Glorious Colors of Fall Leaves Last Longer with Global Warming

(p. A20) IONA, Nova Scotia — A century ago, the flaming fall foliage in Nova Scotia would have long faded by early November. But today, some of the hills are still as nubbly with color as an aunt’s embroidered pillow.
Climate change is responsible, scientists say. As the seasonal change creeps later into the year, not only here but all across the northern United States and Canada, the glorious colors will last longer, they predict — a rare instance where global warming is giving us something to look forward to.
“If climate change makes eastern North America drier, then autumn colors will be spectacular, as they are on the Canadian Shield in dry summers, especially the red maples,” said Root Gorelick, a biology professor at Carleton University in Ottawa. The Canadian Shield is a broad ring of forests and ancient bedrock that extends hundreds of miles from the shores of Hudson Bay.
Over the very long term, the warming planet may have a negative effect on fall foliage, but even then any adverse impact is uncertain. It is not just an aesthetic question, but an economic one as well: The changing colors drive billions of dollars in “leaf peeping” tourism in Canada and the United States.
“From a peeper’s point of view, it’s good news,” said Marco Archetti, the lead author of a 2013 paper at Harvard on predicting climate change impacts on autumn colors in New England.
. . .
The Harvard study, which looked at the percentage and duration of autumn color in Harvard Forest in central Massachusetts from 1993 to 2010, predicted that with current climate change forecasts, the duration of the fall display would increase about one day for every 10 years. Look at it this way: Children born this year could have an extra week to enjoy the colors by the time they are 70.
The study further analyzed data for trees that turn red: red maple, sugar maple, black gum, white oak, red oak, black oak, black cherry and white ash. Only in white ash trees did the duration and full display of color decrease. In the others, the amount and duration of red leaves increased over the course of 18 years.
The Harvard study used data collected by John O’Keefe, the museum coordinator, now emeritus, at Harvard Forest, who made his observations by eye — estimating the percentage of colored leaves for each species and the duration from when 10 percent of a tree’s leaves turned color to when 90 percent had turned.
Those observations have been validated by Andrew Richardson, a professor of evolutionary biology at Harvard, who has since set up a network of 350 “phenocams,” cameras that quantify the duration and intensity of autumn colors in locations from Alaska to Hawaii, Arizona to Maine and up into Canada.
“John’s direct observations on the ground line up pretty well with the camera data,” Professor Richardson said.

For the full story, see:
CRAIG S. SMITH. “How a Changing Climate Helps Add Color to a Leaf Peeper’s Paradise.” The New York Times (Thurs., NOV. 3, 2016): A20.
(Note: ellipsis added.)
(Note: the online version of the article has the date NOV. 2, 2016, and has the title “How a Changing Climate Is Shaping a Leaf Peeper’s Paradise.” )

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