For a long time, the predictable rhythm of the sky played a major role in the daily lives of all living organisms on earth. In the words of Jon Henley in The Guardian, “The pre-industrial night … was widely regarded with dread and fascination in equal measure”. However, the introduction of man-made technology into the natural world began to tilt the scale in irreversible ways. Our world now runs on electricity, allowing humans to transform night into day with a simple light switch.
Unfortunately, this luxury does not come without a cost as we now have what we call “light pollution.” Light pollution is the brightening of the sky during the night due to the excessive redirection of artificial light. Light pollution has proven to be extremely disruptive to the natural daily cycle and continues to impact the environment with a few major consequences: it obstructs the night view of the stars, it hinders astronomers from conducting research at optimal sky conditions, it causes unusual animal behavior, and it impacts the environment in terms of wasted energy.
The Types of Light Pollution
To further dive into understanding light pollution we need to look at all different forms of it. Light pollution happens in five forms: Glare is unshielded light shining into the sky possibly causing temporary blindness and road hazards. Light trespass is unwanted light shining into a private property. Light clutter is usually found in cities and happens when large clusters of various bright lights are combined. Urban skyglow combines the different types of lights and any upward shining light to create a bright glow effect in densely populated areas during the night. Over-illumination can be confused with skyglow and happens when too much light is used to make major buildings stand out.
What a Recent Study Revealed
A recent study conducted by Christopher Kyba at the German Research Centre for Geoscience revealed that from 2012 to 2016 there was an increase of 2.2 percent of artificial outdoor lighting per year, and an increase of 1.8 percent of radiance per year. The study was done using a the Visible Infrared Imaging Radiometer Suite (VIIRS), a calibrated satellite radiometer that was the first to ever be made specifically for night light. Contrary to popular belief, even developing countries such as Asia, Africa, and South America showed a significant level of light pollution, some countries even crossing the world average.
When speaking to CNN Kyba explained, "I was very surprised by the result of the study, particularly in wealthy well-lit countries like the US. When we switch from a sodium lamp to a white LED, what we observe is a decrease in the total amount of light that the satellite can see. But what we saw instead of the US was basically a constant amount of light; new lights were added in other places".
The Impact of Light Pollution on Ecosystems
Animals that sleep during the day and eat during the night are called nocturnal animals. Light pollution poses a serious threat to these animals in particular due to the psychological impact of the night looking like day. According to Kyba, “the introduction of artificial light probably represents the most drastic change human beings have made to their environment.”
“Predators use light to hunt, and prey species use darkness as cover,” Kyba continued. “Near cities, cloudy skies are now hundreds, or even thousands of times brighter than they were 200 years ago. We are only beginning to learn what a drastic effect this has had on nocturnal ecology.”
More animals that are impacted by light pollution are amphibians who use the night for breeding rituals. Artificial night lights disturb and confuse the reproductive activity of animals such as frogs and toads causing an interference with the natural population. What’s more, sea turtle hatchlings that hatch at night also depend on following the light over the ocean to get to the water. Excessive lights deter the turtle hatchlings from reaching the water by drawing them towards different directions leading to their ultimate death.
Impact of Light Pollution on Humans
Humans depend on the cycle of day and night in order to regulate their circadian rhythms and melatonin production. When exposed to light during the night, the body attempts to stop melatonin production leading to sleep disorders, obesity and fatigue. Moreover, a recent Harvard study published in Environmental Health Perspectives revealed that women living in areas with high outdoor lighting had approximately a fourteen percent increased risk of developing breast cancer, with the risk being higher for women working night shifts.
According to Peter James, assistant professor at Harvard Medical School’s Department of Population Medicine, “In our modern industrialized society, artificial lighting is nearly ubiquitous. Our results suggest that this widespread exposure to outdoor lights during nighttime hours could represent a novel risk factor for breast cancer.”
What Can Be Done to Reduce Light Pollution
Fortunately, light pollution can be easily controlled by simply spreading the habit of switching lights off, and only using the amount needed. Moreover, light shields and energy efficient light bulbs are conveniently available and can effectively reduce light pollution. Another option for those interested in further learning about light pollution is the campaign Globe at Night. This campaign promotes light pollution awareness and monitors international light pollution trends over the years.