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Drought, rain and wildfires delaying fall foliage in parts of the US

Compared to fall foliage coverage maps from previous decades, there's a delay this year in the changing color of the leaves.
Posted at 10:50 AM, Oct 11, 2023

At Seneca Creek State Park in Maryland, fall looks to be on a different schedule this year.

"I would say we're probably about a week or two behind the normal leaf change," said James Eierdam, project manager with the Maryland Forest Service in Howard and Montgomery counties. 

Normally, at this point in October, the summer-like green trees in the park would have more of a fall look to them.

"Because of the drought, it's been slowed down by a few weeks," Eierdam added.

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Trees can be a bit like Goldilocks: They don't want it too dry, they don't want too much rain, and the temperatures need to be just right. Otherwise, the mechanisms that lead to brilliant fall foliage can be thrown out of whack.

"This is a red maple. These are one of the more showy trees," said Eierdam, who pointed out the maple would normally have 50% more fall foliage than it does now.. "[It's] also a species that we have a lot of in this area."

This year, though, record-breaking warm temperatures in the summer and into September and October have delayed fall foliage.

"If you have a too-warm beginning of fall, that is not good for the colors of the foliage," said Astrid Caldas, a senior climate scientist for the nonprofit Union of Concerned Scientists. "The trend of warming summers and the high temperatures continuing into the fall is most definitely related to climate change."

It's a trend visible through fall foliage coverage maps from previous decades — comparing the same date in October from 2003 to now — which shows a delay in the changing color of the leaves over vast areas of the country.

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There is also a potential added wrinkle this year coming from Canadian wildfires, which have blanketed parts of the Northern U.S. with thick smoke for days on end. Scientists believe that could affect chemicals in the leaves and impact how bright the fall foliage colors are.

"Whenever there are wildfires, there are particulates, there are particles that come in the air that are pollutants," Caldas said, "and they worry that those can land on the leaves and block the mechanism that actually gets the sun and the light and produces the pigments."

In the long term, scientists say there can also be expected changes to where the trees themselves are now growing.

"Maples might be migrating," Caldas added. "And some trees that are from the South — that are not particularly pretty color for the fall — are moving further north also."

Back at Seneca Creek State Park, James Eierdam said adapting will be key.

"You do what you can do to try to make things better," he said. "You plant more trees, try to diversify tree species to help with adjusting to the new conditions we're under."