Light Pollution's Impact On The Biosphere

Light pollution is a human-made alteration of outdoor light levels from those occurring naturally. It is a form of waste energy that can have adverse effects on human health, wildlife, and the environment. Caused by sources such as streetlights, greenhouses, and satellites, light pollution disrupts the natural cycles of day and night that plants and animals rely on for crucial behaviours like reproduction, nourishment, and protection from predators. It can also lead to light trespass, glare, and sky glow, which can negatively impact human well-being and the ability to observe celestial objects. The effects of light pollution on the biosphere are far-reaching and understanding them is crucial for conservation efforts and maintaining the delicate balance of ecosystems.

Light pollution disrupts photosynthesis and the activities of insects, birds and other animals

Light pollution has a detrimental impact on the biosphere, affecting the photosynthesis of plants and the activities of insects, birds, and other animals.

Impact on Photosynthesis

Plants rely on their photosynthetic capabilities to fuel their cellular processes. Photosynthesis is the process of converting inorganic molecules of water, carbon dioxide, and light into energy in the form of glucose. Air pollution affects photosynthesis and damages overall plant health. Persistent organic pollutants, such as pesticides, antibiotics, and polycyclic aromatic hydrocarbons produced by burning coal, wood, and garbage, contaminate the air and can travel long distances, impacting vast areas. These pollutants settle on leaves, increasing the temperature, killing leaf sections, and plugging stomata openings. This damages chloroplasts, reducing the plant's photosynthetic rate. Additionally, once air pollution settles into the soil, it can contaminate the roots, impairing the plant's ability to absorb nutrients and water, further restricting energy production and growth. Haze, caused by air pollution, also blocks light, reducing the rate of photosynthesis and plant growth.

Impact on Insects

Artificial light at night (ALAN) has been identified as a contributing factor to the reported declines in insect populations. ALAN has wide-ranging negative effects on insects across their life cycles, including inhibiting adult activity, increasing predation, and disrupting reproduction. A study on the impacts of street lighting on moth caterpillars in southern England found a substantial reduction in caterpillar abundance in lit areas compared to unlit sites. Another experiment revealed that ALAN disrupted the feeding behaviour of nocturnal caterpillars. The negative impacts were more pronounced under white light-emitting diode (LED) street lights compared to conventional yellow sodium lamps. With the ongoing shift towards white LEDs, there are concerns about the potential for ecosystem disruption.

Impact on Birds

Birds that migrate or hunt at night navigate by moonlight and starlight. Artificial light can cause them to wander off course and towards cities, increasing the risk of colliding with buildings and towers. Millions of birds die from such collisions every year. Migratory birds depend on properly timed seasonal schedules, and artificial light can cause them to migrate too early or too late, missing ideal conditions for nesting and foraging. Additionally, lighting can attract large numbers of night-migrating birds, drawing them into lit areas where they become entrapped and circle, depleting their energy stores. This phenomenon is more prevalent on nights with low-cloud ceilings or foggy weather.

Impact on Other Animals

Artificial light at night also affects other animals, such as amphibians and mammals. For nocturnal animals, light pollution radically alters their environment by turning night into day. Predators use light to hunt, and prey species use darkness as cover. Cloudy skies near cities are now much brighter than they were centuries ago, disrupting nocturnal ecology. Artificial lights can also impact wetland habitats, disrupting the nocturnal breeding rituals of frogs and toads.

Artificial light at night can disorientate adult and hatchling sea turtles, making them unable to find the ocean

Light pollution is a growing phenomenon that can have detrimental effects on the biosphere. It can disrupt critical behaviours in wildlife, stall the recovery of threatened species, and interfere with their ability to migrate, reproduce, and survive. One species that is particularly affected by artificial light at night is the sea turtle.

Sea turtles live in the ocean but hatch on beaches at night. When they hatch, they have an innate tendency to move towards the brightest direction, which is usually the ocean horizon. However, artificial lighting on beaches and coastal developments can disorientate adult and newly-hatched sea turtles, drawing them away from the ocean and towards potential dangers on land. This phenomenon is known as "hatchling disorientation" and has been recognised as a significant conservation problem.

The attraction of sea turtles to artificial lights can be explained by their instinctive response to seek the brightest horizon, which is typically the ocean. The apparent brightness and glare of artificial lights can overpower the natural cues that guide sea turtles, causing them to ignore other visual and environmental cues and move towards the light source. This behaviour can lead to exhaustion, dehydration, and increased predation risk for the turtles.

The impact of artificial light on sea turtles is not limited to the beach but also extends into the near-shore waters. Studies have shown that even after entering the ocean, sea turtle hatchlings can be strongly attracted to artificial lights on piers or boats, causing them to linger in areas with a higher risk of predation. This disruption to their natural dispersal patterns can have detrimental effects on the survivorship and resilience of sea turtle populations.

To mitigate the impact of artificial light on sea turtles, conservation efforts have focused on reducing light pollution on nesting beaches. This includes turning off unnecessary lights, using special fixtures to shield lights from the beach, employing turtle-safe lighting with less intrusive wavelengths, and educating the public about the issue. By implementing these measures, communities can help sea turtles find their way to the ocean and improve their chances of survival.

