Apples, Almonds, Peaches, Pears: Warmer Winters to Affect Our Favorite Fruits and Nuts

Written by Lisa Hayden on . Posted in Learn

The All-American fruit, the apple, is just one of the popular fruit and nut crops likely to be affected by warmer winters in many growing regions around the globe, according to a new study published yesterday in the online, open-access journal PLoSOne.

The article, co-authored by The Nature Conservancy’s senior climate scientist Evan Girvetz, Ph.D.,  finds that the “winter chill,” a period of cold temperatures when trees go dormant – is likely to be shortened in many of the world’s major growing regions. Each fruit and nut tree has a specific winter chill requirement needed to produce a good crop.

The study, “Climate change affects winter chill for temperate fruit and nut trees,” finds that warm growing regions are likely to experience severe reductions in available winter chill, regardless of the emissions scenario or climate model used, potentially threatening current production in places like the Sacramento Valley in California, the Southeastern United States, Chile’s Valle Central, Yunnan Province in China, as well as South and Southwestern Australia.

The changes in climate and potential effects on crop yields may pose risk of substantial economic losses for an industry worth an estimated US $93 billion annually.

“Changes in winter seasons will change the ranges of many tree crops, and many growing regions may become unsuitable for some of our favorite fruits that are grown on trees, especially apples, cherries, and peaches,” Girvetz said. Other fruits and nuts such as apricots, walnuts, pistachios, plums and almonds are also likely to be affected.

For example, in the Western United States, the “ecological niche” of many fruits and nuts is likely to move north, from California’s Central Valley towards Northern California, Oregon and Washington. However, the study states that “these new, potentially suitable areas have adverse topography, poorer soils, and limited water availability compared to the Central Valley, making the economic viability of production there questionable.”

So, it may be easier for growers to switch crops rather than re-locate orchards to new locations. Growers and plant scientists will also likely need to adapt to changing conditions by breeding tree cultivars for lower chilling requirements, developing tools to cope with insufficient winter chill, and working to better understand the temperature responses of tree crops.

Led by Eike Luedeling of the World Agroforestry Centre in Nairobi, Kenya, other co-authors of the study include Patrick H. Brown of the University of California, Davis, and Mikhail A. Semenov of Rothamsted Research in Harpenden, United Kingdom.

The analysis was based on observed daily weather for more than 4,000 weather stations around the world from the National Climatic Data Center of the U.S., projections from three global climate models, winter chill estimates for two past years (1975 and 2000) and 18 future scenarios generated for the entire globe with The Nature Conservancy’s ClimateWizard tool http://ClimateWizard.org.

To learn more about the study and how orchards that produce your favorite fruits and nuts may be affected by a changing climate, read an interview with Evan Girvetz on the Conservancy’s Cool Green Science blog, also republished at Grist.

Lisa Hayden is a blogger and feature writer for The Nature Conservancy

Photo by: Flickr user storem (Dried fruit market). Used under a Creative Commons license.

Inset photo: courtesy Evan Girvetz

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