The ‘travellers of the sea’, green turtles, have stopped coming to Hong Kong

·5 min read

Green turtles no longer lay their eggs on the beaches of Hong Kong.

Known as the "travellers of the sea", green turtles spend most of their life in the ocean. The only time they come to shore is when they migrate back to the beach where they were hatched to lay their eggs.

The beaches of Hong Kong were one of their nesting sites. From June to October every year, the people of Hong Kong used to enjoy the amazing sight of green turtles laying their eggs on the beaches, and thereafter, the numerous hatchlings scrambling into the waters.

However, such sightings have become quite rare in recent years, as the number of green turtles migrating back to Hong Kong for reproduction has plummeted to an all-time low, mainly because of marine pollutants.

Green sea turtle swimming underwater in lagoon
From June to October every year, green turtles would lay eggs on the beaches of Hong Kong.

Facts about the green turtles

Green turtles are the second largest turtles in the world, and they are the only species that has ever reproduced in Hong Kong.

They can be found throughout tropical and subtropical seas, and they generally lay eggs on beaches near waters with temperatures above 25 deg C.

Five out of the seven known species of sea turtles worldwide have been sighted in the waters along the coast of Hong Kong — red sea turtles, leatherback turtles, hawksbill turtles, olive ridley turtles and green turtles. Among them, only the green turtles reproduce in Hong Kong and Taiwan.

Six of the seven known species of sea turtles have been included in the International Union for Conservation of Nature (IUCN) Red List. There are only around 200,000 fertile female green turtles worldwide today.

The World Wide Fund for Nature (WWF) Hong Kong has ranked green turtles as the second-most popular marine creatures out of ten local species.

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Green turtle trivia

Built-in GPS system:

Around nesting season, green turtles can locate their birthplace and migrate thousands of kilometres back to their hatching beaches to lay eggs. That's why people think these turtles have a built-in GPS system. Lamma Island and Shum Wan Beach in Hong Kong were common nesting sites.

A use for every part:

Green turtles were profitable prey. Their shell is considered a well-known Chinese medicinal material some believe improves overall health, their fat has been used in the production of cosmetics and soap, their skin tanned and used as leather, while their meat is also edible.

Temperature determines gender:

Green turtles don't need gender tests. According to biologists, like many other reptiles, the green turtle's gender is decided by the temperature of their hatching environment. If the nest temperature is high, the hatchling will be female; if it is low, it will be a male turtle.

What's in a name:

Green turtles are not born green. Their pale green comes from the seaweed and large algae they feed on as they grow. These plants leave behind massive amounts of green pigment in the body fat of the turtle.

Lonely turtle:

Contrary to Finding Nemo and other cartoons, sea turtles' lives are not like those depicted by shows. For one, they do not live in groups. And, apart from mating and hatching, they are not in contact with their peers, instead usually swimming alone in the sea.

Green turtle crisis

Green turtles face many major threats, the biggest of which comes from marine debris, a problem that many individuals can work on to directly help sea turtle conservation.

Green turtles face many major threats, and the biggest threat comes from marine debris.
Green turtles face many major threats, and the biggest threat comes from marine debris.

Severe marine pollution:

News of dead sea turtles found in the waters of Hong Kong can be quite rampant. Often, marine litter is found in the digestive tracts of sea turtles, a cause of many diseases in these creatures.

The turtles' limbs or necks can also get entangled by discarded fishing lines, causing them to be dismembered or killed.

Meanwhile, sea turtles often mistake plastic bags for their favourite food, jellyfish, and swallow them, leading to intestinal blockage that results in ulcers.

Hunted as bycatch:

In the past 20 years, many fishermen have tried to catch multiple species when they are out at sea to maximise their profits.

The end result is the global fishery industry capturing millions of sea turtles as bycatch, including green turtles and other endangered species.

Green Sea Turtle (Chelonia mydas), Hatchling Entering the Ocean, Tortuguero National Park, Costa Rica
Green Sea Turtle (Chelonia mydas), Hatchling Entering the Ocean, Tortuguero National Park, Costa Rica

Destruction of nesting sites:

Environmental pollution and urbanisation have greatly impacted the nesting sites of green turtles. For instance, lights on the beaches cause baby turtles to lose their way into the waters and die on the sand.

As humans remove the sand and rocks on the hatching beaches, females cannot find places to lay their eggs and baby turtles die under the hot sun or are eaten by other animals when they fail to scramble past the tiny stones in their paths.

Impact of human activities:

Sea turtle reproduction has been severely affected by human activities. Humans will sometimes disturb the females that are laying eggs, dig eggs out of the nests, catch hatchlings and other things detrimental to these turtles on the hatching beaches.

Global warming:

Do you know that sea turtles can help fight global warming? As one of the very few large marine species that feed on seaweed, they help to maintain the healthy environment of the seabed by doing so.

Without these turtles, overgrown seaweed would block the water flow and cover the ocean floor. In this way, sea turtles ensure the healthy circulation of sea plants and nutrients. In addition, healthy seaweed can help to store carbon.

Similarly, as sea turtles hunt jellyfish, they can reduce the impact on our environment when the jellyfish population is overwhelming.

Unfortunately, the number of female turtles has skyrocketed as a result of climate change and a rise in temperature, leading to gender imbalance, a major problem for reproduction in the world of sea turtles.