Light Pollution: Harming Small Animals, Disrupting Nature's Balance

Light pollution, caused by the excessive or inappropriate use of outdoor artificial light, is having a detrimental effect on wildlife, human health, and the environment. It is a global issue, with light pollution levels rising by around 2% per year. Artificial light disrupts the natural day/night cycles of many organisms, affecting their behaviour, reproduction, nourishment, sleep, and protection from predators. For example, light pollution has been shown to impact the migration patterns of birds, sea turtles, and marine life. It also attracts some organisms, such as moths, frogs, and sea turtles, making them an easy target for predators, while repelling others, effectively causing habitat loss. Furthermore, it can alter the day/night patterns of organisms, resulting in a lack of sleep and disrupting reproductive cycles. Light pollution also has negative consequences for humans, as it can interfere with the production of melatonin, a hormone that helps to regulate metabolism and immune responses, and has been linked to various health issues, including sleep disorders, depression, and an increased risk of certain cancers.

Disruption of the circadian rhythm

The circadian rhythm, or the 24-hour day/night cycle, is an essential biological imperative that governs the sleep-wake patterns and physiological processes of almost all organisms. This cycle is largely influenced by photoreceptors in the eye that are more sensitive to blue wavelengths of light. When it becomes dark, the body produces melatonin, a hormone that has antioxidant properties, induces sleep, boosts the immune system, lowers cholesterol, and helps the functioning of the thyroid, pancreas, ovaries, testes, and adrenal glands.

Artificial light at night suppresses the production of melatonin, which can lead to an increased risk of various health problems. Studies have shown a link between exposure to artificial light at night and health issues such as sleep disorders like insomnia and delayed sleep-phase syndrome, as well as depression, hypertension, attention deficit disorder, obesity, diabetes, and heart disease.

The disruption of the circadian rhythm can also increase the risk of certain types of cancer, particularly breast cancer. A study in Israel found a statistically significant correlation between outdoor artificial light at night and breast cancer, with women living in areas where it was bright enough to read outside at midnight having a 73% higher risk of developing the disease. Additionally, recent scientific discoveries about the health effects of artificial light and its impact on melatonin have led the American Medical Association (AMA) to support efforts to control light pollution and research the potential risks of exposure to light at night.

The impact of artificial light on the circadian rhythm is not limited to humans. Animals, such as birds and sea turtles, that migrate or nest at night can be disoriented by artificial light, leading them to wander off course or away from their nesting sites. This can make them more susceptible to dehydration, predation, and collisions with buildings or other structures.

To mitigate the disruption of the circadian rhythm caused by light pollution, it is recommended to minimize exposure to light at night, especially blue light, which has a stronger impact on melatonin suppression. This can be achieved by using dimmer switches, lower-CCT light bulbs, and color temperature apps that adapt electronic screen colors to the time of day. Proper shielding of light fixtures and directing light downward instead of upward can also help reduce light pollution and minimize its impact on the circadian rhythm.

Impact on wildlife and ecosystems

Light pollution has a significant impact on wildlife and ecosystems, affecting the natural behaviours of many creatures, including amphibians, birds, mammals, insects, and plants. Here are some ways in which light pollution affects wildlife and ecosystems:

Disruption of Natural Behaviours

Light pollution can disrupt the natural behaviours of many creatures, such as reproduction, nourishment, sleep, and protection from predators. For example, the glare from artificial lights can impact wetland habitats, disrupting the nocturnal breeding rituals of frogs and toads.

Alteration of Migration Patterns

Migratory birds that navigate by moonlight and starlight can be led astray by artificial light, causing them to wander off course and towards dangerous urban landscapes. This can result in millions of bird deaths each year due to collisions with illuminated buildings and towers.

Disruption of Sea Turtle Hatching

Sea turtles, which hatch at night on beaches, are also affected by light pollution. Female turtles may be discouraged from nesting on brightly lit beaches and can become disoriented, wandering onto nearby roadways. Additionally, hatchlings, which normally navigate towards the sea, can be drawn towards artificial light sources, leading them away from the ocean and towards potential dehydration, predation, or other dangers.

