Streets flooded with light, dazzling neon signs and a city silhouetted against a bright skyscape on a pitch-dark night may offer a fairyland scenario. But has anyone ever spared a thought about the dark side of too much light? Research has shown that like air and noise pollution, light pollution too has disastrous effects on ecology, wildlife, and human health. Yet there is little or no action, the focus of the green brigade being limited to air, noise, and water pollution. Isn't it time governments, cities, and communities gear up to address this significant and growing threat not only to human health but more importantly, to wildlife, including many species of migratory birds? It is high time we let only starlight and moonbeams illuminate a ‘dark’ night. Tree Take delves deep into the neglected issue of light pollution...
In 1879, Thomas Edison invented incandescent light bulbs, and the modern era of electric lighting began, bringing about a sea change in the lives of people. Gradually the world became awash with artificial light, with streets, houses, buildings, parks, and almost everything lit up. True, it benefited society in innumerable ways, allowing more time for work as well as recreational activities that required light. But there is a flip side too.
When artificial outdoor lighting becomes inefficient, annoying, and unnecessary, it is known as light pollution. Many environmentalists, naturalists, and medical researchers consider light pollution to be one of the fastest-growing and most pervasive forms of environmental pollution and a growing body of scientific research suggests that light pollution can have lasting adverse effects on both human and wildlife health.
Prof Dhruv Sen Singh of Lucknow University is of the view that more research is needed on the subject. Not much work had been done in India in this direction, he said, adding it was known about sound waves that what frequency would be harmful but the same about light was not clear, as to what wavelength of light would be harmful. “It is believed that a visual range of .4 to .7 micron is normal but there may be animals for whom even this may be too much. Increasing tree cover is the only way as it can reduce every kind of pollution. Moreover, there is a conflict between beautification and sustainability. So, somewhere a balance has to be struck,” says the HoD, Geology.
What is light pollution?
In simple terms, light pollution is the presence of any unwanted, inappropriate, or excessive artificial lighting in the atmosphere. It refers to the effects of any poorly implemented lighting source during the day or night. It is not only a phenomenon resulting from a specific source or kind of pollution, but also a contributor to the wider, collective impact of various sources of pollution. Light pollution can exist throughout the day, but its effects are magnified during the night with the contrast of the sky's darkness. It has been estimated that 83 percent of the world's people live under light-polluted skies and 23 percent of the world's land area is affected by skyglow. The area affected by artificial illumination continues to increase. A major side-effect of urbanization- light pollution is blamed for compromising health, disrupting ecosystems, and spoiling aesthetic environments. Studies show that urban areas are more at risk.
Light pollution is caused by inefficient or unnecessary use of artificial light. Specific categories of light pollution include light trespass, over-illumination, glare, light clutter, and skyglow. A single offending light source often falls into more than one of these categories. The term is mostly used about the outdoor environment and surroundings but is also used to refer to artificial light indoors. Adverse consequences are multiple; some of them may not be known yet. Light pollution competes with starlight in the night sky for urban residents, interferes with astronomical observatories, and, like any other form of pollution, disrupts ecosystems and has adverse health effects.
Light pollution is a side-effect of industrial civilization. Its sources include building exterior and interior lighting, advertising, outdoor area lighting (such as car parks), offices, factories, streetlights, and illuminated sporting venues. It is most severe in highly industrialized, densely populated areas and major cities but even relatively small amounts of light can be noticed and create problems. Awareness of the harmful effects of light pollution began in the second half of the 19th century but efforts to address its effects did not begin until the 1950s. In the 1980s a global dark-sky movement emerged with the founding of the International Dark-Sky Association (IDA). There are now such educational and advocacy organizations in many countries worldwide.
Types of light pollution
Light trespass: This occurs when unwanted light enters one's property, for instance, the window of one's home from the outside, causing problems such as sleep deprivation. Light trespass can be reduced by selecting light fixtures that limit the amount of light emitted more than 80° above the nadir.
Over-illumination: Over-illumination is the excessive and unnecessary use of light. Over-illumination stems from several factors, like consensus-based standards or norms that are not based on vision science; improper design, by specifying higher levels of light than needed for a given visual task; incorrect choice of fixtures or light bulbs, which do not direct light into areas as needed; improper selection of hardware to utilize more energy than needed to accomplish the lighting task; incomplete training of building managers and occupants to use lighting systems efficiently; inadequate lighting maintenance resulting in increased stray light and energy costs; "daylight lighting" demanded by citizens to reduce crime or by shop owners to attract customers; substitution of old lamps with more efficient LEDs using the same electrical power; and indirect lighting techniques, such as illuminating a vertical wall to bounce light onto the ground. Most of these issues can be readily corrected with available, inexpensive technology. Most importantly, public awareness is also needed to improve for industrialized countries to realize the large payoff in reducing over-illumination.
