Last updated: August 29, 2025
Article
Spring Is Now Earlier on the Appalachian Trail, Study Reveals
A study of trees and wildflowers along the Appalachian National Scenic Trail used the largest crowd-sourced dataset of its kind. It showed that spring is arriving sooner, especially in places like New England. Pollinators may find it hard to catch up.
About this article
This article was originally published in the "In Brief" section of Park Science magazine, Volume 39, Number 2, Summer 2025 (August 29, 2025).
Appalachian Mountain Club / Madelyn Wood
With their vibrant color displays, wildflowers bring joy to many people. They’re also the origin of domestic flowers and are a vital food supply for pollinators. But there’s evidence that higher temperatures from climate change are reducing their growth, reproduction, and survival. In the temperate forests of the eastern United States, changes in the capacity of these plants to respond to environmental stress are of particular concern. This is because 80 percent of the total plant biodiversity in these forests is attributable to flowering plants. They’re integral to ecosystem health.
A team of scientists studied the impact of warmer temperatures on flowering plants along the Appalachian National Scenic Trail from 2004 to 2023. We published our findings in the journal Ecology in August 2024. A unit of the National Park Service, the trail spans 12° of latitude and 2,190 miles, from Maine to Georgia. Ours is the first study examining spring phenology using citizen science observations along the entire trail. Phenology refers to the timing of biological events (such as flowering) as they relate to natural cycles of seasonal phenomena. It serves as a useful window—a bioindicator—to understand the impacts of a changing climate and planet. Our study shows that spring is coming sooner, and native plants, animals, and forests may not be ready.
Expanding the Scope
The team’s work was made possible by a wealth of data obtained through initiatives aimed at expanding the scope of citizen science phenology data collection. One of these is the Appalachian Mountain Club’s Mountain Watch project, begun in 2004. In 2007, the project’s scope expanded to the entire length of the trail.
The Mountain Watch project collects data in two primary ways. One is by establishing permanent marked plots. Across the trail, many collaborators, including National Park Service scientists and interns, create plots from which the same plants are measured repeatedly through time. The plot data are uploaded to the National Phenology Network database, called Nature’s Notebook. The other way the project collects data is through the iNaturalist application, which captures records uploaded through the app by citizen scientist volunteers.
With 118,250 observations, the combined network and iNaturalist records used for our work were the largest crowd-sourced dataset of any similar phenology study.
Following the network protocol, which gives guidelines for collecting data, we compiled plot data on when plants flowered and when trees leafed out in the spring (March to June). We collected iNaturalist observations of plant species in flower or leafing out in the spring in the Appalachian Trail corridor. The iNaturalist records were verified by at least two independent observers. With 118,250 observations, the combined network and iNaturalist records used for our work were the largest crowd-sourced dataset of any similar phenology study.
Phenological Shifts
We found that, on average, understory plants are flowering 3–10 days earlier for every 1.8°F (1°C) of warming. Understory plants are the small trees, shrubs, and herbaceous plants under the taller tree canopy. These phenological shifts are occurring in all regions the trail passes through. Many flowering plants active during the spring months, particularly spring ephemerals, use a shade-avoidance strategy. Known as phenological escape, this strategy allows them to emerge before taller trees get their leaves. In this way, they can maximize early-season photosynthesis.
© Jessica Weinberg McClosky
Because they’re now flowering and growing leaves even earlier, understory plants have more time to photosynthesize before the canopy closes. But this earlier flowering means there may be fewer insects or other animals around to pollinate them. And the amount of water available at that time may not suit their requirements. Earlier flowering also makes plants more vulnerable to unexpected late-season frosts.
Regional Differences and Knowledge Gaps
One key finding of our research is that warming temperatures are affecting some regions more than others. Our data indicated that New England, for example, is experiencing more rapid changes than other areas along the trail. Wildflowers there are flowering much sooner than trees are leafing out. This means that the risks posed to understory plants may not be the same everywhere across the Appalachian Trail. Actions to address these risks may thus be more urgently needed in some places than in others.
New England, for example, is experiencing more rapid changes than other areas along the trail. Wildflowers there are flowering much sooner than trees are leafing out.
Our data also show that gaps exist in phenology monitoring in some areas, like the mid-Atlantic region. There are far fewer observations, either from permanent plots or iNaturalist, from mid-Atlantic states compared to other areas of the Appalachian Trail. This was somewhat surprising given how many more people live near the trail in places like New York and Pennsylvania.
Research like ours can help land management agencies protect the flowering plants and forests in their care. “Long-term, large-scale datasets are essential for documenting ecosystem response and guiding management,” said Kate Miller, an ecologist with the National Park Service. “The results of this study not only document the value of citizen science but help direct where additional efforts should focus.”
About the author
Jordon Tourville, PhD, is an ecologist with the Appalachian Mountain Club. Photo © Jordan Tourville.
Cite this article
Tourville, Jordon. 2025. “Spring Is Now Earlier on the Appalachian Trail, Study Reveals.” Park Science 39 (2). August 29, 2025. https://www.nps.gov/articles/000/psv39n2_spring-is-now-earlier-on-the-appalachian-trail-study-reveals.htm