More than one third of humanity can no longer see the Milky Way at night and four out of five people on Earth live under polluted skies according a new state-of-the-art atlas of the problem across the globe.

One local expert believes the problem is driving one of New Zealand's fastest-growing forms of tourism - looking at stars in the night sky.

"It's becoming one of our biggest attractions and shaping the whole of tourism in the South Island," said John Hearnshaw, Emeritus Professor of Astronomy at the University of Canterbury.

Map of Europe and the eastern seaboard of the US, as seen on http://cires.colorado.edu/artificial-sky , a website from the University of Colorado which shows light pollution.
Map of Europe and the eastern seaboard of the US, as seen on http://cires.colorado.edu/artificial-sky , a website from the University of Colorado which shows light pollution.

He said more than a million people had visited the Mackenzie Region's International Dark Sky Reserve and the reserve's Mt John Observatory in the past 10 years, especially from Asia, Europe and North America where many people never experience a true night sky.

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"Humanity has enveloped our planet in a luminous fog that prevents most of Earth's population from having the opportunity to view our galaxy," the researchers behind the light pollution atlas wrote on Friday in the journal Science Advances.

Professor Hearnshaw said New Zealand was not as badly affected by light pollution as many other parts of the globe. Even in cities such as Auckland, Wellington and Christchurch, the night sky was at the low end of a sky brightness scale.

Map of New Zealand as seen on http://cires.colorado.edu/artificial-sky, a website from the University of Colorado which shows light pollution.
Map of New Zealand as seen on http://cires.colorado.edu/artificial-sky, a website from the University of Colorado which shows light pollution.

However, the Aoraki Mackenzie International Dark Sky Reserve, one of 10 such reserves in the world, is almost completed unaffected by artificial light.

The light pollution atlas published on Friday, and the work of two Italian researchers Fabio Falchi and Pierantonio Cinzano, found that the world's most light-polluted country is Singapore, where the entire population lives under skies so bright that the human eye never fully adapts to night vision.

Citizens of other countries such as Kuwait, Saudi Arabia, South Korea, Israel and Argentina also have almost entirely obstructed views of the night sky. Not everyone on Earth lives under light-polluted skies, of course. Madagascar, Chad and Central African Republic are among the least-affected countries, with three-quarters of their inhabitants living under skies unimpeded by artificial night light.

But in some parts of the world, the problem is so pervasive that people must travel long distances to reach a piece of land where it's possible to see a pristine night sky. The authors wrote that the location on Earth farthest from having the possibility of seeing a hint of the Milky Way is an area near Cairo in the Nile Delta. Other areas where the Milky Way is no longer visible include parts of Belgium and Germany, areas around Beijing and Hong Kong, and other cities such as London, Boston and Washington.

Holding a third of New Zealand's population, Auckland radiates like a beacon between the harbours.
Holding a third of New Zealand's population, Auckland radiates like a beacon between the harbours.

"By now, we've had a couple generations of people in urban areas who have been cut off from seeing features like the Milky Way," Said Chris Elvidge, scientist at National Oceanic and Atmospheric Administration who was part of the team that created the new atlas.

People in Paris would have to travel more than 500 miles to find skies largely unaffected by light pollution, the study found. For people near Neuchatel, Switzerland, finding a near-flawless sky would require a trip of nearly 850 miles or more to parts of Scotland, Algeria or Ukraine.

"Growing up in Southern California in the 1960s and '70s, my family and I didn't have to go very far to see a pretty good night sky, and that isn't true anymore," said Dan Duriscoe, a co-author of Friday's study and veteran of the National Park Service. "Somebody should care about this in a manner that leaves areas alone, so people have access to this without excessive expense or travel." To think of a future where it requires a pilgrimage just to see an unimpeded night sky, he said, "would be tragic."

The worries over light pollution extend beyond aesthetics. Scientists have studied a broad range of other potential economic, ecological and health consequences. Some research suggests that the problem can disrupt the world's ecosystems, altering the way some animals eat, sleep, reproduce and hunt. Evidence also suggests that artificial light at night can upend the circadian rhythms that humans depend on, increasing the risk of health problems such as depression, diabetes, sleep disorders, obesity and breast cancer.

Friday's study noted that there are strategies and technologies that increasingly are being used to mitigate the effects of light pollution, such as street lamps that direct light only downward and "adaptive lighting," which can use sensors to lower the outdoor lighting at night, especially during periods of little or no traffic.

But the authors behind the new global atlas said that despite those hopeful signs, the world's growing population -- not to mention the threat of indifference to light pollution -- could lead the problem to get only worse. And that would be a shame, they said.

"We all have an idea that the view of the night sky should be one of these cultural monuments, that there has to be a place you can go and experience it," Duriscoe said.

"One viewpoint is that it doesn't matter, because most of us are busy doing other things at night," Elvidge added. "Another viewpoint is that our ancestors and our civilization grew up with people literally studying the skies. At least when I've been out in places with a very clear sky, a dark sky, and you look up and see the number of stars out there, it's awe-inspiring. I feel some enhanced connection to the cosmos."

- Additional reporting from Mike Van Niekerk