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Turning on the lights impacts plants and animals (Image: Archi Banal/Getty Images)

ScienceAugust 31, 2022

Bring back the night: Why we need to preserve darkness

lit up city with illustrations of trees and stars and snails
Turning on the lights impacts plants and animals (Image: Archi Banal/Getty Images)

Humans, and all the species we share a planet with, evolved for total darkness at night. With our urban areas increasingly flooded with artificial light, scientists, doctors and stargazers are making a case to preserve darkness.

The best thing about darkness is also the most frightening thing about it, the reason that makes it so easy to stay inside with the light switched on, and it is this: in the darkness you are small, and the universe is big. Ngā whetū gleam and sparkle. Te marama hovers, luminous, radiating the light of the sun you cannot see. In the darkness, the noises seem bigger, the rustle and chirp of other living things existing, not attending to you. There’s a gift in the darkness, when you wait for it: it’s the gift of noticing that the world sings songs you’re not part of, that a vast universe stretches beyond your skin. It’s as beautiful as it is terrifying. 

In urban Aotearoa – and increasingly in rural areas, too – these gifts of darkness are ignored. It’s the end of winter, and the earth is tilting back towards the sun. Still, twilights are early, and each evening hundreds of thousands of fingers around the country reach for light switches to illuminate kitchen benches and restaurant entrances and hospital corridors, truck stops and car parks and lumber mills. We let the light in. We keep the dark out.

And all that light spills and refracts, tumbles upwards into the sky. The dark is less dark. Only the brightest stars gleam through the haze. Moths, on their way to pollinate flowers, cross the path of a streetlight they mistake for the moon. Confused, they hover, caught. 

For thousands of years, the tilt of the earth covered these islands in a cloak of darkness at the end of each day. The advent of electric light created a way to resist the inevitable darkness, more light for human wakefulness and work. But as normal – and as useful – as electric lighting is, the phenomenon is only a century old, and most of the world’s population didn’t get electricity until much later than that. In Aotearoa, Māori across the country observed the stars in a dark sky, the light of a fire or torch not travelling far. The light of the stars in darkness led people to these islands, and – as the celebration of Matariki reminds us – stars and darkness remain important to Māori today. 

hazy yellow light pollution rises from a city obscuring the sky
Light pollution creates hazy skies, concealing the stars. (Photo: Christophe Lehenaff/Getty Images)

This legacy of darkness can be read in biology, says Margaret Stanley. The associate professor of biology at the University of Auckland studies urban ecology, the way that living things are shaped by city environments. The species that humans share cities with have adapted to natural rhythms of light and darkness; human-created light can disrupt this, creating massive flow-on effects through the ecosystem.

Stanley gives the example of birds. “For birds, singing is absolutely critical to communicating – attracting a mate and holding a territory,” she says. One of the signals for birds to sing is the amount of light: like humans, they have circadian rhythms which are disrupted by light at night. “People complain about lights coming into their bedroom so they can’t sleep – outside in the tree, there might be a bird that can’t sleep for the same reason,” she says. 

But, in urban areas, humans have the power to alter the environment, often disregarding the needs of other species. The Auckland Transport lighting page, for instance, states that the council’s policy is to “alleviate the adverse effects of trees on lighting,” not considering the adverse effect of lighting on trees. Stanley says light can alter or damage how plants grow, form interrelated communities, and get pollinated.

lamp casts light on tree at night
Only thinking about how trees block lighting is an example of being human centred rather than thinking about the needs of other species (Photo: Chai Wai Chevy Wan/Getty Images)

It’s not just plants and animals that need darkness: it’s us. Guy Warman is an associate professor of anesthesiology at the University of Auckland, and studies chronobiology – the technical term for the biological clock. Traditionally, biology students are taught the principle of homeostasis, the assumption that inside an organism, everything is the same all the time. But more recent research shows this is not the case. Warman says our bodies are “rhythmic, strongly rhythmic, and that has an effect on our behaviour and physiology.” 

The biological rhythm is conducted, largely, by exposure to light and dark. “Our body [clocks] have an inaccurate period, and they’re regulated by light and dark,” Warman says. This inaccuracy allows patterns of sleep to adjust for the change in day length throughout the year. The biological clock is embedded in the other systems of the body, like hormones and digestion, and light and dark help these systems to synchronise and communicate. While daylight tends to be stronger than artificial light, it can still impact circadian rhythms. You’re not imagining it: getting out of bed at 7am in the winter dark is much harder than in summer – without morning light, you’re quite literally less awake. 

