Light Pollution Could Be Affecting When Spring Starts

Spring has been starting earlier and earlier in recent years compared to in the mid-20th century, and by the year 2100, researchers estimate that in much of the U.S., plants will bud up to 22 days earlier than they currently do.

Now, a new study suggests that light may be playing a part. Published in Proceedings of the Royal Society B and reported by Gizmodo, the analysis was based on 13 years of citizen scientist-submitted data on the dates when various types of trees have budded in the UK.

The University of Exeter researchers found that between 1999 and 2011, urban areas with more light pollution at night saw trees budding an average 7.5 days earlier than darker regions, where the onset of spring basically didn’t change. They compared tree-budding dates with nighttime satellite imagery and weather data on air temperature, and found that cites’ early spring wasn’t entirely due to the urban heat island effect—which describes the fact that the ubiquitous hard surfaces and lack of greenery in cities make them hotter than surrounding regions—as previous research suggested.

We already know that modern urban lighting is terrible for human health, disrupting circadian rhythms and potentially even contributing to increased rates of breast cancer. It also affects the ecosystem, impacting insect communities, fatally disorienting birds and trapping in beams of light, and more. And this is not the first research to suggest extra-bright nights affects plants—another Exeter study this year found that amber light, like from older street lamps, can inhibit plant growth—but it provides national-level evidence that street lights and other nighttime illumination have a broad effect on the environment.

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