Getting Smart About Light Pollution

Preserving the beauty of the night sky means harnessing technological innovation and social change.

Earth at Night, courtesy NASA

This meteorological-satellite view shows the magnitude and extent of the light-pollution problem. In North America, the eastern seaboard and regions surrounding the Great Lakes are spectacularly lit, but practically every major population centre stands out in this 2012 composite image. Courtesy NASA EARTH OBSERVATORY

To paraphrase a familiar saying about the weather, everybody talks about light pollution, but nobody does anything about it. The problem is pervasive and plain to see. Artificial light dramatically increases sky glow, which obscures the splendours of the heavens. And despite the best efforts of the International Dark-Sky Association (IDA), The Royal Astronomical Society of Canada (RASC) and similar organizations worldwide, the situation seems to worsen each year.

The star-filled night sky our ancestors enjoyed no longer exists for most people. But is this magnificent spectacle really a thing of the past? Not necessarily. It’s important to keep in mind that light pollution is not an inevitable consequence of civilization; rather, it’s a social problem and, therefore, a shared responsibility. This also means that individuals and small organizations have the power to make a difference.


Milky Way, Barry Burgess photo

GLOWING SKY The sight of the Milky Way stretching from horizon to horizon is the dream of all backyard stargazers. And yet for most, that dream is out of reach. Even at the dark location of Bezanson Lake, Nova Scotia, there’s trouble on the horizon—the light dome from Halifax is plainly visible near the centre of this image, despite being some 100 kilometres away. Photo by Barry Burgess

Like any form of pollution, light pollution is, by definition, undesirable. The number of visible stars and the prominence of the Milky Way greatly depend on how much artificial illumination pollutes the nocturnal environment. In the February 2001 issue of Sky & Telescope magazine, John E. Bortle introduced a useful rating system for evaluating and describing the observing conditions from any given location. In the Bortle Dark-Sky Scale, a Level 1 sky is defined as one that is so pristine, the Milky Way casts shadows. By contrast, only the Moon, planets and brightest stars are visible in a Level 8 or 9 sky. Sadly, most Canadians live at this end of the Bortle Scale.

Although light pollution’s adverse effects on stargazing are likely the main concern of most SkyNews readers, there’s more to this story. Light invading your bedroom may disrupt the body’s circadian rhythms, the effects of which can be linked to health concerns such as sleeping disorders, depression, diabetes and even cancer. Wildlife suffers too. Artificial light influences the behaviour of nocturnal creatures and their food sources. Birds, in particular, are badly affected by bright lights and can experience disorientation, leading to fatal collisions with buildings. In New York City alone, tens of thousands of birds are killed or injured annually this way.

This is just the tip of the iceberg. Light pollution’s detrimental impacts are vast, interrelated and still not fully understood. For astronomers, an awareness of the health and wildlife aspects is crucial because they suggest potential allies in the ongoing fight to rein in excessive night illumination.


Lighting Choices, photo by Doug Wortley

LIGHTING CHOICES One of the main challenges municipalities face when converting high-pressure sodium streetlights, above, to LED bulbs is determining the appropriate colour temperature and illumination for a given situation. It’s important to note that provinces have jurisdiction over roadway lighting, while local governments are responsible for other applications, such as residential street lighting and heritage buildings. Photo by Doug Wortley

Light pollution is a multifaceted topic encompassing atmospheric physics, lamp-fixture design, colour temperature, visual glare and more. But in spite of the issue’s complexity, we can focus our attention on one simple question: What are the sources of light pollution? To answer this, we need to distinguish between two broad categories of unwanted illumination: sky glow and light trespass.

Sky glow is the orangish pall we see above cities and towns at night. It’s caused by light shining into the sky either directly or indirectly (reflecting off the ground or buildings). Light trespass, on the other hand, is direct and localized. Your neighbour’s annoying porch light? An automotive dealership’s intense glare? Both are examples of light trespass. The main difference is that you can sometimes avoid light trespass by moving your telescope to a different spot in your yard, whereas the sky glow overhead is much more difficult to escape.