Glare: Glare can be categorized into different types, like blinding glare which is akin to staring into the Sun. It is completely blinding and leaves temporary or permanent vision deficiencies. Disability glare is like being blinded by oncoming car lights, or light scattering in fog or the eye, reducing contrast, as well as reflections from print and other dark areas that render them bright, with a significant reduction in sight capabilities. Discomfort glare may not be dangerous but is annoying and irritating. It can cause fatigue over long periods.
Light clutter: This refers to excessive groupings of lights. Groupings of lights may generate confusion, distract from obstacles (including those that they may be intended to illuminate), and potentially cause accidents. Clutter is particularly noticeable on roads where the streetlights are badly designed, or where brightly lit advertisements surround the roadways.
Sky glow: This is the bright haze above cities that is produced from excessive artificial lighting at night. It is caused by the reflection of artificial light in the sky and its bouncing around the different types of particles in the atmosphere. It dims the visibility of the stars and increases the natural light levels at night.
According to Prof Venkatesh Dutta of the School for Environment Studies, Baba Sahab Bhimrao Ambedkar University, Lucknow, preserving darkness in wild areas such as sanctuaries and reserved forests is crucial for maintaining the delicate balance of ecosystems. Artificial light disrupts the natural behaviour of wildlife, including birds, insects, and nocturnal animals, affecting their feeding patterns, navigation abilities, and reproductive cycles. “Many conservation efforts now prioritize minimizing artificial light to protect biodiversity and enhance the wilderness experience. By allowing these areas to remain dark during night hours, we ensure that wildlife can thrive undisturbed, contributing to the overall health and resilience of these natural habitats. This commitment to darkness not only supports ecological integrity but also fosters a deeper connection between humans and the natural world, promoting appreciation and stewardship of our precious wild spaces,” he said.
“There are organizations and initiatives in both the USA and Europe dedicated to preserving darkness and reducing light pollution in natural areas. One notable example is the International Dark-Sky Association (IDA), based in the USA, which works globally to protect the night environment and promote responsible outdoor lighting practices. In Europe, similar efforts are championed by organizations like the Dark Sky Association of Ireland and the Dark Sky Scotland, which advocate for dark sky reserves and lighting ordinances to minimize light pollution in protected areas. These societies collaborate with local governments, communities, and businesses to raise awareness about the importance of preserving natural darkness for wildlife conservation, human health, and astronomical observation. Such efforts are needed here too,” he elaborated.
Ecological impact
While light at night can be beneficial, neutral, or damaging for individual species, its presence invariably disturbs ecosystems. For example, some species of spiders avoid lit areas, while other species are happy to build their webs directly on lamp posts. Since lamp posts attract many flying insects, the spiders that tolerate the light gain an advantage over the spiders that avoid it. This is a simple example of the way in which species frequencies and food webs can be disturbed by the introduction of light at night.
Light pollution poses a serious threat to nocturnal wildlife, having negative impacts on plant and animal physiology. It can confuse animal navigation, alter competitive interactions, change predator-prey relations, and cause physiological harm. The rhythm of life is orchestrated by the natural diurnal patterns of light and dark, so disruption to these patterns impacts the ecological dynamics. Artificial light does not affect only insects. Turtles, seabirds, shorebirds, and ecosystems at large, are being affected. Artificial light at night can disorientate adult and hatchling sea turtles so that they are unable to find the ocean. Birds are also known to become disorientated by lights, resulting in higher bird mortality due to collisions with artificial structures such as buildings. Migratory shorebirds may be exposed to increased predation where lighting makes them visible. They may also abandon preferable roosting sites to avoid lights.
Studies suggest that light pollution around lakes prevents zooplankton, such as Daphnia, from eating surface algae, causing algal blooms that can kill off the lakes' plants and lower water quality. Light pollution may also affect ecosystems in other ways. For example, entomologists have documented that nighttime light may interfere with the ability of moths and other nocturnal insects to navigate. It can also have a negative impact on insect development and reproduction. Night-blooming flowers that depend on moths for pollination may be affected by night lighting, as there is no replacement pollinator that would not be affected by the artificial light. This can lead to species decline of plants that are unable to reproduce and change an area's long-term ecology. Among nocturnal insects, fireflies depend on their body light to reproduce and, consequently, are very sensitive to environmental levels of light. Fireflies are well-known and interesting to people (unlike many other insects) and are easily spotted by non-experts. So due to their sensibility and rapid response to environmental changes, they are good bioindicators for artificial night lighting. Significant declines in some insect populations have been suggested as being at least partially mediated by artificial lights at night.
