THE IMPACTS OF LIGHT POLLUTION
Like many others, I’ve recently started learning to drive, just as the UK slips into winter. As a result, I’ve become all too familiar with the dazzling glare of full-beam headlights. I’m sure many of you can relate, whether you’re driving, cycling, or walking along a dimly lit road, your eyes adjusted to the darkness, only for your retina to be scorched by a sudden burst of light. These bright flashes don’t just disrupt our vision, they can disorient and blind us, turning a brief distraction into a real danger1. Yet, this modern challenge isn’t just a problem for humans.
Light pollution is a well-known issue – who doesn’t miss the lost beauty of a clear night sky, now dulled by the orange glow that blankets our towns and cities? But its impact extends far beyond aesthetics, it disrupts the natural behaviour and evolutionary adaptations of many light-dependent species. Baby sea turtles, for instance, are drawn to the glow of streetlights instead of the moon as they instinctively search for the sea. Nocturnal animals like owls and badgers, which rely on natural light cues to determine when it’s safe to hunt, become disoriented. While migratory birds, guided by the stars, are thrown off course by artificial lights.
Yet, light pollution comes in many forms, and one of which is only now beginning to gain recognition: vehicle headlight pollution, also known as pulsed artificial light at night. Unlike the more continuous and often lower intensity general artificial light pollution, this type of light pollution is unpredictable, intense, and capable of shooting into previously dark spaces.
THE EXPERIMENT: MOTHS AND PULSED LIGHT
A recent study on the impact of vehicle headlights on insects has shed some light on the situation by exploring the response of a common nocturnal insect: the moth. To begin their experiment the Cornwall-based research team hand caught 428 moths in a butterfly net. These moths were identified down to species level (revealing 64 different species) and placed into completely dark pots to allow them to ‘dark-adapt’ before the experiment began.
The experiment was conducted in the same location that the moths were caught in and involved exposing each moth to a light source simulating a car headlight for 10 seconds. The responses were categorised into five different behaviours: erratic flight (fast random movements), flight-to-light (flying into the light source), positive geotaxis (downward flight normally to hide in low vegetation), negative geotaxis (upward flight normally followed by a return to flight activity seen before light exposure), and no response (a moth just sitting in the pot).
The researchers also explored the effects of different types of light by exposing the moths to either ‘cool’ or ‘warm light.’ Essentially using those white bright LED lights seen in newer cars and supermarket ceilings versus the older styler calmer more orangey lights often used for suburban streetlights.
Middle image taken by author of the paper Madeleine Fabusova, images left and right taken from Canva
KEY FINDINGS: THE IMPACT OF PULSED LIGHT ON MOTHS
So, with all this mothy experimentation, what did our intrepid researchers find?
The study revealed that exposing moths to pulses of light significantly alters their behaviour, with one statistic summarising this well; when released in the dark 86% flew upwards (probably to escape danger) but after a pulse of light only 37% flew upwards. This shows that moths exposed to cool light pulses display significantly more frequent and intense instances of erratic flight and flight-to-light behaviours compared to those exposed to warm light.
At first glance, this might not seem alarming, after all, moths are known for their flighty nature. However, panicked flight like this can have serious consequences. If the light originates from a vehicle, erratic movement increases the risk of moths colliding with it, resulting in a tiny hit-and-run. Additionally, this sudden, chaotic movement leaves moths vulnerable to predators and drains their energy reserves, which are critical for survival.
THE BIGGER PICTURE
But this isn’t just about moths- it’s a problem for us too. Moths are vital pollinators, especially for nocturnal plants and crops like clover and alfalfa, which are crucial for both biodiversity and agriculture2. Without moths, these plants would struggle to reproduce, disrupting entire ecosystems and reducing crop yields.
On a slightly brighter note, however, these most harmful behavioural changes can be addressed relatively easily on our side. As those moths exposed to warmer pulsed lights didn’t have nearly as bad reactions the researchers suggest stopping the increased adoption of bright cool car headlights and instead returning to the warmer headlights of days gone by.
Light pollution is a significant problem that requires large-scale initiatives and government action, but that doesn’t mean individuals are powerless. There are steps you can take at home to help moths and other nocturnal creatures.
HOW TO FIND ANOTHER WAY
Moths are facing steep declines, with 31% of UK species having disappeared in recent decades. However, by creating moth-friendly environments in your garden, you can provide a safe haven for these vital pollinators. The Butterfly Conservation Trust offers excellent advice on how to support moth populations. Some key tips include planting night-scented flowers that attract moths, reducing the amount of hard, barren surfaces like concrete and gravel, and allowing your garden to remain a little wild with untidy corners and native plants.
Additionally, you can help by reducing light pollution in your own home. Installing motion-sensor lights, using lower-wattage bulbs, and directing outdoor lighting downward rather than outward can all minimise light spills into the environment. Simple changes like these will not only benefit moths but can also support other nocturnal species such as bats, owls, and hedgehogs, which rely on darkness to hunt and navigate.
While these actions might seem small, when multiplied across communities, they can make a real difference in protecting biodiversity and reversing the effects of light pollution.
Article written by Joe Walker
Primary Paper
- Fabusova, M., Gaston, K.J. and Troscianko, J. (2024) ‘Pulsed artificial light at night alters moth flight behaviour’, Biology Letters, 20(11). doi:10.1098/rsbl.2024.0403.
Other references
- Dubey, A. et al. (2021) ‘Adaptive headlight system for reducing the dazzling effect to prevent road accident’, 2021 International Conference on Computing, Communication and Green Engineering (CCGE), pp. 1–6. doi:10.1109/ccge50943.2021.9776464.
- Davies, T.W. et al. (2013) ‘Artificial light alters natural regimes of night-time Sky Brightness’, Scientific Reports, 3(1). doi:10.1038/srep01722.
- Dar, A. A. & Jamal, K. (2021). The decline of moths globally: A review of possible causes. Munis Entomology & Zoology, 16 (1): 317-326]
