Light Pollution Has Worsened Worldwide
These two satellite images of Calgary, Canada, were taken from the International Space Station in 2010 (left) and 2015 (right). Many areas on the outskirts are newly lit compared to 2010, and many neighborhoods have switched from orange sodium lamps to white LED lamps

The world’s nights are getting alarmingly bright. A German-led term reported that light pollution is threatening darkness almost everywhere. The transition from sodium lights to LEDs, the so-called “lighting revolution”, was supposed to reduce energy consumption and bring back starry skies, but new satellite data indicate it’s not working out that way. Artificially bright night skies can create a whole host of health concerns for wildlife and humans.

“Honestly, I had thought, assumed, and hoped that with LEDs we were turning the corner,” says Christopher Kyba (German Research Center for Geosciences). Kyba researches the spread of artificial lights and how it affects our nights, and as a former member of the board of directors of the International Dark Sky Association, he also advocates the use of improved lighting practices.

Satellite observations during five Octobers show Earth’s artificially lit outdoor area grew by 2 percent a year from 2012 to 2016. So did nighttime brightness. The observations indicate stable levels of night light in the United States, Netherlands, Spain and Italy, for example. When broken down by country, the results show that in many developing nations, the increases in artificial lighting are well above the global average, as more people gain access to electricity and outdoor lighting equipment for highways, city centers and residential areas.

The findings shatter the long-held notion that more energy efficient lighting would decrease usage on the global — or at least a national — scale. “It is quite disappointing.” The biological impact from surging artificial light is also significant, according to the researchers. People’s sleep can be marred, which in turn can affect their health. The migration and reproduction of birds, fish, amphibians, insects and bats can be disrupted. Plants can have abnormally extended growing periods. And forget about seeing stars or the Milky Way, if the trend continues. About the only places with dramatic declines in night light were in areas of conflict like Syria and Yemen, the researchers found.

The data that the study was based on did not include all wavelengths of light that are visible to the human eye. Specifically, the data does not include “blue” light. Traditional light bulbs (like sodium lamps and most halogen lights) emit mainly in yellow, orange and red wavelengths of light, but many LED light bulbs emit high levels of blue light. As a result, the total increase in light pollution visible to the human eye is actually higher than what’s reported in the paper, the researchers said.

While LEDs can in some cases help to reduce light pollution, the increased use of LEDs also leads to something called the “rebound effect,” Kyba said. As LED lights become more efficient and cheaper, people tend to use them more, rather than holding on to the energy savings.

“The biological world is organized, to a large extent, by natural cycles of variation in light,” Franz Hölker, a scientist at the Leibniz-Institute of Freshwater Ecology and Inland Fisheries and a co-author on the study, said during the teleconference. “And this variation triggers a wide range of processes, from gene expression to ecosystem functions.”

Artificial light, and the subsequent loss of nighttime darkness, is “a very new stressor” that many organisms have not had time to adapt to. “[Light pollution] threatens biodiversity through changed night habits, such as reproduction or migration patterns, of many different species: insects, amphibians, fish, birds, bats and other animals,” Hölker said. “And it can even disrupt plants by causing … late leaf loss and extended growing periods, which could of course impact the composition of the floral community.”

The International Dark-Sky Association , based in Tucson, Arizona, has been highlighting the hazards of artificial night light for decades. “We hope that the results further sound the alarm about the many unintended consequences of the unchecked use of artificial light at night,” Director J. Scott Feierabend said.