The night sky is a natural resource that has been polluted by human activity. One of the most significant impacts on the night sky has been the rise of light pollution. Light pollution is the excessive or misdirected artificial light that shines into the night sky, obscuring the view of stars and other celestial objects. In December 2022, the district administration of Ladakh designated six hamlets within the Changthang Wildlife Sanctuary a “dark-sky reserve” an area whose skies were free of light pollution. The designation meant that the reserve had a responsibility to keep the skies dark, particularly for the astronomical observatories located in the area.
The Impact of Light Pollution
- A new study has found that non-natural light has increased the brightness of the night sky by 9.2-10% every year between 2011 and 2022. Specifically, skyglow has brightened by 6.5% in Europe, 10.4% in North America, and 7.7% in the rest of the world.
- This finding is significant because it disagrees with satellite-based data, which has indicated that the rate of increase has been around 2% per year. The discrepancy is probably due to satellites being unable to ‘sense’ blue light emitted by LEDs and to study light that is emitted parallel to the ground.
- The increase in light pollution is having significant ecological, health, and cultural consequences.
Ecological Consequences
- Artificial light at night is affecting both people and wildlife in important ways. A 2003 report found that lit beaches deter sea turtles from coming ashore to nest. A 2006 review found that skyglow keeps trees from sensing seasonal variations. A 2017 study found that young burrow-nesting seabirds don’t take flight unless the nesting site becomes dark.
- A 2019 study reported that clownfish eggs don’t hatch when exposed to artificial light at night, killing the offspring. A 2020 study noted that skyglow interferes with multiple aspects of insect life and allows insect predators to hunt for longer.
Health Consequences
- Artificial light at night is also having negative impacts on human health. By disrupting the circadian rhythm, artificial light at night can hamper the production of melatonin, an influential hormone in the human body with effects on sleep, moods, and cognition.
- A small 2009 review concluded that circadian disruption which altered melatonin levels can cause increased the risk of breast cancer among night-shift workers by 40%.
Cultural Consequences
- The night sky has also inspired countless works of science and poetry. When Los Angeles had a big power cut in 1994, many people phoned local authorities to report a “silvery cloud” at night. It became evident later that they were really seeing the Milky Way.
- In 2020, Australian researchers wrote in a paper, “The erasure of the night sky acts to erase Indigenous connection to the stars, acting as a form of ongoing cultural and ecological genocide.”
Synopsis
The night sky is a natural resource that has been polluted by human activity. Light pollution is the excessive or misdirected artificial light that shines into the night sky, obscuring the view of stars and other celestial objects. A new study has found that non-natural light has increased the brightness of the night sky by 9.2-10% every year between 2011 and 2022. The increase in light pollution is having significant ecological, health, and cultural consequences. It is important for authorities to safeguard telescopes’ access to dark skies by actively lowering light pollution around their sites, and for individuals to take actions to reduce their own contributions to light pollution. Simple actions such as turning off unnecessary lights, using shielded light fixtures, and installing dimmer switches can all help to reduce light pollution. Additionally, it is important for governments and international organizations to work towards creating global treaties and guidelines to reduce light pollution. This could include regulations on the use of certain types of lighting, such as LEDs, and guidelines for lighting design that take into account the effects on the night sky and the environment.
