A new UK-based study on the effects of artificial light on local insect populations found that light pollution from street lamps disrupts insect behavior, leading to an overall loss of insects.
Previous studies have broadly explored the impact of light pollution on humans, plants, and animals alike — and the results were not good. However, the present study published on Wednesday in Science Advancesis the strongest evidence that scientists have yet on how exactly light pollution adversely impacts local insect populations and, in turn, the food chain that depends on them, according to researchers.
“We found that street lighting strongly reduced moth caterpillar abundance compared with unlit sites… and affected caterpillar development,” the study stated.
The study’s results apply for a localized scale and cannot be used to determine whether national-level populations are declining due to light pollution. However, it adds further weight to existing research on how light pollution affects ecosystems and biodiversity hotspots and highlights the need to shift to alternatives in artificial lighting that would tone down these effects.
The effects on insect populations are wide-ranging: from disrupting reproduction, eating patterns, predation, and general activity, artificial lights at night (ALAN) reduce the abundance of wild insects by a significant degree.
More specifically, artificial light affects how moths lay their eggs and puts them at a higher risk of being spotted by predators. It also affects caterpillar feeding behavior, which subsequently leads to declines in their population too. Light pollution from ALAN thus joins a host of factors, such as climate change and deforestation, as one of the determinants of insect population decline.
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While previous studies examined the effects of lighting on bats and other vertebrates, this study focused on their prey — creatures lower down in the food chain — thereby complementing previous studies. Therefore, the study is concerning because it hints at an alarming loss of insects compounded by artificial light, which will have far-reaching consequences for all the wildlife and ecosystems that depend on them.
Moreover, white light-emitting diodes (LEDs) were found to have the worst impact on local insects and ecosystem processes like pollination and predation. The researchers thus call for shifting away from white LEDs or employing processes such as motion sensors to dim the lights and changing colors and filters to avoid the negative impacts. However, societies have been observed to be leaning further into installing LEDs as street lamps rather than away. In India, for instance, several projects have announced mass installations of LED lights. Andhra Pradesh recently rolled out a flagship program in which it announced that over 4 lakh LED lights would be installed across villages. If the findings of the study are anything to go by, local insect ecosystems will suffer considerable consequences — which will, in turn, affect the wildlife that depends on them and, ultimately, could perhaps even upset agricultural balances.
“If insects are in trouble – as we believe they are and have evidence to support that – perhaps we should be doing all we can to reduce these negative influences,” lead researcher of the study Douglas Boyes of the charity Butterfly Conservation, told the BBC.
