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Monday, July 30, 2012

Street lighting affects invertebrates

Nowadays, much of the world is lit up twenty-four hours a day. This has consequences for invertebrates. We’ve all seen moths and other insects buzzing around streetlights, but the effects of artificial lighting extends much deeper. According to Thomas Davies, Jonathan Bennie and Kevin Gaston of the University of Exeter, even ground-dwelling invertebrates are affected.

The researchers set pitfall traps in the grass either directly under streetlights or midway between them (the darkest area of the street). Occupants of the traps were collected thirty minutes before sunrise and before sunset so that both diurnal and nocturnal creatures were represented.

More organisms were collected under streetlights than between them. Interestingly, the pitfall traps under streetlights yielded significantly more carnivores and scavengers than pitfall traps between lights. This was true for both daytime and nighttime sampling. In other words, it wasn’t just that some creatures were attracted to the streetlights while they were turned on. Different communities of invertebrates were living near streetlights twenty-four hours a day.

Clearly, the communities of organisms found along the roadside are altered by artificial lighting. What’s not clear is how big an effect this has on the entire ecosystem. The authors suggest that further efforts be made to understand the impact of streetlights on the invertebrate world.