Rebecca Boyle writes:

Light is the basis for all life, but it is more than just a source of energy. It is also a source of information, telling organisms when to sleep, hunt, hide, migrate, metabolize, and reproduce. Since the advent of incandescent light bulbs, humans have been interfering with those messages. And the interference is worsening with the spread of LEDs, which consume less electricity and so are often brighter and stay on longer and later than their predecessors.

Since 2012, when a satellite began taking detailed measurements, light emissions have been rising at a rate of 2.2 percent a year on average. Previous work showed that light emissions are growing by as much as 20 percent in some regions. This is faster than the average annual growth of the global economy, the global population, and emissions of carbon dioxide.

“Light is occurring at times, levels, and places where it should not be,” the researcher Franz Hölker told me over a twilight cup of coffee. “And now it is becoming more clear that it can impact whole populations and ecosystems.”

Hölker is tall and silver-haired, and speaks carefully yet emphatically. His blue eyes flash when he gets animated—which happens when he starts talking about moths’ response to light, or points out the omnidirectional downward glow of a streetlamp. A decade ago, he was one of the few scientists calling for more research on artificial light at night. Today he leads a program called the Loss of the Night Network, a multinational, transdisciplinary research group under the umbrella of the European Union. [Continue reading…]