Most Canadians are as likely to see the Milky Way as they are to see a beaver riding the back of a moose.
That’s because almost three-quarters of Canadians live in brightly lit citiesleaving only patches of stars visible to the naked eye.
Now, a new study has found that the night sky may actually be brightening faster than previously thought, with consequences for people, ecosystems and more.
IN a paper published in Science on Thursdaythe authors used data collected by citizen scientists who participated in the outreach program Globe at nightin which participants look at certain constellations and record how many stars they can see.
They found that over the past 12 years, the stars have become increasingly difficult to see, possibly due to increasing light pollution. The change was a seven to 10 percent annual increase in sky brightness, far more than what satellites have detected.
To put it in perspective, the authors note that someone born in an area where 250 stars can be seen will see fewer than 100 in the same location 18 years later.
This illustration shows the effects of light pollution on the night sky, from an excellent dark sky on the left to an inner city sky. (NOIRLab/NSF/AURA, P. Marenfeld)
Satellite data previously showed light emission growth of 2.2% per year from 2012-16 and 1.6% from 1992-2017, which is in stark contrast to the new findings.
But there may be a reason for that.
These satellites are not specifically designed for research, so they are limited in what they can see. Also, satellites can see light emitted straight up, but not from the side.
Map of artificial sky brightness in North America, in double increments, as a ratio to natural sky brightness. Black represents little or no light pollution, while yellow, red, and white represent the most light pollution, where few stars are visible in the night sky. (Fabio Falci, Christopher Kiba, etc.)
There may be other explanations, including the increased use of LEDs, which are brighter and contain more blue light.
“Blue light is scattered more in the atmosphere, so you get more light scattering back to Earth,” said lead study author Christopher Kiba, a light pollution physicist at the German Research Center for Geosciences GFZ in Bochum, Germany.
“[And] when our eyes are dark adapted, they are more sensitive to blue light. So replacing that long-wavelength light with blue light makes things look brighter and makes it harder to see the stars.”
Kyba also theorizes that the trend toward more decorative lighting — on the sides of buildings and in people’s homes, for example — that shines in directions other than up may be a factor.
The research “confirms something many of us have suspected for some time, which is that the rate at which light pollution is increasing worldwide is much faster than we previously appreciated,” said John Barentine, executive director and principal consultant at Dark Sky Consulting, LLC and former head of the International Dark Sky Association, who was not involved in the study.
Brighter does not mean safer
There is a belief that the brighter an area is, the safer it is. But this is not necessarily the case.
“You’ll hear this term ‘security lighting’ – people putting up outdoor lighting and lighting up their property, their yard or whatever. They leave that light on all night because they believe it discourages criminal activity,” Barentine said.
“But I think it would be better to call it insecurity lighting, because it’s more about making people in houses and buildings think that the outside world is a little bit safer because they’ve taken some proactive step, to do so.’
He also noted that most crimes occur during daylight hours.
Improper lighting can actually make people less safe.
“You put glare in people’s eyes, it makes the pupils constrict; they lose depth of field, they lose the contrast of objects with the background, which is important for visual detection at night,” Barentine said.
He acknowledges that the problem of light pollution may not be fully appreciated, and perhaps for good reason.
“I think it’s not on a lot of people’s radar yet, in part because we live in a complex world that faces very big and very present environmental challenges,” Barentine said.
“And we all suffer from problem fatigue at some level, whether it’s the pandemic or climate change or biodiversity loss. You know, we look at the world now and in the near future and it looks pretty scary. “
But this is more than an issue of cultural preservation or how the night sky has affected humanity since our earliest beginnings. It has potential implications for human health, ecosystems and even climate change.
All of these birds died because of overwhelming buildings in downtown Calgary. (Helen Pike/CBC)
In October, on World Migratory Bird Day, the United Nations said light pollution was contributing to the deaths of millions of migratory birds by altering their biological clocks. Birds can see artificial light at night as a longer day. Others may begin their migration earlier than other species and may arrive at their summer destinations before food sources become available.
Birds are also often killed flying into brightly lit glass buildings.
“We need to think about the animals we share the world with,” Kiba said.
Light pollution can also contribute to an increased risk of cancer in humans, and the loss of energy certainly does not help efforts to reduce CO2 emissions.
“The upshot of all of these things is that we are collectively as a species transforming the nocturnal environment in a way that is unprecedented in Earth’s history.” We just don’t know of anything that’s been that consistent and happened that quickly,” Barentine said. “You’re only looking at a period of about 140 years since electric lighting was introduced and became widespread.”
Kyba says increased lightening can even be documented in just a few generations.
“My mother was born in Saskatchewan on a farm with no electricity,” Kiba said. “And every night if he went outside he would see, you know, space. And now my kids have rarely experienced that at all.”
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