‘We took them for granted’: Australia’s cities are losing their stars

In 2016, Ken Wishaw was on holiday in the Grand Canyon in Arizona. Being an enthusiastic stargazer, he wound up giving an impromptu tour of the night sky with his laser pointer to a group of fellow tourists.

“I was blown away when several of them said because they lived in Florida, they had never seen stars before!” says Wishaw, a board member of the Australasian Dark Sky Alliance. “The comment that struck me was ‘we took them for granted, and we lost them’ – to light pollution.”

Light pollution is a challenge not only for stargazers and astronomers, but also for wildlife, affecting everything from moths to wallabies. The problem is growing – between 2014 and 2022, the amount of light from human night-time activity increased by a net 16 per cent, a study published in Nature in April says.

While much of the Australian continent is sparsely inhabited and has dark night skies, our cities have a high level of light pollution, according to the Light Pollution Map, a stargazing app and website.

Melbourne and Perth have the maximum nine out of nine score on the Bortle scale, an internationally used rating of light pollution, along with other big cities such as New York City, Los Angeles, Tokyo, Beijing, London and Paris. Melbourne’s night sky is 69 times brighter than natural and Perth is 50 times natural levels. Sydney ranks slightly lower at 8.7 or 40 times above natural, perhaps because of the dark streaks caused by Sydney Harbour, Botany Bay, other waterways and its surrounding national parks and mountains. Brisbane is 8.5 or 36 times the natural level.

The differences are not necessarily obvious to the naked eye. Wishaw, a retired doctor, says the human eye is an amazing organ that can operate effectively with a huge range of light variation.

In very dark conditions, it can, after about 30 minutes, adapt to the point of detecting a single photon. If there is too much light, it will not adjust fully to protect the photoreceptors at the back of the eye from being overloaded and damaged.

“The eye is useless as an objective judge of darkness,” Wishaw says. “It is constantly changing its sensitivity to suit the brightness.”

After his Grand Canyon trip, Wishaw started his own experiments comparing the night sky at his home in Maroochydore on the Sunshine Coast with Kenilworth, 30 kilometres inland.

Taking a photograph of the same patch of night sky using a camera with the same exposure settings can reveal the difference between light pollution and true darkness. But using the human eye, the only way to judge it is to count the stars, Wishaw says.

On a clear winter’s night in Kenilworth, in the hinterland west of Maroochydoore, you can see more than 2000 stars, Wishaw says. But under the same conditions in Brisbane, you can see only five to 10 stars.

Light pollution is growing even in regional areas. Amateur astronomer and astrophotographer Rodney Watters is located 15 kilometres east of Bathurst in the NSW Central West, a city of 36,000 to 46,000 people, depending on where you draw the boundaries.

“I have been at my current location for 13 years and have seen the light dome from Bathurst grow every year to the point that I am planning to move my observatories to remote locations sometime in the next few years,” Watters says.

The Nature study is based on an analysis of NASA Black Marble data, which shows the lights that can be detected from satellites. The researchers found that night-time brightening increased 34 per cent from 2014 to 2022, but this was offset by 16 per cent dimming in other areas.

Associate Professor Zhe Zhu at the University of Connecticut, a senior author on the study, says the data is of interest to scientists such as astronomers and biologists, and it also provides geostrategic intelligence about the energy and GDP activity of other countries.

Brightening was usually a result of intensified urbanisation, while dimming was usually an abrupt change from a power outage or war conflict. The exception that Zhu’s team observed was that Europe, especially western Europe, had grown “darker and darker” when observed from a satellite over the past 10 years.

“They’re getting dimmer – not because they lost power,” Zhu says. “It’s more that they are having more energy-saving policies as people turn off the lights at night. There are national or citywide policies to regulate people who are using the light.”

The general ambient background light of the night sky is also increasing because of the increase in communication satellites, affecting astronomy and wildlife, other research suggests.

Professor Theresa Jones, a specialist in evolution and animal behaviour and leader of the Urban Light Lab at the University of Melbourne, says artificial light affects all life – bacteria, algae, plants, animals, vertebrates and invertebrates.

“Because life evolved under specific life cycles, putting artificial light into a space that should be dark has implications for all different life forms,” says Jones, a founding co-director of the Australasian Dark Sky Alliance.

The light can change behaviour. For example, insects, spiders and geckos are attracted to light, so it can draw them away from natural habitat good for feeding or breeding into suboptimal locations. Migratory species such as birds may fly off course and land in cities instead of forest. Turtle hatchlings can become disoriented by artificial light and head inland instead of to the ocean.

