Stretching 3,531 kilometers over a wide range of landscapes, the Appalachian Trail in the eastern United States teems with life, especially when winter turns to spring. That annual transition is springing quite a bit earlier now than it has in past years, scientists have found, documenting a slow, but steady, change that has altered the annual rhythms of many of the trail’s ecosystems.
The findings rely on phenology, the science of tracking the timing of natural events. Phenologists have found abundant physical evidence that climate change is affecting Earth’s annual cycles, such as when butterflies first take flight and when leaves take on autumnal hues. One such cycle is the appearance of lustrous new leaves each spring, a process known as “green-up.”