Frogs have been found to inhibit their mating calls when they are exposed to excessive light at night, reducing their reproductive capacity. The feeding behaviour of bats also is altered by artificial light. Researchers have blamed light pollution for declines in populations of North American moths. Almost all small rodents and carnivores, 80% of marsupials, and 20% of primates are nocturnal. Experts who manage the night sky programme in countries like the US say they understand the nocturnality of many creatures and feel that not protecting the night will destroy the habitat of many animals. Sea turtle hatchlings emerging from nests on beaches are a common casualty of light pollution. It is a common misconception that hatchling sea turtles are attracted to the moon. Rather, they find the ocean by moving away from the dark silhouette of dunes and their vegetation, a behavior with which artificial lights interfere.
Juvenile seabirds are also disoriented by lights as they leave their nests and fly out to sea, causing high mortality. Amphibians and reptiles are also affected by light pollution. Introduced light sources during normally dark periods can disrupt levels of melatonin production. Melatonin is a hormone that regulates photoperiodic physiology and behaviour. Some species of frogs and salamanders utilize a light-dependent "compass" to orient their migratory behaviour to breeding sites. Introduced light can also cause developmental irregularities, such as retinal damage, reduced juvenile growth, premature metamorphosis, reduced sperm production, and genetic mutation.
Sudhir Kumar Sharma, PCCF, Uttar Pradesh said: “It is true that excess light can be harmful to humans and can also disturb animals. So, we are going in for intensive tree plantation. We are embarking on Operation Chhaya under which we will plant tall shady trees, particularly at spots where there is too much footfall, like government buildings, railway and bus stations, and other places. We are also making efforts to plant trees on both sides of roads so that they form a green tunnel.” On sanctuaries, he said: “The tourist zone is always outside the core area of the sanctuaries. Leave aside the core and buffer zones, we do not allow any construction, sound, or light pollution in the eco-sensitive zone that is outside the core and buffer zones. It is outside the park or sanctuary, but we regulate all activities, leaving no scope for light, sound, or air pollution.”
Effect on human health
An increased amount of light at night lowers melatonin production, which results in sleep deprivation, fatigue, headaches, stress, anxiety, and other health problems. Medical research on the effects of excessive light on the human body suggests that a variety of adverse health effects may be caused by light pollution or excessive light exposure. Health effects of over-illumination or improper spectral composition of light may include increased headache incidence, worker fatigue, medically defined stress, decrease in sexual function, and increase in anxiety. Outdoor artificial light at night exposure has been linked to risks for obesity, mental disorders, diabetes, and potentially other health issues.
In 2007, "shift work that involves circadian disruption" was listed as a probable carcinogen by the World Health Organization's International Agency for Research on Cancer. Multiple studies have documented a correlation between night shift work and the increased incidence of breast and prostate cancer. Seoul, which had the highest levels of light pollution, had 34.4% more cases of breast cancer than Ganwon-do, which had the lowest levels of light pollution. Moreover, glare is a public health hazard leading to unsafe driving conditions. Especially in the elderly, glare produces a loss of contrast, obscuring night vision. A new 2021 study published in the Southern Economic Journal indicated that light pollution may increase by 13% in preterm births. An eye specialist, while requesting anonymity, said while it was not exactly known how much damage unnatural or artificial illumination could cause to one’s eyesight, it was suspected that it could promote retinal degeneration.
How can the problem be addressed?
In India, unfortunately, hardly anyone is taking action to reduce light pollution and very few are even aware of the problem and its consequences. However, worldwide, many countries have adopted legislation to control outdoor lighting and manufacturers have designed and produced high-efficiency light sources that save energy and reduce light pollution. It is time we follow suit.
First of all, people should use outdoor lighting only when and where it is needed, to make sure outdoor lights are properly shielded and directing light down instead of up into the sky. They should close window blinds, shades, and curtains at night to keep light inside. Town planners can avoid the introduction of light to previously dark areas. They should deploy lighting at the lowest usable intensity, use lighting only where it’s needed, and shield where possible. They should use ‘warmer’ light – meaning more orange tones rather than colours in the harsh white spectrum.
A green activist of Lucknow wishing anonymity said: “Development is coming but at a cost. Just as people are becoming aware of global warming and the greenhouse effect, they should also be made aware of the adverse impact of light pollution. Environmentalists who raise a hue and cry about air, water, and noise pollution should also take up the cause of light pollution and raise it at appropriate platforms.”
To sum up, it is important to find the right balance between function, aesthetics, and the environment. This does not mean there should be no light. It simply means that light must be thought of holistically, considering the environmental, ecological, and human aspects.
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