Nothing has captured the march of wealth and progress like a society's ability to light up the night - first with campfires and torches, then with gas lamps, finally with electric lights. But the extent of artificial lighting at night has been hard to monitor. "In the '70s. we wouldn't have thought to do that, because we'd think, 'That's insane expensive!' But now it's like, you can do this wonderful thing with LEDs".
This graph illustrates the changes in the artificially lit surface of Earth at night.
Outdoor illumination grew at around 3 to 6 percent per year in the second half of the 20 century.
"In the longer term, perhaps the demand for dark skies and unlit bedrooms will begin to outweigh the demand for light in wealthy countries", the team of authors wrote. Urban sprawl is also moving towns farther out.
Earth's city lights. The brightest areas of the world are the most urbanized, but not necessarily the most populated.
They also advice on using more efficient ways to illuminate places such as parking lots or city streets, saying dim, closely spaced lights, for example, tend to provide better visibility than bright lights that are more spread out.
"The world has experienced widespread 'loss of the night, ' with half of Europe and a quarter of North America experiencing substantially modified light-dark cycles", the researchers explained. "The issue is that light has been introduced in places, times and intensities at which it does not naturally occur and for many organisms, there is no chance to adapt to this new stressor". It's also a problem for nocturnal animals, plants, and microorganisms. It can affect plants and even microbes and could already be harming vital interactions between species, such as the pollination of plants and spreading of seeds by key nocturnal creatures.
Seeing the big picture from above, he added, "completely changed how I use light at night". It damages humans' body clocks that heighten the risks of diabetes, depression, and cancer. There's also a lot more awareness of light pollution. The problem isn't recently the LED lights, which are far more effective on the grounds that they require far less power to give a similar measure of light, clarified lead creator Chris Kyba, a physicist at the German Research Center for Geosciences. "And you see things like the bridge in Montreal", Kyba said. The observed decrease in Western Australia is due to wildfires in 2012 that were visible from the space.
But even though Milan, for example, made the switch to LED lights and saw a drop in radiance over the 2012-2016 period, there were increases elsewhere in Italy. The research team looked at five years of data. This means the amount of outdoor lighting has been increasing over the last few years.
NELL GREENFIELDBOYCE, BYLINE: Light pollution can keep people from seeing the stars. A growth in a region's gross domestic product of 13 per cent over the course of the observation period was reflected in a almost matching 15 per cent increase in night lighting.
"Instead, we see countries like the U.S. staying the same and the United Kingdom and Germany becoming increasingly bright", Mr Kyba told BBC News.
And nature is paying a price.
A study published in October found that artificial lighting near waterways draws insects towards the source of the light. Another study this year found an equally direct cause and effect between increased lighting over beach areas and a dramatic decline in sea turtle populations, as hatchlings are lured away from the water and toward the light, where they are snapped up by predators. It might affect wildlife like migrating birds.