God does not approve of street lighting, observed Jean-Jacques Rousseau. That wasn’t an oblique aphorism: it was simple biblical exposition. The God of Genesis is famously keen on maintaining boundaries between domains. There is supposed to be light (‘Let there be light’) and darkness (‘He separated the light from the darkness’ and called ‘the light “day”, and the darkness “night”’). Now, over much of the globe, night has been cancelled. The night sky in Hong Kong is 1,200 times brighter than the unilluminated sky. Millions will never see the constellations so central to the stories humans have told about the cosmos.

The cancellation began when humans discovered fire and used it to extend their days. This was a gentle type of hubris, different in kind as well as scale from the hubris of the Chinese engineers who are said to be about to put artificial moons into space, their orbits synchronised with the night hours of each commissioning city, pumping out light eight times stronger than the light of the real moon. Firelight may blur the border of day and night, but it does some good work. It ignites story and provokes conversation. It salutes and draws attention to the dark. It is allusive and intimate. The electric light we create just stamps on the night. The universe won’t stand meekly by when we’re as insolent as that. And it hasn’t. Johan Eklöf’s book is a chilling account of the nemesis that is gathering pace and fury.

We’re used to hearing about the catastrophic effects of carbon dioxide emissions, deforestation, environmental toxins from industrial agriculture, the plastic in our oceans and our organs, and so on. We hear far less about light pollution. It’s a dangerously under-recognised horseman of the environmental apocalypse.

One third of all vertebrate species and nearly two thirds of invertebrates (including half of all insects) are nocturnal. Mess with the night and you’re messing very obviously with most of the visible organisms on the planet. What’s not so obvious is that you’re really messing with every organism – and not only because diurnal creatures like humans are entangled with everything else. The 2017 Nobel Prize in Physiology or Medicine was awarded to the scientists who isolated the gene that controls the rhythm of all living things, from bacteria to humans. Everything has a biological clock calibrated by light and darkness. Since the earth began, 4.5 billion years ago, there has been a cycle of night and day – a cycle harnessed by the rhythm gene. The cycle is broken by artificial light. Every living thing has a timetable. The timetable is a fundamental element of us all. Disrupting a fundamental element has fundamental consequences.

Eklöf, in a book composed of forty-three very short, accessible chapters, each of which could be read as a free-standing essay, illustrates many of those consequences, building a compelling case against our colonial expansion into and trashing of the night. He tells us about clownfish, whose eggs will hatch only in the dark (no dark, no clownfish); about moths that use the moon for navigation and are disastrously disorientated by bright lights; about insects being drawn in vast numbers to cities and the consequent effects on pollination; about newly hatched turtles, programmed to head west to reach the sea, scuttling instead towards the promenade; about the birds you’ve heard singing in the middle of the night, whose reproductive cycles go haywire in the perpetual day; and about coral reefs imperilled because the synchronous release of the eggs and sperm of coral organisms is dictated by the cycles of the moon, which is now often outshone by LEDs. When it comes to humans, Eklöf looks at the association between artificial light and sleep deprivation, obesity and depression, and between night shifts and (particularly hormone-related) cancers.

Alongside this depressing litany of evidence are Eklöf’s own reflections. They are sensitive and intelligent, and never intrusive. He lets the evidence speak for itself. ‘Let us take back the night,’ he urges. ‘Carpe noctem.’ Amen to that. But it won’t be easy.

Why do we try to abolish the dark? No doubt there are often powerful economic interests at work, wanting to squeeze more productive hours out of the day. And some of the explanation lies in our modern addictions. Screens, which have attained almost total mastery of most of us, annihilate the dark. More than 80 per cent of those between fifteen and twenty-nine take their phones to bed. Many bedrooms are dominated by a television. No doubt, too, atavism is at work. At some level we fear that if the lights go off we’ll be at the mercy of the sabre-toothed tigers which prowled through the infancy of our species and now prowl through our unconscious. But I suspect there’s something deeper and less curable going on even than the dread of being eaten. I think we fear what the uninterrupted dark will show us of ourselves. And, even worse, we have abolished the dark because we can.

That makes the prognosis poor. The well-meaning legislators in parts of Austria and the Netherlands who want to turn off the street lights earlier won’t turn the clock back – or reset the biological clock. Let’s do what we can. Yes, let’s have more dark parks. Yes, let’s set LEDs to emit more moth-friendly wavelengths. Yes, let’s tell the accountants that most urban lamps are poorly placed and that most of the light they produce sloshes unused into the sky. But these are tinkerings. The real problem, as so often, lies in the curious mix of light and dark in the human soul. Any solution must be sought there.