Boulder Scientists Contribute to Global Light Pollution Atlas
A team of scientists led by Fabio Falchi, pioneering researcher with Italy’s Light Pollution Science and Technology Institute, published “The New World Atlas of Artificial Night Sky Brightness” in the June 10 issue of Science Advances.
Artificial skyglow refers to the “luminous fog” created by light in the built environment that interferes with the visibility of heavenly bodies such as stars and planets.
The atlas takes advantage of high-resolution data from the NOAA/NASA Suomi National Polar-orbiting Partnership satellite. The atlas represents the most accurate quantification and mapping of worldwide artificial sky brightness to date.
Boulder scientists Chris Elvidge, of the National Oceanic and Atmospheric Administration’s National Centers for Environmental Information, and Kimberly Baugh, of the University of Colorado’s Cooperative Institute for Research in Environmental Sciences, are co-authors.
Scientists at NOAA, Elvidge said, had been mapping the amount of light escaping into space since 1994. In 2000, they were contacted by Falchi, who hoped to use their product to generate an artificial sky brightness map.
Falchi generated a map in 2001 based on data from the Defense Meteorological Satellite Program.
The Suomi weather satellite, introduced in 2012 with a vastly improved sensor, enabled more sophisticated data generation, the development of algorithms and, eventually, the creation of an entirely new atlas.
The atlas shows that more than 80 percent of the world population — and more than 99 percent of the populations of the United States and Europe — live in light-polluted areas.
The Milky Way is hidden from more than one-third of humanity, including 60 percent of Europeans and nearly 80 percent of North Americans.
Increasingly recognized as a concern by scientists in fields ranging from ecology to astronomy, health care and land-use planning, artificial skyglow poses threats to humans and wildlife.
“We can take what used to be habitat and turn it into non-habitat simply by adding too much light,” said Travis Longcore, assistant professor of architecture, spatial sciences and biological sciences at the University of Southern California.
Humans are also at risk.
“I think that people generally don’t understand that light is a drug,” Longcore said.
“Just like drugs, light can change the timing and abundance of chemicals in your body, hormones, neurotransmitters — all those sorts of things. That’s exactly what drugs do. And we use light as a drug to expose people to light to get them to produce certain things in their body. Light at the wrong time can similarly change your physiology.”
Epidemiological studies, Longcore said, demonstrate a relationship between circadian rhythm disruption and levels of breast and prostate cancers — both hormonal cancers.
The World Health Organization, he said, has called shift work a “probable carcinogen,” because it disrupts circadian rhythms, suppresses melatonin and leads to cancer.
Half of the species on the planet are nocturnal, Longcore said. Artificial night light affects them in two distinct ways.
By increasing brightness, artificial illumination alters predator-prey relationships and other natural behaviors.
“Some species needs darkness. Lack of darkness can interfere with foraging, reproductive timing, bird song and hormonal fluctuations, etc.,” Longcore said.
Glare, on the other hand, attracts insects to lamps, for example, or birds to tall buildings, he said. By altering points of reference, wildlife — such as baby sea turtles heading for the water — can become disoriented — sometimes fatally so.
Artificial sky brightness can be controlled by shielding lights, reducing overlighting or turning the lights off.
Most Italian regions now have laws against light pollution, Falchi said. Since 2000, despite increasing overall luminosity, these regions have stopped the increase in sky brightness. Slovenia has seen similar results.
Falchi and David Keith, a Boulder-based lighting consultant, both support the use of high-pressure sodium lights for their efficiency, affordability and lower emissions of the circadian-altering blue light. LEDs, however, are the “new frontier,” Falchi said.
Boulder’s zoning code, according to Chris Ferro, development review manager, is an “extensive, sophisticated set of outdoor lighting regulations expressly designed to reduce light pollution, encourage dark sky and save energy.”
The code, Ferro said, covers maximum lumens, positioning, shielding and efficiency. The use of metal-halide lights and — in contrast to Keith and Falchi — high-pressure sodium lights, is discouraged for being too inefficient.
There are less than a dozen scientists working in this field worldwide, Elvidge said.