Nature needs the night – and so do we

The adverse impacts of inefficient artificial lighting

In November 2008, Verlyn Klinkenborg (in National Geographic) described how the human race has “invaded the night” with stray artificial light. Is it really ours to occupy? Vast numbers of the world’s species are nocturnal. The invasion of their world by our lighting has consequences that we are only just beginning to investigate and quantify. Wasted light and the trend towards bright, white ‘daylight’ exterior lamps are likely to have played their part in the disappearance of a large fraction of the world’s wildlife in the last 40 years:

Animals disturbed, and killed, as a result of stray light have no curtains to pull. There are many reports of its deleterious effects on large numbers of different species: distracted insects, migrating birds, disoriented fish, reptiles and mammals. Bats, moths, turtles, seabirds…. The list of reports of light disturbing their lives grows ever longer.

Professor Gerhard Eisenbeis, of the University of Mainz in Germany, has led considerable research into the impact of light spill upon insect populations, and speaks of a ‘vacuum-cleaner’ effect, sucking insects to their doom out of habitat areas. In an article in 2011 in the magazine Natur und Landschaft, entitled (in translation) Attraction of nocturnal insects to street lights, Professor Eisenbeis stated that

“Artificial lighting in the environment has had a deep impact on the natural world, especially on nocturnal animals. This takes place against a background of dramatically falling biodiversity in nearly all the Earth’s habitats. At the same time, artificial lighting is only one factor among many environmental pressures. Urban sprawl in the countryside, the conversion of natural habitats to intensive human exploitation and the release of artificial substances have contributed to a situation where biologists speak of the sixth wave of extinctions in the living environment.”

Nobody has said it better than Catherine Rich and Travis Longcore, authors of the definitive book (ISBN 978-1559631297) Ecological Consequences of Artificial Night Lighting:

“Nature needs the night”.

Surely humans are used to artificial lighting by now, aren’t they? The answer is no. Any species, from invertebrate to complex mammal, having evolved for millions of years to the rhythm of a day-night cycle, is not going to change its physiology in just 100 years to adjust to vastly more than the natural dose of light.

Not surprisingly, we find it difficult to cope with a life of international travel across time zones, working night shifts and sleeping in the day, staying up beyond dusk, staring at small, bright screens late into the evening, and living by the social clock rather than the solar one. Dr Steven Lockley of Harvard Medical School, who is a world authority on sleep disorders, writes:

“Access and exposure to artificial light at night have become pervasive in all industrialised nations and increasingly so in the developing world. This light affects all organisms exposed to it, not just humans, and the consequences of such a dramatic alteration in one of the most powerful environmental signals is not yet known. Given its relatively recent introduction, we are only at the beginning of understanding the impact of artificial light on human health. Research over the past 80 years, however, has shown that light exerts very powerful effects on human physiology, endocrinology and behaviour, and, having evolved in a distinct light-dark cycle, it is possible that unnatural exposure to artificial light at night is hazardous to human health”.

The hormone melatonin, a powerful antioxidant, scavenging free radicals and thereby helping to prevent cancer cell damage and proliferation, is secreted during the hours of darkness into the blood by the pineal gland in the brain – it is the biochemical signal of night. The efficiency of our immune system is partly regulated by melatonin. Melatonin levels are governed by the 24-hour circadian clock, which also controls the timing of many other bodily rhythms (e.g., the sleep-wake cycle, temperature, patterns of alertness, moods and performance). The circadian clock has an intrinsic rhythm close to, but not exactly, 24 hours and needs to be reset each day to synchronize with the outside world. The 24-hour light-dark cycle is the strongest environmental time cue to the clock, which in turn entrains its rhythmic outputs, including the melatonin rhythm.

Decreasing our exposure to light in the evening is therefore as important as receiving the right intensity of light during the day. Our bedrooms should be as dark as possible without compromising safety and measures should be taken to prevent exterior lights from shining into them. It is of course the obligation of the owner of the light to ensure this, not the victim of intrusive light.