Light pollution affects bird migration, causing them to wander off course and collide with buildings

Light pollution is a growing issue, with artificial light increasing by around 2% per year globally. It has a significant impact on the biosphere, affecting plants and animals alike. One of the key impacts of light pollution is its effect on bird migration, causing birds to wander off course and collide with buildings.

Birds are drawn to lights, becoming entrapped and circling lit areas, which can deplete their energy reserves. This makes them more vulnerable to predators and increases the risk of collision with artificial structures. Light pollution can also affect the timing of bird migration, as birds may misinterpret artificial light as a longer period of daylight, causing them to migrate too early or too late and miss ideal conditions for nesting and foraging.

Research has shown that bright lights on large buildings attract birds, similar to how porch lights attract moths, leading to fatal collisions. This is particularly prevalent during nights with low clouds or fog, when birds tend to migrate at lower altitudes. Mass mortality events involving hundreds of birds have been documented during migration on foggy nights.

Migratory birds that fly long distances may start and end their journeys in areas with low light pollution but can encounter high levels of artificial light during their travels, disorienting them. Seabirds are another group that is adversely affected by artificial light at night. They can become attracted to and disoriented by lights, leading them to collide with human-made structures or the ground, resulting in injuries or death.

While completely darkening cities is not practical, researchers are exploring effective mitigation strategies. These include using bird-conscious lighting practices, such as limiting lighting to necessary times and areas, using motion sensors, and choosing amber or red lights, which are less harmful to birds.

Light pollution can cause sleep deprivation, fatigue, headaches, stress, anxiety, and other health problems in humans

Light pollution can have a detrimental impact on human health, causing issues such as sleep deprivation, fatigue, headaches, stress, anxiety, and other related problems.

Humans have evolved to follow the natural light/dark cycle of day and night, which governs our circadian rhythm—our biological sleep-wake cycle. However, with the proliferation of artificial light, our exposure to darkness at night has been significantly reduced. This disruption to our natural cycle can have far-reaching consequences for our health and well-being.

Firstly, light pollution can lead to sleep deprivation and fatigue. The bright lights of streetlamps, offices, and electronic devices such as cell phones can interfere with our circadian rhythm and the production of melatonin, a hormone that facilitates sleep. Exposure to artificial light at night can cause a misalignment in our internal clock, resulting in reduced sleep times, impaired sleep quality, and excessive sleepiness during the day.

Additionally, light pollution has been linked to an increased risk of obesity, depression, diabetes, and even certain types of cancer. Research has shown a correlation between high levels of artificial light at night and an elevated risk of breast and prostate cancer. Furthermore, light pollution can contribute to eye strain, resulting in soreness, tiredness, and discomfort in the eyes.

The effects of light pollution on our sleep can also indirectly lead to stress and anxiety. Circadian rhythm disorders, such as those caused by shift work, have been associated with mood problems and an elevated risk of workplace accidents. Disruptions to our natural sleep cycle can impact our mental health, with strong correlations between circadian rhythms and mood, mental health, and seasonal affective disorder.

To mitigate these issues, it is recommended to reduce exposure to artificial light at night, especially blue light, which has been shown to have a more significant impact on melatonin and circadian rhythm. Using dimmers, lower-temperature light bulbs, and color temperature apps that adapt electronic screen colors to the time of day can help reduce the negative effects of light pollution on our sleep and overall health.

Light pollution impacts animal behaviours, such as migration patterns, wake-sleep habits and habitat formation

Light pollution has a significant impact on the biosphere, affecting plants and animals alike. It disrupts the natural rhythm of day and night, which is encoded in the DNA of all plants and animals and is crucial for life-sustaining behaviours such as reproduction, nourishment, sleep, and protection from predators.

Migration Patterns

Light pollution can alter the migration patterns of birds and other animals by disrupting their movements at various scales. At the local level, birds may collide with illuminated structures, while at the regional level, they may alter their stopover sites and aerial connectivity. On a larger scale, light pollution can expose animals to sky glow and altered phenology, which can affect their migration timing and routes.

Wake-Sleep Habits

Light pollution can also affect the wake-sleep habits of animals. A study on great tits showed that artificial light caused birds to wake up earlier, sleep less, and leave their nests earlier in the morning. This disruption of sleep can have negative consequences on the health and well-being of animals, as sleep is essential for them to recover from daily stress and maintain optimal cognitive functioning.

Habitat Formation

Light pollution can also impact habitat formation by disrupting the natural light cycles that many animals rely on to establish their habitats. For example, nocturnal animals may avoid areas with artificial lighting, while migratory birds may abandon their preferred roosting sites to avoid lights. Additionally, artificial lighting can attract and disorient animals, leading them towards dangerous areas or away from their natural habitats.

Overall, light pollution has far-reaching consequences on animal behaviours, including migration patterns, wake-sleep habits, and habitat formation. These impacts can have cascading effects on ecosystems and biodiversity, highlighting the importance of addressing light pollution through nature-friendly lighting design and management.

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