014GL060018/abstract -- source link

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