Bright lights from cities and roads can confuse animals such as birds and turtles. Now a new study suggests that artificial “sky glow” — produced when that light bounces off the atmosphere back to Earth — also could throw wildlife cycles out of whack.

Much of the outcry against artificial sky glow has come from astronomers because it washes out the stars. But many species also depend on sky brightness to set their lunar clock. For example, sky glow can affect how long animals forage for food or when they mate.

The researchers studied sky brightness at night in Plymouth, UK and in nearby rural locations for 10 months. In the countryside, changes in sky glow followed the natural cycles of the moon. “By contrast, natural rhythms of lunar sky brightness were not evident in observations recorded from the sky over Plymouth city centre,” the authors write in Scientific Reports.

On average, urban organisms experience more hours per night in which the sky is as bright as it would be with a full moon, the team says. Nocturnal species could increase their time hunting for food, and their prey might spend more time on the run. — Roberta Kwok | 2 May 2013

Source: Davies, T.W. et al. 2013. Artificial light alters natural regimes of night-time sky brightness. Scientific Reports doi: 10.1038/srep01722.

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