What Is Light Pollution?

Light pollution is, according to Wikipedia, “the presence of anthropogenic and artificial light in the night environment.”

In other words, humans are bathing the night sky, when it should be dark, with artificial light, which is often classified in five discrete ways:

1. Glare, which is when unshielded light (e.g. from car headlights or street lights) spills over into the sky (and maybe elsewhere too), causing a reduction in visibility.
2. Light clutter, which is a factor in urban sky glow (see below), caused by groupings of bright lights, often in cities, for example.
3. Light trespass, which is when unwanted light (e.g. from neighbours, passing traffic) seeps into our homes.
4. Over-illumination, which is another contributory factor to urban sky glow (see below), caused by buildings and other structures being excessively illuminated during the night.
5. Urban sky glow, which is the term for the general halo-like “glow” you find over large towns cities.

How Bad Has It Become?

I don’t think I ever realized how widespread light pollution had become until I moved from a large town in England to a rural area in the USA, where I can see the stars again most night (cloud cover permitting) – because I live 12 miles outside a small town of around 6,000 inhabitants, up in the mountains, with very few neighbours, all of which means light pollution is minimal here.

The contrast between the night sky where I live now and the night sky where I used to live in England, some 14 years ago, is immense.

This beautiful short film shows how the night sky changes the less artificial light there is:

So here are a few facts and statistics about this issue, which is only recently being taken seriously:

1. The problem was first mentioned way back in 1866 when inhabitants of large cities (e.g. London, Paris) started to notice that some stars were no longer visible. And what was it that happened about that time? Street lights were becoming popular.
2. City lights can obscure almost all stars – even on a clear, cloudless night.
3. More than 33% of people cannot view the Milky Way from where they live because it is obscured by light:
   • In Europe, 60 percent of the population is unable to.
   • In North America, 80 percent of people cannot see the galaxy,
   • 98 percent of those living in Israel cannot see it, nor can anyone in Kuwait, Malta, or Qatar.
   • The largest areas with enough light to obscure the Milky Way include Boston to Washington, D.C. in the USA, London to Liverpool in England, and Beijing to Hong Kong in China.
4. One study found that the sky over some cities is more than 500 times brighter than over darker, non-urban areas.
5. It’s not only the light emitted from cities and other large urban areas that causes light pollution – it can also come from gas and oil production facilities, such as one in North Dakota, which NASA shows as being almost as bright as the city of Chicago at night.
6. Experiments have shown that people who live underground can sleep for over 24 hours – and yet only think they’ve taken a much shorter nap. Whether that’s good for you or not, it does demonstrate that the absence of lights plays a major role in how our bodies behave.
7. According to U.S. Department of Energy estimates, approximately 120 terawatt-hours (one terawatt is equivalent to one trillion watts) of energy are used per year in the United States – just for lighting up parking lots, streets, and other outdoor locations.

How Does Light Pollution Affect Humans?

Most animals on earth, including humans, have a circadian clock that governs how the mind and body work based on the time of day – and light conditions.

I’ve already talked elsewhere about how important it is that your bedroom be kept completely free from blue light (e.g. the type emitted by many modern devices such as computers and smartphones), but actually, any light that’s visible when we should be sleeping can cause problems.

1. Darkness stimulates the production of melatonin, which is a hormone that regulates, amongst other things, our sleep patterns. A deficiency of melatonin can therefore result in poor quality sleep and insomnia (especially in older people) in general, as well as cardiovascular disease, depression, fatigue, headaches, and stress. And for those who work the night shift, this can be a serious problem.

   Amidst all the stories about the new COV-19 coronavirus, there are even new reports regarding melatonin’s effect on this virus and its infectiousness, as you can read here (or here if the previous link doesn’t work).

2. Some scientists are proposing that an increase in artificial light (both from outdoor lightings in cities as well as indoors via use of televisions, computers, etc. can lead to increased risks of health issues such as breast cancer, early-onset diabetes, obesity, and prostate cancer.
3. Many animals have a polyphasic sleep pattern – i.e. they sleep for more than one period per day. Humans are currently monophasic (i.e. they tend to get all of their sleep during one extended period), but there is some evidence that we used to be polyphasic too, before the proliferation of artificial light, having two four-hour sleeps per day, with a period in between those where we were awake (even though it may have been dark outside). Studies have shown that it is possible, under the right conditions, to revert to this two-phase sleep pattern.
4. One study from around 2006 suggested that the constant artificial light exposure in neonatal intensive care units (e.g. as used for premature babies, or preemies) may disrupt the baby’s developing circadian rhythm, with the potential later in light to lead to depression as well as other mood disorders.

