Light pollution is disrupting the seasonal rhythms of plants and trees, lengthening pollen season in US cities
City lights that blaze all night are profoundly disrupting urban plants’ phenology – shifting when their buds open in the spring and when their leaves change colors and drop in the fall. New research Yuyu Zhou coauthored shows how nighttime lights are lengthening the growing season in cities, which can affect everything from allergies to local economies. In the study, Zhous and his colleagues analyzed trees and shrubs at about 3,000 sites in U.S. cities to see how they responded under different lighting conditions over a five-year period. Plants use the natural day-night cycle as a signal of seasonal change along with temperature.