Light pollution mapped through levels of impact, with white being most intense: city/inner city sky

Light pollution mapped through levels of impact, with white being most intense: city/inner city sky

LIGHT POLLUTION

Light Pollution, also known as Skyglow, may not appear to be the most urgent problem facing the planet, but it may be the most indicative of humanity's growing separation from nature. Light pollution impacts health of humans and animals, especially nocturnal wildlife, and disrupts ecosystems. It also leads to waste of large percentages of energy and the disruption of astronomical research, among a long list of impacts. Light pollution runs counter to necessity for a green, sustainable future.

However, this problem is one an average citizen can do something about, as Verlyn Klinkenborg states in his article on Light Pollution"Of all the pollution we face, light pollution is perhaps the most easily remedied. Simple changes in lighting design and installation yield immediate changes in the amount of light spilled into the atmosphere and, often, immediate energy savings."

 

% OF HUMAN POPULATION IMPACTED BY LIGHT POLLUTION

Los Angeles, California is one of the most light polluted cities in the world.

Los Angeles, California is one of the most light polluted cities in the world.

IMPACT ON ANIMALS & PLANT LIFE

Fireflies, which used to cover most of lower North America during the months of May through July, are one of the animal species devastated by light pollution. Relying on complete darkness to perform their mating rituals, fireflies have retreated into the last remaining dark areas of their habitat, decreasing their overall population by as much as 90 percent, according to some estimates.

Birds that migrate or hunt at night navigate by moonlight and starlight. Artificial light can cause them to wander off course, migrate too early or too late, and miss Ideal climate conditions for nesting, foraging, and other behaviors. Every year, millions of birds die colliding with needlessly illuminated structures.

IMPACT ON HUMANS

Artificial light emanating from house lights, electronics, and other sources suppresses melatonin, an antioxidant that induces sleep, boosts the immune system, lowers cholesterol, and helps the functioning of the thyroid, pancreas, adrenal glands, and various other parts of the body. The full impact of nocturnal light on the health of human beings is not yet known as many studies are still to be conducted. Research to date suggests that artificial light’s disruption of circadian rhythm is one of the causes of obesity, depression, insomnia, diabetes, and breast cancer.

 

Fireflies in the Blue Ridge Mountains

Fireflies in the Blue Ridge Mountains


Even fish, such as salmon, are susceptible to having their mating processes disturbed by artificial light pollution. Sea turtles often mistake city lights for moonlight shimmering in the ocean.

Trees have been shown to bloom too early due to artificial light. Later-budding trees such as ash trees are most affected by light pollution, which in turn impacts all the animal life that depends on those trees’ natural bloom cycle.

Toronto, Ontario street lit in sodium vapor lights, before LED retrofitting. 

Toronto, Ontario street lit in sodium vapor lights, before LED retrofitting. 

A street undergoing LED retrofitting, lit half in Sodium Vapor (right) and half in LED (left)

A street undergoing LED retrofitting, lit half in Sodium Vapor (right) and half in LED (left)

And these luminaries radiate their light over much of the electromagnetic spectrum and scatter much farther through the atmosphere, even when shielded. 

Cities need to install filters that can remove the LEDs’ blue wavelengths, as well as shields that better aim the lights down. Those fixes are costly. But there are some potential positives to LEDs that aren’t yet widely utilized.

The latest bulbs are tunable, which means streetlights might someday make use of warmer, more natural amber colors. Indoor lights and electronic displays can change their hues throughout the day, keeping you more attentive when you need to be, but dialing back the blue as the sun sets.

L.E.D. REVOLUTION

LEDs (light-emitting diodes) compound the light pollution problem. Most city-dwellers are familiar with the traditional yellow hues of low- and high-pressure sodium-vapor streetlamps, which shine in a narrow range. But broad-spectrum LEDs are the future. The brighter and more efficient streetlights can save cities millions of dollars on their power bills, so municipalities big and small are starting to convert.

The most common bulbs are blue with a special coating that makes them appear white to human eyes. This also causes these LEDs to peak in the short wavelengths astronomers commonly use to observe the night sky. 

  Toronto, Ontario street lit by bright LEDs after retrofitting.

  Toronto, Ontario street lit by bright LEDs after retrofitting.

Light Pollution Visualization.jpg

BORTLE SCALE

The Bortle Scale is a nine-level numeric measure of the night sky’s brightness in a particular location. It quantifies the astronomical visibility of celestial objects and the interference caused by light pollution. John E. Bortle created the scale and published it in the February 2001 edition of Sky & Telescope magazine to help amateur astronomers evaluate and compare the darkness of observing sites. The scale ranges from Class 1, the darkest skies available on Earth, to Class 9, daylight-like inner city skies.

With the estimated light pollution growth of 6% a year, all of developed world may lose its dark skies by the end of the 21st century.