How Does Light Pollution Affect Animals?

In part because of the disruption to animals’ circadian rhythms, light pollution can cause all sorts of changes in animal behaviours:

1. Hundreds of species of birds migrate during the night, but the increase in night-time light is resulting in thousands, maybe millions, of birds colliding with buildings and other structures (e.g. communication towers) and being killed.
2. Fireflies are having trouble finding mates because the light pollution (even from patio lights, for example) is making their own naturally created light more difficult to detect, and this is one reason, so some scientists say, for the decline in may firefly populations.
3. Sea turtles, who lay their eggs on beaches, often try to return to the same beach, even years later, but additional and artificial illumination is causing some to have trouble nesting, and even to become disoriented, leading to them being hit by vehicles. In addition, their hatchlings become confused and instead of heading toward the sea, as they should, they head inland, which can also lead to dehydration and/or exhaustion.
4. More animals are being killed on the road because the changes in light (e.g. glare) are affecting facets of their night-time locomotion.

How Does Light Pollution Affect The Environment?

Other than animal life on Earth, light pollution also has an impact on other life too:

1. Many plants, including trees, depend on the natural changes of seasons and day / night cycles to regulate their own growth – but artificial light is interfering with that. And, of course, this not only affects the plants themselves, but any animals that depend on that plant (e.g. for food or shelter). Some say this is at least one of the reasons why spring might appear to be starting earlier than it used to.
2. According to the International Dark Sky Organization, 30% of the light produced during the night is wasted, which is not only a massive waste of money but also a massive waste of limited resources (e.g. the fuel used to power those lights).

   They also say that this wasted energy is the same as releasing 21 million tons of carbon dioxide into the atmosphere – and it’s estimated you would need to plant well over 800 million new trees each year just to offset that extra carbon dioxide production.

3. Reflected light can contribute to natural ultraviolet rays not reaching the planet, which has a major impact on plant life.

What Can You Do To MInimize Light Pollution

While entire towns, cities, and even countries clearly have a lot they could do on a large scale to minimize light pollution, that doesn’t mean we can’t all play our part, so here are a few suggestions:

1. The US Department of Energy estimates that over one eighth of the electricity used by the average home is for outdoor lighting, so you should consider whether you really need to leave all or some of that lighting on.
2. You can also put any outside lights on a timer, so they shut off automatically at a specified time.
3. Another option for outdoor lights is to use motion-sensitive ones, so they only turn on when they detect somebody (or something) moving nearby.
4. If you do need outdoor lighting, make sure the light is directed downwards (e.g. via shields / shades) so that less of that light escapes upwards.
5. Again, if outdoor lighting is a necessity, can you use lower wattage or energy-efficient bulbs? (There’s a fascinating book, called The Invisible Rainbow, that talks in great detail about how electricity and radio / electromagnetic waves have had a huge and detrimental impact on the health of humans and other animals.)
6. You can prevent indoor lights from “leaking” outside by using curtains or blinds wherever you can.
7. And again, make sure you turn off lights that you are not using.
8. It’s possible that you are being charged for some local street lighting, such as sodium vapor lamps, so you can check with your electricity provider and see if you can cancel that charge – or even have the light removed. Note all will do this, but some will.
9. And on a larger scale, you could start a petition for your local government to decrease unnecessary night-time lighting.

Conclusion

The good news is that more and more “dark sites” are being created.

According to the International Dark Sky Organization, there are already over 130 of these, and in a world first, the tiny pacific nation of Niue (which has fewer than 2,000 citizens – which is less than half the size of the small town I live near) has just received accreditation – for the entire country.

I find it sad that there are people living in major cities (e.g. Los Angeles) who may never have seen the full beauty of the night sky, purely because the city never really goes dark.

And you don’t have to be a professional astronomer to appreciate all that you should be able to see during the night, such as the stars, many of which no longer even exist because the light from them takes so long to reach us here on Earth that they have since died during their light’s journey..

With all of the other significant issues facing life on Earth right now, this may seem like it’s barely worth bothering about, but remember that all life here is interconnected in ways that nobody yet fully understands.

So, it makes sense to do whatever you can to reduce light pollution because, as the saying goes, every little bit helps.

Additional Resources

These are suggestions for those who wish to delve deeper into any of the above:

1. Ecological Consequences Of Artificial Night Lighting
2. International Dark Sky Organization
3. Melatonin Supplement
4. The Invisible Rainbow