City at night
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3 key ways that light pollution negatively impacts nature

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It’s long been known that artificial light impacts the breeding, migration, sleeping, and eating of animals. If you’re skeptical, you don’t have to look any further than an urban backyard for proof. But don’t look for what’s there—look for what’s missing. Native species of plants and animals that would have once been found in the city no longer exist.

“It’s not just because people cut their grass that you don’t see certain wildflowers in the city—it’s because it’s too bright for them to live and they’ve long since disappeared,” explains Robert Dick, Chair of the Light-Pollution Abatement Committee and the manager of the Dark-Sky Preserve Program in Canada. “The environment of the city has entirely changed because of the lights.” 

Unless further action is taken, similar results may occur closer to your cottage. “Plants and animals aren’t going stick around. They’re going to find a place without this problem. As humans start putting up artificial lights at night in the country, animals have to move further and further away,” says Dick. 

The solution is simple though. “Reduce the wattage of lights, make sure they shine nowhere beyond your property line, use amber-coloured CFLs, and turn lights off when you’re not using them,” he advises.

Unless preventative measures are taken, here are some significant ways that nature will continue to be impacted by light pollution:

1. Light pollution affects animals’ ability to navigate and migrate.

Animals make use of stars at night, particularly those on the horizon, to help guide them. It’s estimated that up to 98 million migratory birds in North America die annually from crashing into brightly lit buildings at night. But it’s not just birds that are affected—even in cottage country, nocturnal animals such as porcupines may not be able to navigate due to lit-up porches and roadways.

“Biologically animals have evolved to know that lights are stars and that stars move,” explains Dick. “They actually compensate for the rotation of the earth so over time they’ll walk to the left. If you leave a door light on, they’ll assume that’s a star and they’ll start curving their path and they’ll get lost.” Disorientation can lead to exhaustion, dehydration, and death. 

2. The amount of time dedicated to foraging, mating, and feeding is reduced.

It’s no secret that moths are attracted to bright lights, particularly in the country. When insects mistake artificial light for a natural source, such as the moon, they can become trapped in luminary sources. This not only makes them a prime target for predators, but also reduces the amount of time they can dedicate to mating and feeding. Ultimately, the result is a decrease in the amount and diversity of nocturnal insects, which in turn affects animals that feed on them, such as bats.

On the other end of the spectrum, animals that typically use the cloak of darkness as a means of protection from predators—including salamanders and mice—become reticent to leave their hideaways. This reduces the likelihood that they will devote energy to nighttime feeding and reproduction. 

Finally, even breeding can be affected. In the case of frogs, artificial light causes them to reduce their mating calls at night, which inhibits their ability to reproduce successfully. 

3. Artificial light affects the very structure by which organisms grow, including hormone levels.

Increasingly, research is demonstrating that the amount of light animals are exposed to affects not only their natural circadian rhythms, but their stress and hormone levels as well. Light affects the amount of melatonin that animals produce, which is responsible for controlling the hormones that affect sleep and the immune system.

Case in point: in the study of meadow voles, those that have been exposed to more nighttime light produce young that develop slowly in terms of weight and sexual maturity. Similarly, research has demonstrated that light at night causes deer mice to sexually mature later in the season, which in turns delays mating until the next year.