Overlooked yet Brightly Shining: The Impacts of Ecological Light Pollution

Source: 1920x1080 Resolution Forest Milky Way Night Reflection over River 1080P Laptop Full HD Wallpaper - Wallpapers Den

The night sky used to be pure wonder.  A person would gaze upwards on a clear night and see a huge spectacle of stars and the soft glow of the brushstroke that is the Milky-Way.  The night was the pure opposite of day, it held safety for nocturnal animals and provided a respite for the species that spent their energy during the day.  What do you see when you go outside at night now?  How many stars do you see?  Is it thousands?  Hundreds? A couple dozen?  It is most certainly not the same night sky that your ancestors looked at hundreds of years ago.  What you probably see is only a smattering of the brightest stars and the glow of the nearest cities on the horizon.  The night has lost its darkness.  Light Pollution is to blame, which is defined as "a broad-scale phenomenon, with hundreds of thousands of light sources cumulatively contributing to increased nighttime illumination of the sky".  As the earth lights up at night, it becomes more and more difficult to see the stars and experience natural darkness on our planet.  The Earth's atmosphere reflects back the terrestrial light sources, creating an effect called sky-glow, which outcompetes the light from the stars and moon.

Light pollution is an issue that only grows worse; it is estimated that every year it expands by 3-6%.  In 2016, 1/3 of the Earth's population was unable to view the Milky Way; 3/5 Europeans and 4/5 North Americans cannot see the Milky Way when they step outside of their homes.  The proliferation of light pollution has been driven by affordability of new lighting and development of technologies that allow lights to be brighter.  As lights became cheaper, paradoxically the consumption and abundance increased exponentially, so that the potential savings of affordable technologies was never realized; this demonstrates an economic trend called Jevon's Paradox.  The newer cheaper lights (LEDS) emit blue-light wavelengths, which is reflected in our atmosphere more readily than other wavelengths and thus increases the amount of sky-glow at night.

For a long time, the only complaints regarding light pollution were regarding difficulties with astronomical observations and night-time ascetics.  Scientists viewing celestial bodies and looking to understand outer space were having a tougher time making their observations.  People around the globe noticed that the night sky was brighter and less beautiful to regard.  However, as time went on and the night sky continued to brighten, more effects became apparent that were more worrisome.  Nocturnal animals found less safety in the night then they were accustomed to.  Sleep cycles were disturbed and species were out when they should have been safely hidden in their burrows or dens.  Soon, it was found that ecosystems and biological processes worldwide were under threat of being significantly disturbed by the loss of natural darkness.

A map of the measured light pollution of the United States
Source: Light pollution map

Ecological Light Pollution

When we discuss light pollution's effect on ecosystems and natural cycles, we are talking about Ecological Light Pollution, a term first coined by Travis Langcore and Catherine Rich, who defined it as "light that alters natural light regimes in terrestrial and aquatic ecosystems".  Excluding some extreme examples (such as the deep ocean and isolated caves), every ecosystem on Earth depends on the basic cycle of light and dark to function.  The only constant for the entirety of evolutionary history is the rotation between night and day.  Yet, since the advent of electrical light, human civilization has been eating away at the power of the night, to the detriment of our natural world.

The shift between night and day is important for almost every species of life.  Animals need sleep, and they use natural light levels to signal when they should go to sleep and wake up.  Certain animals perform certain activities at certain times of day.  Species can be diurnal (daytime), nocturnal (nighttime), or crepuscular (dawn/dusk); light or the absence of light is how these groups know when to be active, whether by hunting, mating, foraging, or migrating.

The recognition of ecological light pollution is fairly new, it first appeared in academic journals at the turn of the century.  It is difficulty to study as, unlike other types of pollution, exposure to light photons does not leave chemical traces.  Thus, in order to study it, researchers must perform behavioral or ethographic studies in order to see light pollution's effects.  Despite these challenges, studies have already shown evidence of light pollution's detrimental effects in over 160 different species of animals and even some species of plants.

