The U.K.’s Royal Astronomical Society is urging governments to formally recognize artificial light at night as a pollutant, warning that growing levels of light pollution are harming human health, biodiversity and astronomical research.
The call follows a major conference hosted by the RAS in January 2025, where scientists, policymakers and environmental experts presented evidence showing the widespread impacts of excessive nighttime lighting.
Light Pollution Is Rapidly Worsening
Light pollution is increasing. A paper published in 2023 found that the night sky grew about 10% brighter per year from 2011 to 2022, based on tens of thousands of citizen-science observations. A location where 250 stars were visible in 2011 saw only 100 stars by 202. However, according to the RAS, artificial light pollution is no longer merely an inconvenience for astronomers observing the night sky.
Light Pollution: Risks To Human Health
There is mounting scientific evidence connecting excessive exposure to artificial light at night. Researchers say it is increasingly linked to developing serious health conditions, including type 2 diabetes, obesity, Alzheimer’s, Parkinson’s and retinal damage. There is also evidence to suggest it directly impacts a person’s mood and increases the prevalence of depression and anxiety.
“There is increasing scientific evidence that both are having a significant and lasting impact on the natural environment and human health,” said Marieta Valdivia Lefort, Policy & Diversity Officer at the RAS. “To reverse this devastating damage, we need swift and effective action from both policymakers and legislators before it’s too late.”
Light Pollution: Severe Consequences For Wildlife
Scientists also warned that artificial light is dramatically affecting biodiversity, especially among nocturnal species that rely on darkness for feeding, migration and reproduction.
Evidence presented at the conference showed moth caterpillar populations decline by 52 percent in areas exposed to street lighting. Researchers estimate that about one-third of insects attracted to artificial lights die by morning, often from exhaustion or predation. Artificial light at night was also found to reduce nocturnal plant-pollinator interactions by 62 percent, with consequences for pollination and plant reproduction.
Protecting The Night Sky From Light Pollution
The RAS argues nighttime should be treated as a protected part of the natural environment, requiring safeguards similar to those applied to daytime environmental conservation.
The organization has been collaborating with the All-Party Parliamentary Group for Dark Skies, which was established in 2020 to address light pollution and advocate for dark-sky-friendly planning policies. The RAS is encouraging governments to integrate light pollution into broader environmental legislation, including the UK’s Environment Act 2021. While light pollution is not currently listed as a direct environmental target under the law, the RAS says future secondary legislation could include it.
Light Pollution: Five Principles For Responsible Lighting
To address the growing problem, the RAS recommends adopting five key principles for responsible outdoor lighting:
- Using lighting only for a clear purpose
- Directing light only where needed
- Reducing unnecessary brightness
- Limiting lighting duration
- Choosing warmer-colored lighting instead of harsh white LEDs
Wishing you clear skies and wide eyes.
