In northeastern North America, a mountain range known as the Appalachian Mountains stretches about 500 miles (800 kilometers), starting from the Adirondacks in New York and extending to the Gaspé Peninsula in eastern Quebec. These highlands, known as alpine zones, are the areas above the tree line where trees cannot grow due to harsh, cold conditions. These regions are home to many rare and unique flowering plants, making them important centers of biodiversity. However, these fragile ecosystems are now facing multiple pressures, including climate change, reduced snow cover, changes in atmospheric nutrients, and human activities like hiking and skiing, which can introduce invasive species. A recent study led by Jonathan Chipman, director of the Citrin Family GIS/Applied Spatial Analysis Laboratory at Dartmouth, has provided the first detailed regional analysis of changes in these alpine zones. Chipman collaborated with Jordon Tourville, a terrestrial ecologist from the Appalachian Mountain Club, to examine how these high-altitude areas have changed over the past 40 years using hundreds of satellite images. The research, published in Ecosphere, found that 69% of the studied alpine zones showed significant increases in vegetation, covering 88% of the region's alpine area. This greening is not just happening at the edges of the tree line, as seen in other mountain ranges, but within the alpine zones themselves, with shrubs and other vegetation replacing some of the more delicate alpine plants. The study found that this greening is especially noticeable in areas like the Presidential Range in New Hampshire and Mount Katahdin in Maine. Certain types of plants, such as cushion-tussock and sedge meadows, are thriving in rocky outcrops and other challenging terrain. However, the researchers caution that this increase in vegetation may not be entirely positive. More aggressive plant species could outcompete the rare alpine flora, potentially leading to a loss of biodiversity. The changes are influenced by a variety of factors, including overall warming, the steepness of slopes, sun exposure, snow cover, and nitrogen levels in the soil. Wind also plays a significant role, particularly in the Northeast, where high wind speeds—such as the famous 231 mph (372 km/h) recorded at Mount Washington—keep the alpine zones at lower elevations than they would be at this latitude elsewhere. To conduct the study, researchers used Landsat satellite imagery from 1984 to 2024 to identify and monitor 35 major alpine zones in the region. However, challenges such as cloud cover and the limited availability of older data made it difficult to track changes accurately over time. To address these issues, the team developed a method to use the sparse data effectively, and a pilot study by Irene Ko, a research assistant at the Citrin Lab, helped confirm the importance of this work. The researchers hope their findings will help guide future conservation and land management strategies in these unique and sensitive alpine environments.