1800 K LEDs Could Help Protect Insects From Artificial Light at Night

Artificial light at night threatens insects

Around 40 percent of the world’s insect species could face extinction over the next few decades, largely as a result of habitat destruction, pollution, pathogens, introduced species and climate change.

Artificial light at night is also among these pressures, as it interferes with insects’ natural behaviours.

Over 60 percent of invertebrates are active at night, meaning artificial lighting in their habitats affects them during the hours when they are most active.

This is a global issue. Bright sodium and LED lamps give our surroundings constant illumination, chiefly in the interests of human safety, beside roads, footpaths and railways, through shopping areas, and almost everywhere else in the built environment.

However, a team led by researchers from Germany’s Leibniz Institute for the Analysis of Biodiversity Change says there may be a straightforward means of making conditions safer for insects without undermining people’s needs.

"It is estimated that around one billion insects are affected every summer night in Germany, often dying from artificial light sources," the researchers explain.

Insects may react to artificial lighting in several different ways.

Moths, naturally, are famous for their attraction to lamps, drawn towards the light with little ability to resist it.

Estimates indicate that a third of insects lured to fixed artificial lights, including moths, die before morning, either through exhaustion or because they are eaten by predators.

By contrast, some insects, including New Zealand’s weta, are known to steer clear of artificial light at night. Permanently lit places, along with every resource they contain, are therefore unavailable to these species as habitat.

"The global increase in light pollution and the brightening of the night sky in recent decades therefore pose major threats to insect diversity and are of growing importance for national and international nature conservation," the Leibniz Institute team says.

1800 K LEDs and insect attraction

The team found that where artificial lights must remain on throughout the night, the type of light used can substantially affect insects.

They set up their study across six railway platforms, where lights commonly operate all night despite the locations being within Westhavelland Nature Park, a designated dark sky reserve.

Prior to the experiment, every station was illuminated by warm-white 2000 Kelvin (K) high-pressure sodium (HPS) lamps.

Operating these lamps costs more than using LEDs. This is why the warm glow of sodium lighting has been replaced in many parts of the world by more energy-efficient alternatives.

To assess how different night-lighting types affected insects, the researchers left two neighbouring HPS lamps in place. They replaced the bulbs in two further lamp pairs: one pair received cool-white 4000 K LEDs, while the other was fitted with amber 1800 K LEDs.

They also observed two additional nearby control locations without installed lighting, allowing them to establish normal insect behaviour beyond illuminated areas.

Railway platform study in Westhavelland Dark Sky Reserve

To determine the types, abundance and volume of insects active at each location, the team collected trap samples from July to October 2023 and from April to June 2024. They examined the samples with AI-based image analysis and DNA metabarcoding.

"Our results indicate that insect attraction by outdoor lighting and possible population declines can be reduced through optimized light sources," they report.

"Amber LED lights (1800 K) with low blue light content attracted significantly fewer individuals and species, as well as threatened and legally protected taxa than conventional cool white LEDs (4000 K) and high-pressure sodium lights (2000 K)."

"This reduced attraction is primarily driven by the narrow spectral composition and the absence of short-wavelength blue light in the 1800 K LED."

Following these results, every railway platform light in Westhavelland Dark Sky Reserve has already been changed to 1800 K LEDs.

Although the research took place on railway platforms, its potential applications extend much further.

Comparable results may be possible with streetlights, garden lighting, lights along footpaths and those in parks, helping to safeguard insect biodiversity.

Limits of the artificial light findings

Insects do not all respond to light in identical ways, so the approach may not benefit every species to the same extent. The research considered only nocturnal flying arthropods, leaving uncertainty over how these trials may have affected ground-dwelling species, for example.

Moreover, although being attracted to lights can be fatal for many insects, the authors point out that their measured outcome - reduced observed attraction to lighting - does not necessarily show that the 1800 K LED resolves every possible ecological effect of artificial light.

"Further studies at the species level are essential to improve understanding of taxon-specific responses to artificial light at night, particularly for threatened or legally protected species," they note.

Even so, it provides a useful starting point for making our world more insect-friendly, potentially with nothing more than a visit to the hardware shop.

The research appeared in Biological Conservation.

This article was fact-checked by Michael Irving and edited by Michael Irving. Although we take pride in our process, we are only human. If you notice an error, please tell us.