Rewilding the Dark: The Night Shift Your Garden Depends On

The garden you tend by day has a second life you have almost certainly never seen. When the last of the light drains away and you go indoors, a whole other workforce clocks on. Moths lift from the borders and begin their rounds; bats unspool from the eaves; a hedgehog noses out from under the hedge; and, if you are very lucky and your garden is dark enough, a female glow-worm switches on a small green lamp in the grass and waits. The night is not an empty, sleeping version of the day. It is a habitat in its own right; busy, essential, and quietly disappearing.

And rewilding the dark is a strange and lovely thing to attempt, because it is the one act of rewilding that asks you to subtract rather than add. Not to plant or build or dig, but to let go - to switch off, and give the darkness back.

Meet the night shift

We tend to imagine that when the bees knock off, pollination stops for the day. It doesn't. Moths work the night shift, and they are far better at it than we ever gave them credit for. In a study published in 2023, researchers right here at the University of Sussex watched bramble flowers around the clock and found that although moths made only about 15% of all the visits, the day-flying bees and hoverflies made the other 83%, the moths pollinated the flowers faster and more efficiently than the day shift did, quietly getting a great deal of work done in the short hours of darkness. Bramble becomes blackberries in no small part thanks to moths.

Above them fly the bats. Every one of Britain's species an insect-eater, a single common pipistrelle capable of taking up to 3,000 midges, moths and small flies in a night. On the ground, the hedgehog patrols for beetles and slugs. In the borders, countless nocturnal beetles, flies and other invertebrates go about the unseen business of pollinating, decomposing and feeding everything else. The night, it turns out, is where an enormous share of a garden's living work gets done.

The moth: unsung, and in trouble

The moth deserves special attention here, because it sits at the heart of the whole nocturnal web, and because it is in serious decline. Moths are not just pollinators; their caterpillars are one of the most important food sources in the entire ecosystem. As the insect food-web piece described, it is caterpillars that turn leaves into the protein that raises baby birds, and moths that feed the bats overhead. Pull moths out of the picture and the losses cascade upward through everything that eats them.

Yet that is exactly what's happening. The abundance of larger moths in Britain has fallen by around a third since the late 1960s. Habitat loss and climate change are the main drivers, but there is a third pressure, less obvious and rising fast, that a gardener is unusually well placed to do something about. It is light.

We have been quietly erasing the dark

Artificial light at night has become a genuine, and genuinely underestimated, form of pollution. Using tens of thousands of observations from citizen scientists worldwide, a 2023 study in Science found that the brightness of the night sky is increasing by roughly 10% every year. The lead researcher put it in heartbreaking terms: a child born somewhere they can see 250 stars would, on that trend, see only 100 by their eighteenth birthday. The stars are going out, one by one, beneath a rising tide of 'skyglow', and domestic gardens, along with road verges, are among the most frequently illuminated habitats of all.

It is getting worse, not better, and part of the reason is the very technology sold to us as green: the switch from warm, orange sodium lamps to bright, cheap, energy-efficient LEDs. LEDs save energy, but the cool blue-white light most of them cast is precisely the kind that scatters furthest across the sky and does the most damage to wildlife. We have made our lights greener for the climate and, too often, harsher for the night.

What the light actually does

The harm isn't abstract. It runs right through the nocturnal food web, and the science on it has sharpened dramatically in recent years.

It lures the workforce away from work. Moths are famously drawn to light, and a lit garden pulls them off the flowers and into a fatal orbit around the lamp, where they exhaust themselves, become easy pickings for predators, and often simply die. Artificial light also scrambles their mating, disrupting the pheromone signals by which they find one another in the dark.

It shuts down the night's pollination. In a field experiment published in Nature in 2017, meadows lit with LED streetlamps received 62% fewer visits from nocturnal pollinators than dark meadows, and the plants there produced significantly less fruit as a result; a shortfall the daytime bees did not make up. Worse, the disruption bled into the daytime pollination network too. Switching on a light doesn't just dim the night's work; it damages the day's.

It thins the next generation. Perhaps the most striking finding is about caterpillars. A landmark 2021 study led by the young researcher Douglas Boyes, who tragically died shortly after its publication, compared moth caterpillars in lit and unlit stretches of English roadside. Streetlights had cut caterpillar numbers by almost half in hedgerows (47%) and by a third in grass margins, and disrupted the caterpillars' feeding and development besides. And, tellingly, the damage was worse under white LEDs than under the old orange sodium lamps. Fewer caterpillars means less food for the hedgehogs, songbirds and bats that depend on them; the light is reaching up the food chain to starve the very creatures we love.

