‘Earth’s night is getting brighter’
Study reveals rapid growth in artificial light
We are losing the night.
The distinction between day and night is disappearing in the most heavily populated regions of the Earth, a rapid shift with profound consequences for human health and the environment, according to a paper published Wednesday in the journal Science Advances.
“We’re losing more and more of the night on a planetary scale,” journal editor Kip Hodges said in a teleconference on the paper’s findings.
From 2012 to 2016, the artificially lit area of the Earth’s surface grew by 2.2 per cent per year, according to the study led by Christopher Kyba of the German Research Centre for Geosciences. Kyba and his team analyzed high-resolution satellite imagery to measure the extent of artificial outdoor lighting at night. The study also found that areas of the planet already lit grew even brighter, increasing in luminosity at a rate of 2.2 per cent per year.
“Earth’s night is getting brighter,” Kyba said.
Much of the increase is concentrated in the Middle East and Asia. The observed “decrease” in western Australia is actually due to wildfires in 2012 that were visible from space.
The trend shows no sign of relenting.
“In the near term, it appears that artificial light emission into the environment will continue to increase, f urther eroding Earth’s remaining land area that experiences natural daynight light cycles,” the paper concludes.
The past few years have seen the rapid adoption of highly efficient LED lights for indoor and outdoor use. LEDs use just a fraction of the electricity of traditional incandescent lights and last longer.
But the rapid increase in nighttime lighting observed by Kyba and his colleagues suggests that people are responding to cheaper lighting options by simply adding more light.
“While we know that LEDs save energy in specific projects,” Kyba said at the teleconference, “when we look at our data and we look at the national and the global level, it indicates that these savings are being offset by either new or brighter lights in other places.”
People are particularly attuned to the short- wavelength blue light emitted by most LEDs, but it’s been implicated in sleep deficiencies and other human health problems.
Bright nighttime lighting only started becoming widespread about 100 years ago, meaning we have little idea how humans or other species adapt to it at an evolutionary level. “Artificial light at night is a very new stressor,” said Franz Holker, one of the paper’s authors. “The problem 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.”