The environmental cost of LED street lights

Light pollution could be ‘devastating’ for insect populations.

Devon County Council experimenting with dimming.

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A year ago, the Councty Council started installing LED street lamps – with the appropriate press statements:

New streetlighting contract will reduce carbon emissions – News centre

LED streetlight conversion ‘equivalent of taking 8,000 cars off the road’ – Devon Live

However, it is not all good news for the environment. 

A piece published today looks at the impact of LED street lights on insect populations:

Light Pollution’s Glare Threatens All Kinds of Wildlife

Global insect populations have declined by as much as 75 percent during the past 50 years, according to scientists, potentially leading to catastrophic impacts on wildlife, the environment and human health. Most studies point to habitat loss, climate change, industrial farming and pesticide use as the main factors driving the loss of insects, but a new study in the United Kingdom points to another cause: light pollution.

The ever-increasing glow of artificial light from street lights, especially LED lights, was found to have detrimental effects on the behavior of moths, resulting in a reduction in caterpillar numbers by half. And since birds and other wildlife rely on caterpillars as an important food source, the consequences of this decline could be devastating.

According to Douglas Boyes of the UK Centre for Ecology & Hydrology, street lights cause nocturnal moths to postpone laying their eggs while also making the insects more visible to predators such as bats. In addition, caterpillars that hatch near artificial light exhibit abnormal feeding behavior.

Light Pollution’s Glare Threatens All Kinds of Wildlife — ecoRI News

Street lighting has detrimental impacts on local insect populations

Although this has been known for some time:

The Devastating Role of Light Pollution in the ‘Insect Apocalypse’ | Smart News | Smithsonian Magazine

Four ways to curb light pollution, save bugs: Insects have experienced global declines. Flipping the switch can help — ScienceDaily

On top of that is the ’embedded carbon’ needed to produce new LED lights – as shown by a recent FOI request to the County Council:

Looking at it from a more environmental perspective, what is the environmental cost / carbon generated by producing 79,000 new lights, recycling or disposal of the 79,000 old lights, plus all the carbon emitted by contractors vehicles etc in the process of replacing all the lights across the region?

LED street lights – spend and process – Freedom of information

As it is a worry, as reported last week:

Writing to the council’s cabinet, Councillor Alistair Dewhirst (Liberal Democrat, Ipplepen & The Kerswells) said: “The energy efficiency of these lights is clearly a fact and is helping to improve our carbon efficiency in the council, but it would appear to be at the expense of our insects.” He asked what the council will be doing to “mitigate the harmful effects on our insect population.”

In a written response, Councillor Stuart Hughes (Conservative, Sidmouth), cabinet member for highways, said: “The rating of the new lamps is 3000K (kelvin), which is very similar to the sodium lamps they are replacing. Insects are generally attracted to lighting above 3,000K, therefore any possible effect on the insect population is argued to be neutral when the new lamps are run at 100 per cent brightness all night.

“However, in mitigation, the lighting will operate as part night lighting for the majority of areas and in addition dim to 75 and 50 per cent brightness later into the night.” Cllr Hughes added: “DCC is also extending its management software in new installations where possible, which will give much more control on future dimming. However, we will keep this under review as greater understanding of this topic develops.”

Carbon-reducing lights could be harmful to insects – East Devon Radio

As reported across the local media:

Devon street lights dimmed to boost insects after issue bugs councillor

Devon’s streetlights dimmed to help bugs – Radio Exe

All of this has a knock-on effect:

Effects of dimming light-emitting diode street lights on light-opportunistic and light-averse bats in suburban habitats

There are other ways to reduce the negative effects of LED lights:

One solution to improve conditions around LED streetlights is to include blue light filters. The resulting light would be yellow (just as in earlier lamps), and this light would be less harmful to nocturnal wildlife and people in general. However, using a filter would decrease the lamps efficiency and this fall in efficiency could potentially see sodium lamps take over.

Another method is to dim streetlights between certain hours or during low traffic, as Devon council will be experimenting with. According to the council, the replacement of the older lamps wills see carbon emissions reduced by 75%, but in light of the recent reports on impact with wildlife, Devon will dim their lights during late-night, where there is minimal traffic. Overall, replacing streetlights with LED variants helps to reduce the amount of CO2 produced via electricity production, and white LEDs have been shown to improve driving safety. However, authorities should also consider both the environmental and mental wellbeing of those who live in the vicinity of white LEDs.

LED Street Lights – Great for the climate, not so great for the environment

   
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