Threats

Sea turtles have long played a vital role in the folklore of many world cultures, but this has not stopped them from being exploited by humans for food and income. The earliest known sea turtle fossils are about 150 million years old. However, in the past 100 years increased demand for turtle meat, eggs, skin and shells has lead to a rapid decline in their populations.

Sea turtles are practically exposed to threats at all stages in their life-cycle. In nature, sea turtles nests are predated by monitor lizards, crabs and ants. Once they emerge, hatchlings make bite-sized meals for birds, crabs and a host of predators in the ocean. After reaching adulthood, sea turtles are relatively immune to predation, except for the occasional shark attack. However, it is the pressure of human activities that is threatening the survival of sea turtle around the world. Moreover, the impact of these threats is multiplied by their slow growth and long maturation period.

Artificial lighting

Turtles typically seek dark and undisturbed beaches for nesting. Nesting turtles often avoid lighted areas; therefore strong light and noise from beachfront structures and coastal residents as well as uncontrolled use of torchlight and flash photography by beach visitors can disrupt nesting activity. This too may disturb other nearby turtles from landing or nesting successfully. Also, artificial light can disorientate hatchlings during their seaward crawl and may lead them to wander inland, where they often die of dehydration and predation.

Coastal development

Beachfront development and construction of recreational facilities, walkways and barriers to prevent beach erosion can hinder nesting. Structures such as sea walls and sandbags that are installed in an attempt to protect beachfront property from erosion may block female turtles from reaching suitable nesting habitat. Besides that, removal or replacing of sand or local vegetation cover can alter beach condition that is suitable for nesting. Also, if this activity persists during nesting season, nests may be buried far under the surface or run over by heavy machineries.

Turtle egg harvest

In their lifetime, an adult female turtle can produce thousands of eggs. Each female lays hundreds of egg per nesting season and return to nest only after three to four years. Therefore, the high number of eggs laid per clutch per season is to make up for the high levels of hatchling and juvenile mortalities before reaching adulthood. In Malaysia, turtle eggs are still harvested commercially. This practise of collecting turtle eggs for sale and consumption can seriously threaten turtle populations. Turtle eggs can be ten times more expensive than chicken eggs although their nutritional properties are comparable. Any medicinal property claimed in turtle eggs has never been scientifically confirmed.

Fishing wire and rubbish kills many turtles

Ingestion of debris and plastic

Upon emergence, hatchlings frantically swim to offshore waters, launching their pelagic life searching for edible floating debris or whatever food they can find that accumulate along drift lines. Unfortunately, these drift lines also accumulate non-degradable human litter that is often dumped into the sea. Thousands of sea turtles die from eating or becoming entangled in this debris each year, including packing strip, balloons, pellets, bottles, vinyl films, and styrofoam. Trash, particularly plastic bags thrown overboard from boats or dumped near beaches and swept out to sea, is eaten by turtles and becomes a deadly meal. For example, leatherback turtles feed primarily on jellyfish and their inability to distinguish between a floating plastic bag and a swimming jellyfish in seawater has lead to deaths of many leatherbacks turtles. Therefore, it is important that garbage is disposed of properly and not thrown into the sea or littered on the beach, as tide will carry the rubbish out to sea.

Pollution

Pollution can have serious impacts on both sea turtles and particularly on the food they eat. Turtle disease such as Fibropapillomas may be linked to pollution in the oceans and in nearshore waters. When pollution kills aquatic plant and animal life, it also removes food for sea turtles to eat. Oil spills, urban runoff of chemicals, fertilizers and petroleum all contribute to water pollution. Besides that, weathered oil slicks form tarballs, which may float on the sea surface for months or years, and are often mistaken by sea turtles for food.

Turtles get caught in fishing nets

Commercial fishing

The waters of South China Sea are a major habitat for turtles, but are also the main fishing grounds in Malaysia. Each year, during sea turtle migration across the open ocean between their feeding and nesting grounds, many become entangled in fishing nets and drown. Sea turtles are vulnerable to incidental capture in fishing gears. Globally, shrimp trawling probably responsible for the incidental death of more juvenile and adult sea turtles than any other source.