Light pollution seems an odd thing for us to be worried about but a growing body of research suggests too much light at night can cause harm to plants, wildlife and even us humans.
A good place to start our exploration is with Terri-Lee Reid’s blog post on the Canadian Wildlife Federation website. She notes that migratory birds are especially vulnerable to striking lit windows at night. All too often these widow strikes are fatal to the birds. So much so that Fatal Light Awareness Program (FLAP) Canada has developed a whole program to educate the public in general and building managers in particular. You’d think the opportunity to turn off lights at night and save money and birds would be an easy win-win. Sadly this is not always the case.
Light pollution upending the natural world
Writing in The National Observer earlier this month, Sarah Scoles reviews Johan Eklöf’s new book “The Darkness Manifesto”. In the book, Eklöf describes an evening deep inside Malaysia’s Krau Wildlife Reserve. “One evening, during dinner, one of the film crew’s large lights was left on, directed up toward the sky,”. Lured into the tight column of illumination, a “heavy stream” of the forest’s winged inhabitants “danced in a spiral down toward the light,” he writes. According to Eklöf, this is known as the “vacuum cleaner effect,” and it’s just one way artificial light has a profound effect on the natural world.
The nocturnal illumination that sustains our modern existence seems to disrupt the lives, and circadian rhythms, not just of insects but of animals as varied as bats, birds, plants, turtles, coral, and clownfish (AKA Nemo). Eklöf, a bat researcher and self-proclaimed “friend of the darkness,” is concerned about the cascading ecological effects of what he and other experts call light pollution. In 42 short and digestible chapters, he makes the case that light pollution is a crucial feature of the Anthropocene Epoch. The seeds of light pollution were sowed more than 150 years ago. Artificial light, according to Eklöf, accounts for 10% of our energy use, but just a fraction is actually useful. “Badly directed and unnecessarily strong lights cause pollution that is equivalent to the carbon dioxide emissions of nearly 20 million cars,” he writes.
Scientific research into how light pollution has affected life on Earth is still relatively sparse but drops in insect populations are one example. “The reasons for insect death are many, from urbanization and global warming to the use of insecticides, large-scale farming, single-crop cultivation, and disappearing forests,” writes Eklöf. “But for anyone who’s ever seen an insect react to light, it is obvious that light pollution is a major cause.” Around half of insects are nocturnal and use the dark hours to feed and find reproductive partners. “The night’s limited light protects these insects, and the pale glow from stars and the moon is central for their navigation and hormonal systems,” Eklöf writes.
As for bats, they hunt nocturnal insects, of course, while using the cover of darkness to hide from predators. Particularly in Eklöf’s home country of Sweden, bats live in church towers. In the 1980s, he writes, two-thirds of churches in southwest Sweden had their own personal bat colonies. But Eklöf’s own research suggests that number has dropped by a third. “The churches all glow like carnivals in the night,” he writes. “All the while the animals — who have for centuries found safety in the darkness of the church towers and who have for 70 million years made the night their abode — are slowly but surely vanishing from these places.”
Artificial light also disrupts humans. Most of us cannot see the stars at night, or the Northern Lights. Artificial light disrupts our bodies’ production of melatonin, the hormone that helps control the sleep cycle, with profound effects on our natural sleeping rhythm, writes Eklöf. “We may not be able to cure or prevent depression all at once by cutting down on electric lighting,” he maintains, “but we definitely increase the chances of good sleep in the long run.”
Writing in Explorersweb, Andrew McLemore explores the conundrum: is it better to look up at the night sky or down at our phones? Driven by private companies, there is a movement to surround Earth with brightly lit machines. It is ostensibly about connection, bringing 5G cell service to every corner of the globe. Yet many scientists and astronomers have begun vocalizing their opposition to telecommunications networks that block our view of the final frontier. Light from satellites has begun interfering with the Hubble telescope, prompting astronomers to consider moving it further into space and away from the visual noise. Lovers of the outdoors want to preserve a natural view of the sky — uninterrupted by the streaks of satellites now more common than shooting stars. In a moving polemic published in the Ecological Citizen this month, scientist Kate McFarland made an environmental argument, positing that increased brightness at night could threaten delicate ecosystems throughout the planet. Unlike the light pollution of a metropolis like LA, the brightness created by satellites can’t be avoided by driving to the Nevada desert.
Turning on the night sky
Writing in News Decoder, which aims at children and educators, Tira Shubart outlines the challenges of night-time lighting and how it interferes with the natural world and our view of the stars. At the end of this piece, she asks her young readers to look at local artificial lighting and how it impacts their neighbourhood and what they can see at night.
Writing in The Conversation, entomologist Douglas Boyes discussed how the predictable cycles of day and night have become increasingly blurred. Between 2012 and 2016, satellite measurements revealed that the global area polluted by artificial light grew by 2% each year, intruding ever deeper into biodiversity hotspots like tropical forests. In the UK, as in many other countries, older less efficient sodium street lights are being replaced by brighter and more energy efficient LED lighting.
This change in the colour of artificial light is predicted to have major consequences for wildlife. That’s because white LEDs emit light across the entire visible spectrum. The more wavelengths emitted, the greater the diversity of species and biological processes that are likely to be disrupted. For example, insects are known to be more sensitive to shorter, bluer wavelengths of light, which are largely absent from sodium lighting. Biological processes that are controlled by daylight and internal circadian rhythms, such as reproduction, are more likely to be disrupted or prevented by white LEDS.
To test this hypothesis, Boyes worked with a team of researchers from the UK Centre for Ecology & Hydrology, Newcastle University and Butterfly Conservation, I searched the Thames Valley area for roadsides with both lit and unlit habitats. Around 500 potential locations were whittled down to only those that were more or less identical – apart from the presence of street lighting.
The results, published in Science Advances, were striking. Lighting reduced the numbers of caterpillars by between one half and one third. Lit areas almost universally had lower numbers than their darker counterparts. Sites with white LEDs also had a steeper reduction in numbers compared to sites with sodium lamps. They suspect the reason there were fewer caterpillars in lit areas was because the lighting prevented females from laying eggs, a behaviour that has evolved in darkness. In addition, adult moths can be drawn up to streetlights, where they’re easy pickings for bats. Their recent review article revealed many other plausible mechanisms through which lighting could cause population declines throughout the moths’ life cycles.
Sadly, Dr. Boyes passed away shortly after this article was written.
Europe’s First ‘Dark Sky Sanctuary’ is in Wales
To end this post on a more hopeful note, Jamie Carter, Senior Contributor at Forbes, writes about one of few places in the world where a immaculate dark sky is stuffed with stars while the night air is filled with spooky rasping screams. Just two miles long by half a mile wide, the island of Ynys Enlli two miles off the west coast of North Wales has been named an International Dark Sky Sanctuary—only the 17th in the world and the first in Europe—by the International Dark-Sky Association.