WHY THE STARS ARE FADING

Peter Littlewood, Director, Young People’s Trust for the Environment

Where I live in Bradford Abbas, we don’t have any streetlights. It felt really strange when we first moved here, but it didn’t take long to get used to carrying a torch if setting off around the village after dark. One of the great things about the absence of street lighting is that we get some amazing starscapes on clear nights, like the ones we had at the start of February.

We had a spectacular view of the snow moon - the first full moon in February - which gets its name from the Native Americans, who used the moon to track the seasons. The heaviest snowfall in North America usually occurs in February, hence snow moon. And popping out this evening to put out the bins, I was greeted by Orion on his eternal hunt through the night sky and high above, the wonky ‘w’ of Cassiopeia too.

In urban areas, light pollution is a problem that’s growing rapidly. The human eye should be able to spot thousands of stars in the night sky unaided, but for around 30% of the world’s population, it’s now almost impossible to spot the Milky Way - our home galaxyand many of the constellations too. And more than 80% of the human population lives under light-polluted skies.

On cloudy nights, the skies near cities are now hundreds, or even thousands of times brighter than they were two centuries ago. Even from Bradford Abbas, if you look to the northwest at night, the glow of Yeovil’s streetlights can easily be seen.

It’s alarming how quickly the stars are disappearing from view. Globe at Night, a citizen science study run by US research centre NoirLab, has predicted that a child born today in a place where 250 stars are currently visible will only be able to see 100 of them by the time they reach the age of 18. The brightness of the night sky is thought to be increasing at a rate of 9.6% per year.

Globe at Night’s findings are based on over 50,000 observations reported by citizen scientists from North America and Europe between 2011 and 2022. Participants were shown a range of star maps and selected the one that best matched their view of the night sky.

Ironically, the increasing use of energy-efficient LED bulbs is accelerating the nighttime ‘skyglow’. The amount of blue light that LEDs give off is much higher than traditional sodium streetlights. Blue light suppresses the production of melatonin, the hormone that regulates sleep patterns in humans and other animals. 51% of the UK’s streetlights were LEDs by 2019.

Light pollution also affects wildlife. All animal and plant life on our planet has relied on a predictable day and night cycle. The daily rhythm governs behaviours like sleep, reproduction, feeding and avoiding predators. Light pollution has a serious impact on nocturnal animals, radically altering the nighttime environment they are used to. In highly light-polluted areas, some predator species are given an advantage, because they have an increased ability to see and hunt other species, particularly those that are attracted to light.

That might be good news - in the short term at leastfor bats that like to eat moths, as they tend to congregate around street lighting at night. But it’s not so good for the moths or other insects that end up trapped by the lure of streetlights. Indeed, street lighting is thought to be a major contributor to the ‘insect apocalypse’ we’re seeing across the planet, with huge declines in insect numbers.

Migrating birds can be confused by lights at night, causing them to fly off course and in extreme cases, even to crash into objects like high-rise buildings. Take, for example, Philadelphia, USA on a foggy, rainy night in October 2020. The cloud base was low, so nightmigrant birds were flying low too. Unable to see the stars above that they would normally navigate by and disoriented by the fog, the birds were drawn off course by the city lights. Some 1,500 of them died that night by crashing into the glass of high-rise offices and flats. ypte.org.uk

So how do we solve the problem? Well, outdoor lights can be shielded, so that they point only downwards and don’t spill their light up into the night sky. Dimmers can be added or the amount of blue light given off can be reduced. At home, we can do things like closing the curtains to stop light spilling out into the night and making sure any security lighting is focused carefully.

If you’re interested in seeing as many stars as possible, our closest truly dark skies can be found in the Cranborne Chase Area of Outstanding Natural Beauty. More than half of its 380 square miles still has the lowest level of light pollution in England, so it’s a great place to spot stars!