Caring for the environment  |  14 Jan 2019

A new study is putting the spotlight on insects living in Christchurch’s red zone.

Michelle Greenwood, a National Institute of Water and Atmospheric Research (NIWA) Freshwater Ecologist, is investigating how a change in the colour spectrum of street lights could be affecting the tiny insects that live in and near freshwater.

Michelle Greenwood is studying how LED lighting affects freshwater insects.

NIWA scientist Michelle Greenwood is studying how LED lighting might be affecting freshwater insects. Photo: NIWA

Street lights around the country are being converted from mostly high pressure sodium lights, which emit a yellowish light, to more cost-effective, low energy, light-emitting diodes (LED) which emit a bluer light.

Christchurch City Council is in the process of changing 38,000 local street lights to LED lamps. It estimates the move will save $32 million in operational and maintenance costs over the 20-year lifespan of the LEDs. 

Dr Greenwood says insects are indicators of healthy urban waterways but little is known about how the switch to LEDs is affecting them. If their behaviour is being altered, that could have a flow-on effect for other plants and animals.

“A lot of insects are more sensitive to the blue end of the colour spectrum which means they could be more attracted to the new street lights,” she says.

“If they are attracted to light, they are attracted away from normal activities. They might just fly around and around the light until they’re exhausted and die.”

Dr Greenwood’s research, which is being supported by Christchurch City Council, will look at how changing the colour tones and brightness of street lights near waterways affects the local ecology.

She and her team will observe insects, such as caddisflies, flies and midges, emerging from the Avon River within the red zone, as well as other urban waterways, to see how they behave around the lights.

“The Avon is tidal so it may mean that there are different responses at different locations so we are hoping a pilot study this summer will guide further trials later in the project.

“The really great thing about this is that by using areas in the Red Zone we can carry out our experiments in a real-life, operational scale setting. It’s an area where the houses have been removed but the street lighting infrastructure remains intact.”

The first test will be a pilot study where sheets of clear perspex coated in a sticky substance are mounted next to the light to catch insects. These will be replaced daily.

The pilot is the start of a three-year research project funded through the Ministry of Business, Innovation and Employment’s Endeavour Fund and with support from Scion, the University of Canterbury, the Council, New Zealand Transport Agency and Land Information New Zealand.