Less than 100 years ago, everyone could look up and see a spectacular starry night sky. Now, millions of children across the globe will never experience the Milky Way where they live even the way we used to observe it as kids. The increased and widespread use of artificial light at night is not only impairing our view of the universe, it is adversely affecting our environment, our safety, our energy consumption and our health.
Most of us are familiar with air, water, and land pollution, but we know little that light can also be a pollutant. The inappropriate or excessive use of artificial light known as light pollution can have serious environmental consequences for humans, wildlife, and our climate.
With much of the earth's population living under light-polluted skies, over lighting is an international concern. According to the 2016 groundbreaking "World Atlas of Artificial Night Sky Brightness," 80 percent of the world's population lives under the sky-glow. In the United States and Europe 99 percent of the public cannot experience the natural night.
For three billion years, life on Earth existed in a rhythm of light and dark that was created solely by the illumination of the Sun, Moon and stars. Over the last 50 years, as countries became affluent and urbanized, demand for outdoor lighting increased and light pollution sprawled beyond the city limits and into suburban and rural areas. Now, artificial lights overpower the darkness and our cities glow at night, disrupting the natural day-night pattern and shifting the delicate balance of our environment. The negative effects of the loss of this inspirational natural resource might seem intangible. But a growing body of evidence links the brightening night sky directly to measurable negative impacts.
The 'International Dark-Sky Association' (IDA), a non-profit organization that raises awareness of light pollution, estimates that excessive night-time lighting releases more than 12 million tons of carbon dioxide, the most serious greenhouse gas, into the atmosphere each year. It would take nearly 702 million trees to absorb the carbon dioxide produced by wasted light.
Light pollution may also contribute to other forms of pollution. According to a 2010 study by the 'National Oceanic and Atmospheric Association', photopollution increases air pollution by suppressing a naturally occurring radical that cleans the air at night. Nitrate radical, a form of nitrogen oxide, breaks down vehicle and factory emissions at night. The nightly process prevents the emissions from becoming smog, ozone pollution, or other harmful irritants. The process only takes place at night because sunlight destroys nitrate radical. However, artificial lights from buildings, cars, and streetlights, although 10,000 times dimmer than sunlight, also affect nitrate radical and slow down the cleansing process by 7%. Artificial light also increase the chemicals for ozone pollution by 5%.
Wasted light results in energy waste. A 2007 IDA study estimated that 30% of all light emitted by public outdoor light fixtures is wasted, which amounts to 22 Terawatt Hours (TWh)/year of wasted electrical energy. This is equivalent to the following:
The total amount of wasted electrical energy each year is enough to illuminate over 11 million homes and power over 777,000 cars.
Luminous pollution affects the feeding, sleeping, mating, and migration cycles of all wildlife. Wildlife can also experience disorientation of time when there is too much artificial light at night.
In Mammals such as bats, raccoons, coyotes, deer, and moose can experience difficulty foraging for food at night due to over illumination. They risk exposure to natural predators and increased mortality due to night vision impairment. They also experience a decline in reproduction that leads to a shrinking population.
Birds such as owls and nighthawks use moonlight and starlight to hunt and migrate at night. Artificial lights sources can overwhelm natural light sources, causing birds to be drawn to or fixated on the artificial lights. This results in birds deviating from their intended migration route, flying until they experience exhaustion and collapse, and becoming prey to other animals. Marine birds such as albatrosses are known to collide with lighthouses, wind turbines, and drilling platforms at sea due to their bright lights. In North America alone, 100 million birds die annually in collisions with illuminated buildings and towers.
Sky glow affects amphibians such as frogs, toads, and salamanders in marshes and wetlands. The orange haze confuses and disorients them, which causes a decrease in feeding and mating. It also impairs natural instincts that protect amphibians against natural predators and the elements.
Reptiles such as sea turtles are greatly affected by light pollution. Female turtles nest on dark, remote beaches, but bright coastal lights prevent them from finding safe nesting areas for their eggs. This leads the female turtles depositing their eggs in an unsafe area or the ocean. Sea turtle hatchlings instinctively crawl toward the brightest part on the beach, which for many centuries was the moonlight and starlit ocean; however, excessive lighting on the beach or near the shore confuses the hatchlings and causes them wander away from the ocean. The hatchlings may be eaten by predators, run over by vehicles, drown in swimming pools, or die from dehydration or exhaustion. Artificial lights may also disorient other nocturnal reptiles.
