There was a time when a light in the dark of the night was a beacon. Light has always been a source of hope; like a lighthouse warning ships of a hidden reef or the warm glow of a fire on a cold winter's night. Since humankind learned to control fire, a light in the night has been a comfort to us all and provided a sense of security.
In ancient times, a fire may have been used to ward off large meat-eating animals and protect our ancient ancestors. In modern times, a child may use a nightlight to keep out the shadows and the boogeymen that lurked in them. To humans, light has always been a security blanket and a comfort, protecting us from the unseen waiting in the darkness.
Over time it seems that our use of light has gone from helpful to hurtful. There is growing evidence showing that a brightening night sky can be harmful to human health. It also appears that artificial nighttime light affects insects and other animals. Here are three reasons why we may need to turn off the porch light at night.
1) The stars are disappearing
Who loves seeing a night sky full of stars? Imagine lying on your back on a warm summer night staring up into space looking for a certain constellation, or a shooting star. For many, seeing a night sky full of stars is becoming more of a privilege than a birth rite. The concentrated amounts of artificial light from our homes, offices and industrial buildings are creating an effect known as urban sky glow or light pollution. These artificial light sources are brightening the dark areas of the sky and reducing our ability to see the stars and other heavenly bodies with the naked eye.
Artificial light at night brightens the sky and reduces the amount of contrast that helps bright stars and planets show up against the backdrop of the blackness of space. The contrast of bright and dark objects is what helps our eyes see things in the dark. For instance, when you go to the movies, the lights are dimmed to help the pictures on the screen become brighter. Studies are showing that a suburban sky is 5-10 times brighter than a natural sky, and in major cities, the sky can be 25-50 times brighter; dramatically reducing the visibility of the stars. According to a report from the Royal Astronomical Society, two-thirds of the U.S. population, and more than half of those living in Europe are no longer able to see the Milky Way with the naked eye (1). As a result, people living in cities are having to travel further and further away from home in order to see the Milky Way twinkle in all its beauty. This type of travel requires money, gas, and vehicles, limiting many people's access to what was at one time, a birth rite.
2) Too much night light could cause cancer
Human exposure to artificial light at night for long periods of time is almost sure to cause health problems. Harvard University studies are showing that nurses who are exposed to long hours of artificial light when working regular night shifts are at a higher risk of developing breast cancer and colorectal cancer (2). Not only that but if you are a woman who lives in a neighbourhood where you can read a book outside at night, then you are 73% more likely of developing breast cancer than women who live in areas with the least amount of outdoor lighting (3). The evidence is growing and showing that exposure to outdoor lighting at night may be a known carcinogen.
3) Artificial light's effect on nature
Plants and animals are also affected by the light pollution put into the night. These effects may at first be understood to be impacting only that specific animal or plant, but when we consider how that plant or animal is connected to the rest of nature, the impacts of artificial light on the natural world are much higher.
Trees in their natural habitat use their sensitivity to changes in light to help determine when it is time to flower in the spring or put energy into their roots for the winter. However, regular exposure to artificial light causes a tree to act in ways that are not appropriate to the season (4).
When the tree goes out of sync with the natural cycles of nature, it then changes the patterns and behaviours of the other plants or animals that depend on it. Young trees are more susceptible because they are growing quickly and with a lot of energy already, so the continuous exposure to artificial light triggers them to grow even more, tiring them out and weakening them (5).
You may know that at night, many types of sea turtles come in from the ocean to a sandy beach where they were born, to make a nest and lay their eggs. You may also know that humans love to visit these beaches as well, have a timeshare condo there and make sand castles with their children. The artificial light coming from the condos, homes, and businesses that line the beaches, disorient and discourage the sea turtles from coming onto the beach from the ocean, making a nest, and laying their eggs (6). Baby sea turtles also become disoriented by artificial light and are not able to find their way to the ocean after hatching (7).
Birds are falling dead from the sky in urban areas as they become confused and disoriented by the lights of office buildings as they pass through cities that are along their migration paths. Toronto's Fatal Light Awareness Program (F.L.A.P) estimates that in North America alone over 100 million birds are killed each year by collisions with buildings (8). In large part this occurs because many species of migratory birds travel at night, navigating by the moon and the stars to reach their destination.
