Light pollution is an acknowledged blight on both the rural and the urban environment, but perhaps less known is its detrimental effect on wildlife and even our own health. Vicky Ellis investigates.
We humans seem preconditioned to take rather than give back – perhaps nowhere is this more evident than when it comes to nature and our dark skies.
Dark skies are more than just pretty stars in the sky or moonlit trees on a clear night. As romantic as that sounds, the darkness we inexplicably try so hard to flood out is vital for not just our health and well-being but also the health and well-being of flora and fauna.
As more and more housing is built, along with ancillary infrastructure, the more street lighting, outside lighting, security lighting and garden lighting goes up, with little or no regard for the damage caused to our ecosystems that rely on darkness for their very survival.
Why are dark nights so fundamental? This article hopefully goes some way to explaining how important dark nights are and why they should be protected, embraced and treasured.
The night sky with its wondrous stars and moon are part of our heritage. It belongs to no one and everyone at the same time. There is not one person alive who has right over our night sky and not one person who has the right to rob the joys of the night sky from anyone else. It should be our fundamental right to see, enjoy and benefit from the darkness and the tranquillity it generates.
Over billions of years, life on Earth has evolved to rely on the rhythmic cycle of night and day to govern our physiology. It’s part of nature’s DNA and therefore part of our DNA. Science is now uncovering the deadly effect light pollution has on our flora and fauna, from birds, amphibians, mammals, insects and plants to our own health and well-being.
The process behind these circadian rhythms is initiated by photons signalling via the retina a tiny part of the brain responsible for the secretion of melatonin.
Melatonin begins to increase at dusk and peaks around midnight, relinquishing a cascade of chemical signals responsible for the regulation of sleep and wake cycles, body temperature, metabolism and appetite.
Leptin is one of these hormones. Sometimes referred to as the ‘hunger hormone’, it is released primarily from fat cells and ironically contributes to the regulation of body weight, curbing appetite while we sleep. According to epidemiologist Dr Richard Stevens from the University of Connecticut, who has studied links between ALAN (artificial light at night) and human health, one theory as to why it’s important our appetite is suppressed during the night is because ‘back in the day’ foraging for food when it’s dark would have been a high-risk strategy resulting in the likelihood of us becoming food.
All ALAN, be it computer screens, streetlights shining through windows or indoor and outside lights, interfere with circadian rhythms to varying degrees by interrupting regulation of melatonin. Obesity is one consequence among many and is linked to low levels of leptin.
Other studies have found a strong correlation between low melatonin levels and disrupted circadian cycles with heart disease, diabetes, depression and cancer – particularly breast cancer.
Further studies implicate ALAN as having a negative psychological impact on health. On the other hand, Dacher Keltner, a psychologist from the University of California, claims that observing stars rotating gently above our heads creates a feeling of awe and amazement that can elicit a sense of positivity.
Nocturnal animals, which sleep during the day and come out at night, have their natural rhythm drastically disrupted when their night-time environment is destroyed by ALAN. Predators use light to hunt, while prey species utilise darkness to stay safe and other fauna use night-time features to navigate. When affecting ecology, ALAN is sometimes referred to as ‘ecological light pollution’ and can affect nature down to the tiniest organism. Spiders, for instance, will seek out light sources to spin their webs as insects are attracted to the light, so it makes sense to exploit this to their advantage. The same can be said of bats feeding on moths.
However, this disruption in predator-prey balance can result in crashes in prey populations, as we are witnessing now with insects, especially flying insects. While it is unlikely that ALAN is the sole driver of our insect population crash, it is a contributing factor.
ALAN is just one more avoidable man-made negative that affects nature’s natural balance. Nocturnal insects such as moths navigate at night. ALAN can severely inhibit this ability to navigate, interfering with reproductive success. Artificial light sends moths into a frenzy around the light source, which often results in them either being picked off by predators or dying from exhaustion. Flowers that bloom at night rely on moths for pollination. If there is no other night-time pollinator not affected by light pollution, the plant will be unable to reproduce, drastically altering the local ecosystem with sometimes disastrous consequences.
Many will have heard birds singing at night in an illuminated tree, something that makes us feel uncomfortable because we know it is not right.
Other fauna negatively affected include frogs that use a light-dependent compass to find their way at night, using this light to find their way to breeding ponds. Studies have shown ALAN to also cause developmental deformities such as retinal damage, impeded juvenile development, premature metamorphosis, reduced sperm production and genetic mutation.
Frogs croak at night under cover of darkness during their mating season. ALAN can disrupt this, interfering in successful reproduction and negatively affecting population numbers.
Light and glare from ALAN can have a devastating effect on wetlands, home to amphibians such as frogs and toads and migratory birds. Migratory birds often navigate at night using the moon and stars. ALAN can trick these birds into deviating from their migratory routes, sometimes with fatal consequences. Irresponsibly-lit tall buildings in cities around the world draw these doomed birds, which then collide with them.
