Bringing LED lights to the remote Amazon revealed nuanced threats to insect biodiversity

April 4, 2021

Some kinds of light are more dangerous to insects. (Unsplash/Sergei Zolkin)

Researchers are calling for fewer outdoor white LED lights, after determining that reducing the blue spectrum of artificial light can lessen the attraction of insects to nighttime light sources and minimize the dangers posed to insects.

The study, published March 16 in Insect Conservation and Diversity, found that amber light attracts far fewer insects, suggesting that reducing this threat to insects can be done without sacrificing the numerous benefits of artificial light at night, also known as ALAN.

"Virtually every type of development has artificial light at night, so these recommendations that have come out of this project can be applied in really any sector that's using ALAN," first author Jessica Deichmann said in an interview with The Academic Times. Deichmann is a tropical ecologist with the Smithsonian Institution, where she works on projects exploring the impact of infrastructure development on biodiversity.

Artificial light is ubiquitous in developed societies, but it poses great harm to the animals in that environment. At night, it interferes with insects' ability to navigate, hunt and mate. It also makes them more vulnerable to predators. Many insects simply starve because they cannot escape the light long enough to feed.

The effects of introducing artificial light are especially noticeable in undeveloped areas that have never used it before.

"So when you take the light and you illuminate an area for the first time you're basically, from the perspective of an insect, bringing a giant moon down to earth and putting it right in their faces," Deichmann said. "And that is a problem because they respond more strongly to that stronger stimulus of light, and they cannot get away from it. So when they are drawn to it, they're stuck there in a death spiral."

Blue spectrum light in particular has gained a lot of attention in recent years because while it is the most energy-efficient mode of light, it is also known to have negative effects on human health, including disruption of sleep. Deichmann and her colleagues were interested in evaluating whether the intensity of blue spectrum light made this light more harmful for insects.

Amber LED light is frequently used in photosensitive processes, such as the production of semiconductors and in biomedical research. However, it is significantly less bright than its blue spectrum counterparts, which has made it less desirable for outdoor lighting. 

Research has already suggested that amber LED lights may have less impact on wildlife, but their specific effects on insects have not been fully investigated.

To fill this gap, the researchers set their sights on the Peruvian Amazon, a region almost completely unexposed to artificial illumination. They evaluated three different types of artificial light with varying levels of blue spectrum. Lighting their various test sites in a single night proved a massive logistical effort due to difficulties importing and transporting bulky lighting equipment to these remote regions.

However, this effort paid off. The results were clear.

White LED light, which contains the most blue spectrum, attracted 1.6 times as many insects as yellow light and 1.8 times as many as amber light. Overall, the white light attracted 15.3 times as many insects as the control trap without light.

Notable exceptions were click beetles and fungus gnats, two insect families that contain bioluminescent species in the Amazon. These families were most attracted to the amber light. However, the vast majority of pollinators and vectors for disease were more attracted to the white light.

Considering these findings, the researchers recommend that both current and new developments adopt filtered, amber light in outdoor locations at night to minimize the impact on insects.

"What we're really hoping is that there'll be uptake from this by the private sector that's building new infrastructure and conducting development in remote places," Deichmann said. "It can also be taken up by new communities or existing communities or communities that are becoming recently or newly electrified. And then by the government and national regulations."

However, it is not all up to large governing bodies. Deichmann explained that even individuals can contribute by switching out their personal outdoor LED lighting for amber lights. These small actions can accumulate and they do not just benefit insects, but humans as well. Not only can mass insect mortality significantly damage ecosystem services that people depend on, Deichmann noted, it can also draw insects closer to where humans are.

"Those insects that transmit diseases are also attracted to light, but it doesn't seem like they're so attracted to light to the point of mortality," she said. "[If] I can't convince you that you should be saving insects, then think about yourself. These lighting lessons are important for human health, as well as insects."

The study, "Reducing the blue spectrum of artificial light at night minimises insect attraction in a tropical lowland forest," published March 16 in Insect Conservation and Diversity, was authored by Jessica L. Deichmann, Christian Ampudia Gatty, Juan Manuel Andía Navarro, Alfonso Alonso, Reynaldo Linares-Palomino, Smithsonian National Zoo and Conservation Biology Institute; and Travis Longcore, University of California, Los Angeles.

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