Mount Katahdin, the highest mountain in Maine, is slowly losing its upper alpine habitat, according to a new study by researchers at Dartmouth and Appalachian Mountain Club.
It's called "greening": when vegetation encroaches in areas it hasn't grown previously. Researchers analyzed decades of satellite imagery, paired with records from over a hundred years of high mountain fieldwork.
Katahdin wasn't the only peak to experience this — it's happening at approximately 70% of mountains in the Northeast, according to the study. Overall, roughly 90% of the Northeast high alpine areas are affected. But nowhere as much as the storied peak, known for being the informal end to the Appalachian Trail.
One might think "greening" is a good thing for plants. But researchers said that's not necessarily the case here.
"What we're seeing are rare or endangered alpine plant species that are found in some cases only in this region, nowhere else in the world, on these high mountain tops, and they are potentially being crowded out by other faster-growing plant species," said Jonathan Chipman, the study's co-author.
Chipman is director of Dartmouth's spatial analysis lab. He said the team combined four decades of satellite imagery with over 200 years of on the ground field research to reach their findings, resulting in a first-of-its-kind study: a large, regional-scale survey of all Northeast alpine areas.
The study shows both invasive and native plants are slowly encroaching on areas of the alpine areas where they don't usually grow.
"These alpine zones, which have historically had very cold, extremely windy, very challenging climates for plants to survive in, that perhaps the climate is becoming more mild through this global warming process," Chipman said. "That's not necessarily the only thing that's happening here, though."
Nitrogen from air pollution is also blowing into Maine from factories and power plants in the Midwest, he said. This can feed certain types of plants and possibly damage others.
"We think of it as having historically caused acid rain and acidification of lakes," he said. "But for plants in the Alpine zone, in some cases, it can actually serve as a kind of fertilizer. Certain plants are able to take advantage of this and grow faster due to it. And those plants may potentially be outcompeting others."
Losing the fragile upper alpine habitat will likely have a ripple effect on animals who rely on the habitat, like butterflies, birds and small mammals.
The researchers analyzed decades of satellite imagery, paired with fieldwork, to find their results. Next, they plan to use the satellite data to analyze changes in alpine snowpack in winter.
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