Should We Turn Off the Lights?

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Streetlights and other forms of artificial lighting may affect all ecosystem members, from bugs to humans.
Kevin Murphy

THE GIST

- Artificial lighting, particularly outdoor streetlights, impacts the composition of insect communities.

- Predatory insects and those that scavenge, such as ants and woodlice, appear to gravitate toward streetlights.

- The findings add to the growing concern over "light pollution" and its impact on species, including humans.

Street lighting is changing bug communities and that is affecting everything from the songs birds sing to the makeup of people.

A new study found that scavenger and predator insects both collect near the lights. It also shows for the first time that their composition is affected by the lighting. The study is published in the latest Biology Letters.

In fact, streetlights and other forms of artificial lighting may affect all ecosystem members, from bugs to humans.

"The range of effects of light pollution are really very diverse," lead author Thomas Davies told Discovery News. "They can affect reproductive successes in sea turtles, the timings of bird songs and even the physiology of humans."

He and his colleagues believe that "we are facing an insect biodiversity crisis," which merits our attention because "insects provide crucial services to humans, such as pollination and decomposition to organic matter."

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Davies is a postdoctoral research fellow at the University of Exeter's Environment and Sustainability Institute. He and colleagues Jonathan Bennie and Kevin Gaston deployed several insect traps on grassy vegetation under and between streetlights in Helston, Cornwall, UK.

A total of 1194 ground-dwelling invertebrates representing 60 different species were collected during the study. Individuals were far more abundant within close proximity to street lighting, no matter the time of day. Harvestmen, ants, ground beetles, woodlice, and amphipods (small crustaceans that include fleas) were most prevalent.

"These species are generally more mobile than others, making it more likely that they will encounter habitats that are lit to varying levels of brightness, providing them with the opportunity to make a selection of a preferred habitat," Davies explained.

"Why these species are found more in brightly lit areas is not clear," he continued. "Research on this subject is beginning to highlight that larger species with more sensitive eyes are more susceptible to street lighting, and in the case of this study, the largest bodied mobile invertebrates were predators and scavengers, such as ground beetles and harvestmen."

People with homes closer to street lights may be at greater risk for exposure to certain insects, and even the diseases some of them could harbor. For example, another recent study showed that Triatoma dimidiate, an insect that can carry Chagas disease (an inflammatory, infectious illness), infested houses that were in closer proximity to street lighting, Davies said.

The problems associated with lighting are predicted to continue, given that recent estimates suggest that artificial lighting is increasing globally at a rate of 6 percent per year.

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"We should be concerned about any activity which affects invertebrate communities, but we should also be concerned about the affects of street lighting on other communities as well," Davies said, adding that switching lights off during periods of low usage, dimming lights, and reducing overall artificial light in environments are all possible solutions.

John Hopkins, principal adviser for Natural England, agrees with the study's conclusions and sees it "as a significant piece of research relevant to a developing aspect of public policy." Hopkins explained that the recently published "National Planning Policy Framework for England" requires that local authorities take account the impact of artificial lighting on biodiversity when making planning decisions.

John Hopkins, principal adviser for Natural England, agrees with the study's conclusions and sees it "as a significant piece of research relevant to a developing aspect of public policy." Hopkins explained that the recently published "National Planning Policy Framework for England" requires that local authorities take account the impact of artificial lighting on biodiversity when making planning decisions.

"So far, much of the research has shown that artificial light changes the behavior of individual species," Hopkins told Discovery News. "These effects are very diverse and range, for example, from changes to mate locating success, migration and predation behaviors, among others."

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