Impact on Insect Populations

Artificial lights can also attract and kill insects, which are a primary food source for birds and other animals. Declining insect populations can negatively impact all species that rely on them for food or pollination, disrupting food webs and ecosystems.

Effects on Nocturnal Animals

Light pollution can drastically alter the nighttime environment for nocturnal animals, turning night into day. Predators that rely on light for hunting and prey species that use darkness as cover can be negatively impacted, leading to potential disruptions in nocturnal ecology.

Impact on Plant Growth

Prolonged exposure to artificial light can prevent trees from adjusting to seasonal variations, which can have implications for the wildlife that depend on them for habitat.

Overall, light pollution has far-reaching consequences for wildlife and ecosystems, disrupting natural behaviours, altering migration patterns, and impacting the survival and reproduction of various species.

Light trespass

Additionally, light trespass can have ecological impacts. For instance, it can disorient sea turtles, causing them to move away from the ocean and towards brightly lit areas, leading to dehydration, predation, and death. Similarly, birds that migrate at night can be confused by bright lights, causing them to veer off course and collide with illuminated buildings and towers.

To address light trespass, it is essential to properly manage and direct outdoor lighting. This can be achieved by using shielded light fixtures that focus light downward, reducing glare and minimising light spillage into unwanted areas. Implementing timers, sensors, or automatic shut-off features on lights can also help ensure that they are only active when needed, reducing unnecessary light pollution.

Sky glow

The effects of skyglow include:

• Making it harder to recognize and distinguish stars and planets, or not see them at all.
• Interfering with the ability of birds and sea turtles to follow the moon's glow to guide their migration patterns.
• Attracting insects and small animals towards cities and suburbs, where they may end up on highways.
• Interfering with trees' ability to detect seasonal changes and increasing their chance of being killed by an early frost.
• Negatively impacting human health, including sleep deprivation, fatigue, headaches, stress, anxiety, and other health problems.
• For astronomers, skyglow obscures the stars, and they now need to move their observation stations further away from civilization.
• Increasing artificial brightness, diminishing the visibility of natural light sources like stars across the entire night sky.

To reduce skyglow, it is important to lower the amount of up-facing or unshielded outdoor lighting as much as possible. This can be done by using shielded light fixtures that direct light downward, using warm-coloured LEDs, avoiding floodlights, and using lights only when needed.

Human health

Light pollution has a range of adverse effects on human health. Firstly, it can wreak havoc on our natural body rhythms, interrupting sleep and confusing our internal, twenty-four-hour 'circadian rhythm' or 'body clock'. This cycle is governed by the natural day/night cycle and is linked to a wide range of physiological processes, including brain wave patterns, hormone production, cell regulation, and other biological activities.

Disruption of the circadian rhythm has been linked to several medical disorders, including depression, insomnia, cardiovascular disease, and cancer. For example, reduced melatonin production at night—which can be caused by exposure to artificial light—has been connected to an increased risk of developing cancer. Melatonin is a hormone that is released in the dark and is inhibited in the presence of light. It not only induces sleep but also boosts the immune system, lowers cholesterol, has antioxidant properties, and helps the functioning of the thyroid, ovaries, pancreas, testes, and adrenal glands.

Research has also shown that exposure to artificial light at night can negatively impact human health in other ways, including increasing the risk of obesity, depression, sleep disorders, diabetes, and breast cancer. For example, a study in Israel found a correlation between outdoor artificial light at night and breast cancer, with women living in areas bright enough to read outside at midnight having a 73% higher risk of developing the disease.

Furthermore, glare from poorly shielded outdoor lighting can decrease vision by reducing contrast, limiting our ability to see potential dangers at night. Aging eyes are particularly affected by this.

Finally, excessive artificial light exposure early in life may also contribute to an increased risk of depression and other mood disorders in humans.

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