Dressed for fall in a red flannel shirt and jeans, Dennis Cermak settled down on a dock at Scott’s Run Lake in French Creek State Park and cast his line in search of supper — and some peace.

Upcoming cancer treatments were weighing on Cermak’s mind, so he picked a perfect fall day with clear skies, a slight breeze, and a crystal-blue lake 592 feet above sea level to help calm it. Even more medicinal: a backdrop bouquet of red, yellow, and orange leaves as fall foliage neared its peak.

“I’m hoping for fish tacos tonight,” Cermak, 64, said with a grin Wednesday, standing next to a vibrant birch in the park, which straddles Chester and Berks Counties.

Fall leaf peeping in this region is an event, and people like Cermak, of Spring City, Chester County, flock to parks, take meandering hikes, and go on long drives in search of the perfect hues. But in recent years, some have been disappointed with muted colors, trees that seem to suddenly drop browned leaves, or the sense that fall is coming later and later.

Dennis Cermak, 64, from Spring City, fishes on Scott's Run Lake at French Creek State Park in Elverson, Pennsylvania on Wednesday, October 23, 2019. According to Rick Hartlieb, assistant district forester: William Penn State Forest District, peak fall foliage depends on the weather, like how much moisture there's been and if there's been a drought. He says it is currently peak viewing time at French Creek State Park.
MONICA HERNDON / Staff Photographer
Dennis Cermak, 64, from Spring City, fishes on Scott's Run Lake at French Creek State Park in Elverson, Pennsylvania on Wednesday, October 23, 2019. According to Rick Hartlieb, assistant district forester: William Penn State Forest District, peak fall foliage depends on the weather, like how much moisture there's been and if there's been a drought. He says it is currently peak viewing time at French Creek State Park.

Is it climate change?

“There’s a well-established body of science that explains how our forests will be affected by climate change,” said Ryan Reed, an environmental education specialist with the Pennsylvania Department of Conservation and Natural Resources’ Bureau of Forestry. "Those effects can be seen on a regular basis.

But Reed is quick to caution against reading too much into one season. Hardwoods, which usually offer prime colors during leaf-changing season in Pennsylvania and New Jersey, have been struck the last two years with anthracnose, a leaf disease caused by the fungus Apiognomonia. The disease causes leaves to turn brown and die.

From the source logo.

It’s brought on by unusually wet conditions, such as we have experienced in the last two years. All that rain may be part of climate change.

“As far as day to day, week to week, or even season to season, can you say what you’re really seeing is the result of climate change?" Reed asked. “Any respectable scientist will say no,” he said, referring to the scientific method’s insistence on examining total evidence, not declaring cause-and-effect over the short term.

"But what you can say is that it does fit the theory. I think climate change is so accepted now, that this fits the theory. It’s not a hypothesis anymore.”

Pennsylvania, which boasts “the longest and most varied fall foliage season than any other state in the nation — or anywhere in the world,” according to the state Department of Conservation and Natural Resources, is approaching peak color right now in the Southeastern region.

It is rebounding from a dry spell to be a pretty normal year, said Rick Hartlieb, assistant district forest manager at William Penn Forest District, which includes French Creek State Park. The creek is a tributary of the Schuylkill, and the water ultimately empties into the Delaware River.

Hartlieb said peak foliage this year “is spot on” as he climbed a fire tower with a 360-degree view of nearly 8,000 acres of state land. Peak usually comes about Oct. 25.

Actually, the real start of fall never changes, regardless of conditions, because it is timed to the autumnal equinox, which fell on Sept. 23 this year. Trees react to multiple cues, the lack of daylight chief among them. But they also react to moisture, heat, wind, and pests — all of which can affect leaf color in any given year.

And all of those factors can play out differently across the region, even within neighborhoods.

How people view leaf color is also a subjective experience, with some preferring reds over yellows or orange. Any change in the pattern can be disappointing, depending on your perspective.

How long intense color lasts and the proportion of reds, yellows, and fuchsias can also change year to year. As climate change causes tree patterns to shift, as scientists say it will continue to do, color combinations will change.

Pigments cause leaf colors. Chlorophylls produce the greens of photosynthesis, the process by which trees convert sunlight to food. When days shorten, trees can no longer use the sun for food and chlorophyll drains away, allowing other pigments to shine.

Peak fall foliage is seen at French Creek State Park in Elverson, Pa., on Oct. 23.
MONICA HERNDON / Staff Photographer
Peak fall foliage is seen at French Creek State Park in Elverson, Pa., on Oct. 23.

Carotenoids produce orange. Xanthophylls produce yellows. Anthocyanins, red pigments, aren’t made in the summer and appear only in fall.

Sugar maples can turn yellow and red, for example. Tulip poplar is known for its yellows. If one type of tree is dominant in the area, that means one color will really pop. But climate change is expected to alter the mix of colors as trees more prominent in the South take root in Pennsylvania and New Jersey.

A DCNR report found that since the early 20th century the commonwealth has seen a temperature increase of 1.8 degrees Fahrenheit. Winter temperatures have seen the fastest rise, increasing 1.3 degrees Fahrenheit per decade from 1970 to 2000 in the Northeastern U.S., according to the report.

Many people, however, say they are noticing something else — a more muted fall.

Fallen leaves float in Scott's Run Lake at French Creek State Park in Elverson, Pa.
MONICA HERNDON / Staff Photographer
Fallen leaves float in Scott's Run Lake at French Creek State Park in Elverson, Pa.

“The fall colors are simply not arriving,” said Charles Hurst, a Haverford resident. “Leaves turn from green to rust or brown, then drop. There are a few vivid yellows, little orange, and almost no bright red. It’s not only this year but a trend.”

Hurst said he’s noticed it since about 2008 and said it’s a hot topic in his house.

Patricia Leopold, with the Northern Institute of Applied Climate Science, said studies show warmer conditions delay the onset of peak colors and decrease the amount of time they’re visible.

“We can see that looking at observations over the past 100 years,” Leopold said. “The growing season for trees has shifted. The leaves are coming on or budding sooner.”

She said the process of senescence, the scientific word for the end of leaf season, is changing.

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Jason Grabosky, a Rutgers professor and tree expert, said it has been a less-than-stellar season for New Jersey residents.

"My experience was that it generally didn’t peak as much as it dragged out even to this week in several species,“ Grabosky said, attributing that to a mild autumn.

With climate change, he said, “some species will be winners, some species will be losers, and we’ll move on.”

“As species change, colors will change," Grabosky said. "But we don’t know how. Ash trees, for example, with the presence of emerald ash borers, will be less present in our canopy. What replaces it will be something new, but we really can’t predict that.”

He said a warmer fall generally means fewer reds, which leaf peepers seem to enjoy most. Yellows will be the big winners.

“I usually say it’s going to be a phenomenally beautiful year depending on where you are standing at the moment. I think it’s important that people get outside and appreciate what they do get,” Grabosky said. “Try to find the beauty in it. When you think about what’s happening, it’s really amazing.”

Editor’s note: “From the Source: Stories of the Delaware River” is produced with support from the National Geographic Society, the Lenfest Institute for Journalism, and the William Penn Foundation. Editorial content is created independent of the project’s donors. This article also is part of Covering Climate Now, a global collaboration of more than 250 news outlets to strengthen coverage of the climate story.