In her book "Stardust," Swedish author Hanna Anensen reflects on humanity's impact on Earth. The book documents a group of teenage students' responses to the question, "What have you missed because of climate change?" Surprisingly, two answers pointed to the same issue - light pollution.
According to data from the recent report "The New World Atlas of Artificial Night Sky Brightness" published in the journal "Science," over 80% of the global population, including nearly all Americans and Europeans, live under skies tainted by light pollution. This light pollution means that 6 out of 10 Europeans cannot see the brilliant Milky Way. In Europe, as high as 88% of land residents are disturbed by light pollution at night.
Disruption to Circadian Rhythms and Sleep
Light pollution not only destroys the beauty of the night sky but also leads to increasingly severe environmental problems. Each year, the illuminated area on Earth's surface and the intensity of artificial light in the night sky are growing at a staggering rate of 2.2%. Alicia Pellegrina, a researcher at the Andalusian Astrophysics Institute in Spain, emphasizes that this growth trend cannot be ignored.
Recent studies have revealed the serious impact of light pollution on people's health. A study published in the American Heart Association's journal "Stroke" for the first time linked increased exposure to artificial light and bright outdoor nighttime lighting to a higher risk of stroke. Analyzing data from over 28,000 adults, researchers found that those exposed to more light at night had a 43% increased risk of cerebrovascular disease compared to those with less exposure to outdoor light at night.
Previous research has shown that exposure to outdoor light at night is associated with increased risks of diabetes and hypertension, and may also have negative effects on people's circadian rhythms and nighttime rest. These are all known risk factors for stroke.
Pellegrina points out that the presence of artificial light at night has two direct effects on the body: altering the circadian rhythm and suppressing melatonin (the sleep hormone) synthesis. The circadian rhythm is the body's internal clock that regulates physiology and behavior based on the alternation of natural light and darkness. However, exposure to strong artificial light at night disrupts this clock, leading to changes in circadian rhythms and putting the body in a state of confusion. Additionally, melatonin is only secreted at night. Therefore, it is inferred that artificial light pollution can have adverse effects on people's health.
Impact on Coastal Ecosystems
While posing a threat to human health, light pollution also has profound effects on coastal ecosystems. In a study in New Zealand, scientists found that "skyglow" significantly affects the growth patterns of three-spined sticklebacks, thereby impacting their foraging abilities. These fish typically reproduce and grow based on lunar cycles, but the nighttime artificial lighting in surface waters disrupts this natural rhythm.
Light pollution data from Wellington City shows a significant increase in nighttime lighting levels 60 kilometers from the city center. Three-spined stickleback samples affected by this change showed noticeable alterations in their growth patterns, resulting in different body shapes compared to normal fish. This change not only affects their swimming and foraging abilities but also makes their lives in brightly lit waters increasingly challenging.
Even the smallest changes in marine ecosystems can trigger a series of chain reactions in the food chain. Small species like three-spined sticklebacks may experience short-term fluctuations in numbers that could evolve into larger-scale, longer-term impacts, posing a substantial threat to offshore fisheries.
Correcting Excessive Urban Lighting
Faced with the serious challenge of light pollution, urgent action is needed to correct the current state of excessive urban lighting. The Spanish newspaper "El País" points out that the increasing number of streetlights, illuminated advertising screens, and other light sources in cities not only diminish livability but also result in unnecessary energy waste and environmental pollution.
Pellegrina emphasizes that light pollution primarily stems from the overuse of artificial light. Therefore, it is essential to reconsider the use of artificial light. For example, adopting better and more sustainable lighting solutions, avoiding direct light into the sky, and limiting the lighting time in public places. She suggests using lights within the visible spectrum for human eyes, while avoiding the use of white lights and other light sources that have a significant impact on the environment. These light sources tend to scatter into the atmosphere, obscuring the stars in the night sky and disrupting astronomical activities.
Pellegrina states, "Only through collective efforts can we reduce the threat of light pollution to the Earth's ecology and human health, allowing the stars to illuminate our nights once again."
