If you’ve ever tried to see the stars at night, you may also have found that it’s nearly impossible because there’s so much light everywhere. So much light floods our night skies that the term “light pollution” has emerged, describing any adverse effect of artificial light including sky glow, glare, light trespass, light clutter, decreased visibility at night, and energy waste.

In June 2016, it was estimated that one third of the world's population could no longer see the Milky Way. This included 80% of Americans, and 60% of Europeans.

Main types of light pollution

The three main types of light pollution include glare, light trespass and skyglow (in addition to over-illumination and clutter).

Glare from unshielded lighting is a public-health hazard—especially the older you become. Glare light scattering in the eye causes loss of contrast, sometimes blinds you temporarily and leads to unsafe driving conditions, for instance.

Light trespass occurs when unwanted light enters one’s property, for example, by shining unwanted light into a bedroom window of a person trying to sleep.

Skyglow refers to the glow effect that can be seen over populated areas. Skyglow is the combination of all the reflected light and upward-directed (unshielded) light escaping up into the sky (and for the most part, unused).

Shielding lights significantly reduces all three of these types of light pollution.

What’s the problem with too much light?

Light pollution affects many animals since light and dark often signals when to eat, sleep, hunt, migrate, or reproduce. That means light pollution alters and interferes with the timing of necessary biological activities. Artificial light at night disrupts nocturnal pollination networks and has negative consequences for plant reproductive success. In one study, artificially illuminated plant–pollinator communities, nocturnal visits to plants were reduced by 62% compared to dark areas. 

Could light pollution be contributing to the decline of coral reefs? More than 130 different species of coral on the Great Barrier Reef spawn new life by moonlight. Every October or November after the full moon, the reefs spew sperm and eggs into the ocean in what looks like an underwater blizzard. When the two sex cells combine amid the flurry, fertilization begins. Bright urban lights can mask the moon’s phases, throwing the corals’ biological clocks out of sync, according to Oren Levy, of Bar-Ilan University in Israel. This can cause the reefs to release their reproductive cells late or not at all, decreasing their chances of producing offspring.

Since most songbirds migrate at night, light pollution disrupts their circadian rhythms and can disorient birds during migration. Bright lights at night on large buildings attract birds in the same way that bright porch lights attract moths, which can result in fatal collisions.

Sea turtles lay their eggs on beaches, and when they hatch, the hatchlings move away from the dark silhouettes of the sand dunes toward the brighter horizon of the ocean. However, many coastal areas are becoming heavily populated and these artificial lights draw the baby sea turtles away from the safety of the ocean towards land where they can suffer dehydration, encounter predators, or be run over by cars. Any reduction in the amount of artificial lights near beaches can help protect newly hatched sea turtles.

Florida’s Fish and Wildlife Conservation Commission states, “Even one artificial light source can disrupt normal flight activity, long-distance migrations, or even attract insects that don’t normally move from their habitat.” When these bugs stay on the light for too long, they tend to die from overheating. Moths are typically the victim, which then affects the birds and bats that feed on them because they lose a food source.

Light pollution also affects the life cycle of plants and can prevent them from growing flowers and reproducing. This affects the pollinators of these plants and also their own life cycles. It also affects humans. According to the National Academies Press’ Booklet “Resources on Pollinators,” one-third of human food requires a pollinator.

Amphibians are an important part of forest and aquatic ecosystems; and because they are very sensitive to environmental changes, they serve as an important indicator species of the health of ecosystems. However environmental stresses have caused their populations to decline around the world and light pollution may play a big part by changing both foraging and breeding of nocturnal amphibians.

Zooplankton called Daphnia normally dwell deep underwater in the day and ascend to the surface at night to feast on algae. Darkness triggers their migration. But marine ecologists have found that nighttime lighting can prevent the zooplankton from floating up to their meals, which could lead to algae blooms that overwhelm the other life in a lake.

Trees evolved with regular day to night cycles so they can measure light with a kind of molecular clock. This clock tells them how long the sun is out for, the season and distance from other trees measured by the shadows those trees cast.  From this information, trees decide when to photosynthesize, when to send out leaves in spring, leaf coloring and when to shed leaves. Artificial light wreaks havoc with this system by extending the length of a day which changes flowering patterns and storing up energy to survive the winter.

Light pollution also affects human beings. Humans, too, need natural darkness for sound sleep and good health. Cool blue white light at night from sources such as LEDs, fluorescent and metal halide lights interfere with the body’s circadian rhythms by suppressing melatonin and increasing cortisol, a brain chemical released when we are stimulated or excited. High cortisol levels make it difficult to fall asleep or experience deep sleep, which our immune systems need to fight illness and disease.

What’s being done to reduce light pollution

Light pollution is one of the easiest pollutions to clean up. Taking steps to reduce light pollution doesn't mean living in the dark - it's about making light more efficient and beneficial.

