Like moths to a flame
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.
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.
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.
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?