by Andres Clavier, Freshwater Stewardship Education Intern
We live in a world constantly surrounded by artificial light, but we may not realize how much it affects us and the planet. Light pollution is a serious problem that goes beyond obscuring our view of the stars; it also has significant impacts on human and natural ecosystems. To understand the issue, we must explore the nature of light pollution, its various forms, and how it impacts our world.
Light pollution is unwanted, inappropriate, or excessive artificial light that can affect wildlife behaviour, human health, and environmental quality. It is also a form of waste energy. It can be classified into different types, each with its own characteristics and effects.
Skyglow
Skyglow is the brightening of the night sky over inhabited areas. It is caused by the excessive and/or misdirected artificial light that scatters and is affected by the particles and molecules in the air. This reduces the visibility of celestial objects such as stars and planets and also affects the natural cycles of wildlife. Nocturnal birds, mammals and insects tend to change their behaviour due to a brighter sky in the night hours, and that brings negative consequences for their survival.
For example, the Swainson’s Thrush (Catharus ustulatus) is a migratory bird of Canada that relies on celestial cues for navigation during its extensive migratory routes (Cochran & Mouritsen, 2007). However, light pollution from urban centers and infrastructure can gravely interfere with their natural navigational abilities. When these birds encounter the artificial brightness of cities, they can become disoriented and drawn off course, leading to “fatal light attraction” (Evans Ogden, 1996).
Consequently, many thrushes suffer from exhaustion, increased vulnerability to predators, and fatal collisions with buildings and structures. The alteration of their migratory patterns can also lead to missed breeding opportunities and disruption in their lifecycle, posing long-term consequences for their populations (Longcore & Rich, 2004).
Glare
Glare refers to excessive brightness that causes visual discomfort, making it difficult to see properly. It is often the result of poor lighting design or unshielded fixtures, which emit light in multiple directions. You can find this effect in streetlights, headlights, billboards, coach lights, or windows. Streetlights cause a common case of glare without proper shielding, which makes it challenging for drivers, cyclists, and pedestrians to see clearly.
Light Clutter
Light clutter is bright, confusing, and excessive groupings of light sources. It can be found in urban areas where there are many different types of lighting fixtures, such as signs, advertisements, decorations, or security lights. Light clutter can create visual noise and confusion, making it hard for humans and wildlife to identify relevant information in their environment, such as landmarks.
Light Trespass
Light trespass occurs when unwanted or intrusive light spills over into areas where it is not needed or wanted, for example, from one property to another. This can alter the natural behaviours of animals and plants and disturb people’s privacy and sleep quality in their homes, particularly their circadian rhythms.
A species that is affected by light trespass is the Canadian Lynx (Lynx canadensis). This apex predator relies heavily on its keen nocturnal senses to hunt. The unnatural brightness emitted from expanding urban areas and roadways can disrupt the lynx’s night-time hunting efficiency by altering its visibility and masking the subtle movements of its prey (Rich & Longcore, 2006). Light pollution also affects the behaviour of its prey, making them potentially less active during times they usually would be, increasing the lynx’s challenges in securing food (Beier, 2006).
Such disruptions can lead to nutritional stress, decreased reproductive success, and increased vulnerability to other threats in their environment. As urban sprawl continues, understanding and mitigating the impacts of light pollution on apex predators like the Canadian lynx becomes crucial for preserving ecological balance.
Impact on Urban and Natural Environments
Recent research found that the night sky may be brightening faster than originally thought, with a seven to 10 percent annual increase in sky brightness over the past 12 years (Falchi & Bará, 2023). Canada is not exempt from this reality.
According to ASTROlab, 2023, in large Canadian cities, more than 95% of stars that can normally be seen with the naked eye are no longer visible due to light pollution. This has consequences for humans, ecosystems, and more. For example, nighttime lighting can confuse migrating animals, modify predator-prey relationships, and even alter competitiveness within the same species (ASTROLab, 2023). It is also important to note that light pollution wastes energy and money, as poorly designed lighting systems consume excess electricity. Light pollution also impacts scotobiology, the study of darkness.
In natural environments, light pollution disrupts the natural behaviours of nocturnal animals and affects their habitats. It can interfere with reproduction, navigation, and feeding patterns, ultimately impacting ecosystems. A well-known case of light pollution effects is sea turtle hatchlings drawn towards artificial lights on the shore instead of the moonlit ocean, leading to a high mortality rate due to exhaustion and predation.
These negative effects also occur in other water ecosystems, such as rivers and lakes. The most visible consequence is in cyanobacteria. Light is an essential factor for this microorganism, and changes in light intensity can alter their growth and metabolism (Wang, et. al, 2022), and this, at the same time, can affect the food web and carbon cycle of the environment.
Get informed, and make a difference!
Understanding the different forms of light pollution and their effects is the first step toward finding solutions. By embracing responsible outdoor lighting practices, shielding fixtures, and choosing warm, gentle hues, we can begin to mitigate the impact of light pollution on both urban and natural environments. Preserving the beauty of the night sky is not just an aesthetic pursuit—it is an essential part of maintaining the delicate balance of our planet’s ecosystems and human health.
Watersheds Canada’s education toolkit will help you protect our night skies, ensure safer habitats for wildlife, reduce energy consumption, and improve human health by reducing disrupted sleep patterns caused by excessive artificial lighting. Protecting our freshwater areas and the wildlife that live there is important, and it is our collective responsibility to harmonize our actions accordingly. You can do your part by sharing the resources and information from Watersheds Canada’s light pollution awareness campaign!
References
ASTROLab. (2023) Light: A Form of Pollution? Canada under the stars. https://astro-canada.ca/la_pollution_lumineuse-light_pollution-eng
Beier, P. (2006). Effects of artificial night lighting on terrestrial mammals. In Ecological Consequences of Artificial Night Lighting (pp. 19-42). Island Press.
Cochran, W. W., & Mouritsen, H. (2007). Migrating songbirds recalibrate their magnetic compass daily from twilight cues. Science, 318(5852), 890-893.
Evans Ogden, L. J. (1996). Collision course: The hazards of lighted structures and windows to migrating birds. Fatal Light Awareness Program.
Falchi, F., Bará, S. (2023) Light pollution is skyrocketing. Science. 379(6629), pp. 234-235. DOI: 10.1126/science.adf4952.
Longcore, T., & Rich, C. (2004). Ecological light pollution. Frontiers in Ecology and the Environment, 2(4), 191-198.
Rich, C., & Longcore, T. (Eds.). (2006). Ecological consequences of artificial night lighting. Island Press.
UNEP (2023) Global light pollution is affecting ecosystems – what we can do? https://www.unep.org/news-and-stories/story/global-light-pollution-affecting-ecosystems-what-can-we-do
University of Exeter. (2021) Rapid increase in global light pollution. ScienceDaily, 14 September 2021. www.sciencedaily.com/releases/2021/09/210914111302.htm
Wang, Z., Li, G., Huang, H., Zhang, W., Wang, J., Huang, S., & Zheng, Z. (2022). Effects of solar radiation on the cyanobacteria: Diversity, molecular phylogeny, and metabolic activity. Front. Ecol. Evol.(10). DOI: https://doi.org/10.3389/fevo.2022.928816
This education toolkit is generously funded by:
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