Stop unnecessary lighting of empty buildings at night – the world needs more darkness

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Johan Eklöf’s Manifesto of Darkness opens like a gothic novel. A cemetery in the middle of the night. Shadows move in the sweep of a torch. Strange sounds beyond its beam. Yet this is no fantasy. For the past 20 years, as the sun sets, Eklöf has been drawn to old churches in a remote corner of Sweden in the name of science. He is a biologist and ecologist who studies bats. His research reveals that these creatures are under threat. Their enemy is light.

Our demonization of darkness dates back to ancient mythologies and religions. “Let there be light” is the call of Christianity to save us from temptation, death and the devil. Rather, Eklöf asks to think of darkness not as the absence of light but as something substantial, something to be cherished. He quotes journalist Åke Lundqvist: “Light is diluted darkness. The speed of light is often evoked, in a kind of admiration. The speed of darkness is much slower, the darkness falls gently and quietly, like balm for the soul.

Researching for my book Sentient taught me that we have two senses of vision. One offers us clear and cerulean days; the other inked starscapes. Derived from the Greek for light and dark, they are called photopic and scotopic vision. We assume that our scotopic vision is a mere second compared to that of owls or foxes. However, when volunteers are immersed in darkness so deep they cannot tell whether their eyelids are open or closed, scientists have shown that the human eye is exceptionally sensitive. The reason we remain unaware of our talent for darkvision is that we rarely get to use it.

Since the invention of the light bulb less than a century and a half ago, the night has continued to disappear. Nighttime satellite images of our burning planet may be mesmerizing, but they reveal just how much darkness we have banished. We spend one-tenth of our total energy consumption on artificial light and most spills into the sky. Eklöf does not criticize lighting, but its indiscriminate excesses: the omnipresence of streetlamps and projectors, the nocturnal light of billboards and empty office windows, the lighting of schools and empty parking lots.

In the 1980s, two-thirds of the several hundred churches in the area where he lives were inhabited by brown long-eared bats. Iron Age steeples and cemeteries have served as refuges for lodges and rich hunting grounds: the order of hundreds of years. Then, some churches have succumbed to the trend of spot lighting their facades. Today, the number of long-spiked brown colonies has halved, and Eklöf is blaming the loss of darkness. “Bats dare not emerge. In their eyes, the day is still in full swing and dangers await them,” he explains. Then cites studies from England of bats that chose starvation over straying into the light, despite the inevitable assortment of insects drawn to its beam.

Every night, as we fall into a senseless sleep, one-third of all vertebrates and two-thirds of all invertebrates fidget. The night is their niche; their biology evolved for the dark. Clownfish eggs, mated by the moon, do not hatch if exposed to light. Baby turtles who used to find the ocean by its reflected moonlight are driven onto the beaches toward the brighter lights of the city. Streetlights interfere with the ability of female cabbage moths to make pheromones, so they fail to attract their lovers, while male glowworms fail to see the glow of theirs. As winters approach, mountain ash trees delay leaf drop and blackbirds sing late at night, both tricked into thinking spring is in the air. Moreover, we humans suffer from the erasure of darkness.

While making documentaries for BBC Horizon, one of my most memorable interviews was with the founding director of the Institute for Computational Cosmology. Professor Carlos Frenk has spent his illustrious career with his eyes glued to the sky. We sat under the vaulted ceiling of Durham Cathedral and discussed the latest images from the Hubble Space Telescope. He made a seemingly insignificant point and explained that this faint pulse of light was the most distant in time anyone had ever seen. I was amazed – not by the divinity despite the location – but by the majesty of nature.

Today we are blinded by the spectacular sweep of the cosmos by the light we invented; “only a fragment, half a percent” of once single stars are now commonly seen. Skies uncontaminated by light pollution are rare. However, if you find yourself on a dark night in Nevada’s Death Valley, the Milky Way will be so bright that it will cast shadows. You will be able to see the farthest object in perceptible space without a telescope. Light from this Triangle Galaxy will have begun its journey across 3 million light-years to you, “coincident with the birth of our own genus, Homo”.

The Darkness Manifesto is a compelling title, but the book doesn’t read like a shrill decree. It takes us on a gentle but sometimes meandering journey: poetic and philosophical at times, intimate and expansive at others. “Carpe noctem”, Eklöf tells us. “It’s time to recover the night.” And I am, like a moth in the light.


Sentient by Jackie Higgins is now available in paperback at £9.99. The Darkness Manifesto is published by Bodley Head at £16.99. To order your copy for £14.99, call 0844 871 1514 or visit Telegraph books

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