Light pollution not only disrupt the darkness, it affects our health, and the behaviour — and survival — of wildlife.

Every summer, once school lets out, my family and I rush up to the cottage to escape the sticky heat of the  city to cool down by the lake. We run through the lush forests, breathing in the smell of the woods. We roast marshmallows after dark, look up at the stars, and, later in the summer, wish on every shooting star from the Perseid meteor shower. 

This year my sister and I made it a ritual to go swimming after dark. Every night we would race out of the house, towels in hand, bodies bathing-suit-clad, ready to cool off after a long day in the sun. We would hurry down the stairs and laugh as we’d hobble along the gravel path down to the lake on our bare feet. We would gaze in awe at the fireflies flying above and around us lighting up the forest. Once we got to the lake we would drop everything and run off the end of the dock, eagerly bracing ourselves for the blast of the cool water on our skin. We would swim and tread water looking up at the stars, just soaking in the moment. Some nights we would talk about everything and nothing at the same time, others we would swim in silence trying to memorize every sensation and feeling: the smell of the warm summer night, the feel of the cold lake seeping into our skin, the sound of the spring peepers filling the air. We’d look around and relish the utter beauty of the fireflies dancing and the stars casting light on us, making us feel so small in this giant galaxy of ours. 

Part way through the summer, as the days began to get shorter, we noticed a hazy glow coming from behind the island, staining a section of the sky. We learned that it was light pollution coming from town. We started wondering about how it affects the animals and the environment. We learned that in addition to disrupting the beauty of the night sky, the light also has an impact on us and the wildlife around us. One effect is that it disrupts wildlife behavior and relationships between predators and prey: some prey need the darkness to escape from their predators, while some predators use it to hunt. An example of the kind of disruption that can happen is with the zooplankton that lives in our lakes. Zooplankton uses the darkness as cover so they can feed on the algae at night without the threat of predators eating them. When there is light pollution it means it isn’t bright at night and it isn’t safe to feed.That, by extension, can lead to over-population of algae. When there is too much algae, it depletes the oxygen in the water, killing fish. 

If the effects on wildlife weren’t enough, it also affects us and our brains, by altering our melatonin levels and circadian rhythms. Those changes can sometimes cause depression and mood disorders, according to one study. Other research found that  light pollution is the factor most strongly associated with the development of Alzheimer’s disease in people under 65.

With further research we learned that the town has a bylaw in place to try to prevent this by reducing the use of street lights, but apparently that isn’t enough even in places trying their best to prevent this. As soon as we got back to the city I looked up at the sky and saw no stars. I just felt this overwhelming sense of sadness, and the need to do something about it. Go to Dark Sky International to learn more, and for responsible lighting tips!

Read more about light pollution in The Dying of the Light, a speech by another Bluedot Institute student, presented at the 2025 Climate Leadership Retreat at Martha’s Vineyard.