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. One of Kyba’s images show the change in the amount of nighttime lighting from 2012 to 2016.
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.
These observations probably understate the true increase in lit areas and light intensity because the satellites used in the study are not sensitive to blue light wavelengths emitted by LED lights.
The trend shows no sign of relenting.
“In the near term, it appears that artificial light emission into the environment will continue to increase, further eroding Earth’s remaining land area that experiences natural day-night light cycles,” the paper concludes.