It silences a small green lamp. And then there are the glow-worms - not worms at all but beetles, whose wingless females climb the grass on summer nights and glow to call down a passing male. In a garden washed with artificial light, that faint, patient signal is simply drowned out. The male never sees her. It is one of the quietest tragedies of light pollution, and one of the most moving.

Rewilding the dark: less is more

Here is the good news, and it's considerable: this is the cheapest, fastest, most immediately effective rewilding you will ever do, because it costs nothing and works the instant you do it. Light pollution, unlike almost every other environmental problem, vanishes the moment you remove the cause.

Turn it off. The single best thing you can do for the night shift is to give it back the night. Treat darkness as the valuable habitat it is, and question every outdoor light you own. Does the patio really need to blaze all evening? Does the security light need to fire at every passing cat? Most garden lighting is on not because anything needs it but because we never thought to switch it off.

If you must light, light gently. Where light is genuinely necessary, the principles are simple and they map almost exactly onto what wildlife needs: use it only where required; shield it and point it downward so it lights the path and not the sky; keep it as dim as possible; put it on a motion sensor or timer so the garden is dark for all but a few moments; and above all choose warm, amber-toned light rather than harsh blue-white LED. A low, warm, shielded, occasional light is a world kinder than a bright white lamp left on till dawn.

Leave dark corridors. Bats and hedgehogs travel along the unlit edges of things. Keep your boundaries and hedges dark so they remain the wildlife highways described in the habitat corridors piece, rather than walls of light the shyer species won't cross.

Plant the night garden. Give the moths a reason to visit by planting for them: night-scented, pale-flowered species that show up and give off perfume after dusk; honeysuckle, evening primrose, night-scented stock, sweet rocket, jasmine. And, as the Sussex researchers suggest, letting a patch of bramble or flowering scrub bloom feeds the moths generously and rewards you with blackberries.

Skip the bug zapper. Those electric insect-killers slaughter vast numbers of harmless and beneficial insects while barely denting the biting ones. In a wildlife garden they do nothing but harm.

Go and meet the night shift. Best of all, get to know the world you're protecting. A moth trap run on a warm evening (the moths released unharmed at dawn) reveals an astonishing, jewel-like diversity most people never suspect was living in their garden; a glow-worm survey or a bat walk opens up the same hidden kingdom. It is hard to love the dark until you've seen how alive it is.

Let the dark come back

Almost everything else in this series has asked you to do something; plant a tree, dig a pond, build a log pile, leave the mess. This one asks the opposite. It asks you to stop; to switch off the light; to resist the modern reflex that every dark corner is a problem to be solved with a lamp.

Do it, and you hand back a whole world in an instant: the moths returning to the honeysuckle, the bats working the dusk, the hedgehog going undisturbed about its night, the glow-worm's small green lamp finding its mate at last, and, above it all, the slow return of the stars we have half-forgotten we ever had. In a garden that's truly alive, the kindest light is very often no light at all.

References & further reading

• Anderson, M., Rotheray, E.L. & Mathews, F. (2023). "Marvellous moths! Pollen deposition rate of bramble is greater at night than day," PLOS ONE. (University of Sussex — moths as efficient nocturnal pollinators.)

• Butterfly Conservation / Rothamsted — The State of Britain's Larger Moths (roughly a third decline in larger-moth abundance since the late 1960s); "Why is light pollution bad for moths?"

• Boyes, D.H., Evans, D.M., Fox, R., Parsons, M.S. & Pocock, M.J.O. (2021). "Street lighting has detrimental impacts on local insect populations," Science Advances, 7, eabi8322; and the companion review in Insect Conservation and Diversity (2021).

• Knop, E. et al. (2017). "Artificial light at night as a new threat to pollination," Nature, 548, 206–209. (62% fewer nocturnal pollinator visits; reduced fruit set.)

• Kyba, C.C.M. et al. (2023). "Citizen scientists report global rapid reductions in the visibility of stars from 2011 to 2022," Science. (Night-sky brightness increasing ~10% per year.)

• Owens, A.C.S. & Lewis, S.M. (2018). "The impact of artificial light at night on nocturnal insects: a review and synthesis," Ecology & Evolution.

• DarkSky International — the five principles for responsible outdoor lighting (useful, targeted, low level, controlled, warm-coloured). https://darksky.org/

• Bat Conservation Trust; UK Glow Worm Survey; Butterfly Conservation's Moth Night — getting to know the nocturnal garden.

• Companion pieces in this series — on the insect food web, habitat corridors and ten ways to rewild your garden.