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Like moths to a flame

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Matt Walker Matt Walker | 10:01 UK time, Thursday, 26 May 2011

Moths around an electric light blub (image: Dr John Brackenbury / Science Photo Library)

A burning conservation issue? (image: Dr John Brackenbury / Science Photo Library)

Like a literal moth to a flame, insects of all kinds are attracted to light bulbs.

Desperate it seems to fly into the light, they repeatedly thwack themselves on a bulb until, finally, they perish.

Such kamikaze-like death flights occur again and again, in almost every household kitchen, on every porch, around every camp light.

In fact it is such a common behaviour it seems wholly unremarkable.

But remark on it I will due to a report just published by Buglife, a conservation trust that seeks to protect invertebrates.

According to Buglife, the use of artificial light by people is significantly affecting the ecology of a range of invertebrates, including moths, beetles, caddisflies, mayflies, lacewings, aphids, hoverflies, true flies, dragonflies and damselflies, among others.

Artificial light is becoming such a problem that Buglife is imploring us to change our habits, and to be careful about where we place bright lights, think about when we switch them on, and even consider changing the way we install solar panels.

It is an issue I’d like to hear your thoughts on. First to see whether you agree it is a problem. And if so, how you would recommend society goes about addressing it.

Insects attracted to a street lamp (image: Drew Makepeace)

Insects attracted to a street lamp (image: Drew Makepeace)

It’s not an issue that can be dismissed out of hand. From a conservation perspective, for the vast majority of insect species the death of a single individual is negligible. But the deaths of thousands, millions or even perhaps billions of insects, dying on lightbulbs across the land, may have an impact.

It is not just insects dying that is the problem, says the report. While many insects seem fatally attracted to bright lights, levels of artificial light may be so high in some places that it changes the behaviour of some species, affecting their ecology, and potentially the ecosystems in which they live.

For example, species such as dragonflies, mayflies and aquatic beetles are attracted to polarised light, caused by light reflecting off or scattering off surfaces. It is how they find the surface of a pond, which polarises light in the same way. But artificial sources of polarised light, such as dark buildings, cars, road surfaces, solar panels and maybe the large areas of plastic sheeting used to shield arable crops, may also attract the insects – luring them away from their natural habitat.

Some invertebrates are repulsed by too much light, says Buglife. The size of habitat available to earwigs, cockroaches, woodlice, earthworms and scorpions might be reduced due to artificial lighting, while plankton in lakes and ponds may not migrate to the surface as they should. Light, in effect, creates “no go areas” for many species.

Bright lights can influence how long species lay dormant and influence their circadian rhythms, which in turn might impact their migration, as has been shown for monarch butterflies. 

Map of light pollution in the UK in 2000 (image: CPRE)

Map of light pollution in the UK in 2000 (image: CPRE)

The list goes on: some insects may simply become less active, as nocturnal species are fooled into thinking it is sunrise. There is evidence that night flying insects stop flying in light polluted areas while speckled wood butterfly larvae take longer to grow in illuminated areas, and are predated on more as a result.

Even fireflies and glow worms, which rely on bioluminescence to attract mates, may be scuppered by the false declarations of love emitted by street lamps and porch lamps. You can read the report “A review of the impact of artificial light on invertebrates”. It is long and detailed.
It is easy to think that animals are habituated to natural phenomena such as light, or noise. But we are only just beginning to research whether that is actually true.

For example, it is now taken for granted that underwater sounds produced by sonar or engineering equipment may disturb large mammals such as whales and dolphins, even thought it is still unclear to what degree.

But a review published last year suggested that fish too may be suffering from underwater noise pollution.

No one had really paid the issue any attention, assuming fish lived in a silent world. Yet most fish hear well and sound plays an active part in their lives, says the scientists who did the review. Increasing noise levels may therefore severely affect the distribution of fish, and their ability to reproduce, communicate and avoid predators.

On land noise pollution is becoming a major threat to the welfare of wildlife, according to a scientific review published in late 2009.

Sounds produced by vehicles, oil and gas fields and urban sprawl interfere with the way animals communicate, mate and prey on one another. The sounds are becoming so ubiquitous that they may threaten biodiversity, said that review's authors.

That is why the Buglife report is interesting. Because, like these previous reports, it is highlighting an issue that is little considered. Yet these issues of light and noise pollution are likely to get worse as urban sprawl continues, and our cities, towns and roads are lit ever more brightly.

But there are two important caveats.

