Street lights are a necessity in a 24-hour world. Most of us might go to sleep when night falls, but there are plenty of people who only really come alive at night. While street lights might provide the illusion of safety, we should remember that sometimes this unnatural light attracts unsavory characters, both human and otherwise.

Scientists at the University of Exeter recently discovered the proliferation of urban street lights is having a profound effect on the communities of insects and other invertebrates that live beneath them. Their report, published recently in Biology Letters, found that bug communities living near bright street lights were composed of a higher number of predatory and scavenging individuals, indicating that street lighting changes the environment at higher levels of biological organization than previously recognized.

To arrive at this conclusion, researchers set 28 traps for the bugs in Helston, a market town in West Cornwall, UK. Some of the traps were placed directly under street lights, while the rest were in dark regions midway between lights. The traps were left for three nights before the team collected them. According to ScienceDaily, they collected 1,194 individuals covering 60 species. As expected, more bugs were caught under the street lights than away from them. What the team didn’t anticipate was the high proportion of predatory and scavenging species, such as ground beetles and harvestmen (also known as daddy long legs), found near the lights at all hours of the day.

This concentration is troubling because invertebrate biodiversity in the UK has been dwindling for some time. A wide spectrum of insects are needed to keep vital processes, like pollination and the breakdown of organic matter, going strong. While the study is small, both in scope and sample size, the scientists say it indicates serious and previously unanticipated impacts of human development on the structure and function of ecosystems.

“Our research shows, for the first time, the changes that light pollution is making to entire communities of invertebrates,” said lead author Dr. Tom Davies of the University of Exeter’s Environment and Sustainability Institute. ”We now need to examine what impact this is having on other communities and how this may be affecting important ecosystem services and whether we should change the way we light urban spaces.”

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