How Light Pollution Is Tricking the Trees

Light at night fools trees into thinking it's springtime. Poznukhov Yuriy/Shutterstock

The effects of light pollution are no secret.

Some studies have linked artificial light at night to increased risk of diabetes, obesity, depression and some cancers, as well as obvious sleep disorders. Light at night disrupts wildlife and ecosystems, throwing off the biological clocks of nocturnal animals. And that doesn't even count the estimated $3.3 billion wasted each year lost to "sky glow"— the artificial brightness of the night sky — just in the U.S.

Now researchers have found that light night skies also can trick some trees into blooming earlier than usual, at least in the United Kingdom. The study was published in the journal The Proceedings of the Royal Society B.

Led by Richard ffrench-Constant, an entomologist at the University of Exeter, the researchers used data from citizen scientists who recorded the budburst, or the date when green leaves just begin to emerge on a budding tree. They used the information for four tree species: European sycamore (Acer pseudoplatanus, known as sycamore maple in North America), European beech (Fagus sylvatica), Pedunculate oak (Q. robur) and European ash (Fraxinus excelsior).

European ash tree budding in spring
The European ash tree (Fraxinus excelsior) is one of the trees the researchers studied that budded earlier the lighter it was. ArgenLant/Shutterstock

They then used satellite data to measure how intense the light was at each tree's location. Using meteorological data, they controlled for air temperature, because typically trees use temperature cues to determine when to bud, but some studies suggest they rely on light cues, too.

The researchers found that although the European sycamore wasn't impacted by light pollution, the other three species budded earlier as the light became brighter. The European ash budded as many as seven days earlier than usual due to light pollution.

"It was an amazing result, really," ffrench-Constant told LiveScience. "Even though we've gone through a ridiculous amount of trouble to control for the effect of heat in our study, obviously, the combination of climate change and artificial lighting is a double whammy. Both of these are going to push spring in a forward direction."