Climate Change and Fall Colors

Photo by John R. Taylor

Fall is ending, and with it the annual fall colors. But the part of the U.S. best known for fall colors – the Northeast – is being studied for possible foliage changes due to climate change. It applies to the Northwest as well.

Biologists at the University of Vermont have begun a study designed to determine how temperature affects the development of autumn colors and whether a warming (or cooling) climate could mute them, prolong the foliage viewing season or delay it.

The scientists are using a three-year, $45,000 U.S. Department of Agriculture grant to measure the color pigments in leaves exposed to varying temperatures, hoping to find a pattern. The study starts in October, although some experiments are already under way.

“It is getting warmer, and people want to know how that’s going to affect this big process that’s so important to us,” said research associate Abby van den Berg. In the past, temperatures have periodically gone up and down. For example, in Burlington, Vermont (home of the University of Vermont), temperatures now are comparable to what they were in the early 1950s. The 1960s were much colder, and things have warmed back up since the 1980s.

The three-week period of peak foliage color — usually from the end of September to mid-October — is among the busiest of the year for Vermont tourism, bringing in an estimated $364 million, according to state officials. It’s also an important time for tourism in the other New England states, including New Hampshire, Maine, and Massachusetts.

“It’s a critical season for us,” said Allison Truckle, owner of Tucker Hill Inn, in Waitsfield, which does about 40 percent of its business in autumn.

Leaf color is affected by many things, but for now the research will focus on temperature. The experiment is starting with the researchers’ assumption that the brilliant colors are promoted by cold nights followed by warm, sunny days. “Do cold nighttime temperatures affect and promote fall coloration?” is a key question in the study.

Specifically, the study is focusing on anthocyanin synthesis, the red pigments that are created in the fall. The study also will look at whether cold daytime weather plays a role. In the fall, chlorophyll (green pigment in leaves) changes in response to decreasing day length, revealing the yellow to orange anthocyanin pigment.

In preliminary experiments so far this year, the study has been subjecting groups of sugar and red maple saplings to a range of temperatures. Some of the test subjects are kept in a constantly refrigerated box with a window to let in sunlight, some potted saplings spend their days outdoors and then are moved into a cooler at night, and some just remain outdoors with no artificially altered temperature.

Every few days, leaves are tested with handheld meters to measure their chlorophyll and anthocyanin content.

So far, it’s too early to tell what effect temperature is having, but the researchers expect to have results before the three years is up.

In previous years, University of Vermont researchers found a link between the amount of stress on sugar maples during the growing season — marked by a lower level of nitrogen in leaves — and the onset and amount of red in the leaves. Trees that were experiencing a little more stress tended to start turning color a little earlier and making more red.

The story above is based on an article by Lisa Rathke of the Associated Press. 

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About George Taylor

Climatologist, husband, father (3), grandfather (2)
This entry was posted in Climate, Climate Change and tagged , . Bookmark the permalink.

One Response to Climate Change and Fall Colors

  1. Babygirl says:

    The above picture is beautiful

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