Light Pollution's Impact: Animals Affected By Artificial Night Lights

Light pollution, caused by the human-made alteration of outdoor light levels, has harmful effects on wildlife and ecosystems. Nocturnal animals are particularly vulnerable to the drastic changes in their environment caused by light pollution, as their nighttime activity is disrupted, and they are exposed to predators. Light pollution also affects diurnal animals, such as bees, squirrels, and humans, by altering their day/night patterns and reproductive cycles. Specific animal species affected by light pollution include sea turtles, birds, fireflies, salmon, frogs, cougars, bats, butterflies, and insects such as moths.

Frogs and toads are affected by light pollution, which disrupts their breeding rituals

Research has shown that artificial light influences the mating calls of many species of tree frogs. In brightly lit areas, male tree frogs stop or reduce their mating calls, which has the potential to decrease mating opportunities and negatively impact spawning success. This reduction in mating calls may also affect female mate choice, potentially leading to changes in population dynamics.

Frogs and toads are also attracted to streetlights, where they forage for insects. While this may benefit them in terms of finding food, it also endangers them by increasing their risk of being hit by automobiles. Additionally, the presence of artificial light may increase their detection by predators, further impacting their survival.

The impact of artificial light on amphibians is complex and varies depending on the species and their ecology. However, in many cases, it appears that artificial light has negative consequences for amphibian populations, including reduced growth rates, delayed reproductive maturity, lower fertility, and decreased survival.

Further research is needed to fully understand the long-term impacts of artificial light on frog and toad populations, as well as its possible synergistic interactions with other environmental stressors.

Insects are drawn to artificial light, which can lead to their depletion and death

Artificial light has been known to have harmful effects on wildlife and ecosystems. Insects, in particular, are drawn to artificial light, and this attraction has been observed to cause their depletion and death. This phenomenon has been a topic of curiosity and investigation for centuries, with the earliest written records of insects being trapped by artificial light dating back to the Roman Empire.

Recent research has provided new insights into this behaviour. It was previously believed that insects were attracted to light sources, but new evidence suggests otherwise. By using advanced motion-capture technologies and high-speed infrared cameras, scientists have discovered that insects do not fly directly towards the light but instead exhibit three common behavioural motifs: orbiting, stalling, and inverting.

Orbiting occurs when insects fly in a stable circular path around the light source, maintaining their bodies tilted towards the light. Stalling is characterised by insects steeply climbing as they face away from the light, causing them to slow down and eventually stop. Inverting happens when insects flip over and crash into the ground, often due to disorientation.

These behaviours are a result of a disrupted dorsal light response, a mechanism that helps insects maintain their orientation during flight. Normally, insects keep their backs pointed towards the brightest part of their visual field, usually the sky, to know which way is up. However, artificial light sources confuse this mechanism, causing insects to mistake the light for the sky and tilt their bodies towards it. This leads to erratic and disorienting flight patterns.

The impact of artificial light on insects is significant, and it is contributing to the global decline of insect populations. Insects play crucial roles in ecosystems as pollinators and predators of nuisance insects. Therefore, understanding and mitigating the effects of artificial light on insects is essential for conservation efforts.

Some ways to minimise these effects include reducing unnecessary and unshielded lights, especially upward-facing lights, and avoiding ground reflections. Additionally, using shielded lights with lower colour temperatures and long wavelengths (such as amber or red lights) can reduce the glare and visibility of lights to insects, minimising their attraction and disruption.

Sea turtles are disoriented by artificial light, which can lead them away from the ocean

Light pollution is a human-made alteration of outdoor light levels from those occurring naturally. It has harmful effects on wildlife, ecosystems, energy usage, and climate change. Sources of light pollution include streetlights, greenhouses, and satellites.

Sea turtles are one of the many species affected by light pollution. They live in the ocean but hatch on beaches at night. When sea turtle hatchlings emerge from their nests, they find their way to the sea by detecting the bright horizon over the ocean. On a natural beach, the brightest direction is most often the open view of the night sky over, and reflected by, the ocean. However, artificial lights can disorient them and draw them away from the safety of the water.

The apparent brightness and glare of artificial lighting often lead sea turtle hatchlings astray. To a hatchling on a beach, an artificial light source appears bright because it is relatively close by, yet it is not intense enough to brighten the sky and landscape. The resulting glare makes the direction of the artificial source appear overwhelmingly bright—so much brighter than the other directions that hatchlings will ignore other visual cues and move toward the artificial light no matter where it is relative to the sea.

In Florida alone, millions of sea turtle hatchlings die each year due to disorientation from artificial lighting. They wander inland, where they succumb to dehydration, predators, or being run over by cars. Artificial lighting also affects nesting female sea turtles, who may spend valuable energy moving toward lights and away from the water instead of returning to the sea after nesting. Additionally, nesting females may be attracted to roads, where they are at risk of being hit by vehicles.

To reduce the impact of light pollution on sea turtles, coastal communities have implemented measures such as turning off beachfront lights during the turtle nesting season and using special fixtures to shield lights from the beach. These efforts aim to minimize the amount of artificial light visible from nesting beaches, helping sea turtles find their way to the ocean and reducing disorientation and potential threats.

Birds can be distracted during migration and hunting, causing them to wander off course

Light pollution has various effects on birds, including distraction during migration and hunting, which can cause them to wander off course. Birds that migrate or hunt at night navigate by moonlight and starlight, and artificial light can cause them to veer off their intended paths. This can lead them towards dangerous, illuminated landscapes in cities, where they face threats such as colliding with glass buildings.

Nearly all birds in North America—about 80%—migrate twice a year, and 70% of those species travel at night. Nocturnal migration has many benefits, such as better weather conditions and fewer predators. However, it also makes migratory birds highly susceptible to light pollution.

Light pollution has intensified and expanded from urban areas, and with the advent of LED lighting, it is growing in North America by up to 10% per year. This increase in artificial light at night (ALAN) has been linked to several issues for birds, including disruption of circadian rhythms and disorientation during flight.

Research has shown that light pollution acts as an amplifying agent, drawing more songbirds into urbanised areas. It often coincides with other environmental threats like water, air, and noise pollution, further disrupting birds' behavioural and physiological processes.

Understanding the impact of light pollution on birds is crucial, as it can inform conservation actions and help reduce bird deaths.

Mammals such as bats and cougars avoid illuminated areas, exposing them to predators

Light pollution has a detrimental effect on mammals such as bats and cougars, causing them to avoid illuminated areas. This makes them more susceptible to predators and can result in habitat loss.

Bats, for example, are highly sensitive to light. While some species of bats are attracted to streetlights, seeking an easy meal among the insects that gather there, others avoid these lit areas. This puts them at a disadvantage as they are outcompeted by their better-fed counterparts.

Cougars, too, are known to avoid brightly lit areas when travelling at night, even if it means waiting until dawn to continue their journey. This behaviour can leave them hungry and decrease their chances of survival.

Artificial light also disrupts the biological clocks of nocturnal mammals, affecting their circadian rhythms. Studies have shown that exposure to even moderately bright light can shift the circadian clock by 1-2 hours for these animals. This, in turn, can impact their foraging behaviour and increase their risk of predation.

Additionally, light pollution can act as a barrier for mammals, fragmenting their habitats. For example, slow-flying bats avoid passing through illuminated areas as it exposes them to predators such as owls and other birds of prey.

The effects of light pollution on mammals such as bats and cougars highlight the need to address this issue. By reducing light pollution and advocating for responsible lighting practices, we can help protect these mammals and preserve their natural habitats.

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