Discussing fall foliage with the experts can make you feel a little like you’re on an episode of Are You Smarter than a 5th Grader?
“The leaves change color — you remember this from elementary school — because of chlorophyll,” Kyle Cotner, the creator of The Foliage Report, said to me, demonstrating outsized confidence in my grade-school recall. “If you remember back to an art class,” Dr. Howard Neufeld, a professor of biology at Appalachian State University who’s also known as the Fall Color Guy, prompted me later, “if you have a red pigment, what’s its complementary color?” (Folks, it’s not “blue” — it’s green.)
But while the autumn portion of the tree life cycle may be a staple of primary school pop quizzes, it’s also a dizzyingly complicated phenomenon and one that’s been behaving … well, oddly. “There’s much less overall consistency and pattern,” Dr. John O’Keefe, the lead phenology scientist at the Harvard Forest, told me of the fall color he’s been seeing recently. “It’s just bigger extremes. And that’s, of course, one of the things that climate change is causing: wilder swings.”
Neufeld, who works out of North Carolina, has seen the same thing in his neck of the woods. Looking back over his 17 years of data recently, he noticed that “the peak color was always the same time of year: the 10th to the 20th of October,” he told me. But “starting in 2017, it’s all over the place.” Sometimes the peak colors would come two weeks late; other times it’d be early, or arrive on time. “As a biostatistician, I went back and I calculated how variable the timing was. And it’s twice as variable in these recent years as it is in the first eight years,” he said.
Neufeld stressed that his observations are not statistically significant yet, but he suspects that in a few more years, and with a few more data points, they will be. “My suspicion is that it’s the beginning of a climate change effect,” he said.
This sort of unpredictability is especially worrying because leaf peeping is estimated by Neufeld to be a $25 to $30 billion industry in the eastern U.S. alone during a strong fall color year. The number of fluctuating variables — from rainfall to temperature to cloud cover to fungi to one badly timed windstorm — can leave the towns and people who rely on autumn tourism feeling destabilized. Will this year be a good year? Will it not be, and word will get out, suppressing the crowds?
If there were ever a year for climate change to be impacting fall colors, it’d be this one. But the precise reason came as some surprise. It’s not the late heat, but the abnormal amount of rain that’s been the more significant variable at a local level. As Neufeld pointed out, “September was the warmest on record — but not in North Carolina and especially not in the mountains.”
That precipitation, which is also more likely because of climate change, has been both a boon and a bust for fall color. “With so much rain, the colors will not be as vibrant [in the northeast],” said Cotner, who tracks the trends nationally. “I’ve noticed places like Stowe, Vermont, are much duller this season and turning brown … I can tell you, I’m truly disappointed with the region compared to last year.”
But at the same time, the rainy trends in the Western United States have pulled the region out of its drought and created “probably the best [fall color] year in a decade,” Cotner went on, “especially the three all-star states: Colorado, Utah, California. Utah probably wins.”
While the main theme of fall leaves has been to expect the unexpected, it’s also true that “there is a slight trend toward [peak color] getting later over the 30 years that I’ve been watching,” O’Keefe, in Massachusetts, noted. It’s an observation that tracks with the greater climate research: Between 1952 and 2011, fall decreased from 87 days to 82 days, chipped away at by the lengthening summer. In general, “sunny days and cooler, crisp nights are when we develop the brightest colors,” O’Keefe said, but fall temperatures have increased on average by 2.7 degrees Fahrenheit across the U.S. since 1970, Climate Central reports, and by as much as 4.5 degrees in parts of Vermont.
Of course, there’s more in jeopardy than tourism and Caitlin Covington’s Instagram content. Should the weird fall weather continue, then the actual makeup of the fall scenery could also start to change. Less hardy trees of one color might be beaten out by more competitive trees of another. Southern trees could begin to move north, and northern trees could retreat into Canada, or uphill to cooler elevations. Spectacular orange-and-yellow-and-red hillsides might become more monochromatic. When the forest ecologies change, the autumn landscapes will change in turn. Leaf peepers are just witnessing the aftermath.
But remember those brilliant 5th graders? They’ve got a part in all this, too. Fall colors “get more people out seeing nature than almost any other time of the year,” Nuefeld said. “So I'm hoping that when people go out and see them, they have a better appreciation of nature and want to do something to preserve it, so that their kids can go out when they’re their age to see the full color, too.”
