Will global warming increase plant frost damage?

Widespread damage to plants from a sudden freeze that occurred across the Eastern United States from 5 April to 9 April 2007 was made worse because it had been preceded by two weeks of unusual warmth, according to an analysis published in the March 2008 issue of BioScience. The authors of the report, Lianhong Gu and his colleagues at the Oak Ridge National Laboratory and collaborators at NASA, the University of Missouri, and the National Oceanic and Atmospheric Administration, found that the freeze killed new leaves, shoots, flowers, and fruit of natural vegetation, caused crown dieback of trees, and led to severe damage to crops in an area encompassing Nebraska, Maryland, South Carolina, and Texas. Subsequent drought limited regrowth.

Rising levels of atmospheric carbon dioxide are believed to reduce the ability of some plants to withstand freezing, and the authors of the BioScience study suggest that global warming could lead to more freeze and thaw fluctuations in future winters. This pattern is potentially dangerous for plants because many species must acclimate to cold over a sustained period. Acclimation enables them to better withstand freezes, but unusual warmth early in the year prevents the process. A cold spring in 1996, in contrast to the 2007 event, caused little enduring damage because it was not preceded by unusual warmth.

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