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Atacama Desert's stellar skies face growing light pollution threat
The Atacama Desert in Chile, one of Earth's last havens for unspoiled stargazing, is losing its darkness to artificial lights from expanding cities and industries, astronomers warn.
The value of darkness
At 2:00 AM in Chile's Atacama Desert, the absence of light reveals a breathtaking night sky. The Milky Way stretches overhead, while distant galaxies like the Magellanic Clouds-whose light has traveled 200,000 years to reach Earth-are visible to the naked eye. This unparalleled clarity has made the Atacama a global hub for astronomy.
"Few places on Earth offer such ideal conditions," says Itziar de Gregorio-Monsalvo, a senior astrophysicist at the European Southern Observatory (ESO) in Chile. The region's remoteness and arid climate have long shielded its skies from light pollution, attracting telescopes like ESO's Very Large Telescope (VLT) and the upcoming Extremely Large Telescope (ELT).
Encroaching artificial light
Yet this darkness is now at risk. Artificial lights from nearby cities, mining operations, and industrial projects are gradually brightening the skies. A 2025 study found that global light pollution increased by nearly 10% annually between 2011 and 2022, reducing visible stars from 250 to just 100 in some areas.
For astronomers, the stakes are high. Two-thirds of the world's major observatories now exceed the 10% brightness threshold deemed harmful to observations-a limit set in the 1970s. The Atacama remains one of the last sites below this threshold, but its future is uncertain.
Industrial threats and regulatory gaps
The most immediate danger comes from industrial expansion. In 2025, ESO warned that the proposed Inna complex, a megaproject by AES Andes, could increase light pollution at Paranal Observatory by up to 50%. Though AES Andes canceled the project in early 2026, citing business priorities, astronomers fear similar proposals will emerge.
"The legal frameworks haven't changed," says Eduardo Unda-Sanzana, an astronomer at the University of Antofagasta. "If we lose urgency, another project could appear in 2026."
Current regulations allow industrial projects to proceed if they keep light pollution below 10%, a threshold astronomers argue is outdated. "For Paranal, even a 1% increase is harmful," Unda-Sanzana explains. The International Astronomical Union updated its guidelines in 2025, recommending site-specific limits, but enforcement remains weak.
Global consequences
Light pollution isn't just an astronomical issue. Ecologists warn it disrupts ecosystems by tricking animals into altering behaviors, while psychologists link fading stars to declining mental well-being. Some researchers now classify excess light as a "hard pollutant," akin to chemical contamination.
For astronomy, the loss of dark skies could hinder discoveries. Ground-based telescopes like the ELT, with its 39-meter mirror, provide unmatched detail but cannot function under bright skies. "If we let artificial light spread, we risk cutting ourselves off from the universe," de Gregorio-Monsalvo warns.
A race against time
Astronomers are pushing for stricter regulations, including a "secondary norm" to cap regional light levels. "This would let authorities intervene if pollution exceeds limits," Unda-Sanzana says. Without action, the Atacama's darkness-once abundant-could vanish.
"These are endangered environments," Unda-Sanzana adds. "If we don't protect them now, we won't get a second chance."
"Fifty years ago, dark skies were common. Now, they're scarce. We must act before it's too late."
Eduardo Unda-Sanzana, University of Antofagasta
