Climate change is making fall temperatures warmer, on average, and disrupting the annual display of fall foliage in the eastern U.S.
, fall foliage has been appearing behind schedule—continuing a long-term trend that, according to one recent study of maples by researchers at George Mason University, has pushed the appearance of fall colors back more than a month since the 19th century. Temperature is not the only driver; precipitation or the lack of it, extreme weather, and insect infestations also play a role. As climate change affects all those factors, it’s making the timing of peak foliage harder to predict.
As temperatures drop and days grow shorter, signaling an end to the growing season, trees respond by ending chlorophyll production and absorbing any remaining nutrients—in effect laying down stores for winter. In Maine’s Acadia National Park, scientists have noted a possible link between warm nights in September and delayed fall colors.
“Both of us expected to see a change, and a pretty large one, but both of us were surprised that the signal was so strong,” says Garretson.