Sea Turtles

Threats and Impacts

Some of the main threats to the turtles resulting from human activity are as follows:

• The removal of eggs from nests. In Costa Rica it is illegal to take or sell turtle eggs but it is common for poachers to take the eggs Gandoca Beachand sell them on the black market. This trade is based on the false belief that turtle eggs are an aphrodisiac.
• The destruction of critical habitats. These include areas where the turtles feed, their migratory routes, mating and nesting sites. These include areas where the turtles feed, their migratory routes, mating and nesting sites.
• Incidental fishing. The fishing industry is responsible for the death of a large number of turtles each year as many drown after becoming trapped in the large nets mainly used for catching squid.
• Solid and liquid waste. Chemicals and plastics dumped in rivers often find their way into the sea and pose a threat to the turtles by polluting their habitat.Turtles mistake the blue plastic bags, used to protect bananas on the plantations surrounding Gandoca beach, for jellyfish, their natural prey.
• Development of coastal areas. Pollution resulting from the residual waters of ever growing coastal communities, erosion of beaches and the use of electric lighting in areas where turtles nest are all factors that are leading to a decline in the sea turtle population. Due to deforestation beaches become covered with tree trunks and branches that prevent turtles from crossing the berm to nest.
• Hunting. Turtles are often hunted illegally either for their meat or their shells from which products such as jewellery are made for sale on the black market.

Mass tourism is another threat to the turtles if it is uncontrolled and people are able to visit the nesting beaches without the supervision of specialist guides. Crowds of people and contact with the turtles can prevent them from nesting and they will return to the sea without laying their eggs.

Egg poaching

The eggs are collected because aphrodisiac and special nutritional properties that the people adjudged to them. This is one of the oldest human activities. Initially, it was done to satisfy hunger, but with improved means of transport and preservation of the product with refrigeration, consumption has become more intense and the eggs have become an article of trade that is exchanged for money or other goods.

Light pollution

The hatchlings are directed towards the sea, oriented by the light that is observed in the horizon, guided by a gradient of light located between the sky and the ocean.

When artificial lights like commercial, residential, lights security or recreation lights , iluminate nesting beaches, the hatchlings are oriented towards in land, where they can die squashed by some vehicle, depredated by dogs and other domestic animals, or died because of sun exposure.

In the case of the adult females, the lights in the coast cause a negative feedback omitting to nest.

Both situations results in a decrease in the ability of the nesting populations to produce new individuals and to perpetuate their species.

Data originated data of the analysis of the coastal lights of communities in Beach Grande and Tortuguero (Costa Rica), confirm that the turtles prefer to nest outside the sites of influence of the lights. The green turtles specifically nest where there is no light.

Coastal erosion

Beaches and dunes are a fragile ecosystem that does not get many nutrients to support its vegetation, which is needed to help prevent erosion.

Sea turtles contribute nutrients to dune vegetation from their eggs. Every year, sea turtles lay countless numbers of eggs in beaches during nesting season.

Along one twenty-mile (32 km) stretch of beach in Florida alone, for example, more than 150,000 pounds of eggs are laid each year. Nutrients from hatched eggs as well as from eggs that never hatch and from hatchlings that fail to make it into the ocean are all sources of nutrients for dune vegetation. A decline in the number of sea turtles means fewer eggs laid, less nutrients for the sand dunes and its vegetation, and a higher risk for beach erosion.

The use of sand as a material for construction, reparation and raw material for concrete causes coastal erosion. When sand is removed, the currents create alterations in the coastal dynamic, eroding large parts of the beach and eggs. Sediment plumes from the rivers deposited on the marine bottom can change current patterns and lead to coastal erosion that affects nesting.

Illegal trade

This human activity, due to its mercantile nature, attaches an economic value to the meat, eggs, carapace and other sub-products,inducing the expansion of other threats, such as hunting, egg collection and even visits to nesting sites. Trade defi nitely encourages human actions that increase mortality and diminish the species capacity for regeneration.

Hawksbill scutes are as prized as ivory, rhinoceros horn, gold and some precious stones. The magnitude and long history of the global market for hawksbill shell has strongly influenced the survivorship of the species ).

Called “bekko” or “tortoiseshell”, the scutes that cover the carapace of the turtle are composed of keratin, the same substance that forms nails, hair and rhinoceros horn. Tortoiseshell is a richly colored material and in the hands of experienced artisans it can be soldered, molded, cut and converted into infinite products. Current prices of some tortoiseshell articles make this one of the most valuable products of animal origin; a kilogram of raw, unworked shell can sell for thousands of dollars. (Chacón, 2004)

Hunting

In the history of the humanity, sea turtles have been use as a nutritional resource or for the production of accessories (sea turtle shells and leather).

Generally, the hunters harpoon them in the sea and also wait on the beach for the females to arrive to lay eggs to then capture them, overturn them on their shell, exposing them during hours to the sun to avoid their escape.

The turtles die by sun exposure or due to the hunter's beatings. This type of hunting in addition to being a factor of mortality, is also a cruel practice that has been criticized by ecologists, journalists and the community in general.

Solid waste and Oil spills

Solid waste, particularly when floating in the marine environment presents a problem for many larger species. These risk harm both from entanglement and from ingestion. Marine turtles would appear to be particularly susceptible to this problem and have been observed with such products as balloons, plastic bags, tar balls and polystyrene (styrofoam) in their guts. Floating plastic bags look similar to jellyfish which are an important component of the diet of some species. Even at low levels of ingestion these can interfere with gut function and metabolism, and may have toxic effects. Larger objects may lead to asphyxiation or block the gut and lead to death by starvation.

The contamination by solid remainders not only affects the turtles in the beach, but also it affects the general condition of the feeding habitats and migration. It is common that the turtles and other organisms confuse these remainders with food and die by asphyxia when not being able to swallow it, they are also trapped by the rubbish and pieces of nets that float in the water.

Chemical polluting agents such as petroleum, pesticides tanks, industrial unloadings and agricultural remainders, are responsible in some level to the mortality of marine turtles every year. The environmental contamination damages important coastal ecosystems, including marine grass, reefs of chorale, manglares and communities of seaweed.

The continuous deterioration of the marine grass and coralline communities can be disastrous for the marine turtles survival, due to its dependency on these systems to nourish themselves and to take refuge (National Marine Fisheries Service and U.S. Fish and Wildlife Service 1998). Between the industries that contribute more to the liquid contamination are: petroleum refineries, food tanneries, distilleries, processors, chemical factories of paper and plants, among others.

Coastal development

Coastal development includes the construction of structures that alter the morphology of the coastal zone, where lighting is installed, noise generation is increased, and the arrival of visitors is promoted.

Contamination and the loss of biodiversity are characteristic of this threat. The conversion of a coastal zone into a tourism area with high urban development predominates in the Caribbean.