Changing climate changes colors


Orange fall foliage surrounds the Petoskey clock tower. Image: Petoskey Area Visitors Bureau

By Reese Carlson

Climate change means that the Great Lakes region’s trademark red, orange and yellow fall leaves will be more intense for a shorter period in the next decade.

The warming climate will also cause the leaves to change later in the season, scientists say.

But the impact is uncertain. Other factors related to climate could mute colors or cause less colorful trees to take over the region’s forest.  Warmer fall nights and continued drought throughout much of the Great Lakes region means that fall leaf color will start later and end sooner, said Howard Neufeld, a professor of plant physiology at Appalachian State University.

“We’re already seeing changes that I would associate with climate change,” Neufeld said. “A less predictable fall is the main indicator. In previous years, you could predict the day when peak colors would be seen year after year.”

In the past eight years, predictions have been twice as variable, Neufeld said. Sometimes peak would be on time, the next year two weeks late, and then the following year it was a week early.

Trees depend on signals for the color changing process to begin, said Bradley Hutnik, a forest ecologist and silviculturist with the Wisconsin Department of Natural Resources. The darker and colder autumn days are the main signals for the tree.

“What happens in the fall is longer nights, longer periods of dark,” Hutnik said. Those are triggers to shut the leaves off from producing green chlorophyll, allowing other pigments to start to be seen.

Prolonged warmer weather produces a stress signal in trees, which causes more vibrant leaf colors in some species, Neufeld said.

But while the trees may be prettier, they may not stay around as long.

The National Oceanic and Atmospheric Administration reported that from 2014 to 2022, the northern hemisphere experienced its nine warmest Octobers on record. The fourth warmest October on record in 143 years was reported in 2022.

“These trees are used to certain fall weather,” Neufeld said. “So when there’s a period of drought or what feels like a prolonged summer into October, the trees might just drop their leaves without changing colors or the colors might be very muted. The signal gets confused. They also might be more of a vibrant red from stress before quickly dropping the leaves.”

But  the future of fall foliage could look completely different, Neufeld said. The continued warmer autumn weather would cause a slow migration of trees toward typically colder regions. Seedlings that end up in a more favorable habitat for growth, like the colder northern regions, will continue to thrive and produce offspring. For the Great Lakes region, this could mean more yellows than red in the fall foliage, as hemlock and aspen trees slowly migrate north.

A 2017 study by Songlin Fei, a researcher with Purdue University, shows that this phenomenon is already occurring throughout the eastern United States.

Fei and his team analyzed U.S. Forest Service data over three decades for 86 tree species. They found that certain species shifted an average of 0.63 miles per year. They also found that increased precipitation in the Midwest is leading to a westward 0.93 mile shift per year in hardwood species, which require minimal water for survival.

The study concluded that tree migration is changing forest ecosystems in uncertain  ways. What scientists do know is that tree species are growing in regions where they previously did not thrive.

Changes in fall foliage will affect more than just the gorgeous array of reds, oranges and yellows that are so attractive to the eye. They have an economic cost.

For many northern Michigan cities the changing fall leaf colors mean an influx of leaf-peeping visitors. Jim Powell, executive director of the Petoskey Area Visitors Bureau, said that October can bring in 250,000 to 300,000 overnight visitors, not including the day trippers or people traveling the whole region up the coast.

“The phone rings all day with 50 phone calls a day with people wanting to know when it will be peak fall colors,”  Powell said. A big tourist attraction is the Tunnel of Trees, a 20-mile stretch of M-119 along Lake Michigan. Drivers are surrounded by beautiful fall foliage.

“People are anxious to catch that at the right time,” he said.

So, when is the best time for fall foliage viewing?

Smoky Mountains, an online visitor guide to the Smoky Mountains region, releases a yearly fall colors timeline for the nation. It is based on previous data and weather conditions. Here is the predicted timeline for the Great Lakes region:

Oct. 9th: Peak colors in the eastern region of Upper Peninsula, the north eastern region of Lower Peninsula and northern New York. Near peak colors in the western region of the Lower Peninsula and most of Wisconsin and southern New York.

Oct. 16th: Peak colors in Wisconsin’s northern, eastern, and western regions along with northern Ohio and southern New York. Near peak colors in northern Illinois, northern Indiana, and the middle region of Ohio.

Oct. 23rd: Peak colors in the middle regions of Minnesota, southern Wisconsin, northern Illinois, northern Indiana, and the middle regions of Ohio. Near peak colors can be found in southern Minnesota, southern Ohio and the middle regions of Indiana and Illinois.

Oct. 30th: Peak colors in southern Indiana, southern Minnesota, and middle Illinois. Near peak colors can be found in southern Illinois.

Nov. 6th: Peak colors in southern Illinois with all other Great Lakes states being past peak.

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