In 1994, when an earthquake led to a power outage in Los Angeles, a lot of anxious residents called local emergency services to report seeing a strange ‘giant, silvery cloud’ in the dark sky. Little did they realise it was in fact the Milky Way, which they would have been able to see had it not been for the urban sky glow caused by excessive use of artificial light.

According to a study in 2016, artificially illuminated sky is experienced by 80% of the world population, and this figure rises to 99% for both the US and Europe. Artificial lights almost give us the power to manipulate nature, offering us more time for work and recreational activities, yet excessive use of artificial light is now recognised as a source of pollution. As illustrated, light pollution significantly affects humans’ experience of night time, interfering with our experience to view and ponder the night sky. But this is not the only negative impact of this form of pollution.

Given the serious impact of light pollution on both humans and animals’ life, it is high time we did something about this pollution.

Light pollution can drastically impact the life of animals. While the inability to view celestial bodies in the example have fairly little impact on humans’ life, this disruption can have significantly more serious effects on animals who rely solely on the stars and the moon for navigation.

If you have seen Planet Earth II, you might remember that scene when baby sea turtles, who were meant to follow the full moon to the sea, ended up in the wrong direction due to light pollution on the beach. Celestial bodies also provide visual cues for migratory animals, especially birds, and unnecessary excessive light can cause these birds to fly towards the wrong direction, and potentially collide towards dangerous object. In addition, day and night length is also visual cues of seasons for a lot of bird species, who can miss their ideal migrating season due to confusion caused by artificial light.

Light pollution directly affects humans’ health, too. This is mediated by several light-dependent endocrine and neurobiological mechanisms controlling physiological and behavioural processes. For example, the secretion of melatonin, a hormone naturally secreted by the pineal gland in the dark, would be reduced by excessive exposure to light at night. This can cause sleep disorders, impacting our daytime performance and alertness.

A view of a city in a shallow valley at night but the landscape is lit up by the artificial light from the city
City wide pollution. Source: flickr


Melatonin also regulates the body’s level of oestrogen and growth hormone, which are involved in the cancer process, hence the suppression of melatonin caused by excessive exposure to artificial light may encourage the development of some types of cancer. Another function of melatonin is reducing activity of the sympathetic nervous system, which would reduce norepinephrine turnover in the heart, reducing LDL cholesterol uptake, reducing risks of heart diseases. Because of this, light pollution, which can cause reduction in melatonin secretion, can potentially lead to higher risks of heart diseases.

Given the serious impact of light pollution on both humans and animals’ life, it is high time we did something about this pollution. And believe it or not, you can help! The most obvious solution would be to start turning unnecessary lights off, especially outdoor lighting. If you have your outdoor light on for a sense of security, that’s most likely unnecessary, for there is very little evidence for lights reducing crime rates.

artificially illuminated sky is experienced by 80% of the world population

If you happen to be a little forgetful, motion sensing lights could be a great option for reducing unnecessary use of lights. You can also help by sharing all the facts and information you know about light pollution to your friends and family members, who are most likely not even aware of this problem. A lot can be done towards reducing light pollution if more people are aware of this potentially life threatening issue.

If you want to read more about a spectacular natural form of light pollution try this one where Science Editor Rhys Davies looks into the science of the Northern Lights!

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