Street Lights Affect Delicate Ecosystems
May 24, 2012

Street Lights Affect Delicate Ecosystems

Brett Smith for

Civilization has long been derided for intruding upon the habitats of wild animals, and even man´s smaller neighbors have been affected by the wheels of progress.

Another measure of this impact can be seen in how street lighting is having a transformative effect on communities of insects and other invertebrates living near them, according to researchers at the University of Exeter in the United Kingdom.

A report published in Biology Letters showed that invertebrate predators and scavengers were more likely to be found near the lights, even during the day.

“Our study shows that light pollution could be having a dramatic effect on wildlife in our towns and cities,” said lead author Tom Davies of the Environment and Sustainability Institute at the University of Exeter.

“We need to be aware of how the increase in artificial lighting is impacting on the delicate ecosystems on which we all rely. Our research shows, for the first time, the changes that light pollution is making to entire communities of invertebrates. 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."

During the course of their study, the team set 28 traps in Helston, the southernmost British population center of about 10,000. The traps were placed just under and between street lights that were 35 meters apart.

Over the course of three nights, the traps gathered 1,194 individual specimens covering 60 species. The researchers found that the traps under the lights gathered larger numbers over the course of the experiment than those not placed directly under lights. They also found the street light traps to contain more scavenging and predatory species such as ants, beetles and harvestmen, or “daddy longlegs.”

Researchers also noted that the plants around the traps were all very similar and appeared unaffected by the lights, having no effect on the study´s results.

Insects being drawn to the streetlights are exhibiting the phenomenon known as phototaxis. The most popular example of phototaxis is the moth which can be seen fluttering about a light source on a summer´s night. Moths are considered positively phototactic, while cockroaches, which scurry from the light, are considered negatively phototactic.

Some scientists suggest that moths use the moon as a primary reference point and have the ability to adjust their flight paths as the Earth's rotation causes the moon to move across the sky. However, there is no current evidence to support this theory.

Davies stressed his team´s study was small and preliminary, but that it invited future study into much wider-ranging environmental effects, especially on how these findings impact the larger food web.

"Invertebrates in the UK at least are undergoing a bit of a biodiversity crisis and have been for some time now, and they're very important for a number of ecosystem services such as pollination and the breakdown of organic matter," he explained to BBC's Jason Palmer.

"So the impact of street lights on invertebrate communities could be very, very important, could be problematic, but we simply don't know at the moment - we need to do the research."