Vic Duran

Light pollution makes trees bud at least a week before normal, say researchers.

Here’s yet more info on how trees are so much more complex than we tend to think. In addition to warning each other about pests, and actually drooping as if tired when they’re “asleep,” there’s evidence they respond to light pollution by budding earlier in the year, in effect making for a premature spring.

At least that’s the case in the U.K., according to researchers at the University of Exeter in Cornwall. They took satellite images of the region’s nocturnal landscape and compared them to citizen-gathered data on when various tree species bud. The result: “We find that budburst occurs up to 7.5 days earlier in brighter areas, with the relationship being more pronounced for later-budding species,” they write in Proceedings of the Royal Society B.

(The researchers compared light pollution in the U.K. (left) to the budding time of trees such as sycamore (right). (Proceedings of the Royal Society B)

Scientists have known for a while that artificial lights (especially in the red spectrum), while usually not enough to trigger photosynthesis, can alter a tree’s sense of “day,” leading to different budding/flowering times and extending its overall growth. The Exeter study proves it’s happening on a widespread scale and quantifies the abnormal growth effect from the U.K.’s legion of street lights and businesses.

Trees getting an early start to the year—why should anybody care? For one thing the survival of other organisms can be tied to trees’ schedules, the scientists say in a press release:

Researchers believe early bud bursting will have a cascade effect on other organisms whose life cycles work in synchronicity with the trees. The proliferation of the winter moth for example, which feeds on fresh emerging oak leaves is likely to be affected which may in turn have some effect on birds in the food chain that rely on it for food.

There’s evidence nighttime illumination lets trees cling to their leaves longer into the cold months. That means when the first winter storm arrives to cover them with snow or ice, the added weight on all the leaves is likely to break more boughs and branches. Longer periods of greening also allow leaves to potentially suck in more air pollution through the year, eventually harming the whole tree. The researchers suggest local governments use this new data to manage “light levels in our urban environment in a sustainable way."

About the Author

Most Popular

  1. photo: Developer James Rouse visiting Harborplace in Baltimore's Inner Harbor.
    Life

    What Happened to Baltimore’s Harborplace?

    The pioneering festival marketplace was among the most trendsetting urban attractions of the last 40 years. Now it’s looking for a new place in a changed city.

  2. photo: NYC subway
    Transportation

    Behind the Gains in U.S. Public Transit Ridership

    Public transportation systems in the United States gained passengers over the second and third quarters of 2019. But the boost came from two large cities.

  3. Equity

    What ‘Livability’ Looks Like for Black Women

    Livability indexes can obscure the experiences of non-white people. CityLab analyzed the outcomes just for black women, for a different kind of ranking.

  4. photo: San Diego's Trolley
    Transportation

    Out of Darkness, Light Rail!

    In an era of austere federal funding for urban public transportation, light rail seemed to make sense. Did the little trains of the 1980s pull their own weight?

  5. photo: San Francisco skyline
    Equity

    Would Capping Office Space Ease San Francisco’s Housing Crunch?

    Proposition E would put a moratorium on new commercial real estate if affordable housing goals aren’t met. But critics aren’t convinced it would be effective.   

×