Wednesday, October 22, 2014

As Planet Warms, Scientists Predict Changes for Autumn Leaf Season

In this October 1998 file photo, a farmer chops corn in front of a hillside of color in Richmond, Vt.  (Credit: AP Photo/Toby Talbot) Click to enlarge.
The phenomenon of brilliant red and gold autumn foliage might change due to the large amount of carbon dioxide we put in the atmosphere, and the resulting warmth that carbon traps inside.

The higher concentration of carbon dioxide itself might actually make fall colors brighter, Howard Neufeld, a professor of physiological plant ecology at Appalachian State University, explains in a Tuesday piece in The Conversation, citing research published in the journal New Phytologist back in 2010.  But the higher temperatures that result from large atmospheric concentrations of carbon dioxide could result in longer summers and shorter autumns, thereby delaying the onset of future colorful leaf seasons and causing them to be shorter in duration.

Changing temperature patterns could also cause those colors to come in splotch[il]y — that is, all the trees won’t change at once.  “As the climate warms, the finely-tuned timing of the fall’s color display may lose its synchronization,” Neufeld writes, citing research from the Royal Society.  “Rather than the well-timed symphony of color that we’re used to now, we might see unsynchronized patches as each species changes over the course of the season.”

End of Growing Season Date 1982-2008 (Credit: Click to enlarge.

Scientists have been predicting changes to the autumn foliage season for years now, primarily due to the fact that fall has been starting later and later in the U.S. since 1982, as the graph above shows.  According to research published in the journal Global Change Biology in 2011, America’s growing season has ended roughly two weeks later in 2008 compared to 1982, affecting not only the onset of leaf season itself, but the tourism industry supported by it.  As Climate Central’s Brian Kahn has noted, the foliage season generates $8 billion in revenue every year for New England alone.

But now scientists are seeing other factors of climate change come into play for the autumn leaf season.  Changes in precipitation, depending on the area of the United States, could impact the brightness and brilliance of fall colors.

The northeastern United States, for example, is facing an increased likelihood of extreme precipitation and flash flooding events due to climate change, according to the most recent National Climate Assessment.  If that occurs, Neufeld notes that the color of leaves will be duller.  “Too much rain lowers the intensity of fall color – not because it washes out the colors (an old wives’ tale), but rather because cloudy skies and low light cut down on photosynthesis and production of those vital anthocyanins,” he writes.

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