Green Sea Turtles: Understanding Their Unique Ecological Challenges

what is the cause of green sea turtles

Green sea turtles are an endangered species of sea turtle, named for the greenish colour of their fat, which comes from their diet of seagrass and algae. They are the world's largest species of hard-shelled sea turtle, and the only herbivores among the different species. Green sea turtles are found in tropical and subtropical waters worldwide, and are highly migratory, travelling long distances between feeding grounds and nesting sites. They are threatened by human activity, including overharvesting of their eggs, hunting of adults, accidental capture in fishing gear, and loss of nesting beach sites. Conservation efforts are underway to protect green turtle populations and nesting sites.

Characteristics Values
Scientific Name Chelonia mydas
Common Name Green sea turtle, black (sea) turtle, Pacific green turtle
Description Single pair of prefrontal scales, small and blunt head, serrated jaw, heart-shaped shell, paddle-like limbs
Size 3-4 feet in length, weighing 240-420 pounds
Diet Herbivore: seagrass and algae
Habitat Tropical and subtropical coastal waters, coral reefs, seagrass beds, lagoons
Range Worldwide, with significant populations in the Atlantic, Pacific, and Indian Oceans
Status Endangered
Threats Habitat destruction, fishing bycatch, poaching, climate change, disease

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Overharvesting of eggs and hunting of adults

Green sea turtles have been hunted and killed for their fat, meat, shells, and eggs. Despite regulations increasing over the past century, hunting has largely contributed to the decline of the species in ways that are difficult to reverse.

Overharvesting of Eggs

Historically, green turtles were killed in extraordinarily high numbers for their fat, meat, and eggs. This led to a catastrophic global decline in the species. Although it is now illegal in many countries, including the United States, to kill green turtles and collect their eggs, in some areas, they are still killed for their meat or shells, which are supplied to the wildlife trafficking trade. This remains a threat to their recovery.

In some cultures, turtle eggs are considered a delicacy. In Java, Indonesia, sea turtle eggs were once a popular delicacy. However, due to decreasing populations and the threat of a tourist boycott, Indonesia restricted turtle trade and consumption in 1999.

Hunting of Adults

Green turtles are still routinely harvested for various purposes, including meat, shells, and traditional medicines. Despite their endangered status, poaching sea turtles isn't illegal everywhere, which causes problems for conservation programs.

In West Africa, sea turtles are killed for use in medicine and some traditional ceremonies. In the Cayman Islands, sea turtles were once a source of fresh meat for early visitors and explorers. Historically, the turtles' skin was tanned and used to make handbags, especially in Hawaii. Ancient Chinese cuisine considered turtle flesh a delicacy, especially that of the green sea turtle.

Commercial farms, such as the Cayman Turtle Farm in the West Indies, once bred green turtles for commercial sale. The farm provided turtle meat products to the local population, for whom turtle had been a traditional part of their cuisine for centuries.

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Accidental capture in fishing gear

Green sea turtles are attracted to the bait on longlines and get caught on the hooks or entangled in the lines, often drowning as they are unable to reach the surface to breathe. They can also suffer internal injuries from swallowing hooks or external injuries from entanglement, including strangulation or amputation.

Trawls are another destructive form of fishing gear, catching an estimated 20 pounds of bycatch for every pound of target species. Turtle Excluder Devices (TEDs) have been effective in reducing sea turtle mortality in trawl fisheries, but their use is not yet regulated worldwide.

The WWF has encouraged the use of TEDs in shrimp trawlers, which allow turtles to escape from nets, and supported innovations such as circle hooks, which reduce marine turtle deaths without affecting swordfish and tuna catches.

Bycatch is a widespread problem for green sea turtles, and with the expansion of fishing activity, this threat is becoming more significant. It is essential to implement measures to reduce accidental capture and protect these endangered species.

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Loss of nesting beach sites

Green sea turtles are an endangered species, with a 90% population decrease over the past 50 years. One of the biggest threats to their survival is the loss of nesting beach sites.

Uncontrolled coastal development, vehicle traffic on beaches, and other human activities have directly destroyed or disturbed sea turtle nesting beaches around the world. In addition, rising sea levels caused by climate change are leading to the loss of nesting beach habitats. Shoreline hardening or armoring (e.g. seawalls) can result in the complete loss of dry sand suitable for successful nesting.

The loss of nesting beach sites is a significant concern for the survival of green sea turtles as they are highly migratory creatures and travel great distances, sometimes thousands of kilometres, between their foraging grounds and nesting locations. Green sea turtles are unique in that they return to the same beach where they hatched to lay their own eggs. This is known as natal homing.

To protect nesting beach sites, many countries have laws and ordinances in place. However, due to the long-range migratory movements of sea turtles between nesting beaches and foraging areas, long-term international cooperation is essential for the recovery and stability of nesting populations.

In the United States, many coastal communities in Florida have developed lighting ordinances to help more hatchlings reach the sea. In addition, restoration efforts are underway in places like the Gulf of Mexico, where nesting beaches are being restored and enhanced.

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Ocean pollution and vessel strikes

Green sea turtles are under threat from ocean pollution and vessel strikes. Ocean pollution, including marine debris, oil spills, and chemical contaminants, poses a significant risk to green sea turtles at all stages of their life. They may ingest toxic metals, plastics, and other pollutants, leading to health issues and death. Pollution also degrades their habitats, including nesting beaches and marine environments, disrupting their life cycles and food sources.

Vessel strikes are another major threat to green sea turtles, especially in high-boat traffic areas such as marinas and inlets. As green turtles surface to breathe, they are vulnerable to collisions with boats, which can result in injuries or fatalities. Commercial and recreational vessels pose significant dangers, particularly during peak tourism months when millions of recreational boaters congregate in coastal areas. Efforts to reduce vessel strikes include educating boaters about turtle presence and implementing speed restrictions or no-go zones in critical habitats.

Green sea turtles are also threatened by bycatch, or unintentional capture in fishing gear, which can result in drowning or fatal injuries. Additionally, coastal development and rising sea levels due to climate change contribute to the loss and degradation of their nesting habitats. Conservation efforts are crucial to protect green sea turtle populations and their habitats from these various threats.

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Climate change

Green sea turtles are under threat from climate change, which is causing a range of issues for these endangered species. One of the most significant impacts is the loss of nesting beaches due to rising sea levels. Sea turtles have a unique ability to return to the same nesting site decades later to repeat their ancient nesting ritual. However, with melting polar ice caps and rising sea levels, these beaches are starting to disappear. In addition, the increase in nesting beach temperatures is impacting the gender ratio of hatchlings, with more females than males being produced, which poses a significant threat to genetic diversity.

Warmer ocean temperatures also affect ocean currents, which can alter the migratory patterns of sea turtles and impact the distribution and abundance of prey species. This can lead to sea turtles being introduced to new predators and can harm the coral reefs that they depend on for survival. Coral reefs, which are an important food source for sea turtles, are already in danger due to rising temperatures, which cause a "bleaching" effect that kills parts of the reef.

The combination of these factors means that climate change poses a significant threat to green sea turtles, and there are concerns that it could contribute to their extinction. While there is debate about the best course of action to address climate change, there are simple steps that individuals can take to make a difference, such as reducing energy consumption, recycling, and planting vegetation along beaches.

Frequently asked questions

Green sea turtles are caused by the female green sea turtle returning to the beach where she hatched to lay her eggs. The female digs a hole in the sand and covers it up after laying her eggs.

The scientific name of the green sea turtle is Chelonia mydas.

Yes, green sea turtles are endangered. They have been listed as endangered since 1982.

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