Like Moths to a Flame

The easiest group to study the effect of light pollution upon are, perhaps, insects.  This can be done simply by laypersons.  Just flick on an outside light at dusk or nighttime and see what happens.  You will soon have a collection of insects tapping away at the light source, unable to escape from its alluring glow.  Many different types of insects are entranced by artificial light: moths, beetles, lacewings, wasps, crickets, midges, and flies, to name a few.  Often times, if the source stays on all night, the insects will die of exhaustion before the dawn can break and free them from their hypnotic trance.  

An Example of a light trapping Insects
Source: Why Are Bugs Attracted to Light? | Interesting Facts (bestunknownfacts.blogspot.com)

These deadly night traps can have quite an effect, especially when you take into account that approximately half of all insect species are nocturnal and require several hours of continuous darkness in order to acquire food and find mates.  Even if a particular insect does not die while imprisoned in a light trap, they will certainly be thwarted from accomplishing their goals for the night.  Individuals captured in traps also become more vulnerable to natural dangers that are already around.

Insect predators, such as birds, mammals, and other insects, have been proven to utilize artificial light traps.  They camp out near sources of light and wait for the buffet line of mesmerized bugs that will make an easy meal.  I have seen this recently at home; a resourceful spider set up a web next to a window on my porch, at night light spills out of the window and draws in a constant source of prey to its web.  Insects caught in light traps and dying of exhaustion or being eaten by predators are effects that are easy to observe, but other impacts of light pollution are harder to discern by the common observer.

The majority of insects utilize the stars, the moon, or polarized light to navigate at night, both for short trips or for long migrations.  Light pollution masks these navigational aids.  Fireflies, a favorite insect of mine in the summertime, are especially susceptible to the impacts of light pollution.  They use their flashing bioluminescence to attract mates, yet artificial lights confuse them and throw a wrench into the necessary machinations of reproduction.  If light pollution continues on its current trajectory, 2,000 different species of fireflies are endangered of becoming extinct. 

Fireflies in a natural environment
Source: How Swarms of Fireflies Sync Their Flashes - The New York Times (nytimes.com)

Crickets are similarly light sensitive.  They normally perform their cricket song during the transition between night and day.  They use these songs to mark their territory and to find mates.  With artificial lights creating a bright night, the crickets are confused when to start their songs, decreasing mating success and increasing their risk of predation.  Studies have even shown that cricket nymphs (young crickets) grow stunted when regularly exposed to artificial light.

Overall, the impacts of light pollution, coupled with other threats such as pesticides and changing climate, have been bad news for insects.  The biomass of insects worldwide has been steadily decreasing; every year it is estimated that the number of insect species decreases by 3%.  In a hundred years, there may be few species left.  You likely have experienced the loss of biomass in your own personal life, through what is called the windshield effect.  A few decades ago, during the summer especially, it was common to have your windshield absolutely splattered with insects whenever you took a long road trip.  Nowadays, you can drive for hours and barely get any bugs on the window.  Thats a good thing for driver visibility, but its a bad indication of the environment, especially when you remember what essential roles insects can play, like pollination, pest control, and their place filling the bottom of the food chain.

Poor Little Tweetee Bird

Another group of animals who are greatly impacted by light pollution are birds.  Again, the average person can easily observe how artificial lights effect birds; we have all been sitting quietly in our home when we are suddenly startled by a large "thump" sound.  Investigating, we find a smudge on the window and perhaps a crumpled body of a bird who flew into the glass at high speed.  Birds are both attracted to and disoriented by artificial light, which causes them to become trapped in suburban and urban areas and then subsequently collide with windows, causing injury and death.  A recent study estimated that 988 million birds are killed annually due to building collisions in the United States alone.  In the spring of 2017, a single high-rise in Galveston, Texas was found to be responsible for the deaths of 400 birds.  Just this year, during the first week of October, 961 birds were found dead outside the McCormick Place Lakeside Center, Chicago, on a single day!  Those are stunning numbers.  

