Streetlights dimmed ahead of concerns LED bulbs harm insects

A mullein moth Caterpillar on a verbascum plant

The study found fewer moth caterpillars in areas with LED lights than in those with old-style sodium lights. - Credit: Rodney Womack

Council bosses say they had already taken action to dim some of Norfolk's streetlights, as a study found the LED type bulbs are more harmful to insects than traditional ones.

More than 20,000 of Norfolk's main road streetlights, including in Norwich, use LED technology and work to convert 15,000 more is under way.

New LED street lights in Beeston Regis. PHOTO: ANTONY KELLY

Thousands of street lights in Norfolk have been switched to LED. - Credit: Antony Kelly

But scientists have found whiter lights are having an impact on some insect populations.

Field studies by the UK Centre for Ecology and Hydrology, Newcastle University and Butterfly Conservation found the abundance of moth caterpillars in hedgerows under LED street lamps was 52pc lower than in nearby unlit areas.

That compared with a 41pc lower abundance in hedgerows lit by old-style sodium lighting.


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Meanwhile, in grass margins, the moth caterpillar numbers near LEDs were a third lower than in unlit areas, whereas sodium lights had little effect on abundance in this habitat.

Picture shows an elephant hawk mothPicture courtesy of Norfolk Wildlife TrustFor EDP News

An elephant hawk moth. - Credit: Norfolk Wildlife Trust

Scientists said LED lights could be modified by dimming or using filters to reduce the impact on insects.

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And county council bosses said some of the measures the report recommended had already been adopted before the report was published, including dimmed lights.

A county council spokesperson said: “We are aware of the report and are pleased to say that Norfolk County Council has already implemented many of the mitigation measures mentioned in the investigation.

"Across Norfolk we have implemented dimming of some of our street lighting during hours of the night where usage is low, and have also implemented part night lighting, ensuring some streetlights turn off completely for around five hours each night.

"While we do seek to minimise the wider implications of lighting on wildlife, highway safety must be at the forefront of our decision making: as such, in line with our current policy, the county council will not install any further street lighting unless there is a proven highway safety need.”

The council says for each street that is upgraded to LED lights the average percentage energy saving is more than 70pc, while cutting carbon emissions.

The county council's work on streetlights, carried out with partner Amey, won the authority a sustainability award in 2019.

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