What is Light Pollution?

• It is the modification of natural light at night, caused by unwanted, inappropriate, or excessive anthropogenic artificial light sources. It’s a consequence of industrial civilisation and urbanization.
• Building exterior and interior illumination, advertising, outdoor area lighting (such as car parks), offices, industries, street lights, and illuminated stadiums are some of its sources.
• Moonlight and starlight serve as important cues for marine organisms and their glow can easily be washed out by artificial light. 

• Components of light pollution include:
• Glare: Excessive brightness that causes visual discomfort
• Skyglow: Brightening of the night sky over inhabited areas
• Light trespass: Light falling where it is not intended or needed
• Clutter: Bright, confusing and excessive groupings of light sources.

Marine Light Pollution

• When thisartificial light is used excessively or poorly, it becomes light pollution and disrupts the natural patterns of wildlife, contributing to the increase in carbon dioxide (CO₂) in the atmosphere.
  • The scientists found that 1.9 million km2 of the ocean experience biologically significant amounts of artificial light pollution to a depth of 1 metre.
    • This represents about 3% of the world’s Exclusive Economic Zones (EEZs).
  • Significant areas of the ocean are seeing light exposures to depths of 10 metres, 20 metres, or more.
    • In areas with very clear water, the light at night can reach depths of more than 40 metres.
  • Sources:
    • Coastal development(e.g., buildings, streetlights, billboards, ports, piers, docks and, light house).
    • Vessels(e.g., fishing and merchant marine vessels), harbours and offshore infrastructure such as oil rigs.
    • Some of the common types of artificial lights in the marine environment are LED, fluorescent, metal halide, and plasma lamps.
      • White LEDs produce broad spectrum light that is sensed by a wide range of organismsand have a peak at short wavelengths (blue and green light) to which many marine organisms are particularly sensitive.

Note:

• The Earth is getting artificially brighter, at a rate of 2.2% per year. As a result of these brighter nights, the impacts of artificial light at night (ALAN) have become an increasing focus in terrestrial ecology.
  • As per studies, non-natural light increased the brightness of Skyglow, by 9.2-10% every year between 2011 and 2022
• Research has shown that ALAN is a major form of anthropogenic pollutionthat can affect a wide range of biotic processes, including physiology, behaviour, animal movements, species interactions, community structure and reproduction.

Artificial Lightning Affect the Marine Ecosystem

• Disruption of Normal Cycles:As per the study, it already took marine organisms an evolution of over millions of years to adapt to natural light and now the threat of ever-increasing anthropogenic light pollution has been posing several threats to them.
  • Artificial light can easily wash out the glow of moonlight and starlight consequently disrupting their hormonal cycles, inter-species behaviour, and reproduction cycles.
• Illustration:For instance, to lay their eggs, female sea turtles try to find a quiet, dark spot and avoid light. However, due to artificial lightning, they may end up not coming ashore at all.
  • Moreover, their hatchlings head toward inland lights instead of moonlight on the water and then die of dehydration or starvation.
• LEDs Worsening the Impact:The ever-growing usage of LED lighting is also altering the very nature of artificial light.
• Suggestion:
  • Encouraging land-based Lights Out efforts(local, state, and regional campaigns to darken skies) to help migrating birds that are drawn to light at night. It will also benefit marine systems near coastal cities.
  • Increasing the usage of red light in coastal areasas much as possible and putting up barriers to shield the coastline from artificial light.
    • Red light, having the longest wavelength in the visible spectrum, doesn’t penetrate as far into the water.