Common glow worm (image: Andrew Cooper / NPL)

Female common glow worms lure males (image: Andrew Cooper / NPL)

Because few people have considered them, little science has been done to fully research the scale of the problem. The Buglife report is packed full of references to scientific studies done, but the trust acknowledges that further work needs doing to establish the true impact of artificial light on invertebrates and the environment as a whole.

The second caveat is what do we do about it?

Lighting is used to for security, safety and to enable us to work and play in places and at times we wouldn’t otherwise. To state the obvious, when it’s dark, we can’t see without it.

Buglife recommends reducing the brightness or wattage of lighting, and the number of lights.

It also suggests changing the wavelengths of some – such as using narrow spectrum Light Emitting Diodes (LEDs) that don’t produce ultraviolet (UV) light seen by many insects, and incorporating patterns of rough or painted glass on solar panels to break up the polarised light they reflect.

Simpler measures might include changing the direction in which lights face, avoiding painting large structures with colours that attract insects, and creating Dark Sky Preserves, where artificial lighting is banned.

But are these proposals realistic? And should governments, businesses, local authorities or we, the public, take the lead in enacting them?

Would you embrace the dark to save our six-legged friends and their companions?


  • Comment number 1.

    Thank you for this article. I would hardly describe myself as a tree hugger but the overuse of lighting here in the States is ridiculous & wasteful.
    When I purchased my home in a rural area one of the first things I did was to unscrew the glaring outside mercury bulb that was burning 24/7. Each morning I had found numerous dead moths & beetles under the light. It doesn't take a biologist to figure out this has to have a harmful effect on nature. Plus, I was tired of sweeping up dead bugs.

  • Comment number 2.

    I live in a semi-rural area of N. Bristol. Virtually no pedestrians, and very few cars, use this area after 10pm. Yet within 20 yds. of my front door are 5 street lights- left on all night of course. The night sky is virtually invisible, never mind the effect that it has on the local wid life. And they are supposedly non-polluting lights! The council won't turn them off after midnight. Heath and safety, of course!

  • Comment number 3.

    Can somebody explain why the picture at the top of the story shows two day-flying Skipper butterflies ‘supposedly’ attracted to light...as well as a night-flying Yellow Underwing moth...? I'd have thought the photographer (John Brackenbury) would have known better...or has somebody muffed their 'Photoshopping'...?

    Otherwise, it’s an interesting story. Local authorities should be forced to put shades on all street lamps to prevent the spill of light into the night sky – this efficiency measure alone would allow the wattage of the bulb to be reduced, with a knock-on effect of lower power usage and saving council tax payers millions of pounds…maybe somebody should tell Chris Huhne…our esteemed man of green credentials and Secretary of State for Energy and Climate Change.

  • Comment number 4.

    Was just going to say..... why is there a picture of 2 Skipper butterflies with a Yellow Underwing moth when Mike beat me to it!

    Interesting article, I think we should all take care of the electricity we use. Not only to protect wildlife, but to help with the waste of producing so much electric and of course our purses!

  • Comment number 5.

    "Would you embrace the dark to save our six-legged friends and their companions?"

    Yes! But even more to be able to see the stars! Please turn off some of the street-lights - at least from 11:30 pm - 6:00 am.

  • Comment number 6.

    @Anthony Kaye.

    I work for the Highways department in a county South of Bristol.
    Those street lights legally have to be there. If they weren't there, the 1 pedestrian that decides to take a walk at 3 in the morning in pitch black, WILL be hit by a car, or fall in the road or something, WILL injure themselves and WILL sue the County.
    It's basic safety regulation laws, both for Human safety of those involved, and for the Safety of the public funds that have to pay out when Johnny Idiot falls over and decides they deserve compensation.

    That money then can't be used to fix pot holes and other road defects. So the street lights are there to save human lives. The street lights have to be in any residential area.

  • Comment number 7.

    I was wondering about those butterflies in the photo, too.....

  • Comment number 8.

    Thanks to everyone for pointing out the image contains two butterflies as well as a moth - something also noticed here by Ben Anderson, one of our producers in the Natural History Unit. The alt tag data should need adjusting, but the image still highlights the issue: that insects of many varieties are attracted to, and influenced by, artificial lights.

  • Comment number 9.

    Mutlipack(?).New letter.Space to explain. 2 streetlights gave perfectly adequate illumination here previously. 3 new poles went up. I wrote asking why. I got a badly spelt, poorly punctuated, syntactically obtuse reply seeming to suggest that a lady complained the bridle path to the woods from our crossroads was dark. Unable to put a light there, (technical problems) they put them round the crossroads!. We're now better lit up than Cape Canaveral on launch night!

