Light Pollution's Impact On Sea Turtles' Habitat And Health

Light pollution is a significant threat to sea turtles, affecting their ability to navigate and survive. Sea turtles rely on light to navigate towards the ocean, but artificial light sources can disorient them, leading them inland towards roads and buildings where they face dehydration, predation, and collisions with vehicles. Light pollution also impacts nesting behaviour, as female sea turtles seek out dark beaches to lay their eggs. Artificial lighting discourages nesting and can cause females to return to the ocean without nesting, endangering the survival of hatchlings. Conservation efforts, such as the use of turtle-friendly lighting and ordinances regulating artificial lighting, aim to mitigate the effects of light pollution on sea turtle populations.

Light pollution disrupts the natural light cues used by sea turtles for dispersal

Light pollution can cause sea turtles to become disoriented and travel inland instead of towards the sea. This is because hatchling sea turtles have an innate tendency to move towards the brightest direction, which is usually the ocean. However, artificial lighting along the coast can confuse and misdirect newly emerged hatchlings by appearing brighter than the sea surface horizon.

Hatchlings that crawl towards artificial light sources are following the same instinctive response that leads them seaward on naturally lit beaches. The apparent brightness and glare of artificial lighting are often what lead 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 addition, artificial light on and around the water can continue to disorientate turtles once they have reached the ocean. This can cause them to linger in nearshore waters, increasing their risk of predation, dehydration, or exhaustion.

Light pollution can also deter nesting turtles. Female sea turtles instinctually seek out dark places to deposit their eggs. Bright lights can deter females from coming ashore at all. If they do come ashore, they can be lured away from the sea.

Lights along the coast can cause hatchlings to travel inland instead of towards the sea

Light pollution along the coast can cause sea turtle hatchlings to become disoriented and travel inland instead of towards the sea. This is because hatchlings have an innate tendency to move towards the brightest direction, which is usually the open view of the night sky over the ocean.

Artificial lighting from coastal developments can confuse and misdirect newly emerged hatchlings, as the lights appear brighter than the sea surface horizon. This can cause hatchlings to be attracted away from the sea, increasing their risk of death by predation, dehydration, or exhaustion.

For example, on Anna Maria Island in Florida, a popular nesting site for sea turtles, there wasn't a single half-block area in 7 miles where hatchlings could be released and make it to the sea without being disoriented by artificial lights.

Hatchlings that crawl towards artificial light sources are following the same instinctive response that leads them seaward on naturally lit beaches. The apparent brightness and glare of artificial lighting often lead hatchlings astray. To a hatchling, an artificial light source appears bright because it is relatively close by, yet not intense enough to brighten the sky and landscape. The resulting glare makes the direction of the artificial source appear overwhelmingly bright, so much so that hatchlings will ignore other visual cues and move towards the artificial light no matter where it is relative to the sea.

In addition, lights on piers and boats can also disorientate hatchlings once they reach the ocean, potentially causing them to linger in nearshore waters and fall prey to fish.

Light pollution can deter nesting turtles

In Florida, disorientation from artificial lighting causes thousands of hatchling deaths each year and is a significant marine turtle conservation problem. In the 1990s, there was no lighting ordinance in place to protect sea turtles, and people were unwilling to turn off their lights. Suzi Fox, director of the Anna Maria Island Turtle Watch, recalls that "there wasn’t one half-block area in 7 miles where you could release a hatchling and have it go to the sea".

In addition to deterring nesting turtles, artificial light can also cause hatchlings to become disoriented and wander inland, where they often die of dehydration or fall prey to predators. Therefore, it is crucial to reduce light pollution near nesting beaches to protect both adult female sea turtles and their hatchlings.

To address this issue, the Commonwealth Department of Environment and Energy in Australia is developing guidelines to reduce the impact of lights on marine turtles and other wildlife. These guidelines recommend using natural darkness as a starting point and adding light only when necessary, as well as employing smart controls such as motion sensors and timers. It is also suggested to lower light intensity, avoid lights with blue wavelengths, keep lights close to the ground, and use non-reflective surfaces.

Furthermore, some coastal communities in Florida have passed ordinances requiring residents to turn off beachfront lights during the turtle nesting season. While these ordinances are a step in the right direction, they are not always enforced and do not address the broader issue of sky glow from nearby cities.

Artificial light on and around water can disorientate sea turtles

Light pollution from artificial lighting on and around bodies of water can disorientate sea turtles, causing them to wander inland instead of moving towards the ocean. This phenomenon is observed in hatchlings of all species of sea turtles and has been recorded in Taiwan, Greece, Mexico, the Caribbean, and the United States, especially in Florida.

Hatchling sea turtles have an innate tendency to move towards the brightest direction, which, on a natural beach, is the open view of the night sky over the ocean. However, artificial lighting along the coast can confuse and misdirect these turtles, as the lights appear brighter than the sea surface horizon. As a result, the turtles are attracted away from the sea and towards the artificial light sources, increasing their risk of death by predation, dehydration, or exhaustion.

Additionally, artificial light on and around the water, such as boats at anchor or jetties, can continue to disorientate hatchlings that have reached the ocean, causing them to linger in nearshore waters. This increases their chances of becoming prey to fish that are also attracted to the light.

Light pollution not only affects hatchlings but also adult female sea turtles. Bright lights can deter females from coming ashore to nest, and if they do come ashore, they may be lured away from the sea.

Light pollution can cause sea turtles to become easy prey for predators

Light pollution near sea turtle nesting beaches can cause hatchlings to become disoriented and crawl inland instead of heading towards the ocean. This makes them susceptible to predators as they wander away from the safety of the sea. They can also become easy prey for fish if they linger near jetties or boats that are illuminated at night.

Hatchlings have an innate tendency to move towards the brightest direction, which is usually the ocean horizon. However, artificial lighting along the coast can confuse them and cause them to crawl in the wrong direction. This disorientation can lead to exhaustion, making them even more vulnerable to predators.

Even a single bright light near a nesting site can cause all the hatchlings on a beach to head inland. As they expend their finite energy reserves searching for the ocean, they become easy targets for predators.

Light pollution can also deter female sea turtles from coming ashore to nest. Bright lights can interfere with their natural instinct to seek out dark places for nesting. If they do come ashore, they may be lured away from the sea, making them more vulnerable to predators on land.

The impact of light pollution on sea turtles can be mitigated by reducing artificial lighting near nesting beaches and using turtle-safe lighting, such as low-pressure sodium-vapor lighting or red lights, which emit a narrow portion of the visible light spectrum that is less intrusive to turtles.

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