Some of the birds killed in one day at the McCormick Place Lakeside Center
Source: Birders’ Joy Turns to Shock as Massive Migratory Wave Leads to Mass Mortality Due to Collisions With Chicago Buildings | Chicago News | WTTW

Similar to insects, birds utilize the night sky and moon in order to navigate.  This navigation is essential in both small journeys (like finding the way back to one's nest) and large migrations undertaken by thousands of individuals.  In North America, 71% of terrestrial bird species migrate and 80% of these migratory birds do so at night.  That is a lot of birds who are losing access to their navigational tools due to our porch and street lights.  Light areas, like neighborhoods and cities, can act as light traps for birds and capture them in a disoriented haze.  These large light traps increase the chances of collisions and also make the birds easier prey for predators, as they become confused and exhausted.  No wonder our pet cats are always bringing home dead birds for our viewing pleasure.

The effects on bird species is not just limited to injuries like from slamming into windows; there are also physiological and medical consequences.  In a controlled environment study, it was shown that Swallow chicks, when exposed to artificial light, grew stunted and underweight compared to those exposed to a natural light cycle.  Artificial light has also been shown to dampen the immune system of sparrows.  This is a troubling finding in the era of COVID, as zoonotic diseases have become a major source of concern for the medical community.  Sparrows are carriers for the West Nile Virus and Hepatitis C; thus when their immune systems are weakened, there is a greater chance of these diseases being passed to human beings.  It is cascading effects like these, that make the impact of ecological light pollution more widely threatening.

Implications Far and Wide

In an overarching sense, ecological light pollution is an under-studied phenomenon.  A majority of species and systems have not yet been profiled to see what the effect of artificial light may be on them.  However, there is a good collection of studies that at least imply a far and wide effect.  As of now, studies have been able to prove a direct negative impact of ecological light pollution on 160 species of animals.  

Some cases are well known, as in aquatic turtles, which have been a focal species for conservation groups for some time.  Turtle hatchlings naturally move away from low dark silhouetted objects (representing dunes and vegetation) and move toward flatter and brighter areas to get to the ocean.  Beachfront lighting and development remove these silhouettes, causing the hatchlings to scatter in random directions.  The already low survival rate of hatchings is made even lower and the critically threatened turtles are put even further at risk.  Egg-laying females avoid the lighted areas as well, making them unlikely to venture into hatching grounds and halting the repopulation process before it can even begin.

Hatchlings Confused by Artificial Lights
Source: Look, it’s sea turtles! – Traversing the globe one problem at a time (nus.edu.sg)

Much has been said already about light pollution's effects on animal species, but vegetation can also be directly impacted by light pollution.  Trees planted near streetlamps have been proven to retain leaf cover up to two weeks later than those in natural lighting.  Artificial light can cause flowers to bloom too early or too late.  Large trees such as oaks and beeches can be triggered to bloom up to a week early by light sources such as streetlights, and smaller plants (which are more sensitive) can be caused to bud even earlier in the late winter when chances of reproductive success are limited.  When the plants do flower, those subject to artificial light can be visited by 62% less pollinators, impacting survivability and reproduction of these plants.  Johan Eklof, author of The Darkness Manifesto, describes the effect documented in meadows: "normally they (the meadows) attract large numbers of aphids, but a late flowering or absence of flowering (triggered by artificial light) can decimate populations of aphids, which in turn affects green lacewings, shortwings, ladybugs, flowerflies, and the insects we are used to seeing flying over the meadows and that live on flowers and aphids.  The domino effect begins and the ecosystem is disrupted."

A photo showing how vegetation can be basked in Artificial Light
Source: https://www.treehugger.com/how-light-pollution-is-tricking-trees-4861061

The effects of ecological pollution are far reaching and cascading.  They can even transfer over to other important systems, like economics.  Take the example of bats, an animal who is famously nocturnal and thus vulnerable to light pollution.  A decrease in bat populations spells trouble for the agricultural industry, as bats provide natural insect control for crops; in the United States alone, the economic worth of insect control by native bats is estimated to be $3 billion annually.  Bats also provide pollination, disease control (through their insect control), and are a generous source of fertilizer that many human populations take advantage of (guano).  If bats were to become rare due to the encroaching threat of light pollution, the resulting impact would be greatly felt in the human sphere.

What is Being Done?  What Can Be Done?