Dark Sky Reserves

An IDA International Dark Sky Reserve is a public or private land area possessing an exceptional or distinguished quality of starry nights and nocturnal environment that is specifically protected for its scientific, natural, educational, cultural, heritage and/or public enjoyment. Reserves consist of a core area meeting minimum criteria for sky quality and natural darkness, and a peripheral area that supports dark sky preservation in the core. For a list of certified dark sky parks: https://www.darksky.org/our-work/conservation/idsp/parks/

The Central Idaho Dark Sky Reserve is a 1,416-square-mile (3,670 km2) dark-sky preserve near the Sawtooth National Recreation Area, in the U.S. state of Idaho. It was designated on December 18, 2017 and is the first gold-tier dark sky preserve in the United States.

“Jasper National Park is one of 17 designated Dark Sky Preserves in Canada,” says Myriam Bolduc, marketing manager for Tourism Jasper. “At 11,000 square kilometers, we are the second largest Dark Sky Preserve in the world, and we are the largest accessible Dark Sky Preserve—meaning there’s a town within the limits of the preserve.”

To become a Dark Sky Preserve, the area had to eliminate visible artificial lighting while putting measures in place to educate the public and nearby towns about light pollution. The sky glow from outside the border of the preserve had to match that of a natural sky glow. Today, 97 percent of the park is a designated wilderness area, free of light pollution, with roads and trails providing easy access to year-round stargazing sites.

Governments Act to Reduce Light Pollution (and energy costs)

From 2014-2016 the US Department of Energy’s Outdoor Lighting Accelerator (OLA) worked with 25 partners (including three states, 16 cities and 6 regional energy networks) committed to upgrade 1.3 million street lights that will ultimately save cities an estimated $48 million/year.

Across the pond, the European Union adopted new roadway lighting guidelines, employing a ‘As Low As Reasonably Achievable‘ (ALARA) principle. The specific guidelines, intended to reduce energy use as well as light pollution, are consistent with the Low Impact Lighting (LIL) standard promoted by German, Italian and Slovenian members of the European Environmental Bureau in the past decade.

Many cities have taken the lead in re-doing their lights to reclaim the night and decrease energy waste. Flagstaff, Arizona, was the first city to be designated a Dark Sky Community by the International Dark-Sky Association, and Chicago is in the process of retrofitting its fixtures. So far, concerns about dimmer, sparser lighting possibly causing an uptick in crime or decreased safety at night have not been supported by the data; in Chicago’s West Garfield Park, more brightly lit alleys actually led to an increase in reported crime. And anecdotally, people are finding that less glaring lighting makes it easier to see in unlit areas, because our eyes adapt more quickly to the dark.

What cities can do to reduce light pollution

Motion sensitive street lighting is a pretty self-explanatory idea, and one that has become reality on this Barcelona street. Lights come on as people and moving objects approach, illuminating an area in advance, thus reducing wasted light and wasted energy.

Street lighting encased above and to the sides channels light downwards – where it is needed – and reduces the amount of wasted light. Known as ‘cutting off light at the horizontal’, this ensures that light is used to illuminate the ground, not the sky.

Switching to low watt bulbs is a straightforward way of reducing light pollution. Moving away from bluish-white lighting could be a bigger contributor to reduced light pollution on an urban scale. Replacing LED with warm-white lighting creates a win win situation. The Spanish market city of Vélez-Málaga (seems the Spanish are big on lighting innovation) recently adopted a dimmable warm-white light system for its streets, giving it lower watt lighting on demand and better illuminating its historic streets in the process.

Earth Law as an additional solution to light pollution

Earth Law Center is building an international movement from the ground up, one that gives better grounding to the idea that humans have a responsibility for how we impact the world around us. The belief that nature - the species and ecosystems that comprise our world - has inherent rights has proven to be a galvanizing idea, and we work with local communities to help them organize around the rights of nature to protect their environment from the threats that they see.

The heart of the ELC approach is to seek legal personhood for ecosystems and species, a designation similar to that given to corporations in U.S. law, and one that if done well will imply both rights for the entities so designated and responsibilities on the part of human beings and societies to respect those rights.

Our work includes helping governments adopt and implement laws, policies and practices that protect other species, ecosystems, and the elements of the natural world -- water, air and land.   Our work also includes providing education about how individual people and communities can live better as part of Nature and as its stewards, rather than its masters.

Restoring the natural Dark Skies of night is consistent with our commitment in that it takes a more holistic view of ecosystems and fellow species by respecting the rights of all living things to exist, thrive and evolve.

What individuals can do to reduce light pollution

In addition to motion sensors, shielded lighting, blue to warm light and low watt bulbs – solutions abound for reducing light pollution.

• Install reflectors to outline a driveway instead of putting in a row of lights. Reflectors are cheaper to purchase, free to use and are unaffected by power outages.

• Dimmer switches on household lights, both indoor and outdoor save energy and reduce light pollution

• Eliminate, reduce or turn off late night decorative lighting and/or outdoor lighting during late night hours when outdoor areas are not in use.

• Some power companies bill you for “Nearby Outdoor Lighting” which could mean the lamp across the street. Check your bill for the $5 - $10 a month for this service and call to ask for the charge to be terminated and the light be removed.

• The IDA Fixture Seal of Approval for dark sky friendly fixtures which minimize glare, reduce light trespass, and keep the night sky dark.

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