4) The money talks
Money is a language that many of us understand. If you can save money somewhere, you probably will. The International Dark-Sky Association states that in the United States alone, 1.5 billion dollars annually is wasted every year on electricity that is lighting up the sky, and 12 million tons of carbon dioxide is made creating this energy (9). The reason for this is only because the light fixtures used are not effective at directing the light where it is needed, with much of it lighting up the night sky.
What can we do?
It is important to keep in mind that these are only a few from a long list negative effects that night lighting is having on humans, plants, and animals. The truth is that science is only now catching up to assess the effects of human development on the environment. In Canada and the US, there was a time when one could smoke cigarettes in hospitals, airplanes, and restaurants unquestioned. We no longer allow this because it has become clear how damaging cigarettes can be to human health. However, the effects of nighttime artificial light exposure have crept in under the radar, with little to no attention or investigation until now. Funding research into the effects of nighttime artificial light on humans, plants and animals have been minimal because light pollution is still low on, "the list of important environmental issues needing study (10)."
In the meantime, people can assess their use of night lighting to figure out if it is really necessary. Are those 48 floodlights set up around the perimeter of your house necessary? If so are there ways in which you can shine the light more directly to where you need it. The International Dark-Sky Association rates light fixtures to see if they are low-glare fixtures and companies like Starry Night Lights make fixtures that have lower amounts of light pollution.
Believe it or not, you may be paying for street lighting that you may have thought the municipality was paying for. Call your utility provider to see if you are and if so they are happy to turn out the light for you and save you some cash. If you do want to have outdoor lighting, switch them to motion sensor lights, with low-glare fixtures.
It's for the birds! Support programs like F.L.A.P.'s lights-out program that raise awareness and lobby businesses to turn out their lights in their office buildings at night. Or in other words it is for the plight of the flight, so turn out the light.
1. "The First World Atlas of the Artificial Night Sky Brightness." Monthly Notices of the Royal Astronomical Society, vol. 328, no. 3, 2001.
2. JNCI: Journal of the National Cancer Institute, Volume 95, Issue 11, 4 June 2003, Pages 825–828, https://doi.org/10.1093/jnci/95.11.825
3. Danilenko, Konstantin V., et al. "Influence of Timed Nutrient Diet on Depression and Light Sensitivity in Seasonal Affective Disorder." Chronobiology International, vol. 25, no. 1, 2008, pp. 51–64., doi:10.1080/07420520801903976.
4. Longcore, Travis, and Catherine Rich. "Physiology of Plant Responses to Artificial Lighting." Ecological Consequences of Artificial Night Lighting, by Winslow Briggls, Island Press, 2013.
5. Chaney, William R. "Does Night Lighting Harm Trees?" www.extension.purdue.edu/extmedia/FNR/FNR-FAQ-17.pdf.
6. Chepesiuk, Ron. "Missing the Dark: Health Effects of Light Pollution." Environmental Health Perspectives, vol. 117, no. 1, Jan. 2009, pp. A20–A27., www.ncbi.nlm.nih.gov/pmc/articles/PMC2627884/.
7. Salmon, Michael, et al. "Seafinding by Hatchling Sea Turtles: Role of Brightness, Silhouette and Beach Slope as Orientation Cues." Behaviour, vol. 122, no. 1/2, 1992, pp. 56–77. JSTOR, JSTOR, www.jstor.org/stable/4535039.
8. "FLAP Canada." FLAP - Fatal Light Awareness Program - Working to Educate & Engage People About The Safety of Migratory Birds in the Urban Environment, flap.org/faqs.php.
9. "Chaney, William R. "Does Night Lighting Harm Trees?" www.extension.purdue.edu/extmedia/FNR/FNR-FAQ-17.pdf.
10. Chepesiuk, Ron. "Missing the Dark: Health Effects of Light Pollution." Environmental Health Perspectives, vol. 117, no. 1, Jan. 2009, pp. A20–A27., www.ncbi.nlm.nih.gov/pmc/articles/PMC2627884/.