Is Fall Foliage Falling Back?

By Susan Littlefield

We're all used to setting back our clocks in late autumn to "fall back" from daylight savings time. Now, scientists are investigating whether we need to start resetting our "leaf peeping" clock as well. Studies in Europe, Japan, and the U.S. indicate that climate changes due to global warming may be delaying the onset of the changing colors of fall foliage.

The appearance of the bright reds, oranges, and yellows of fall leaves as the seasons change comes about as cooling temperatures, decreasing daylengths, and changes in soil moisture levels cause the green chlorophyll in leaves to break down, unmasking the autumnal hues. The timing and intensity of this color change varies with year-to-year fluctuations in fall weather, as well as fluctuations in the growing conditions earlier in the season. So it is hard to know for sure how climate change and fall foliage are related.

Still there are indications that climate change is having an effect. In Vermont, state foresters at the Proctor Maple Research Center found that seven out of the last ten growing seasons ended later than the statistical average. And satellite data from NASA showed that in the period from 1982 to 2008, the end of the growing season lengthened by six and one-half days. There may be economic as well as ecological ramifications to changes in the fall foliage show, if later or less colorful fall foliage reduces the numbers of leaf-peeping tourists in areas like New England.

The study of timing in nature is called phenology and much of the basic data collected for research in this field comes from interested citizen scientists recording their observations of seasonal changes. The USA National Phenology Network is composed of citizen scientists, government agencies, non-profit groups, educators, and students working together to monitor the impacts of climate change on the plants and animals in the U.S., collecting and sharing information to provide researchers with much more information than they could collect alone.

To read more about the scientific efforts to document later fall foliage colors, go to: Burlington Free Press. To find out more about participating in the USA National Phenology Network, go to: USANPN.

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