Bright areas on this map show where the sky glow from artificial lighting blots out the stars and constellations/Science Advances, Falchi et al.; National Park Service, Jakob Grothe; CIRES, Matthew Price; CU-Boulder

National parks are known as refuges for endangered plants and animals, but they're quickly becoming the last places to see the Milky Way in the United States. Dark skies above national parks and the research of a National Park Service scientist were integral to a new article that expands the knowledge of light pollution and its impact on the night sky around the world.

The New World Atlas of Artificial Sky Brightness, published this month by Science Advances, shows that more than 80 percent of the world and more than 99 percent of the U.S. and European populations live under light-polluted skies.

The National Park Service Natural Sounds and Night Skies Division is viewed worldwide as a leader in the protection of dark night skies. The atlas draws on scientist Dan Duriscoe’s seminal research and on-the-ground measurements of night sky brightness, amassed over the past decade of fieldwork in over 100 national park areas. The resulting datasets helped calibrate and corroborate data from NOAA satellite images of light scattering into the atmosphere. Duriscoe’s tests also provided essential data for the light pollution model, and helped establish international methods in use today for reporting the impact of artificial light on natural environments.

“Few places on Earth offer pristine dark views to the rising Milky Way and starry constellations, and light pollution is a bright filter upon this vast canvas,” Duriscoe said in a release. “Verification of NPS ground measurements with satellite data from NOAA creates an accurate model for predicting night sky quality in national parks and locations around the world, which can be used to increase opportunities for park visitors and stargazers to enjoy this rare and diminishing resource.”

The atlas project was led by principal investigator Fabio Falchi of the Light Pollution Science and Technology Institute in Italy, with additional expertise from Duriscoe, the National Oceanic and Atmospheric Administration, Deutsches GeoForschungsZentrum, and the University of Haifa in Israel.

“With the loss of dark sky views, the ancestral stories of celestial phenomena that so richly express our connection to these orbiting bodies are all but forgotten,” Duriscoe said. “And this is more than a matter of nostalgia. Humans need opportunities for wonderment and contemplation of the universe, and animals need darkness for protection, navigation, nesting and predation.”

Skies over half the land of the U.S. are light-polluted, the atlas shows. The darkest places in the United States are in the Colorado Plateau, a region of the Southwest covering parts of Utah, Colorado, New Mexico and Arizona. National parks in this area include Capitol Reef, Mesa Verde, Arches and Canyonlands. Some parks in this area have been certified as International Dark Sky Parks by the International Dark-Sky Association.

The New World Atlas model provides a compelling illustration that sky glow extends large distances from cities, and offers a tool for national parks to work in partnership with all stakeholders to pursue restoration of night skies. Industries and individuals alike can also do their part to minimize light pollution by adopting simple solutions, such as switching to shielded fixtures that direct light downward instead of into the surroundings, and using amber, or warm-colored bulbs, instead of cool blue LEDs, which amplify sky brightness two to three times above the typical output.

“Even one of these changes can make a difference in the palette of night,” Duriscoe said.