Back in 1807, London became the first city on the planet to have a street illuminated by gaslight lamps. To the city's residents, it must have seemed like a wondrous thing to have evening turned into a simulated version of daytime.
But a little more than two centuries later, artificial lighting has spread across so much of the planet that the darkness of night is steadily vanishing. Today, 80 percent of the world's population now lives in places where the sky glows at night from lights on streets and buildings. Artificial light has become another form of pollution — one that scientists say poses threats both to the natural environment and to human health.
The extent of light pollution is evidenced by a November 2017 study in the journal Science Advances, in which researchers used measurements taken by satellites to study the artificial brightness of Earth's surface during nighttime. They found that between 2012 and 2016, the outdoor area that was artificially lit grew at a rate of 2.2 percent per year. As more spaces are being illuminated, they've become brighter as well, with the radiance of those areas increasing at an annual rate of 1.8 percent.
As this summary of the findings in USA Today explains, the researchers found nighttime brightness stayed the same in the U.S. and 38 other countries during the time period studied, while it increased in 79 countries — mostly in fast-developing areas in Asia, Africa and South America. Only 16 nations — including Syria, whose cities have been devastated by a brutal civil war — saw decreases in light. And artificial lighting seems to be growing the fastest in areas that didn't have a lot of it until recently.
But those increases are just part of the story. Christopher Kyba, a scientist at the GFZ German Research Centre for Geosciences and the study's corresponding author, says in an email that the increasing transition to high-efficiency LEDs for outdoor lighting, which have been touted as a way to reduce our dependence upon fossil fuels and slow climate change, may not be saving as much electricity as envisioned.
"Despite great success with reducing energy for lighting in specific projects — e.g., LED transitions in individual cities — cheaper light seems to be leading to increased use," Kyba explains. "That means that LEDs overall aren't reducing total energy consumption for outdoor lighting anywhere near as much as it would appear."
Worse yet, there's growing evidence that our excess illumination is having harmful effects on people. In 2016, the American Medical Association issued a warning that the conversion to high-intensity LED streetlights — which emit a large amount of blue light that increases glare — actually made it more difficult for drivers to see at night. The AMA added that the wavelengths at which the lights operate suppress melatonin, a hormone that helps us to sleep.
"It is estimated that white LED lamps have five times greater impact on circadian sleep rhythms than conventional street lamps," the AMA noted. Research indicates that such disruption may be a significant factor in obesity and other ailments.
And it's not just humans who are being affected.