Researchers say nocturnal light pollution is rising significantly worldwide, according to satellite imagery.
The Science Advances study showed that artificially lit surfaces grew by 2.2 percent per year, in size and brightness, from 2012 to 2016.
The study found that lighting changes varied by country, pointing to noticeable decreases in places such as war-ravaged Yemen and Syria. Developing countries have experienced the fastest growth in light pollution, the study detailed, since emissions are influenced by Gross Domestic Product.
For example, the United States and Spain remained the same, while most nations in South America, Africa and Asia grew.
"Earth's night is getting brighter. And I actually didn't expect it to be so uniformly true that so many countries would be getting brighter," GFZ German Research Centre for Geoscience's Christopher Kyba explained at a news conference.
The team had analyzed five years of images from the Suomi NPP satellite before concluding the increases in light pollution. The findings are based on data from the Visible Infrared Imaging Radiometer (VIIRS), a satellite designed especially to monitor nightlights.
Since the VIIRS cannot "see" light at wavelengths below 500 nanometers or "blue" light – which humans can see – researchers have theorized that the magnitude of light pollution is likely being understated.
The study is among the first to examine the effects of lighting as seen from space.
"This is concerning, of course," said Frank Holker of the Leibniz Institute of Freshwater Ecology and Inland Fisheries.
"We are convinced that artificial light is an environmental pollutant with ecological and evolutionary implications for many organisms from bacteria to mammals, including us humans and may reshape entire social-ecological systems."
Researchers were quick to inform that "loss of night" on a planetary scale could cause negative effects on human health, ecosystems and even astronomical research.
"Today's announcement validates the message IDA has communicated for years," Arizona-based International Dark-Sky Association (IDA) Executive Director Scott Feierabend said.
Feierabend pointed out repercussions including harm to wildlife, human wellbeing and compromised public safety. "We hope that the results further sound the alarm about the many unintended consequences of the unchecked use of artificial light at night."
IDA has campaigned for the last 30 years to bring attention to the known and suspected hazards associated with the use of artificial light at night.