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Artificial Light at Night: State of the Science 2026

Nighttime view over a rugged mountain valley and winding river beneath the Milky Way. A glowing road traces through mist-covered forests in the foreground, while dozens of bright satellite trails streak across the star-filled sky, intersecting above the landscape. A brilliant planet or star shines near the horizon, highlighting the contrast between the natural night sky and increasing human activity in orbit.
 Credit: Martin Moline

Article by John Barentine
Dark Sky Consulting

With every passing year, awareness of light pollution grows. We read more news stories, consume more digital media, and listen to more podcasts about it. A survey of the contents suggests that the message is clear: artificial light at night (ALAN) is a threat to people and planet. But rarely do news stories go into much depth on what we know about the topic. In an era of social and political polarization and misinformation, it can be difficult to separate the signal from the noise.

In 2022 DarkSky International released the first report called “Artificial Light at Night: State of the Science.” Its goal was simple: make the best of what we know about light pollution accessible to the greatest number of people.

That first report relied on thousands of papers in a curated database of scientific research reports on light pollution. Its text distilled decades of scientific research into a few pages of understandable language. A bibliography consisting of hundreds of citations backed its claims. It probed at the unknowns, identifying the most pressing research questions. And we licensed the contents under a Creative Commons license to enable its re-use.

Each year, we update the report with the latest results from scientific studies of ALAN. This involves reviewing hundreds of papers and looking for the common threads tying them together. We highlight new and sometimes unexpected findings. We gradually ‘modernize’ the citations. We also look for interesting figures in papers that represent certain concepts particularly well.

The 2026 report is now published, containing research published in 2025. Here are some of the key themes emerging last year:

  • Researchers increasingly identify ALAN as a widespread environmental pollution. Yet it’s hard to convince governments of this. Legal scholar Yana Yakushina puts it this way in her recent paper: “Within rapid technological developments, some environmental problems remain unnoticed until it is impossible to ignore them.”
  • There are clear, compounding effects of both light and other kinds of environmental pollution. These include noise and air pollution. Researchers speculate that the combined effect is “greater than the sum of the parts”. We are only beginning to understand the ecological and public health consequences of this.
  • Ecosystem-scale effects of light pollution are beginning to come into focus. In particular, ALAN may be decreasing annual net ecosystem exchange by enhancing “ecosystem respiration”. That changes how carbon cycles in and out of biological systems. And it suggests a connection to the global climate.
  • ALAN is causing ecological changes that may have profound effects, especially in cities. For example, it may be changing the length of growing seasons faster than temperature increases. And ALAN may inhibit seasonal hibernation of insects, including those that carry human diseases.
  • Social science research shows continued obstacles to awareness and change. People living in light-polluted places may ironically make it more difficult for them to see ALAN as a pollutant. We’re also learning more about the influences that make people more or less tolerant of lighting changes aimed at reducing light pollution.
  • “Space light pollution” is on the rise. New work shows that as more pieces of human-caused debris orbit our planet, the night sky may get brighter everywhere.
ALAN-State-of-the-Science-2026-ENDownload

With every new finding comes more questions. How can we know which outdoor lighting policies are most effective? Are organisms evolving responses to light pollution? Can we determine some relationship between the amount of ALAN and the level of security in outdoor spaces at night? How much influence is ALAN from outdoor sources in particular affecting the ecology or human wellbeing? Is it possible to find a true “efficiency metric” for outdoor lighting that considers its undesirable effects? And how will new uses of outer space, such as the deployment of orbital sunlight reflectors, change nighttime conditions on Earth?

One question we can answer with certainty is whether these topics will continue to interest researchers. There is no sign that their attention is waning. And with each passing year we find more recognition of light pollution studies as a scientific field of its own. We can expect to learn much more to guide our advocacy efforts.