Pie Chart

2015 data from the U.S. Department of Energy.

In 2015, the U.S. Department of Energy (DOE) conducted a thorough inventory of light­ing sources throughout the United States. The government survey revealed that streets, highways and parking lots account for three-quarters of outdoor lighting, while building exteriors are responsible for nearly all the rest. The sources include high-mast lighting for stadiums and sport fields, poorly shielded street and area lighting, brightly illuminated commercial buildings and exterior lights on private residences.

An often-overlooked contribution is from indoor lighting used in commercial buildings and office towers. The glare escaping from the building’s interior far exceeds that of the surrounding car lot. The DOE study includes interior lighting, but it’s difficult to quantify the amount of light escaping the buildings.

Vehicle headlights are another rarely considered source. In most urban and suburban locations, automobiles typically contribute between 5 and 10 percent of the sky glow from 5 p.m. to 9 p.m. Fortunately, for much of the year, these hours overlap with astronomical twilight, when backyard stargazers are unlikely to be troubled by the extra light.


Light pollution, photo by Doug Wortley

(MIS-)AIMING HIGH “Decorative” lights shine up into the sky, rather than down on the ground where they would assist pedestrians and vehicles. Such fixtures waste energy and create hazardous glare. Shielding these lights or pointing them down is an easy way to reduce light pollution. Photo by Doug Wortley

Given that roadways and parking lots account for most sky glow, it makes little sense to focus on residential lighting (porches, driveways, security systems and the like), annoying though they can be. Installing dark-sky-friendly lights on our homes may make us feel good (and we definitely should lead by example!), but these measures alone cannot solve the sky glow problem. To make a real dent, you have to take on City Hall but in a way that’s both smart and respectful.

An adversarial approach may be tempting—municipal engineers and city councillors are often thought to be concerned only with budgetary issues, while ignoring the social and environmental benefits of dark skies. Yet speaking as a community planner and a municipal engineer, respectively, we’re not your enemy. We care about light pollution too. However, we’re necessarily constrained by public-safety considerations as set down in government regulations, building codes and recommended best practices. We’re employed by the municipality, but our ultimate responsibility is to the taxpayer—and that’s you.

From an engineering perspective, our options are somewhat limited. We can design appropriate street-lighting layouts and oversee the upgrading of existing high-pressure sodium sources to energy-efficient LED sources. We can select full-cutoff fixtures that minimize overspill and glare while producing optimal distribution. We can further specify the appropriate LED colour-temperature bulbs for residential and commercial/industrial applications. But it’s worth remembering that most lighting engineers are not amateur astronomers, so the concerns of night sky enthusiasts are unlikely to be top of mind. Changing that municipal mind-set is something the RASC and IDA can—and do—strive to accomplish.

It’s not enough for skywatchers and other concerned citizens to simply demand that City Hall “do something” about light pollution. All of us must work together as a community to publicize and address the effects of excessive nighttime lighting. It may be difficult to capture the attention of taxpayers by describing the benefits of dark skies for astronomy buffs, but light trespass is a different matter. Few people want to have their bedrooms brightened by their neighbour’s security lights. Everyone wants safe roads—something not helped by glare from poorly designed or implemented street lighting. All taxpayers want to see their money spent efficiently and not wasted on unnecessary or needlessly bright lighting. In other words, if we focus on areas of general public interest, we’ll have greater success reducing both light trespass and sky glow.


Sky Conditions, Vancouver Island. Photo by Doug Wortley

WINTER OF DISCONTENTMENT Reasonably dark conditions are relatively easy to find on Vancouver Island, British Columbia, but in many locations, this isn’t the case. The view of the winter sky above was captured near Lake Cowichan—a half-hour drive from the small city of Duncan, whose lights are responsible for the bright glow on the left side of the frame. Photo by Doug Wortley

Despite the daunting challenges ahead, there are signs of progress and indications that society’s attitudes toward wasteful lighting are changing. A half-century ago, BC Hydro (the province’s electricity utility) proudly left the lights on all night in its downtown Vancouver head office as a beacon to the future of electrical power. Today, that same utility takes every opportunity to encourage its customers to turn off lights and use energy-efficient appliances to conserve power.

