Spring has been coming early to UK cities.
Using citizen scientists to record budding trees over 13 years, researchers have discovered that the first leaves of spring burst forth earlier in light-polluted areas, as if plants are fooled by all the artificial light brightening the sky. Some tree species, particularly late bloomers, can even get their leaves over a week early.
The study, published in the Proceedings of the Royal Society B, asked participants to record the date when young leaves from species of sycamore, beech, oak, and ash started to leave the bud casing. (They also noted the locations of the trees they were observing.) The researchers measured those recorded dates against satellite maps of light pollution.
Scientists are concerned that the early buds could affect other plants and animals whose lives depend on trees. Studies have already shown that light pollution messes with the sleeping patterns of humans and wildlife.
The effects may be even worse if the tree lives directly under artificial lighting.
"Our finding that the timing of bud burst of woodland tree species may be affected by light pollution suggests that smaller plants growing below the height of street lights are even more likely to be affected," said lead author Professor Richard ffrench-Constant in a press release.
The researchers were also able to determine that the urban heat island effect (where built-up areas trap more heat than open rural spaces) wasn't what was causing the early budding events: Even in less populated areas, brightness had more of an effect on the buds than temperature.
Ffrench-Constant suggested experimental research would be the next step in unraveling how light pollution changes ecosystems.
The study was relatively limited in scope: After all, the citizen scientists only looked at four species of trees, and only in the United Kingdom.
The study authors said they hope that their research will spur local governments to examine how and what kind of streetlights they use in their area.
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