Western Morning News (Saturday)
Seeing darkness in a new light
Conservation charities are worried about the damaging effects of light pollution on night-flying insect populations. Charlie Elder reports
Hear the term pollution and one thinks of slicks of oil washed up along shorelines, rafts of plastic waste floating in oceans and strewn across beaches, the corpses of dead fish in poisoned rivers and rubbish littering our roadside verges.
But there is another insidious form of pollution which could be having a serious impact on biodiversity and yet seldom gets a mention – light pollution.
This may in part be because it predominantly affects invertebrates, the myriad little creatures that are too often taken for granted. Added to which we depend upon artificial illumination and have become used to having streets, offices and homes bathed in constant light after dark.
Now the invertebrate charity Buglife is campaigning for a reduction in unnecessary and costly artificial light, which it argues has detrimental impacts on wildlife and in terms of energy consumption.
And this week the organisation Butterfly Conservation released details of a study which shows that streetlights reduce the abundance of moth caterpillars in grass verges by a third and in hedgerows by almost a half compared to unlit roadside habitat. Modern white LED streetlights appeared to be even more detrimental than older sodium lamps which cast an orange-yellow light.
Butterfly Conservation’s field research, involving the UK Centre for Ecology & Hydrology and Newcastle University, provides illuminating evidence of a link between light pollution and population changes among moths.
Richard Fox, associate director of recording and monitoring at the conservation charity, said the “gut feeling” following the study was that female moths may lay fewer eggs in habitat illuminated by streetlights, leading to lower caterpillar abundance.
And, of course, fewer caterpillars would have a knock-on effect in terms of the species that depend on moths for food, such as bats, birds and small mammals.
Few of us now experience crystal clear, star-filled night skies, free from the glow of street and other night lighting. Artificial light at night can directly affect a range of wildlife, from bats adapted to hunt in pitch blackness to birds which migrate at night. Moths which we see spiralling around outside lights expend unnecessary energy while also being at increased risk of injury and predation, while other invertebrates that are not directly attracted may also be affected by lighter surroundings at night, with evidence it can disrupt mating, feeding, navigating, development and even their ability to hatch at the correct time.
Two-thirds of invertebrates are partially or wholly nocturnal, and even species active by day can be impacted by the loss of complete darkness at night.
Glow-worms, for example, use luminescence to attract mates and evidence shows a decline in the abundance of glow-worm populations living in close proximity to artificial light. And dung beetles navigate using the moon and stars. Under light-polluted skies, they become disoriented and unable to find their way, while around artificial lights they roll dung towards the source which creates dangers in manmade environments.
“Light pollution should be treated with the same contempt with which we treat all other forms of pollution,” Buglife argues. “Yet it has increased from a variety of sources, including residences, sports facilities, public infrastructure such as lighting along motorways, retail buildings, and industrial activity.”
In 2011, the charity reviewed the effects of light pollution on invertebrates, with its report concluding that artificial light “in the wrong place at the wrong time adversely affects the life cycles and survival of invertebrates”.
A wide range of invertebrates depend on the natural rhythms of day and night and seasonal and lunar changes, so artificial light can disrupt feeding, breeding and movements. Light reflected off shiny surfaces even attracts aquatic insects away from water.
“Developments in lighting technology have led to major increases in the distribution and intensity of artificial light in the past few decades and its growth is continuing largely unchecked,” the Buglife report said, adding: “Because invertebrates are so
fundamentally important to healthy ecosystems and because declines and threats mean that many species are already listed as national priority species, it is imperative that avoidable threats to their wellbeing are avoided.”
The new Butterfly Conservation study adds weight to the growing concern about artificial lighting, against a backdrop of biodiversity losses and depleted insect populations.
Launching its new campaign this week, Buglife said light pollution was an environmental issue that had been “pushed to the side-lines for too long”, adding that it was “a form of pollution that can be solved, quite literally, with the flick of a switch”.
“Of course, in reality, this isn’t
possible for every light, however methods exist to limit the amount of light pollution we generate,” the charity said. “Reducing the number of lights we use, the length of time lights are left on, and especially shielding and redirecting lights can help. “But individual actions alone will not solve the problem. A united effort must be made, led by national policy, to reduce existing levels of light pollution and ensure any new lighting does not add to the problem.”
In short, we need to be more switched on to the dark side of lighting.