Dead moths lodged between a light bulb; a sleepless night for a city dweller; a cancer diagnosis. While seemingly unrelated, all three are interconnected to a surprising – and highly visible – culprit.
During the night, across the world, millions of lights illuminate buildings and roads. While they help us see better, these lights have perhaps counterintuitively had a negative effect on many parts of the natural world because they disrupt the circadian system of nocturnal creatures and cause negative health effects for humans. As society increasingly gravitates towards urban centers, a look at the harm generated by our overly-lit environment is timely.
After its invention in 1879, the light bulb quickly gained traction throughout a world which was suddenly amazed by this new technology. Street lamps were placed along the edges of sidewalks and companies created dazzling displays to catch the eye of potential customers. While artificial light helped humans master darkness, it has also impacted the environment in ways both surprising and shocking.
One area into which this issue is steadily creeping is the animal kingdom. Most wildlife species rely on natural light to help them function during the day. When an animal senses light, they know when they must awaken. When they no longer feel or see it, they know they must sleep. Light pollution has altered this instinctive discernment by confusing animals about the natural light cycle and making them stay out longer during the day than they should.
Natural light also assists animals in interpreting the seasons, especially those that go into hibernation. Artificial beams tend to awaken hibernating animals earlier because they bother their circadian system. While sometimes hibernating animals will awaken ahead of schedule and fall back asleep, once their body comes into contact with lights, it will make this process harder.
During bird migrations in the spring and fall, light pollution disorients these creatures, causing them to send out poor navigational calls for other members. These birds try to follow the call, but end up crashing into brightly lit signs, radio towers, and buildings.
Sea turtles have also fallen prey to light pollution. Beaches are now surrounded by lights to entertain visitors during the evening, but these lights disrupt sea turtle egg laying and hatching. A study published in Environmental Health Perspectives found that female sea turtles are irritated by light and will move to extreme locations to get away from it. If the mother is unable to find a suitable spot, she’ll crawl back into the ocean and dispose of her eggs in it.
Additionally, when sea turtles hatch, they become confused with the surrounding light and attempt to crawl toward an illuminated area which they think is the moon shining on the ocean, a compass they use to safely swim to sea. While not fatal at first, they are unable to find their way back to the ocean and risk being run over, becoming a meal, or suffering severe dehydration.
Besides the animal kingdom, humans have experienced a variety of side effects caused by this problem. Due to light pollution affecting the circadian system, studies have found that it can cause insomnia because it hinders the production of melatonin, a natural sleep hormone.
In addition, a 2016 study by Redhwan A. Al-Naggar and Shirin Anil raised concerns that light pollution could heighten the risk of certain hormonal cancers, such as breast and prostate. When the body is unable to produce melatonin due to light at night (LAN) exposure, it stresses the body and makes it more susceptible to this illness. It could also hurt one’s immune system because constant light encourages the production of cytokines, a stress hormone that creates inflammation. One study showed that areas with higher LAN exposure tended to have an almost 50% increase in breast cancer compared to areas that didn’t.
Perhaps one of the most ubiquitous aspects of light pollution is its blocking of celestial objects which prevents humans from experiencing the wonders of astronomy. While one might see hundreds of stars at night in spite of artificial light, there are millions more that secretly shine behind the glow of these.
It’s believed that over 80% of the world’s population now lives within skyglow which is a thick inhabited area cluttered with light. One of the worst destinations for light pollution is Singapore, which constantly keeps its lights on due to numerous airport terminals and its populated financial hub in Marina Bay. Researchers have found that due to thick light pollution throughout the country, it’s virtually impossible now to see the Milky Way.
Little surprise then that one of the most commented-on topics by astronauts looking back to Earth regards how the world itself appears lit even when in darkness. The Anthropocene – palpably, demonstrably, verifiably – is here; long live the Anthropocene.
Rachel Kester for Times Media Mexico
The Yucatan Times