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Climate change is impactÂing olive oil proÂducÂtion in California, with drought and temÂperÂaÂture extremes affectÂing crop yields. The changÂing cliÂmate also influÂences insect popÂuÂlaÂtions, such as the olive fly, which can lead to increased infesÂtaÂtions in regions with mild temÂperÂaÂtures.

Winter storms over the holÂiÂday seaÂson no longer just make us think of flight canÂcelÂlaÂtions and school closÂings, but also how cliÂmate change bears its face in the increase of seriÂous weather and extreme temÂperÂaÂture shifts. This is parÂticÂuÂlarly relÂeÂvant for agriÂculÂture, and has changed the way farmÂers and ranchÂers in California, as well as the rest of the counÂtry, conÂsider how, when, and where they plant their crops.
The most immeÂdiÂate issue for the olive affected by cliÂmate change is rainÂfall. For California, 2013 was the driÂest year on record since such numÂbers have been kept, datÂing back over 150 years. Less rainÂfall means stunted olive oil proÂducÂtion, with few options for farmÂers when water prices remain high. This perÂtains to the bulk of American olive oil proÂducÂtion, conÂsidÂerÂing that 90 perÂcent of olives grown domesÂtiÂcally come from California.
This lack of rain, and the low harÂvest numÂbers that may folÂlow stand in stark conÂtrast to 2012, when wideÂspread drought in Europe sent EU olive oil prices soarÂing, sitÂuÂatÂing California growÂers with the chance to grab marÂket share in the heart of the Old World.
The Pacific Institute, an orgaÂniÂzaÂtion that conÂducts research on susÂtainÂable alterÂnaÂtives reported that regÂuÂlated deficit irriÂgaÂtion, in which irriÂgaÂtion is applied durÂing the most drought-senÂsiÂtive growth stages of a crop, can sigÂnifÂiÂcantly reduce water use, might be approÂpriÂate for use on olive ranches.
Extremes in temÂperÂaÂture, which are also growÂing in freÂquency, pose grave risks to a olives as well. In 1998, severe cold temÂperÂaÂtures caused sigÂnifÂiÂcant losses for olives in California, and was espeÂcially damÂagÂing to citÂrus fields. Olive trees can norÂmally hanÂdle brief cold snaps, but sub- freezÂing temÂperÂaÂtures that last longer than a few hours will damÂage new, small branches, and may preÂvent fruit proÂducÂtion.
The variÂabilÂity in chillÂing hours, which garÂner less attenÂtion than frost, are equally imporÂtant to overÂall olive vitalÂity. Dennis Baldocchi, a proÂfesÂsor in the Department of Environmental Science, Policy, and Management at UC Berkeley has pubÂlished research indiÂcatÂing that accuÂmuÂlated winÂter chill hours are declinÂing in the growÂing regions of California, which affects a range of crops from olives to plums to almonds. A subÂstanÂtial amount of chillÂing hours (between 32 and 45 degrees Fahrenheit) are necÂesÂsary for olive flower bud develÂopÂment, which facilÂiÂtate the plant’s moveÂment out of its vegÂeÂtaÂtive state so fruit can be proÂduced.
Climate does not only affect olive trees directly, but changÂing temÂperÂaÂtures also influÂences insect diverÂsity and freÂquency for a given area. A recent artiÂcle in the University of California’s California Agriculture jourÂnal reported that risÂing carÂbon dioxÂide levÂels will exacÂerÂbate most insect and pest probÂlems in the State. This is parÂticÂuÂlarly relÂeÂvant to the olive fly, olive’s most notoÂriÂous and costly pest, but studÂies show that this effect may actuÂally operÂate in a counter-intuÂitive way.
The olive fly, which was first detected in the US in 1998 outÂside Los Angeles, canÂnot tranÂsiÂtion from egg to adult under high sumÂmer temÂperÂaÂtures, and existÂing adults have reduced flyÂing abilÂity durÂing such heat. In fact, some ranchÂers in California’s Sonoma and Napa counÂties believe that last summer’s mild temÂperÂaÂtures are the reaÂson for increased olive fly infesÂtaÂtions in the region, withÂout stretches of sumÂmer heat to reduce the fly popÂuÂlaÂtion. Together, these effects creÂate a comÂplex web of our changÂing cliÂmate and olive oil proÂducÂtion, whose future will require furÂther sciÂenÂtific research, careÂful monÂiÂtorÂing, and in the end, some rain.