Light can also alter the physiology of humans and wildlife alike, including metabolic processes, reproduction, growth and development. Researchers at Latrobe University have found that artificial lights can disrupt the reproductive cycles of tammar wallabies, for example.

Marnie Ogg, a dark sky campaigner who has run stargazing tours with her husband astronomer Fred Watson for two decades, says her time running the Sydney Observatory gave her fresh insight into the thirst of people of all ages to explore the night sky and to “understand their place in space”.

She supports Vivid Sydney because it gets people out and about, festival lights go out at 11pm each night, other lights are dimmed to make the entertainment lights more effective, and the event runs for only three weeks. However, Ogg points out that when Vivid was first mooted, there was meant to be a corresponding dark sky festival, but this never happened.

Some lighting festivals go on too long and have a detrimental effect, Ogg says. She includes in that the Bruce Munro Field of Light installation at Uluru that was meant to run for a year and is now 10 years old. A spokesperson for Voyages Tourism Australia, the operator of Ayers Rock Resort, Uluru, says the installation uses low-intensity, spatially contained lighting and operates for limited hours – up to three hours after sunset and again briefly before sunrise – and monitoring shows healthy populations of wildlife.

Ogg also objects to the Harry Potter Forbidden Forest Experience in Melbourne because it was located in a nature reserve with lots of nocturnal animals. (A spokesperson for Fever, which runs the Harry Potter experiences, says an ecological assessment is done before every event and the style and duration of lighting is carefully planned to avoid harm.)

“They’re never a short-term thing,” Ogg says. “Even with Vivid, I heard people ringing in to the radio the other day, saying, ‘we should have it in suburbs, and we should have it everywhere, it should go longer’ – but if we keep lighting everything up all the time, then we’re not winning the battle

“I’ve been working with some country towns that want to have dark sky status, and they go about looking at that, and they might if they’re lucky, get $2500 or $5000 to run a festival with Destination NSW or [the equivalent in] whatever state they’re in as an inaugural flagship event, but they can get $100,000 if they run a light festival, plus they get all the lighting support from these massive organisations that will wheel in and put lights in.”

Jones at the University of Melbourne says light pollution is actually the easiest of any human-induced pollutant to fix “because you can literally switch it off”. On the other hand, “the lights are there because humans need them”.

There are three ways to tackle this conundrum, Jones says. First, good lights directed only into the place they are needed rather than spilling out into the environment like a big ball of light. Second, reducing light intensity and having them on only when needed. Third, changing the colour of the lighting to avoid throwing blue light – a problem with early LED lighting – because this is more attractive to animals and more disruptive to physiology.

While urbanisation has generally made the skies brighter, Ogg says there are pockets of progress on a more localised level, and she is getting a lot of interest from councils around Australia asking how and what they can do.

In Sydney, Northern Beaches Council created an Urban Night Sky Place at Governor Phillip Park and Barrenjoey Headland. It is successful, Ogg says, partly because the peninsula is surrounded by water and national park.

“That makes it unique, I would say in the world, to have a place so close to a city to be able to see the night sky and even the Milky Way so well,” Ogg says.

“It took them six years, and in doing that, they retrofitted some lights and turned lights down, and that sort of became a council project, not just within that area. I’ve noticed that across the northern beaches area, where I live, the lights are getting warmer, they are getting less intense, and they’re only being used when they need to be.”

The northern beaches of Sydney are noticeably darker than the rest of the city on the light pollution maps but, Ogg says, there is also progress in other places. The Sydney Harbour Bridge was relit to remove the upward-pointing lights, for example.

Jones says there are few dark spots in Melbourne. “It’s very sprawling, so we have lights over a much, much bigger area … so you’re getting light spill from all of the outer regions into the centre as well, and vice versa,” she says.

Dark Sky International has certified several dark sky places in Australia. In NSW, besides Palm Beach, there is the Warrumbungle Dark Sky Park near Coonabarabran and Kestrel Nest EcoHut in the Snowy Mountains in NSW. In Queensland, Winton is a dark sky community, near the Jump-Up Dark Sky Sanctuary. In South Australia, there is the River Murray Dark Sky Reserve, Arkaroola Wilderness Sanctuary, and Carrickalinga dark sky community on the Fleurieu Peninsula. Victoria does not have any official dark sky parks.

The Sunshine Coast Council has created a 900-square-kilometre dark reserve in its hinterland and is waiting to see if Dark Sky International will ratify it.

Attitudes are changing. “When I first started talking about it, all these people were thinking that I wanted to live in a cave and turn all the lights off and never ever have light on again – that’s absolutely not the case,” Ogg says. “I think it’s just a few more years off, and then we might actually see a downward trend in Australia for light pollution, hopefully.”

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