Light pollution is getting worse, but there is a movement to make our skies dark again

CNN

05-02-2025

When a series of lightning strikes took down power across New York City on the night of July 13, 1977, streetlights, neon signs, and the bright lights of houses and skyscrapers went dark.
And just like that, for the first time in decades, the Milky Way could be seen streaked across the black sky, speckled by thousands of shimmering stars.
'I saw a (starry) sky from my location in the Bronx,' said Joe Rao, a meteorologist and amateur astronomer who was living in New York City on the night of the blackout, 'which I had never seen before and have never seen again.'
Barring a freak power outage, the light emanating from towns and cities due to unnatural light sources is so bright that it washes out the stars. Today one-third of all humans, including 80% of North Americans, cannot see the Milky Way.
For a growing number of people, natural darkness has been lost. When the lights went out in 1977, New Yorkers could see how much they were missing.
Light pollution, the term for the brightening of the night sky by unnatural lights, is increasing worldwide. On average, skies are getting 10% brighter each year globally, with the fastest rate of change in North America.
Many species are suffering the consequences. Every year, up to one billion birds in the US are killed by colliding with buildings, a global crisis exacerbated by bright lights drawing them off their migratory paths at night. Unnatural lighting can disorient insects, and affect the leaf development of trees. A 2017 study found that light pollution poses a threat to 30% of vertebrates and more than 60% of invertebrates that are nocturnal.
Nesting sea turtles, which rely on the reflection of light on the water from celestial bodies to guide them to the ocean, can be disoriented by unnatural lights around beaches, resulting in fatal dehydration or predation.
'We've found sea turtles in elevator shafts,' said Rachel Tighe, lighting project manager at Sea Turtle Conservancy, a Florida-based nonprofit funded by the National Fish and Wildlife Foundation. For the animals, she added, 'it's confusion and chaos.'
And humans are affected, too. While the health implications of unnatural light are still being investigated, research has linked light pollution to obesity, depression, sleep disorders, diabetes, and cancer.
'We know that if you start to shift temperatures you have really profound impacts on organisms across ecosystems, so you would imagine that if we start to mess with light cycles, we might have similarly profound impacts,' said Professor Kevin Gaston, a light pollution expert at the University of Exeter, in the UK. 'We're all ultimately dependent on this stuff for our very existence.'
There is hope.
Unlike other environmental issues like climate change and deforestation, the problem of light pollution could be curbed overnight — by turning off the lights.
In 2020, the small town of Crestone, Colorado, switched off its streetlights when it ran out of money to pay the electricity bill. At night, the streets were dark, but the sky above was bright with stars.
'At the next meeting (of the Board of Trustees), someone said, 'You know, we kind of like it dark,'' recalled Kairina Danforth, mayor of Crestone at the time. Inspired to preserve natural darkness, the town decided to leave the streetlights off.
Soon, Crestone became one of a growing number of towns around the world officially recognized as a Dark Sky community by DarkSky International, an organization that promotes the battle against light pollution.
'We are probably the only Dark Sky community in the world that has no residential lights because they couldn't afford to pay the bill,' said Danforth. 'Now there's a strong communal support for our dark sky.'
As Crestone, and the residents of New York City in 1977, can attest, a total blackout will bring back the stars instantaneously. But efforts to tackle light pollution need not be so extreme to make a big difference, said Ruskin Hartley, CEO of DarkSky International.
'The solutions are simple,' he said, 'and they don't involve giving up anything apart from bad quality lighting.'
Light pollution experts abide by the mantra: 'keep it low, keep it shielded, keep it long.' In other words, ensure that lighting is low to the ground, that it is targeted to avoid light leaking in all directions, and, if possible, that it has a long wavelength, typically observed as amber colored. Finally, turn lights off when they're not needed.
Some communities are following DarkSky's recommendations by retrofitting their lighting fixtures to reduce light pollution, or simply turning off more lights. DarkSky International has worked with communities and nature reserves in 22 countries to provide support and give official accreditation to areas that have made positive changes. Nearly 300 areas are now accredited.
In 2022, DarkSky, in collaboration with the Czech Republic, developed a European policy brief on reducing light pollution, recommending that 'all light should have a clear purpose,' that it 'should be directed only to where needed,' and that it 'should be no brighter than necessary.' The brief suggests using current EU legislative frameworks — on biodiversity, climate change, and energy efficiency — to push for light pollution mitigation measures.
As of October 2022, 20 pieces of nationwide legislation that concern the mitigation of light pollution had been introduced in nine member states of the European Union since 2000, according to the Czech Republic's Ministry of the Environment.
Countries are further incentivized by potential economic advantages. Electric-powered indoor and outdoor lights consume 17% to 20% of global electricity production, according to the European policy brief, and cutting usage means cutting costs. Areas with dark skies are also benefitting from astrotourism, a growing trend in which tourists travel to stargaze in locations with lower levels of light pollution.
'(Under) the stars are the places we told our first stories,' said Hartley. 'For many communities, these have been erased and lost because of the scourge of light pollution. But more and more are starting to recover and rediscover this.'
Wildlife is benefitting, too. The Sea Turtle Conservancy has changed over 30,000 lights and estimates it has darkened over 45 miles of nesting beach in Florida since 2010, possibly saving as many as tens of thousands of hatchlings. 'It's really cool to be able to see such a change so quickly,' Tighe said.
Despite positive changes, stemming light pollution is an uphill battle.
Even in some parts of Chile's Atacama Desert, one of the darkest places on Earth, you can now see a distant glow emanating from nearby La Serena, one of the country's fastest-growing cities, said Hartley.
'You can't escape it anymore, and it is just a product of waste and ignorance,' he added. 'How can we get more people to care about this?'
For Rao, who was 21 on the night that the Milky Way appeared above his house in the Bronx, and is now 68, optimism for the fate of our skies is at an all-time low. 'I'm beginning to wonder whether anybody is going to be able to see a good dark sky anymore, 30, 40 years from now,' he said. 'It's very, very sad.'
But as the movement to save the dark grows, there is still a faint hope that a star-studded future is possible.