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What we lose without the dark

Johan Eklöf’s The Darkness Manifesto shows how artificial light is harming the natural world – and what we can do to reverse it.

By Melissa Harrison

Ten o’clock at night and it’s too late to start watching a film. I can’t stand to see any more news, but I’m not ready to turn in, and the dog is gazing hopefully at me from her basket. “Alright,” I say, levering myself up off the sofa, and instantly she’s at the front door. I clip on her reflective collar and shrug a hi-vis gilet on over my coat, but I don’t take a torch: I want the rhodopsin, a protein in my eyes, to develop and give me night vision, a process that takes about half an hour.

I live in a rural village with no streetlamps, no lights illuminating our church and no lit roads nearby. A neighbour keeps a dim porch light on and a glow leaks out around the closed curtains of nearby cottages, but unless there’s a moon when darkness falls it’s unconditional, absolute. In bed at night it can be hard to tell whether your eyes are open or closed, an utterly normal experience for most of human history, but increasingly rare now – especially in the Global North.

The Darkness Manifesto, by the ecosystem ecologist Johan Eklöf, opens in Västergötland in his native Sweden, where the attic of a wooden church is scattered with a fragile confetti of butterfly wings left by brown long-eared bats. In the 1980s, two-thirds of churches in the region had their own bat colony; since then many have installed floodlights, and levels of general light pollution have skyrocketed. As Eklöf explains in this well-researched and surprisingly lyrical book, this light pollution is likely the reason why the number of bats in Västergötland has decreased by a third.

It’s now clear that light pollution is a key driver of the sixth mass extinction: the catastrophic, human-driven loss of both species and abundance taking place on our watch. Night is, for a third of vertebrates and nearly two-thirds of invertebrates, the period in which they find food, mate and migrate, and researchers are beginning to understand the disruption caused to these behaviours by alterations in light levels.

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Whether nocturnal, diurnal or crepuscular, all plants and animals have evolved alongside an alternating pulse of light and darkness, nearly all living cells in every living being working in harmony with that circadian rhythm. Darkness is a vital trigger for the biological processes of every creature, including humans, but with the invention of artificial light we have reduced the amount of darkness suddenly – though not irrevocably.

The Bortle scale – which measures the brightness of the night’s sky – runs from one to nine. One denotes a completely dark sky in which up to 6,000 stars can be identified with the naked eye, and nine represents the greyish-orange skyglow above London, in which only the moon and – on a very clear night – the Plough and Orion constellations are visible.

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Stepping out of my cottage I see the breathtaking scatter of the Milky Way arching over the village in a velvet-black, level two sky. It takes me back 40 years to my childhood, when my dad would point it out from our back garden in Surrey, explaining that I was looking out into space through the spiral arm of our galaxy. It’s been estimated that light pollution increases by at least 2 per cent globally per year, and that garden now lies under a level five sky in which the Milky Way is almost invisible, as it is now for four out of five people in Europe.

During that same period, insect numbers – and those of obligate insectivores, such as bats and many birds and mammals – have crashed. The rate of insect decline is eight times faster than that of birds or mammals, with one study showing that they could be all but gone within a century. Given their role as food for other creatures, pollinators of plants and decomposers of organic matter, that would threaten life on Earth. The majority of insects, Eklöf explains, use either the moon and stars or polarised light, or both, to navigate: brighter light sources, or the obscuration of the stars by light pollution, disrupts their ability to find food, pollinate plants and reproduce.

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About 40 per cent of insect species are now at risk of extinction, with moths the hardest hit – particularly those in urban areas. Studies have found that moths’ hearing is less attuned to bats’ ultrasound when under streetlights, making them easy prey. The reason? They think it’s daylight, when birds are the greater danger: they’re alert for the wrong type of predator.

Birds are affected by light pollution too: it makes them more susceptible to disease, alters reproductive timings so that eggs hatch when there isn’t enough food to feed chicks, and each year millions of migrating birds are drawn to their deaths by lighthouses or spotlights. The catalogue goes on and on: wallabies born at the wrong time of year due to the light from a naval base, sea turtles hatching and heading towards the lights of a city rather than the sea, corals unable to time the release of sex cells without clear light from the moon. The consequences of our mania for light are everywhere.

My eyes have adjusted to the night, and as I walk around the village I can see a tiny pipistrelle hunting above me, trying to put on weight ahead of its winter hibernation. There were brown long-eared bats in the attic of the house I grew up in, and I can remember the scatter of Lepidoptera wings on the rafters, just as Eklöf describes in the church. I’m so lucky to live somewhere still dark enough for both bats and insects – albeit in nothing like the numbers there should be – and lucky, too, to see so many stars overhead, something visitors to the holiday cottage next door always comment on. Many people are motivated to preserve and restore nature, and interest in dark sky parks – a protected area that restricts artificial light – is growing; surely a change in the public’s desire for brightness is in reach?

Given the energy crisis it’s interesting to note that lighting makes up a tenth of our global energy usage. And it’s ripe for being made more efficient given that most exterior light is either unnecessary, too bright, the wrong colour or badly directed, spilling out and up into the sky. Eklöf quotes one study which shows that emissions from inefficient lighting in Europe and the US could be equivalent to that of 20 million cars. A Chinese plan to send an artificial moon into orbit to light the city of Chengdu all night every night might save energy, but would be catastrophic for the natural world. France has now passed legislation on light pollution, aiming to regulate everything from brightness, timing, colour and temperature to the use of screens and shades. Compliance will be mandatory by the start of 2025; it must be hoped that other countries follow suit.

The savings delivered by LEDs are in danger of being offset by the sheer numbers of them in use, but Eklöf suggests that by using shades, timers and different colours of diode it’s possible to light roads, paths and walkways safely while minimising disruption to wildlife, and saving energy too. I’d have liked greater detail about how this can be achieved; though there is a manifesto at the end of the book, it’s more motivational than practical. Even so, The Darkness Manifesto is a powerful contribution to our understanding of the harm we’re causing, and a clarion call for change: unlike many of the complex issues facing the planet, protecting the darkness is truly within our grasp.

The Darkness Manifesto: On Artificial Light and the Threat to Our Ancient Rhythms
Johan Eklöf, translated by Elizabeth DeNoma
Bodley Head, 240pp £16.99

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This article appears in the 19 Oct 2022 issue of the New Statesman, State of Emergency