Light Pollution Causes Tress to come back to Life Earlier in Spring

Row of trees in a Norwegian public parkBritish researchers found that artificial light in the public space such as streets and parks pushes trees into producing leaves a week earlier than they should in spring. The team explained that earlier springs may have a detrimental impact on birds and insects.

Scientists at the Exeter University in the U.K. found that the phenomenon affects various types of trees including the beech, ash, sycamore and oak. After analyzing tree buds they learned that these trees exit hibernation about 7.5 days earlier.

Biologists explained that moth caterpillars and birds will be the most affected. If tree buds sprout a week earlier, young caterpillars will have to feed on older leaves that are laden with an anti-pest chemical called tannin. As a result, there will be fewer insects for birds to eat.

Lead author of the research Richard Ffrench-Constant noted that past studies had also shown that birds’ and animals’ natural rhythms are affected by artificial light, but the effect of light pollution on vegetation has been often overlooked.

Ffrench-Constant added that a 7.5-day delay is a “significant difference.” Nevertheless, the difference will not negatively impact trees, researchers explained, except for a few “colder nights.” The delay could actually help plants as fewer insects will chew on their leaves.

Ffrench-Constant thinks that if moth caterpillars don’t adapt to the light stimuli and hatch earlier they will be forced into a tannin-rich diet which will surely take a heavy toll on their development.

Subsequently, songbirds will have fewer insects to catch and feed on.

Scientists explained that trees produce leaves earlier because they take the red light on the artificial light’s spectrum for solar light. So, the team is confident that authorities could equip cities with street lights lacking the red wavelengths such as LED lights and easily solve the problem. LED lights will also not hamper moths’ role of nighttime pollinators.

The recent study was based on data gathered by “citizen scientists” who were asked to write down when they first saw different types of trees in leaf. Next, biologists at Exeter University compared the data with satellite imagery of light pollution.

Dr Kate Lewthwaite, a manager for the citizen science project, stated that urbanization currently affects nature in ways that cannot be predicted. Lewthwaite noted that human activities affect wildlife’s habitat and food sources alike.

The study was published this week in Proceedings of the Royal Society B journal.

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