  • Comment number 10.

    That may be true but they don't legally have to be on all the time, as proved by cost-saving councils. And a young driver was killed in our area a few weeks ago when he hit a lamp standard during the day. Can one sue for reckless installation of poles?

  • Comment number 11.

    Not enough is being done to curb light pollution and over-lighting generally. There is not only the significant cost to our wildlife to be considered, the maintenance of lighting all night long also has a human cost. There are many studies that show that light at night, disturbing peoples' sleep, results in reduction in melatonin production which is known to be a cause of cancer. The UK has had the Clean Neighbourhoods and Environment Act in force since mid 2006 but light pollution (included as a statutory nuisance in that Act) has not abated. The main culprits for all night excessive lighting are local authorities who do not live up to the expectations of the people who fund their activities. A prime example is Stockport Council whose lighting of the main A6 through the town from the Manchester border is lit using lighting that exceeds the (design code) required level by a good 50% (92% more in one area) and is now using metal halide bulbs that use at least 60% more energy (possibly 80% if low loss gear used previously) for less light output than the old and more suitable low pressure sodium bulbs. Of course, the Government saw to it that the Councils can create more light pollution unabated whilst the taxpayer is subject to a criminal action for the same offence. The Local Government Ombudsman is likewise determined to ensure that Councils can do what they like despite statements on websites like Stockport Council's that claim they are "greener" than the reality shows.

  • Comment number 12.

    Response to Mutlipack_can13 (comment 6 above): The provision of streetlights is not a legal requirement on any street or road. It is discretionary on the part of a Council. “Johnny” may well be, of course, a tax payer so quite why he is considered an idiot is a little baffling. In any event, dark roads at night unlit would see cars using headlights – cars are not invisible at night without streetlights for the vast majority of cases, I would have thought, because they have their own lights. May be the reason for “Johnny” to be falling and hurting himself is because the money wasted on lighting (white light much less efficient than the old low pressure sodium) could have been used to repair the roads and pavements.

    The use of white lighting, prevalent now in many new schemes, has several disadvantages. A reason for installation is usually given by Councils as better colour recognition. However, as any street lighting engineer will appreciate, colour is not important on main roads, negative contrast is. That is, main road / traffic route lighting is required to be designed to put light onto the road so that objects are silhouetted against it. Over-lighting causes not only reduced contrast (lit objects / people hence more dangerous) but increased light pollution and attraction to insects from further afield. Add to this that metal halide lighting generally contains mercury (remember the mercury lights that were so despised years ago for this reason?) and you have an ecological disaster. White metal halide also has a significant amount of UV light (not present in other road lighting sources) that is even more attractive to insects and causes tiredness due to ocular distress to drivers at higher speeds on motorways (ref the good design on the M65 in Lancashire). All in all, the “new and improved” white light is nothing more than a money making gimmick that gives problems all round. Better to stick to low pressure sodium lighting which uses just over 50% of the energy required by metal halide for the same light output. By the way, crime is NOT reduced by lighting - the A6 in Stockport, lit by metal halide, sees a lot of vandalism at night under the white lighting.

    It’s worth bearing in mind that it is widely accepted that an illuminance level of 2.5 lux is sufficient for face recognition which begs the question why Stockport Council are shiningupto 20 times this onto the road surfaces around here with white lighting. They shine over 4 times that level into bedroom windows unnecessarily (none required).

  • Comment number 13.

    It is a really important issue if such large numbers of invertebrates are estimated at being affected by light pollution, invertebrates interact with lots of different species providing a food source to many and contribute so much to ecosystems processes such as pollination of plants. I agree that there is an overuse of lighting in some urban areas but i think it will be hard to convince people to cut back on the use of lighting as mentioned in the blog, lighting is used for many purposes.

    The main concern i have is for safety. As a 22 year old female student i am often required to walk home in the dark after a long day of studying especially in the winter months and I feel that many areas are not well lit at all. I am a zoology studnet and am very passionate about wildlife and biodiveristy, i agree that light and sound pollution are major problems for biodiversity, but at the same time, in student areas where crime is higher, i feel that artificial lighting should be increased and so my opinion is torn. I think if lighting were to be reduced, areas would need to be assessed individually for their requirment of lighting and there should be a way for residents of these areas to express their opinion on the situation


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