Not only will the current forests simply move north. The colors themselves could fade. The chemicals that create yellow, gold, and orange colors lie dormant within tree leaves all year long. In the spring and summer, the green color—chlorophyll—overwhelms them. Then in autumn, the greens fade in response to shortening days and the underlying colors become visible to the naked eye. Under most conditions, those yellows and pale oranges will emerge in the fall no matter what. The chemical that produces red leaves, anthocyanin, is different. That color must be produced each year by a precise, yet not fully understood, combination of sugar, temperature, and light.
That bright red color is a particular signature of maple trees, which make up an unusually large percentage of New England forests. Locals are justifiably proud of those maples. Steven Kelley, who lives near the coast in southern Maine, has operated the website Leafpeepers.com for 13 years. The site compiles foliage reports from all over the country, but most visitors are interested in New England. “It’s because we have the maples,” he explains. “The maples will turn that brilliant, violent red, that really popping red.”
Scientists have found that those spectacular reds, so dependent on exterior forces, are particularly endangered by irregular weather. Three years ago, the University of Vermont Proctor Maple Center received a $45,000 grant from the Department of Agriculture to study how warming fall temperatures could also affect that signature bright red in maples. The team is currently conducting the project’s final round of experiments. Abby van den Berg, a research assistant professor working on the Maple Center project, explained that the team has found that crisp fall air is part of what makes maples red. “If cold tends to promote the red color,” she said, “it would be natural inference that if we had less cold temperatures during autumn, then that might impact the level of development.” Barrett Rock, a professor at the University of New Hampshire, uses spectral analysis on satellite photos of autumn forest cover. He's found sugar levels in maples dropping, a phenomenon that is already leading to more muted reds.
Amateur observers of regional color have intuited this for years. Scotty Johnston, a 72-year-old Connecticut resident who serves as the guided-tour company Tauck’s “fall foliologist,” says that the region’s cold weather is what makes it so special. “I don’t like to pooh-pooh the South, but between you, me, and the gatepost, they don’t have the cold snap,” he told me. “The cooler temperatures are not as extreme, so the snap is not triggering the reds.” Tauck, which helped pioneer New England foliage tourism in the 1920s, is conducting 25 tours this season, with some packages costing more than $4,000 a person. (The company recently began reaching out to tourists in Europe and Australia.)
Bob Bower, a 61-year-old organic farmer in central New Hampshire, was out selling pumpkins, syrup, and homemade soap at the 64th annual foliage festival in Warner, N.H., on a recent weekend. “We’re boiling sap earlier and earlier,” he told me. “We’re growing vegetables later, and we haven’t had a hard frost yet. And it’s not just this year. It’s been consistent.” It was 80 degrees out as we talked, and the canopy of trees above us was green. Bower said it was the first year he could remember that the leaves hadn’t turned by the time of the festival. And he’s right: Several ongoing studies throughout the region are finding signs of fall occurring later and later in the calendar year.
It would be more than a tourism loss to see the forests fade and retreat. Thoreau understood this back in 1862. “A village needs these innocent stimulants of bright and cheering prospects to keep off melancholy and superstition,” he wrote. “Show me two villages, one embowered in trees and blazing with all the glories of October, the other a merely trivial and treeless waste, or with only a single tree or two for suicides, and I shall be sure that in the latter will be found the most starved and bigoted religionists and the most desperate drinkers.” It’s not all that grim yet, but winter is on the horizon.