(ORDO NEWS) — City lighting that stays on all night dramatically disrupts the phenology of urban plants by shifting the time when buds open in the spring and when their leaves change color and fall off in the fall, a new study reports.
It shows how nighttime lighting lengthens the growing season in cities, which can affect everything from allergies to local economies.
Yuyu Zhou, assistant professor of environmental science at Iowa State University, and colleagues analyzed trees and shrubs in about 3,000 locations across US cities to see how they responded to different lighting conditions over a five-year period.
Plants use the natural day-night cycle as a signal of seasonal changes along with temperature. The scientists found that artificial lighting pushed back spring bud break by an average of nine days compared to areas without nighttime lighting.
The timing of fall leaf color change was more complex, but leaf change was still delayed by an average of almost six days across the 48 states.
This shift in plant biological clocks has important implications for the economy, climate, health, and ecological services that urban plants provide. Changing the growing season can increase the vulnerability of plants to spring frosts.
It can also lead to mismatches in the timing of other organisms, such as pollinators, on which some urban plants rely.
A longer active season for urban plants also means an earlier and longer pollen season, which can exacerbate asthma and other breathing problems.
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