A 'remarkably average year' for fall colors in mid-October, before climate change dulls them

Predicting when our trees will begin their vibrant autumn transition is a developing science, but arborists say Illinois is looking at a mid-October peak after a relatively average year of weather.

As climate change increases the likelihood of extreme temperatures, however, scientists are concerned that events like heat waves, drought and flooding could disrupt the timing of when trees change color and dull the radiant hues that many look forward to seeing each fall.

Christy Rollinson, a forest ecologist with the Morton Arboretum, said the appearance of fall colors is often guided by the seasons leading up to it. While our previous years have been characterized by springs that were either too wet or too dry along with summers in drought, this year has made for a more optimal autumn.

“Right now here in northern Illinois, it's a remarkably average year, a remarkably average late summer,” Rollinson said. “Predicting the best day of fall color is an ongoing science, but right now I would expect to have rich timing for fall color.”

While Rollinson said the Arboretum is a great option for leaf peepers who want to see a diversity of trees — including whole collections dedicated to species known for bright color — some of the best species to seek out anywhere in the suburbs are sugar maples, red maples and honeylocust.

Maples tend to concentrate further north in hardwood forests, especially in Wisconsin, and honeylocust are more centralized in the southern half of the state. Rollinson said she thinks honeylocust, which displays brilliant shades of bright yellow, are an “unsung hero” of fall.

“When it comes to finding color, it can be a really fun scavenger hunt. Each tree, each place is going to change color at a slightly different time,” she said. “It's a great opportunity to explore not just far-flung places or places like the Morton Arboretum, but also your own neighborhood, and appreciate the differences of how each tree or each neighborhood is responding to this to the same set of fall conditions.”

For a wider look at when peak fall foliage will arrive, a map from the Smoky Mountains website predicts when we will see the most vibrant colors nationwide — down to the day.

The map predicts the greater Chicago area will see its peak Oct. 24. It can be found at tinyurl.com/2022FallColors.

We're the lucky ones

While our region is experiencing a more predictable year of weather, other areas of the country are undergoing the type of extreme conditions that can interfere with when and how trees change color.

Andy Finton, a conservation ecologist with the Massachusetts chapter of the Nature Conservancy, said New England is in the tail end of a dramatic, “unprecedented” drought that has caused its famous fall foliage to arrive earlier and to appear less vibrant.

“Trees can't maintain the full set of leaves, and so they're withering early, which means they never get a chance to go through that fall process where they're producing the bright reds,” Finton said. “We're seeing some early changes. We're seeing some browns and withering and even falling leaves here in September already before the leaves ever get a chance to change color.”

Finton said it takes crisp, sunny days and cool nights to produce the most vibrant colors. While events like drought can cause leaves to change and fall earlier, extreme heat has the opposite effect.

The season is pushed later, and though the oranges and yellows that lurk beneath a leaf's green chlorophyll will eventually emerge, the tree doesn't have the optimal conditions for producing the dramatic red pigment that autumn is known for.

“One of the biggest trends we're seeing is that fall colors are coming later and sometimes less dramatic, less brilliant because of climate change,” Finton said.

Not just climate change

He added that changes in how and when fall foliage transforms is the most visual expression of forest health — and climate change is not the only cause for concern.

Rather, global warming works in concert with other stressors on our trees such as invasive insects and diseases, as well as humanmade sources such as infrastructure that fragments existing forests.

“When climate change stresses a tree with drought or too much heat, it becomes more vulnerable to some of these insects, pests and pathogens, and so that the two in synergy can weaken forest health,” he said.

Trees themselves represent a vital nature-based solution to climate change: They take in carbon dioxide and store it in their tissues as they grow, reducing the amount of greenhouse gasses released into the atmosphere.

Our region's trees currently store 21 million tons of carbon, and an additional 542,600 tons are sequestered each year. The plants' collective carbon capture services are valued at more than $4 billion, according to the Morton Arboretum's 2020 Tree Census.

Despite the many challenges our forests are facing today, Finton said they are extremely resilient, and there are ways to help protect them, such as guarding against invasive species, conserving large and intact forests, and planting new trees.

Though concerns about the timing and vibrancy of fall foliage do exist, Finton said the biggest message is that the color will always be there.

“One of the most important things that people should know is they should get out there and enjoy it,” he said. “Experiencing it is one of those things that engages people and brings people closer to nature. It's always going to be there. It might change year over year, but get out there, enjoy it, appreciate it and support the conservation of our forests.”

• Jenny Whidden is a Report For America corps member covering climate change and the environment for the Daily Herald. To help support her work, click here to make a tax-deductible donation.