Impact of Light Pollution

• Plants are affected by three characteristics of light: Quantity, quality and duration. Quantity of light refers to the total concentration or intensity of the light. Light quality indicates the wavelength of the light and duration refers to the total period for which light is present. Light pollution has the potential to alter one or more of these characteristics. Broadly speaking, light pollution affects plants by interfering with photoperiodism. Based on their sensitivity to light, plants are classified as long-day plants, short-day plants and day-neutral plants. The presence of artificial light, beyond natural light hours, can disturb the photoperiods of these plants. Several biological activities in plants, such as pigment formation, leave shedding and the onset and breaking of bud dormancy are determined by the photoperiod. The presence of artificial night lighting alters the natural photoperiod and, therefore, upsets the plant’s development. Many plant species (such as night-blooming cacti, for example, Queen of the Night Epiphyllum Oxypetalum) bloom only at night and depend on nocturnal pollinators for pollination. Increasing lighting can prevent flowering and pollination in such plants and hamper reproduction.
• Similarly, animals are also affected by light pollution. Crepuscular (active only at dusk and dawn) and nocturnal (active only during the night) animals depend on the duration of day (light) length to start / stop their daily activities. Exposure to artificial light interferes with these activities, decreases their chances of finding food and mates and exposes them to predators. While light pollution can potentially affect any organism, its effects are particularly pronounced on insects, amphibians, sea turtles and migratory birds.
• Artificial light at night is one of the prominent causes of global decline of insects. Amphibians are sensitive to ambient light and can detect light intensity at far below human limits. Amphibians perform their mating calls at night. Long exposure to artificial light can interfere with this process and affect their reproductive success.
• Sea turtles lay their eggs on beaches. When the eggs hatch, the hatchlings find their way to the sea by detecting the bright horizon over the ocean. However, artificial lights on the coasts draw them away from the ocean and in the wrong direction. This process exposes them to several dangers.
• Light pollution also affects endangered leatherback and loggerhead sea turtles. On Canada’s Atlantic coast, baby turtles on beaches look for moonlight reflecting from the water. This helps them find their way to the ocean. But light pollution can lead them to cities instead. Because of this, fewer sea turtles reach maturity and breed. This puts the survival of the species at even more risk.
• Nocturnal birds use moonlight and starlight for navigation and hunting and thus, become disoriented by a large amount of artificial light. The collision of birds with brightly lit high-rise buildings, lighthouses, wind turbines and sea-based drilling platforms results in the death of numerous birds and is a common phenomenon in many cities.
• Light pollution makes migration difficult for many birds. The Prothonotary warbler depends on stars to find its way from Ontario to the Gulf of Mexico. But light from tall buildings and outdoor advertisements hides its view of the night sky. This means fewer birds survive to reach the areas where they breed or find food during the winter.
• Artificial light causes major sleep disturbances in humans. The circadian clock, which is a 24-hour day / night cycle, affects physiologic processes in practically all organisms. Brain wave patterns, hormone generation, cell regulation and other biologic functions are examples of these processes. In human beings, disruption of circadian clock has been associated with a variety of medical issues, including depression, sleeplessness, cardiovascular disease and cancer.

• Photoreceptors are light-sensitive cells in the retina. The retina is found at the back of your eye. Photoreceptors are responsible for converting light into signals. Our brain interprets these signals as images of the world around us. There are three types of photoreceptors - rods, cones and intrinsically photosensitive retinal ganglion cells or ipRGCs. Rods help us see light and dark. They are very sensitive to light. Cones help us to see colours. Glare can hurt your eyes because it can damage or kill rods and cones. This can lead to vision loss or impairment. Scientists think ipRGCs help rods respond to light at many different brightness levels. They may also help regulate circadian rhythms. Circadian rhythms are like an internal clock that our bodies follow every day. Many circadian rhythms are controlled by the light signals around us. So light pollution can disrupt our circadian rhythms.
• The photoperiodism is a phenomenon of plants in response to the length of light and dark period in a day. The changes in the light period and dark period duration are considered as photoperiods. In plants photoperiodism involves in the maintaining the flowering process. On the basis of the response towards photoperiodism the plants are classified into short day plants and long day plants.

Some of the plants like; rice, cucumber, and corn are considered as day-neutral plants because their blooming process is regardless of the length of the light period like the long day and short day plants.

Reduction of Light Pollution

• Reducing light pollution implies many things, such as reducing sky glow, reducing glare, reducing light trespass, and reducing clutter.
• The method for best reducing light pollution, therefore, depends on exactly what the problem is in any given instance. Possible solutions include:

1. 1. Utilizing light sources of minimum intensity necessary to accomplish the light’s purpose.
   2. Turning lights off using a timer or occupancy sensor or manually when not needed.
   3. Improving lighting fixtures, so that they direct their light more accurately towards where it is needed, and with less side effects.
   4. Adjusting the type of lights used, so that the light waves emitted are those that are less likely to cause severe light pollution problems.
   5. Evaluating existing lighting plans, and re-designing some or all of the plans depending on whether existing light is actually needed.

Initiatives taken

• International Dark-Sky Association (IDA): Global organization protecting the night sky and reducing light pollution through guidelines and dark sky preserves.
• Globe at Night: Citizen science campaign reporting light pollution levels to raise awareness and support reduction efforts.
• International Year of Light (IYL): UN initiative promoting sustainable lighting practices and addressing light pollution.
• The Dark Sky Scotland Project: Promotes dark skies in Scotland through collaboration and implementation of effective lighting solutions.