How light pollution disorients ecosystems

Living things depend on the daily cycle of light and dark which governs behaviors such as reproduction, sleep and migration

Looking at the night sky, stars and other astronomical objects is an absolute delight. Who can forget the synchronized movement of fireflies on a dark night?

While these phenomena can still be observed in rural areas, they are becoming increasingly rare in densely populated urban areas. The presence of artificial light in the environment is one of the main reasons for this. In addition to restricting our ability to observe the wonders of nature, the presence of excessive light has serious repercussions on living beings.

Light pollution

Light pollution is an undesirable consequence of outdoor lighting and usually occurs due to excessive and inappropriate artificial light. There are five overlapping components of light pollution: urban sky glow, light intrusion, glare, uplight, and clutter.

Urban sky glow refers to the brightening of the night sky over populated urban areas. The fall of light into an area where it is not wanted or needed is called light intrusion. Glare is the excessive brightness of light, causing visual discomfort and disability. Uplight is directed towards the open sky, causing a very strong and localized form of light pollution. Clutter refers to an excessive grouping of lights, commonly found in overlit areas.

Poor placement of signage and streetlights, excessive and inappropriate use of light, high population density, and higher road and traffic density contribute significantly to light pollution. Sometimes certain environmental conditions such as smog, fog, and high levels of airborne particles also increase the intensity of light pollution.

Impact of light pollution on plants, animals and humans

Light pollution interferes with the biological activities of living organisms, rather than their rhythm. Living things depend on the Earth’s daily cycle of light and dark which governs behaviors such as reproduction, sleep and migration. Artificial light at night has negative effects on these behaviors.

Plants are affected by three characteristics of light: quantity, quality and duration. The amount of light refers to the total concentration or intensity of light.

The quality of light indicates the wavelength of the light and the duration refers to the total period that the light is present. Light pollution has the potential to alter one or more of these characteristics.

Generally speaking, light pollution affects plants by interfering with photoperiodism. Based on their sensitivity to light, plants are classified into long-day plants, short-day plants, and day-neutral plants. The presence of artificial light, beyond the hours of natural light, can disrupt the photoperiods of these plants.

Several biological activities in plants, such as pigment formation, leaf shedding, and the onset and breaking of bud dormancy, are determined by photoperiod. The presence of artificial night lighting alters the natural photoperiod and therefore disrupts plant development.

Many plant species (such as night-blooming cacti, for example, queen of the night Epiphyllum Oxypetalum) flower only at night and depend on nocturnal pollinators for pollination. Increased lighting can prevent flowering and pollination of these plants and hinder reproduction.

Similarly, animals are also affected by light pollution. Crepuscular (active only at dusk and dawn) and nocturnal (active only at night) animals depend on the length of the day (light) 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 main causes of the worldwide decline of insects. Amphibians are sensitive to ambient light and can detect light intensity well 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 out to sea by sensing the bright horizon above the ocean. However, the artificial lights on the coasts keep them away from the ocean and in the wrong direction.

This process exposes them to several dangers. Nocturnal birds use moonlight and starlight for navigation and hunting and are thus disoriented by a large amount of artificial light. Collision of birds with brightly lit high-rise buildings, lighthouses, wind turbines and offshore drilling rigs results in the death of many birds and is a common occurrence in many cities.

Artificial light causes significant sleep disturbances in humans. The circadian clock, which is a 24-hour day/night cycle, affects physiological processes in virtually all organisms. Brain wave patterns, hormone generation, cellular regulation, and other biological functions are examples of these processes.

In humans, disruption of the circadian clock has been linked to a variety of medical problems, including depression, insomnia, cardiovascular disease, and cancer.

Reduction measures

We should only use light where and when it is needed. Installing lighting based on time and motion sensors can help achieve this goal. Wherever possible, efficient lighting should be used and directed down to the ground and not up to the sky.

Good lighting design should maximize visibility of the intended object and minimize glare and light trespass. Artificial light should be minimized in environmentally sensitive areas such as routes for migratory birds and beaches with active hatching of turtle eggs.

Appropriate guidelines should be introduced regarding lighting on highways and roads in or near forest areas. Awareness of this lesser-known form of pollution needs to be raised so that we can fine-tune our activities to reduce negative impacts and make the world a better place for all beings.

The opinions expressed are those of the author and do not necessarily reflect those of Down to earth