Climate change and leaf-peepers: Effects of temperature and extreme precipitation on senescence and visitation

The spectacle of leaves changing color makes autumn a popular time for tourists to visit New England. Here, “leaf peeping” is a billion-dollar industry, and Acadia National Park is no exception. Maples blaze red and orange in lowlands and lakeshores, and birches turn entire hillsides to gold. Yellowing marsh grass shimmers in the late afternoon light; the sea, rich with plankton, is full of life. And, increasingly, summer temperatures linger later, providing more time for people to enjoy being outside.

Over the past 20 years, September and October have had the greatest increases in visitors to Acadia. To what extent are they coming for foliage or weather? Are the leaves turning later in the year? Is the foliage season shorter or longer, and why? These questions are the focus of research by Stephanie Spera, assistant professor of geography at University of Richmond.

Spera will first study the season itself. Acadia has become warmer and wetter, spring arrives earlier, and fall appears to be trending later. Temperature and precipitation have been correlated with the length and vibrancy of fall color. Some studies show that a hot summer, rainy fall, and even nitrogen pollution are related to a shorter, duller foliage season, while a later color change is associated with warmer, earlier spring and fewer fall storms. Spera will test these relationships by tracking when the leaves begin to change (using a “brownness index” based on satellite data and photography) and analyzing rain and temperature measurements from stations in Acadia and across the Northeast.

“One of the goals of the National Park Service is to provide for high quality recreation experiences,” said Adam Gibson, Social Scientist with Acadia National Park. “Understanding the motivations and expectations of visitors helps us do that.”

To study changes in fall foliage, Spera will use satellite data verified with photographs submitted by volunteers. Spera seeks submissions of unfiltered photographs of Acadia from before the year 2000 to create a more complete data set. “We plan to use satellite data to help us map fall foliage over time, but like all technology, the farther back in time you go, the lower the quality of the data,” she said. “Historic photos of fall color will help us fill in the gaps.”

Spera also established fixed photo stations at several locations within Acadia where volunteers can take pictures to help validate satellite data.

For more information or to submit photos, visit

Read more:

Spera’s article about her research in The Conversation

Spera talks with Heather Goldstone for Living Lab Radio

Article by Dick Broom in the Mount Desert Islander

More media coverage:

Researchers using photos to study impact of climate change on fall foliage, Canadian Broadcasting Corporation

Scientists want your photos of Acadia in the fall, News Center Maine

Is Fall moving? National Parks Traveler podcast

Fall foliage: Leaf-peeping in Maine, Maine Public