The majority of municipalities don’t have specific dark sky policies or bylaws to regulate or reduce lighting, but there are notable exceptions. The City of Vancouver has initiated an Outdoor Lighting Strategy that focuses on improving public safety, enabling attractive and accessible outdoor spaces, reducing light pollution, minimizing ecological impacts and reducing energy use. The city plans on implementing new standards for better lighting practices and developing regulations and policies to reduce light pollution in residential and commercial areas and on private land.

Ultimately, the future is “smart lighting,” where roadways, parking lots and building exteriors are dimmed or switched off when they’re not needed. And that smart future is possible today. As our cities and automobiles become increasingly “intelligent” via Internet of Things connectivity, adaptive controls offer community planners and municipal engineers the ability to provide nighttime illumination exactly when and where it’s needed. This technology is currently more expensive than existing “dumb” streetlights controlled by photosensors or timers, but the all-important return on investment that energy savings can yield is capturing the attention of municipal finance departments.

Of course, dimming and turning off outdoor lights when they’re not needed are also tremendously effective ways of reducing light pollution and saving the night. For most people, however, this is a secondary benefit. Tell taxpayers they can save money, and they’ll climb aboard the same bandwagon amateur astronomers are riding. Then everyone wins.

Finally, take heart in knowing that community planners and municipal engineers are on the side of the stargazers. While our priorities and focus may differ, we have a common goal. Remember, at its root, light pollution is a social problem. As John Barentine, the IDA’s director of public policy, says, “It’s not about removing lighting but, rather, changing the way people think and feel about lighting.”


To learn more about light pollution’s causes, effects and solutions, check out these excellent websites:
The International Dark-Sky Association, the world’s preeminent light-pollution-abatement organization, has a tremendously resource-rich website.
For a map showing worldwide sky glow conditions, go to
To learn about the RASC’s efforts to combat light pollution, visit:

Lindsay Malbon is a graduate of Vancouver Island University’s Master of Community Planning Program in Nanaimo, British Columbia. She’s the author of the guidebook Saving the Starry Night: What Cities Need to Know About Light Pollution.

Ian Ashdown is a Vancouver-based lighting research scientist and amateur astronomer who revels in the darker sky visible from 300 metres up the North Shore mountains when fog rolls in to blanket city lights.

This article originally appeared in the March/April 2019 issue of SkyNews.

Categories: Resources
2 comments on “Getting Smart About Light Pollution
  1. As a darksky advocate for over 10 years now, I have to disagree with the statement “it makes little sense to focus on residential lighting (porches, driveways, security systems and the like), annoying though they can be.”

    Business and residential exterior lighting account for a large percentage of bad lighting contributing to skyglow. In my mid size city alone there are hundreds of thousands of buildings with poorly shielded lights left on all night. Some are lit up like small stadiums. LED is making this worse because those switching to it are using brighter and whiter light (more blue). If you factor that each of these buildings have multiple exterior lights that quickly adds up to millions of lights from businesses and residential buildings contributing to skyglow, not just light trespass.

    If the war on light pollution is to be won, it will be with a mind shift by society, business and residential (property owners), that see the value and importance of using low intensity lighting that is shielded and doesn’t pollute the night sky or the environment. Just like recycling is today. It may also require education and enforcement by municipalities through bylaws. But to say it makes little sense to focus on residential (or business) lighting is short sighted in the grand scheme of light pollution in my opinion.

    Unfortunately that statement in this article makes it impossible for me to share this with my local officials that I’ve been discussing light pollution with for many years. It would derail my efforts to see a lighting bylaw be drafted and implemented.

  2. kevan hubbard says:

    One strange thing I find is illuminating roads nobody lives on as cars,etc, have guessing lit roads cause an increase in speed and therefore accidents.or what of floodlit churches yet those that do it tell us the glory of God is within….yes within the power companies bank accounts!

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