“Sleep is really undervalued,” Warman says. “It’s seen as a waste of time, but it’s essential for immune function, memory consolidation, wound healing, clearing byproducts from our body and brain.” The widespread availability of electric light, as well as work cultures that create an environment for revenge procrastination, do not encourage people to pay attention to their need for rest, and – closely connected – their need for darkness. 

The Milky Way, shot from Wānaka. Dark skies are important for regulating our circadian rhythms of sleep and wakefulness. (Photo: Sellwell, via Getty)

It’s understanding the cultural, social, spiritual, and biological value of night that inspires the work of people across the country who advocate for protection of the darkness. 

One way this is being done is through dark-sky places. The International Dark-Sky Association, or IDA, is a global organisation that can accredit locations that protect darkness. In Aotearoa, there are four such places: Rakiura and Aotea, which are dark-sky sanctuaries; Aoraki-McKenzie Basin, which is a dark-sky reserve; and the smaller Wai-Iti dark-sky park near Nelson. 

There are more than ten other communities around the country in the process of getting accredited. These projects are linked by Aotearoa’s Dark-Sky Network, an organisation aiming for New Zealand to eventually be the first accredited dark-sky nation. 

On a practical level, becoming a dark-sky place means meeting stringent requirements to shield and dim lights, making sure that all outdoor lighting only goes to where it is needed, rather than spraying uselessly into the sky. Managing a dark-sky place means taking regular readings of the darkness, ensuring it’s pristine, and holding public events to connect communities with each other and the glimmering blackness above. 

lines of light show the location of streets. hazy dark sky and light pollution
Light pollution in Christchurch shows how light directed into the sky wastes energy. (Photo: Sky Images/Getty)

“Our night sky is a taonga,” says Ralph Bradley, manager of the Wai-Iti reserve. A keen astronomer, Bradley started the six-year process to create the park after he couldn’t get planning permission for an observatory on his own property. While not everyone can get to dark-sky spaces, he says creating darkness can start in your own backyard, with shielding lights and using fewer of them, helping to make night safer for the creatures who depend on darkness.

It also makes a lot of economic sense to protect darkness, says Nicky McArthur, an ecologist who became involved with dark-sky protection due to her role protecting the Hutton Shearwater birds endemic to the Kaikōura region. Fledgling shearwaters, leaving the safety of their alpine nests for the first time, mistake a lit road for the shine of light on seawater and crash into solid ground. Working with the council to dim streetlights to prevent this tragedy, McArthur realised that preserving the darkness of Kaikōura could create tourism opportunities for the South Island seaside town in wintertime. But getting local businesses and developers to understand has been a struggle. 

“I need people to know that we’re not going to be in the dark, we’re not going to switch the lights off,” she says. Shielding outdoor lights, directing the brightness downwards, doesn’t mean reverting to a pre-electricity age: instead, it helps humans and animals to have dark when they need it, and light when they need it too. 

Dark-sky certification is only one way to protect the darkness. City councils, in providing street lighting, are one of the main sources of light pollution (although commercial and industrial lighting is a concern too). The numbers are staggering: there are 124,000 streetlights in Auckland, 48,500 in Christchurch, and 13,000 in Dunedin. In recent years, many councils have been phasing out older, less efficient sodium lights, and replacing them with LEDs, controlled by a central management system that can manage the lights remotely. Running these lights costs millions of dollars each year, but installing shielding and dimming lights once traffic volumes are low – now standard practice – can reduce the expense as well as the amount of light spill. 

But while the practical changes brought in by dark-sky projects or LED lights matter, it’s also vital to change our cultural relationship to darkness. “We want light everywhere at night so we feel safe,” says Stanley. But while lighting may create a feeling of safety, there’s no strong evidence that it materially reduces crime. Instead, over-lit cities waste vast amounts of energy and prevent people from the biological, psychological and cultural benefits of darkness and stars.

“I think we’ve forgotten to look up,” says McArthur. “The night sky evokes awe and wonder – it has been so critical through the history of humanity, for explorers, for Polynesian navigators.” Keeping the sky dark ensures that that awe can be passed on to future generations, a reminder that our human bodies are subject to the same rhythms as those of  other animals and plants. After all, the brilliance of the stars isn’t going anywhere; making friends with the darkness lets more of their light filter in.

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