By this point, you have been hopefully convinced that light pollution is an active threat to nearly all ecological systems on earth, and that a wide range of living species are experiencing adverse effects resulting from the growing loss of natural darkness.  What do we do with this information?  What can be done?  Is anything currently being done?  Happily, the short answer to these questions is "much".  While its impacts are large, light is the only type of pollution where its lasting impact is almost non-existent once the source is removed.  Spilled chemicals may take decades to be removed from the soil, but the effects of light are gone the moment the switch is set to "off".

As the species that created artificial light in the first place, our tendencies towards innovation and perfection can work in our favor.  Technology is always being improved, so the thought is that we can thoughtfully design better methods of lighting to directly address light pollution.  To use an example from before, the LED has been widely implemented as a light source due to its low cost of production and energy efficiency.  However, Jevon's Paradox has resulted in people lighting more and more space and increasing the intensity of these lights.  But if we limit ourselves and decide on appropriate lighting levels, we can realize environmental and economic benefits.  In the last decade, the City of Los Angeles changed all of their existing streetlights to LEDs but ensured that the lighting level of each was not changed.  This has resulted in an estimated $6 Million savings annually, an approximate 60% savings.  By keeping lighting levels constant innovative technologies can address the issue while providing economic incentives.

A graphic showing how LEDs are attractive to combat Light Pollution
Source: South Hayward LED lighting project shines a light on energy savings and waste reduction | Bay Area Rapid Transit (bart.gov)

Another benefit of LEDs is that the wavelength of the light can be adjusted.  We can change lights away from the harsh blue-light that is shown to be more disruptive, and promote light that is more appropriate for the time of day (warmer or red-wavelength light closer to darkness).  To successfully make these changes, there are billions of people to convince and scores more lights to adjust; but luckily there are already groups and organizations that have signed onto the cause.

Ecological light pollution has garnered large interest in recent times and numerous organizations have taken up the mantle of pushing back against the growing brightness.  Perhaps the foremost organization fighting against the loss of the night sky is the non-profit group, DarkSky International.  DarkSky was formed in 1988 and was originally focused on astronomical light pollution.  The founders were all either professional or amateur astronomers and they lamented the celestial objects that were no longer visible due to the expansion of artificial light in the 20th century.  As the group grew, they sponsored research and soon found more reasons to mourn our loss of darkness, including those ecological in nature.  

Now the group provides education, outreach, and training about light pollution and its detrimental effects on Earth.  They also provide methods to reduce one's light footprint, suggested language for legislature to assist the issue (at all levels, state and federal), and actively campaign for a reduction in artificial light across the globe.  They are a great first resource for anyone interested in learning more or getting involved: DarkSky International | Protecting the night skies for present and future generations.  For example, they provide the Principles for Responsible Outdoor Lighting, which anyone and everyone can follow:

1. All light should have a clear purpose (ask yourself, is it really needed?)
2. Light should only be directed where it is needed
3. Light should be no brighter than necessary
4. Light should be used only when it is useful
5. Use warmer color lights where possible.

DarkSky International provides free outreach materials like this graphic
Source: Materials for public outreach | DarkSky International

In addition, DarkSky International provides designations and certifications for places and regions that have natural dark skies.  The designations include: Dark Sky Park, Dark Sky Place, Dark Sky Reserve, and Dark Sky Communities; each designation having its own metrics and requirements to satisfy the certification.  Once certified, places often see increases in tourism as people travel to see the natural dark sky in all its glory.  It also provides a good resource for those looking for a beautiful starry night.  Just go to DarkSky's website and find a Dark Sky Place near you!

The organization has begun to certify Dark Sky Countries, where a country can be recognized for its natural dark skies as well as its policies and legislature that help impede the growth of light pollution.  New Zealand is actively trying to become one of the first countries to achieve the certification.  The initiative is being led by a coalition of indigenous groups (tribes of Māori) who wish to have a closer relationship with the night sky and the lunar calendar that their culture traditionally uses.  One member of this coalition, Rangi Matamua, puts his interest in the project beautifully:

Looking at the sky and connecting to it sits at the heart of humanity.  Its one of the earliest activities every single culture on the planet did, and the night sky is intrinsically connected to who we are as a people.  We're changing the way we understand the world and the things that are important to us.  We need to try and put together better way of using lights and caring for our night sky

A View of a New Zealand Night Sky
Source: Wellington at Night by Michael Jordanoff / 500px

  The Audobon Society is another organization that is fighting light pollution, with their national Lights Out program.  This public-education initiative provides information about light pollution and provides steps and best practices for individuals to make an impact.  The Audobon Society focuses on light pollution's detrimental effect on migratory birds and every year they make a concerted effort for people to turn off unnecessary light during peak migration season.  A success story, promoted by Audobon, is that of a sky-scraper which was responsible for 30,000 bird deaths over a 20-year period; thanks to influence by Audobon, the building turned down its lighting and saw a decrease of bird mortality by 80%.

