Let there be dark: the battle to save our sky from light pollution

NOAA-20 probably has the best view of the North York Moors, even though it’s 512 miles away. In one sweep – on a clear night – the weather satellite can see the whole national park, from the forests in the south near Scarborough to the heather-covered moorland just south-east of Middlesbrough.

When Richard Darn walks these hills – on a clear night – he can’t quite make out NOAA-20 as it scurries from pole to pole because the skyglow from Middlesbrough pollutes the darkness. Yet down in the southern forests, the night sky is pristine and ideal for satellite spotting. Places with truly dark skies like this are shrinking. In the areas where you can see why the ancients decided that a group of stars looked like a great bear, or scorpion, or Orion the hunter, the faintest dots of the constellations are being drowned in skyglow, or winked out by a brash neon sign or stray security light.

The North York Moors National Park authority is concerned about this. On Monday, it will decide whether to commit £50,000 to a “dark skies” plan, to identify where those signs and security lights could be tweaked or shielded.

Darn is an astronomer who hosts stargazing parties and works with several national parks, including the North York Moors, on dark sky conservation. “My personal feeling is that light pollution is significantly worse,” he says. “It’s not so much street lighting, it’s all the other ancillary light – supermarket car parks, lumberyards, industrial plants or even people’s houses.”

“These days, people erect two or three of these absolutely searingly bright white LEDs. We don’t realise the profound effects it’s having, putting up light domes over small farms or villages – places that had no light dome before – and transforming the night-time scene from something quite beautiful into something numbingly banal.”

The national park authority’s plan is to do a “lighting audit” of farms, pubs, campsites and other premises to improve the darkest areas, says Mike Hawtin, a senior park officer. It will potentially offer grants of up to £2,500 – funded by Sirius Minerals, a local mining company – if it decides lighting needs to be replaced or shielded.

Why is darkness so important? Stargazing is a vital human activity, according to Darn, and listening to him talk makes it hard not to share his enthusiasm for watching shooting stars and the expanse of the Milky Way, or knowing where to find the Andromeda galaxy.

“Where we live in space is as profound as where you live in the country or Europe or the globe,” he says. “You can see miraculous things, and you start to think of how long the light’s been travelling to get to your eye. And if you weren’t out there, if you weren’t somewhere dark, you wouldn’t see them.”

But the soothing effect of watching the heavens is not the only reason why dark skies are being embraced by the national parks of the North York Moors, Northumberland, the South Downs and the Yorkshire Dales. There is growing evidence that lighting up the night is affecting biodiversity and the welfare of creatures both nocturnal and diurnal, while also leading to insomnia and other health issues for humans.

“These aren’t trivial shifts – these are similar kinds of scales of shift as climate change produces,” says Kevin Gaston, a professor of biodiversity and conservation, who runs the Ecolight project at Exeter University’s Environment and Sustainability Institute.

Huge numbers of species use daylight information as a clock, Gaston says. So birds may decide to migrate or lay eggs at a particular time of year, based on how much light there is. If they arrive too soon, before insect populations have boomed, they risk starvation. “The cues you might be using to decide when to lay your eggs and for nestings to emerge may be increasingly disconnected from when the food that you want to feed those chicks is actually available,” he says.

It’s not just birds. Turtle hatchlings can be disoriented by skyglow and move away from the sea. Insects attracted to light are easier prey, which unbalances ecosystems. The International Dark-Sky Association lists more than 2,600 studies on the impacts of artificial light on clownfish, mice, worms, bats, coral reefs, katydids and tree sparrows.

Even short periods of light can have an impact. Memorial light beams at the site of the World Trade Center in New York are shone on one day a year, 11 September, but they lure as many as 160,000 migratory birds off course, circling the beams. Now they are switched off periodically to let the birds disperse. There’s also evidence that the brighter, bluer street lights that replaced the orange glow of low-sodium lighting of the 1970s and 80s are having an impact on humans. A study in South Korea last year found an association between artificial light at night and the prescription of sleeping pills. There is already provision for local authorities to tackle light pollution, but they often lack the resources to do much about it, according to Emma Marrington of CPRE, the countryside charity. “Lighting can be a statutory nuisance in the same way that noise is,” she says. “So you can complain if you’ve got a real issue with the neighbours’ security light, for example. The environmental health team should support you in monitoring the lighting and then mediating.”

CPRE runs an annual star count, encouraging people to check light pollution in their area by asking how many of Orion’s stars they can see. “If you can see fewer than 10, you’re under severe light pollution but if it’s more than 30 you’ve got pristine night skies,” Marrington says.

Yet even people in cities can still find decent conditions to see events such as the annual Geminids meteor shower, which peaked is due to peak on the night of 14-15 December this year. “You don’t need to travel thousands of miles to see the Milky Way or shooting stars,” Darn says. “Sometimes just taking a walk in your local wood at night gives you an improvement straight away. You might not have a pristine dark sky, but you can have a night sky that’s really aesthetically beautiful.”