Light Pollution – The Cost of Seeing in the Dark

Looking up into the night sky, it’s easy to think that the pitch black abyss you’re seeing is dark – but it wasn’t long ago that it was the only thing lighting up the night. Now that no city ever seems to sleep, the impacts of artificial light shining on the natural world are coming to light.

How Light changes Biology

Natural changes in lighting causes melanopsin-containing cells in the human eye to respond to the blue component of light that is coming in. A low component of blue light results in melatonin being released, making you sleepy, and a high component of blue light results in melatonin production being suppressed (ERCO GmbH, 2023). This is the reason you might’ve heard that blue light screens are “bad” for you to use before bed – it can disrupt this cycle based on natural daylight and can keep you from falling asleep.

But humans aren’t the only species regulated by light. Artificial light exposure at night, or ALAN, can lead to detrimental effects on other animals.

ALAN is a problem for birds because of the fact that many species migrate at night – even if the species of bird is typically diurnal. It is especially important to consider the effects of ALAN in Hamilton because of our local ecology. The Atlantic and Mississippi flyways, which Hamilton is situated under, together form migratory paths for more than 700 different species of bird (Woodstream Corporation, 2024). Local areas such as Cootes Paradise and the RBG provide valuable stopover habitats for any birds in the area.

The night is cooler, making it less likely for birds to overheat or catch daytime thermals that may throw them off route, and predators are more easily avoided in the dark. Most importantly, migratory birds use the moon and stars to orient themselves north to south (Thomas, 2018) – which is where ALAN becomes a problem.

Light coming from sources other than the moon and stars causes disorientation in migratory birds, and can cause them to circle the source until exhaustion, or even strike illuminated buildings at night. This “attraction” to light causes a disproportionate dispersion of birds in large metropolitan areas compared to areas that are less brightly lit (Thomas, 2018). Living in these areas comes with risks of their own for birds, including predation from cats or risk of being struck by cars.

Interruptions in natural processes is a common theme with light pollution. For fireflies, another species commonly affected, the interruption is in their reproductive process.

On early, dark summer nights, bright flashes can be spotted as male fireflies float through the air in an attempt to attract female fireflies hidden in the grass below. The females are attracted to males with the brightest lights, and when they see a suitable mate, they respond with a flash of their own in the grass to invite the male to take part in mating.

When ambient light from inside houses, light posts, or passing cars is present during mating, it leads to an interruption in this process that leads to less larvae being born the next year. 18 species of firefly between the USA and Canada are threatened with extinction due to the impacts of light pollution and other environmental factors like habitat loss and pesticide usage. (Hina, 2023)

Between the adverse effects on mammals, birds, and bugs, nocturnal and not, it’s easy to see the benefits to reducing the use of ALAN.

So what can be done?

There are a variety of small and large scale solutions that can be implemented to help reduce the production and the effects of ALAN for all different sorts of animal.

Putting lights on a timer, dimmer, or motion sensor can help reduce light use to only when it is needed. If there is room in a building that is normally emitting light, consider applying bug mesh or anti bird collision stickers to the outsides of windows to allow birds to distinguish them from open air (Snyder Sachs, 2023).

Using warm coloured LED lights, instead of blue toned LEDs, can reduce how far light can travel as blue light has a larger geographical reach due to its shorter wavelengths.

A lot of ambient light comes from streetlights that do not focus their light to where it is needed – creating street lights that focus light directly down to light the street, and not the sky, is important to stop what is called light trespass (Royal Astronomical Society of Canada, 2025). Advocate for the implementation of streetlights that do not shine unnecessarily.

There are already some great programs that are helping to reduce the amount of ALAN we are producing. “Lights out Toronto” is an awareness campaign started to reduce the amount of unnecessary light being used during the migratory season.

Always feel free to organise and spread awareness! Run your own awareness campaign to inform people about why light pollution is harmful.

Retaking the night – Levels of a dark sky preserve

A dark sky can be important for animals to regulate their biological needs, but a lack of artificial light can have intrinsic value for people, too.

Many astronomy groups advocate for the protection and preservation of dark skies on 3 levels –

Dark sky preserve

A special area where light pollution is minimized in all ways possible, creating a better environment for the organisms of the area, and giving us incredible views of the night sky. There are three dark sky national park preserves in Ontario; Point Pelee, Bruce Peninsula, and Fathom Five.

Nocturnal preserve

Areas where artificial light is highly restricted in an effort to primarily protect nocturnal nightlife. Though it may not be used for astronomical viewings, the preserve may deliver public education programs about the importance of the nocturnal environment.

Urban star parks

Areas closer to urban environments where light usage is strictly controlled with measures in place to prevent the unneeded use of artificial light at night. Skies are generally brighter due to proximity to cities.

Visiting your local dark sky preserves helps to keep them protected! Take advantage of a night under the milky way. ( Royal Astronomical Society of Canada, 2021)

Works Cited:

Hina. “Fade into the Night: Fireflies Facing Threats from Climate Change and Light Pollution.” Toronto Star, 15 July 2023, www.thestar.com/news/canada/fade-into-the-night-fireflies-facing-threats-from-climate-change-and-light-pollution/article_32f70475-4ab0-5c56-ac19-f4fadc3f440d.html. Accessed 27 Apr. 2026.

Snyder Sachs, Jessica. “How Light Pollution Impacts Wildlife & How You Can Help.” National Wildlife Federation, 4 July 2023, www.nwf.org/Home/Magazines/National-Wildlife/2023/Summer/Cons2ervation/Light-Pollution-Wildlife.

ERCO GmbH. “What Is Melanopic Light Effect?” Erco.com, ERCO GmbH, 18 Apr. 2023, www.erco.com/en/designing-with-light/lighting-knowledge/led/melanopic-light-effect-7737/. Accessed 27 Apr. 2026.

Woodstream Corporation. “Bird Migration: Birds of the Atlantic Flyway.” Www.perkypet.com, www.perkypet.com/articles/atlantic-flyway-migration.

Thomas, Adam. “City Lights Setting Traps for Migrating Birds: How Birds Are Drawn to Artificial Light Pollution in Urban Areas.” ScienceDaily, 2018, www.sciencedaily.com/releases/2018/01/180119125817.htm.

Royal Astronomical Society of Canada. “Dark-Sky Sites Program.” RASC, 8 Jan. 2021, rasc.ca/lpa/dark-sky-site-program.

Image Citations:

Jonathan, S. (2025) Cedar Waxwing. [Photograph]. INaturalist. https://www.inaturalist.org/observations/311245836

Kayvan, M. (2019) Northern Bruce Peninsula. [Photograph] Unsplash. https://unsplash.com/photos/time-lapse-photo-of-stars-on-the-sky-7yKLAXqcl0Y