Will a whole generation grow up in perpetual twilight?

It’s becoming increasingly difficult to see stars in the night sky from any urban location—and it’s getting worse thanks to the spread of LED lighting, say scientists.

New research led by the University of Exeter shows that light pollution has increased by at least 49% over 25 years globally, a figure that accounts only for light visible by satellites.

However, the researchers suggest that the actual increase in light pollution could be up to 270% globally—and as much as 400% in some regions.

Light pollution from streetlights and homes can impact the natural environment—and probably account for the huge decline of insect populations. A world without insects is a world without humans.

The study, published today in the journal Remote Sensing, looked at light emissions from 1992 to 2017. It shows that the power of global satellite-observable light emissions increased from 1992 to 2017 by at least 49%.

“The global spread of artificial light is eroding the natural night-time environment,” said first author Dr Alejandro Sánchez de Miguel of the Environment and Sustainability Institute at the University Exeter. “This study provides clear evidence not only of how bad light pollution has become as a global problem, but also that it is continuing to get worse, and probably at a faster and faster rate.”

Why?

Light pollution: what is to blame?

Solid-state light-emitting diodes—LEDs—the same technology that supposedly saves local authorities money. “Contrary to popular belief, the installation of “broad white” LED streetlights, while potentially providing some energy savings, has increased light pollution and also the impacts on organisms such as moths,” said Dr Sánchez de Miguel.

LEDs emit blue light, which goes undetected by satellite sensors, but increases visible light that interrupts astronomical observations.

The researchers say that LEDs may have increased radiance in the visible spectrum as high as globally 270%, and up to 400% in specific regions.

Light pollution: where is it getting worse?

It’s a global problem, but the researchers found persistently increasing light pollution in Asia, South America, Oceania and Africa —as seen by satellites.

In Europe, detected light increased until around 2010 and then levelled off, while in North America it appears to be in decline.

Light pollution: why LEDs are masking the problem

However, that’s not the whole story. “To take the UK as an example, if you ignore the effect of the switch to LEDs—which has been extensive—you get the false impression that light pollution has recently declined,” said Dr Sánchez de Miguel. “However, correcting for this effect shows it has really increased, and potentially very markedly.”

“Over the past 25 years, the transition to solid-state LED lighting has been accompanied by rapid increases in light pollution globally,” said Ruskin Hartley, Executive Director of the International Dark-Sky Association. “Without concerted action to reverse this trend, the impact on the natural environment will accelerate, further exacerbating the biodiversity crisis, wasting energy, and meaning a whole generation will grow up in perpetual twilight.”

Wishing you clear skies and wide eyes.