Insects such as moths are naturally attracted to light and may use all their energy to stay near a source of light. This interferes with mating and migration as well as makes them vulnerable to natural predators, which reduces their population. This also affects all species that rely on insects for food or pollination.
Humans, like plants and wildlife, are regulated by circadian rhythms, the physical, mental and behavioral changes that occur in a 24-hour cycle. The circadian clock regulates physiologic activities such as brain wave patterns, hormone production, and cell regulation. The rhythms respond to the light and darkness around an organism. Disrupting these rhythms can result in a variety of health problems, including sleep disorders, anxiety, depression, diabetes, cancer (particularly breast and prostate cancer), cardiovascular disease, immunological disorders, and obesity.
Melatonin, the naturally occurring hormone that regulates the sleep and wake cycle, is acutely affected by light pollution. The hormone is activated by darkness and repressed by light. Melatonin deficiency can result in anxiety and mood disorders, insomnia, and elevated estrogen/progesterone ratio.
Astronomy is one of the oldest sciences in human history, and has made countless contributions to technology, economy and society with applications like personal computers, communication satellites, mobile phones, Global Positioning Systems (GPS), solar panels, and Magnetic Resonance (MRI) scanners. Today, astronomy helps us determine the Sun's effect on Earth's climate, and identify any potential threats to Earth from space. In order to conduct observation and research, astronomers require dark skies. Light pollution alters our view of the sky and stars, but no group of people is more affected by this phenomenon than astronomers. Light spill and sky glow interferes with astronomical equipment, and makes viewing faint celestial bodies difficult even with the aid of a telescope.
Photopollution occurs in a variety of forms, including light trespass, glare, sky glow, and light clutter. One source of light can result in multiple forms of pollution. Here is how you can identify each form of light pollution.
Light Trespass: Light trespass, also known as spill light, occurs when a light fixture casts illumination beyond the property lines, unintentionally illuminating other homes, businesses, or areas. Spill light is the most subjective form light pollution because there are no guidelines to determine when, where, or how much light is unwanted. A common example of spill light is light from a streetlight coming through a window and illuminating a bedroom, light from outdoor wall lights that direct light up towards the sky rather than towards the ground, or light from a neighbour's floodlight or security light shining over the fence and illuminating your property.
Glare: Glare is the visual sensation one experiences when stray light, light in the visual field, is greater than the light to which the eyes are adapted. Glare, depending on the intensity, can result in reduced contrast, color perception, and visual performance.
Sky Glow: Sky glow originates from natural and man-made sources; however, poorly designed and targeted artificial lights are the main cause of sky glow. Sky glow occurs when light is emitted directly into the atmosphere, accidently or purposefully, where it is scattered by dust and gas molecules, creating a dome-like orange glow that covers the night sky. The glow reduces the contrast between the stars and the galaxies in the sky, making celestial objects difficult to see even with a telescope. Light domes also affect the polarization of moonlight, which nocturnal animals use to navigate. Glow domes are visible in cities and towns throughout the world, and they appear in a variety of sizes such as large domes over metropolitan hubs or small domes above over-illuminated commercial areas and sport complexes or stadiums. Cloud coverage, snow, trees, and the quantity of dust and gas molecules in the atmosphere can amplify sky glow.
Light Clutter: Light clutter is the excessive grouping of bright lights that cause confusion and distract from oncoming or surrounding objects. Light clutter is visible on roads surrounded by unshielded street lights and brightly lit advertisements or signs. This creates a hazardous environment for drivers and pilots because it competes with traffic and navigation signals. Clutter contributes to other forms of light pollution, including light trespass, glare, and sky glow.
Light pollution affects every citizen. Fortunately, concern about light pollution is rising dramatically. A growing number of scientists, homeowners, environmental groups and civic leaders are taking action to restore the natural night. Each of us can implement practical solutions to combat light pollution locally, nationally and internationally.
The good news is that light pollution, unlike many other forms of pollution, is reversible and each one of us can make a difference! Just being aware that light pollution is a problem is not enough; the need is for action. You can start by minimizing the light from your own home at night. |