A BBC report in 2003 confirmed that the vast majority of today’s children “have never experienced total darkness”, being surrounded all night, outside and indoors, with artificial lights. The report was quoting research sponsored by a power company, Powergen, which found that a startling 98% of British children do not sleep in darkness. In one in three households, a night-light remains on actually in the children’s bedrooms, at an estimated cost of £468 million a year. Powergen’s energy efficiency manager, Mike Newell, reportedly said:

“Coupled with the effects of street lighting, many of our children will grow up without ever knowing what true darkness really is.”

More and more research is being reported linking exposure to artificial light to human health problems. As a result, the American Medical Association (AMA) voted unanimously on June 16 2009 to support efforts to control light pollution, on the basis that, in their words:

  • “Many species (including humans) need darkness to survive and thrive;
  • Glare from bad lighting is a public-health hazard — especially the older you become. Glare-light scattering in the eye causes loss of contrast and leads to unsafe driving conditions, much like the glare on a dirty windshield from low-angle sunlight or the high beams from an oncoming car;
  • Wasted light represents unnecessary energy and CO2 production”.

The AMA passed a resolution calling for:

  • “All future outdoor lighting to be of energy-efficient designs to reduce waste of energy  and protect the environment;
  • Light-pollution reduction efforts and glare-reduction efforts at both national and state levels; and
  • All future streetlights to be of a fully shielded or similar non-glare design to improve the safety of roadways for all, but especially vision-impaired and older drivers”.

The AMA encompasses the medical societies in all 50 U.S. states, and more than 120 specialist societies.
The British Independent newspaper reported in 2006 on research by Dr David Blask and colleagues (U.S. National Cancer Institute and National Institute of Environmental Health Sciences, Environmental Health Perspectives. Sept. 2007, 115(9): 1357-62), investigating why the incidence of breast cancer in rich countries is about five times greater than in developing nations. The study involved scientists grafting human breast cancer tumours onto rats, and then infusing them with blood taken from women during the day, in the early hours of the morning, and after being exposed to light at night. The ‘dark-night’ blood slowed the growth of the tumours by a reported 80 per cent; blood taken after exposure to the light had the opposite effect.

In 2008 a study at the University of Haifa, Israel, by chronobiologist Professor Avraham Haim, doctoral student Itai Kloog, and Professor Boris Portnov concluded that exposure to light at night may be a significant cause of breast cancer. Breast cancer is the second most common type of cancer in the USA, and the most common in the UK, and in Israel. The Israeli researchers stated that women in street-lit towns are “37 per cent more likely to suffer from the disease than others in dark areas, and (the risk is) a further 27 per cent higher in areas with the highest amount of outdoor lighting” (Chronobiology International 2008, and 2011 Feb. 2011, Vol. 28, No. 1). The work was described to delegates at the Eighth European Dark-Sky Symposium in Vienna (2008) by Itai Kloog, who related how NASA satellite images had been used to compare light emitted from various towns and villages throughout Israel with breast cancer statistics from the Israeli National Cancer Registry. The researchers also investigated as controls many other factors (socioeconomic, environmental, and genetic) of the women’s lives. “We are not saying that light at night is the only, or even a major factor in breast cancer,” said Kloog. “However, the strong correlation is there. It must be taken into account.”

Studies elsewhere, by other researchers, of night-shift workers (for example, nurses and flight attendants) have found rates of breast cancer considerably higher than normal. Interestingly, rates of breast cancer in totally blind women have been found to be less than average.

Professor Charles Czeisler of the Harvard Medical School commented in 2006:

“If light were a drug, the government would not approve it.”

Professor George Brainard, director of the Light Research Program at Philadelphia’s Jefferson Medical College, said, also in 2006:

“Humans evolved on a planet without electric light over thousands and thousands of generations. The body is designed to be alert and awake during daytime hours and to sleep at night. Now we have a 24/7 society that isn’t in harmony with our biological design.”

So the doctors and academics, echoing the dark-sky campaigners, stress that we tamper with our age-old day/night responses at our peril.

Evidence piles up that the indiscriminate use of light is not as harmless as was once thought. When we finally get lighting right, it will be good not only for our view of the stars above, but also for the very fibres of our being.

Further research is required to understand fully the impacts of artificial light on all classes of living things and the environment as a whole. The precautionary principle applies: enough is known about the ‘dark side of light’ to take action now.

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