It is not only non-profits and community groups that are fighting back against the encroaching light, governments are also starting to do what they can to bring back the natural dark.  The first place recorded as doing so was Flagstaff, Arizona, which is home to a major astronomical lab.  Originally the citywide light ordinances were to support the lab and amateur astronomers, but the residents have begun to notice and enjoy the ecological benefits.

France and Germany are examples of countries with nation-wide light ordinances in effect to dull the negative effects of artificial lighting.  France did so with its Decree of 27 December, 2018 on the Prevention, Reduction, and Limitation of Light Pollution.  The decree: "Establishes technical requirements for the design and operation of outdoor lighting installations and imposes these regulations on both public and private property owners.  It contains a number of prescriptions that apply to various lighting situations, from parks and gardens, to building exteriors and parking facilities.  It is designed to prevent, limit, and reduce light pollution, including excessive disturbance to persons, fauna, flora or ecosystems, causing energy wastage or preventing observation of the night sky."

Some of the helpful provisions of this law include:

• Outdoor lighting curfews
• Limits on the allowed emission of light directly into the night sky (upward light ratio)
• Reduced influence of glare: outdoor lighting must conform to a requirement that at least 95% of the light emission is confined to angles at or below 14.5 degrees from the horizontal
• Restrictions on the emission of blue light
• Allowable illumination levels
• Light trespass into dwellings is prohibited
• Use of skybeams, lasers, or similar high-intensity light is generally prohibited
• Nighttime lighting of waterways is generally prohibited

A Photo from a Series that imagined sky views of Cities without Light Pollution
Source: Clear Sky at Night: If Light Pollution Cleared | Under Lucky Stars

For those that may be nervous about such light restrictions being an overstep of government, light ordnances are not a new concept.  During WWII, coastal light ordinances were strictly enforced to protect shipping lanes in the United States, as the outlines of ships created by lighting of towns and cities made them easy prey for U-Boats.  Great Britain found itself in country-wide light ordinance during the blitz.  Back then, the ordinances were to protect lives from bombs and bullets, but now they can protect the ecosystems and our general well-being.

While there are no national light ordinance laws in the United States, over 19 States, Puerto Rico, and the District of Columbia all have legislation to combat light pollution; such acts are called Dark Sky Legislation.  These examples of existing legislation, plus the number of organizations that are actively pushing for more legislation and awareness, give hope to a situation that is, ironically, dark.

Turn out the Lights, Embrace the Night

Ecological light pollution is an all-encompassing, ever-growing, and dire problem.  As human civilization grows at an exponential rate, and our use of artificial light grows with it, we face the issue of a planet that is losing its dark night sky.  The vast majority of creatures and plants on Earth depend on the night and day cycle to balance their health, behaviors, and navigation.  Left unchecked, light pollution will have catastrophic consequences on every ecosystem that it impacts.  Yet, light pollution is a very unique type of pollution.  With a flick of a switch, the source can be turned off, and without an active source, the lasting effects of light pollution are zero.  No multi-billion dollar clean-ups or hazardous waste monitoring needed, just good old fashioned common-sense and moderation.

If we are intentional and respectful with our use of artificial light, many of the ecological, economical, and astrological impacts of light pollution can be mitigated.  It is possible to create a culture around artificial light that maintains safety and comfort, while also restoring the light/dark cycle that has been a constant since the dawn of life and the companion to evolution.  Some may be hesitant to change their habits and to allow the darkening of our planet from what it is now.  But they would do well to remember that our planet has only been bright for a little over a century, and it would be easier to change a century of human behavior than it would be to change millions of years of evolutionary and ecological developments.

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