Modern Street Lights Disrupt Camouflage of Coastal Species, Exposing Them to Predators

Animals
An illustration of a Littornid snail under broad spectrum lighting
A Littornid snail loses its protective camouflage (left) and becomes more visible under broad spectrum lighting (right). University of Plymouth

Modern, energy efficient street lights might feel like a welcome comfort when walking along the beach at night when it’s so dark the ocean has become a black expanse with only occasional dots of light from passing boats. But for species that forage and feed in the dark, broad spectrum lighting can interfere with the camouflage they rely on for survival.

A new study — one of the first to investigate the capacity of artificial light at night (ALAN) to interfere with the camouflage processes of species that live along coastlines — has found that these new advances in lighting being used across the globe can greatly improve the ability of a predator to distinguish prey against a natural background, the University of Plymouth said in a press release. Just how much depends on the color of the organism, which means that species with certain variations in color are more at risk.

The study, “Broad spectrum artificial light at night increases the conspicuousness of camouflaged prey,” was conducted by University of Plymouth and Plymouth Marine Laboratory (PML) researchers and published in the Journal of Applied Ecology.

“This study clearly indicates that new lighting technologies will increase the conspicuousness of prey species by reducing the efficacy of their camouflage,” said Ph.D. candidate at the University of Plymouth Oak McMahon, who was the research leader while studying for an M.Sc. in applied marine science, as reported by the University of Plymouth. “Our findings revealed that species of Littorinid snails found commonly on our coastlines will remain camouflaged when illuminated by older style lighting. However, when illuminated by modern broad spectrum lighting, they are clearly visible to predators and at far greater long-term risk as a result.”

In the study, the researchers studied three different color changes of Littorinid snail commonly seen in coastal areas around the world. They studied how coastal predators would see the snails when lit by a variety of lighting, including Low Pressure Sodium (LPS) lighting used in the 20th century, modern broad spectrum lighting of three types — High Pressure Sodium (HPS), Metal Halide (MH) and Light Emitting Diodes (LEDs) — as well as natural sun and moon light.

They found that LPS light did not interfere with the effectiveness of the snails’ camouflage, but in most cases light from the sun and moon, as well as the MH lighting and LEDs, made yellow snails much more visible than the olive- and brown-colored snails.

“Our findings revealed that species of Littorinid snails found commonly on our coastlines will remain camouflaged when illuminated by older style lighting. However, when illuminated by modern broad spectrum lighting, they are clearly visible to predators and at far greater long-term risk as a result,” McMahon said, as Earth.com reported.

Lecturer in marine conservation at the University of Plymouth Dr. Thomas Davies, who was the senior author of the study, said that, according to some predictions, in about five years 85 percent of the market for street lighting around the world will be made up of LED bulbs, reported the University of Plymouth.

“As technologies develop, there has been a shift from narrow spectrum to lighting that enables us to live and travel in a safe, secure manner. However, estimates suggest that a quarter of the planet between the Arctic Circle and Antarctica is now being affected by night-time light pollution,” said Davies, as reported by AZoCleantech.

In order to mitigate the negative effects of ALAN on coastal species, the amount of lighting used could be reduced, lights could be shielded, lighting spectra could be decreased and lighting could be limited to peak usage times, the researchers said in the study.

“The shift from the orange glow over cities, typical of my youth in the 1970s and 80s, has now shifted much more towards energy efficient wide spectrum LEDs which even enables us humans to correctly perceive colour,” said PML Head of Science for Marine Biogeochemistry and Observations Dr. Tim Smyth, who was co-author on the research, as the University of Plymouth reported. “This work shows that this advancement has additional ramifications for the natural world, which is having to adapt at an increasing rate to the artificial changes we are making to the environment. We need to learn to adapt our technologies to avoid the worst consequences of their adoption.”

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