Christchurch street lights are helping insects thrive - NIWA

New NIWA research has found an overhaul of the street lights in Christchurch could be helping insects thrive.

The four-year study compared how insects react to older yellow streetlights and the new, blue LED's the city is changing to.

Researchers have been trying to figure out how different types of street lights impact the lives of insects.

"Looking at if we took older streetlight technologies like high-pressure sodium (HPS) that emit orange light, and compared how many insects were attracted to that kind of light compared to new LED streetlights," NIWA Freshwater Ecologist, Michelle Greenwood said.

Over four summers, the research team set up sticky traps to get a better idea of how many insects are attracted to different streetlights.

"The red circles are caddisflies that we’ve got, we’ve got quite a lot of midges and there’s probably some mayflies on there as well," Greenwood said.

Their findings were not what they expected.

"The conversion to LEDs actually we ended up with fewer insects being attracted to them, which was contrary to what we thought, we thought there would be more insects attracted to them because they emit more blue light," Greenwood said.

The old-style streetlights are less efficient but give off more light which the insects are attracted to. The new LED lights aren't as bright so the bugs don't buzz around as much as they used to. And that's good news for local ecosystems.

Streetlights distract insects from their usual night-time habits, which can have a knock-on effect for the whole food chain.

"You are taking them out by attracting them to lights and so they're not going to mate and go about their processes of laying eggs," Lincoln University entomologist Mike Bowie said.

And when bugs hang around street lights too often, predators catch on.

"We might end up getting the predators getting an advantage taking out too many of the moths, and in some cases you could cause an extinction of some of these species," Bowie said.

So while we think of streetlights as tools to help us get around at night, the types we have and how we use them could have far-reaching consequences for the animal kingdom too.