Threats to sea turtles occur at practically all stages in their life-cycle. Their nesting beaches are threatened by beachfront developments, poorly managed tourism activities and sand mining. Their eggs are still commercially harvested in some parts of Malaysia. The hatchlings lead a pelagic life and are threatened by pollution like tar balls, plastics and styrofoam. The juveniles of many species of turtles depend on coastal habitats as feeding grounds. Destruction and loss of these habitats to human activities can seriously affect their survival. The adults are often caught in fishing gears, either incidentally or for their shell and meat. All these threats are compounded by their slow growth and long maturation time in the wild.
Turtles typically seek dark and undisturbed beaches for nesting. Beachfront development and construction of industrial plants, recreational facilities, buildings, parking lots, walkways and barriers to prevent erosion can interfere with their nesting. Sand mining or removal of vegetation cover can ultimately alter beaches suitable for nesting. Nesting turtles and their newly emerged hatchlings are impacted by artificial lighting. Nesting turtles often avoid lighted areas while hatchlings are disorientated in their seaward crawl by artificial lights. All artificial lights should be shielded from reaching nesting beaches or lessen the impact by using low pressure sodium lamps.
Uncontrolled use of nesting beaches by visitors or tourists can disrupt nesting activity through their use of torchlights and excessive flash photography. Their activities on the beach can also disturb other nearby turtles from landing or nesting successfully. Visitors to the beach should also refrain from polluting the beach with litter, building campfires or making excessive noise.
Each female adult turtle lays hundred of eggs per nesting season. They however seldom return to nest every year but do so only after 3 – 4 years. In their lifetime, each female, if given the chance to live, can produce thousands of eggs. The reason why so many eggs are layed is not for man to harvest but to compensate for the high levels of mortality faced by hatchlings and juveniles before attaining adulthood. To sustain a population, it is estimated that 70 percent of the eggs deposited should be retained for incubation. In depleted populations, 100% of the eggs deposited should be incubated. Excessive collection of turtle eggs for sale and consumption can seriously threaten turtle populations. In Malaysia, sea turtles are not hunted for meat. While 100% of the eggs are incubated in some locations, such as in the Sabah Turtle Islands, the eggs are still harvested commercially in some parts of Peninsular Malaysia.
The price of turtle eggs today cost ten times more than that of chicken eggs. The nutritional properties of turtle eggs are not much different from chicken eggs. Any medicinal property claimed in turtle eggs is untrue and has never been scientifically substantiated.
The turtle eggs that are sold usually contains life in the form of a developing embryo. The embryo develops rapidly and within 10 days, a pumping heart forms and can be easily seen. Unlike eating chicken eggs which often has no embryo, eating turtle eggs is the same as eating a living turtle.
Green turtle hatchlings emerging from their nest at night. (Photo credit: PinShang)
Hatchlings on emergence head immediately for the sea and swim frantically to offshore waters. They then lead a pelagic existence searching for whatever food they can find that accumulate along driftlines and floating debris. Unfortunately, all garbage that we dump into the sea also gather along these driftlines. Oil slicks which weather into tarballs similarly accumulate in these driftlines. These tarballs may drift in the sea surface for months or years. Mounting evidence has shown that numerous hatchlings die as a result of consuming these debris which they mistake for food.
It is important that garbage is disposed of properly and not thrown into the sea. One should also refrain from littering the beach as the tide will carry the litter out to sea. Non-biodegradable waste like polythene bags, styrofoam, and tar residues are especially hazardous to turtle hatchlings.
Little is known about the age of juveniles when they first leave their pelagic habitats to settle in shallow coastal areas. However, except for leatherbacks, juveniles of other species of turtles have been spotted or caught in various coastal habitats. Pollution, alteration and destruction of coastal marine environments threaten not only the survival of juvenile sea turtles but other marine life forms. In some nations, juveniles are actively hunted for meat or used as stuffed specimens for decoration in homes.
Sea turtles are vulnerable to incidental capture in fishing gears. This occurs in coastal waters during the nesting season, at their feeding grounds or when they migrate between these locations across the open ocean. Drift-nets, trawls, longlines or even the floatlines of fish-traps have been found to kill adult and juvenile turtles. Scientists have estimated that over 21,000 sea turtles are captured with over 12,000 killed annually in driftnets operated by just one country in the West Pacific and South China Sea. The combined catch of all nations which fish in these areas would be phenomenal.