The Alarming Effects of Light Pollution on Your Plants and Garden
Light pollution, which currently affects a quarter of the planet and is increasing by approximately 6% each year, has led to an increase in the number of disrupted circadian rhythms for living beings, including plants.
Here's an outtake of an informative article from BBC.com on the effects of light pollution on plants:
While its impacts are still being studied and vary widely across species, scientists do know light pollution is affecting how plants grow and reproduce. It disrupts their seasonal rhythms, their ability to sense and react to natural light, and their fragile relationship with pollinators.
The effects aren't all that dissimilar to jet lag. Say you're flying from London to New York. Since you're traveling to a place five hours behind your home base, you're effectively gaining five hours of either day or night (depending on when you're travelling), which throws your circadian rhythm off kilter. The resulting jet lag can leave you feeling foggy, sleep-deprived, and generally under the weather for several days. That's just the result of one circadian rhythm disruption. Now imagine you're a tree on the side of a city street constantly being exposed to artificial lights from street lamps, cars, and buildings. If your internal system always thinks it's daytime, it can turn your life upside down.
"Plants are like animals in that they need a sleep cycle to process stuff, and what they do is they put attention on different activities at different times of the day. So they need to know the time of day," says Joanne Chory, professor at the Salk Institute for Biological Studies in San Diego, California.
Plants have photoreceptors, 13 that we know of, that they use to determine things like day length. This helps them know when to bloom and, for deciduous trees, when to drop leaves – arguably two of the most important events in a tree's calendar. Five of the photoreceptors absorb near-infrared light from the Moon and starlight, and eight absorb a type of UV light. By artificially extending the length of the day, light pollution can trigger these photoreceptors to the point where a plant's flowering pattern changes.
"Plants will get stressed out under [artificial] light. They can photosynthesise more, and because they are there's more stress," says Brett Seymoure, an ecologist and assistant professor of biological sciences at the University of Texas at El Paso. "It's just like a bodybuilder who's just always working out." When a plant photosynthesises, they're taking in energy, and if they're doing that all the time, it can be overwhelming and create a reactive type of oxygen that kills the plant.
Normally, as days grow shorter, deciduous trees stop the production of chlorophyll, the primary pigment used in photosynthesis, and pull nutrients out of their leaves, which is why they change colour and eventually fall to the ground. "But since they're just constantly bombarded by street lights, they don't get that photoperiod, so they're going to hold on to their leaves a lot longer, and they could lose all those leaves that have this chlorophyll which is actually very energetically costly," says Seymoure.
Just like jet lag affects humans, light pollution can also stress pollinators' bodies by reducing their sleep and recovery time, ultimately making it harder for them to pollinate and reproduce.
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Read more about how light pollution affects plant life:
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