Fatal Light Awareness Program (FLAP) in America states that brightly-lit tower blocks in Toronto could be responsible for tens of thousands of bird fatalities a year.
The volume of flora and fauna negatively affected by ALAN is so far-reaching that it would be impossible to list each species, but they range across the spectrum to include such animals as turtle hatchlings, some of which turn the wrong way at night. Instead of heading for the moonlit ocean, tragically they are drawn to the bright lights of towns and roads.
Crime and safety
We often hear people panic at the mere suggestion streetlights are turned off after hours, citing safety as a primary reason. Others are that streetlights make people ‘feel’ safer and that the accident rate might increase ‘tenfold’ if street lighting is removed, either in towns or on dual carriageways, and crime rates will soar. It may come as a surprise, but these perceptions are not backed by science or fact, and in some cases, it is quite the opposite: street lighting can do more harm than good when it comes to crime and safety.
Many people reside in the countryside with no street lighting for miles and manage to survive quite adequately, avoiding being run over, burgled or attacked, while cars do not suddenly lose control when no streetlight is on.
A number of studies make the same findings, but two major papers draw similar conclusions:
The first study found, in summary, the following results:
- Switch-off (permanently turning off streetlights) was not associated with an increase in night-time traffic collisions or crime
- Part-night lighting (for example streetlights switched off between midnight and 6am) was not associated with an increase in night-time traffic collisions or crime
- Replacing conventional yellow lighting with white light was not associated with an increase in night-time traffic collisions and was associated with a reduction in crime, though estimates were imprecise
- Dimming of conventional yellow light or white light was not associated with an increase in night-time traffic collisions and was associated with a reduction in crime, though estimates were imprecise
It concluded that turning off streetlights resulted in “little evidence of harmful effects… on road collisions or crime in England and Wales” and “found no evidence for an increase in collisions where street lighting was reduced at night”.
The second study of reviewed literature concluded: “In the light of these findings it can be considered highly unlikely that the Cambridgeshire part-night lighting scheme will cause an increase in crime.”
What are the figures for rural crime, where few or no streetlights occur, as opposed to towns, often heavily peppered with streetlights?
According to statistics from the Office for National Statistics 2018-19 crime and justice bulletin, the rate of violence against any one individual was 20.2 per 1,000 population in mainly rural areas compared with 29.5 per 1,000 population in mainly urban areas.
For sexual offences the rural figure was 2.2 per 1,000 against 2.8 per 1,000 urban areas and the rate for recorded crime was also lower in rural areas than urban areas, for example robbery, domestic burglary and vehicle offences. The figures here were 4.3 per 1,000 population (rural) versus 9.5 per 1,000 in urban areas.
There is of course more reason for these figures than just a lack of streetlighting in rural areas, but these figures may tell us that streetlighting does not seem to have any influence on keeping people safe at night.
It has been found that ALAN can increase atmospheric pollution negatively, affecting the air we breathe. A recent study presented by Harald Stark from the National Oceanic and Atmospheric Administration found that ALAN destroyed nitrate radicals and in so doing prevented the natural night-time reduction of atmospheric smog produced by fumes generated from cars and factories.
Every night the nitrate radical NO3, which is destroyed by sunlight, builds up during the night, neutralising some of the nitrogen oxides (NOx), which pollute the air during daylight hours, leading to increased levels of ozone (O3), which can cause breathing difficulties.
Further research, cited by Kelly Beatty in her article Night Lights Worsen Smog, claims to show that this clean-up is inhibited due to nitrate radicals being destroyed by vertical night-time light-glow spillage emanating from outside lighting on the ground.
Astronomers who study the night sky are particularly sensitive to even the lowest levels of light pollution. Indeed, skyglow can destroy their chances of studying the night sky completely.
How can we reduce the impact of ALAN?
Of course, the one preferred default is no light at all. However, the type of bulb you use can have a huge impact on how many insects are attracted, especially winged insects.
It is recommended that we use warm-coloured LED bulbs for outside lighting and avoid white LED sources. A study by Michael Justin from the University of North Carolina found incandescent light bulbs were attracted the highest number of insects, followed by CFLs (compact fluorescent lamps), halogen globes and cool-coloured (such as blue) LEDs.
The second-best light was the ‘bug light’ and surprisingly the winner, with the fewest insects attracted, was the warm LED bulb.
We can use light fittings that angle the light down where it is needed and do not allow the light to flood out across fields and into the night sky. As pretty as that lantern is, it’s not night-friendly. Further, lighting need be kept on only when necessary – we can turn it off once in bed or when our visitors have left. These are only small gestures in the great scheme of things, but if everyone did this it would collectively make a huge difference. Who knows, we might even get back our night sky and nature can begin to slowly mend.
Sunday, September 13, 2020