Currently, there are seven living species of sea turtles. These fascinating animals can be very sensitive to disturbances in their environment.
The International Union for Conservation of Nature (IUCN) contemplates three levels of threat among living beings. In the first place, the level of low risk —with two categories: “least concern” and “almost threatened”—; the second level includes threatened species—in three categories: “vulnerable”, “endangered” and “critically endangered”; and the third includes extinct species. In addition, it has a specific level for those species for which there is not enough data to classify them in other groups —insufficient data category—.
Of the seven species of turtles that exist in the world, all except one are threatened, to a greater or lesser degree; the only one that does not appear, occupies the category of insufficient data.
vulnerable turtles
The IUCN classifies three species of sea turtles as vulnerable . The loggerhead sea turtle ( Caretta caretta ) is distributed among 10 populations in temperate and subtropical regions throughout the Pacific, Atlantic, and Indian oceans, and in the Mediterranean Sea. The total population of this species is unknown, although evaluating the number of known nests, it is estimated that there are between 36,000 and 67,000 reproductive females. Unfortunately, this population decreases year after year .
On the other hand, we have the olive ridley sea turtle ( Lepidochelys olivacea ). Although it reaches high latitudes on North American coasts, it prefers equatorial waters and the southern hemisphere. It is distributed throughout the Pacific, Atlantic and Indian oceans, and reaches the northern coast of Australia. We do not know what world population there is of this species, but we do know that it is decreasing.
For its part, the leatherback sea turtle ( Dermochelys coriacea ) is the largest sea turtle known today. It is also distributed throughout the Mediterranean Sea and the Atlantic, Pacific and Indian Oceans, although in the latter it is only found in the most northeastern and southwestern regions, avoiding the area that runs from the northwest, in the Arabian Peninsula, through the center of the ocean and to the south-eastern zone, in the Australian western coasts. Although their populations do not show significant fragmentation, a constant decline is observed ; There are also no censuses available that allow the global population to be inferred.
endangered turtles
Although it is distributed in both hemispheres in the Atlantic and Pacific Oceans, in the center of the Indian Ocean, and can be found in the Mediterranean, the green turtle ( Chelonia mydas) is a species listed as endangered. With very little data, there is no way to be sure what its world population is, although we do know that it is declining worryingly. It has been in danger of extinction since it was cataloged in 1982, and despite efforts to preserve the species, it has not improved much in the last 40 years. In fact, during the last three generations, it is estimated that the population of reproductive females has decreased between 50 and 70%.
critically endangered turtles
Highly sensitive to human disturbance, the hawksbill sea turtle ( Eretmochelys imbricata ) is one of the most endangered sea turtle species. It has been endangered since 1982 and critically endangered since 1996, with its population increasingly decimated.
According to data obtained in the breeding areas, during the last three generations, the reduction of the population of reproductive females is estimated at 80%, which is disastrous for the species, and probably supposes a path towards extinction. Certain protection and conservation policies, especially those carried out in the Caribbean and in Cuba, have documented a local but significant increase in the populations that nest there, but these are occasional changes in trend, which are still far from signifying a overall positive effect.
Among the sea turtles with a more restricted distribution is the Kemp’s ridley sea turtle ( Lepidochelys kempii ). Breeding populations are only known off the coast of the United States and in the Gulf of Mexico. Although they have been observed on the Atlantic coasts of Spain, Portugal, France and the British Isles, it does not seem that they breed on this side of the pond, and they are probably only seen when they are passing through. Endangered since 1982, it became critically endangered in 1996, and currently its population is estimated at 22,341 individuals, which do not form subpopulations. Observing previous censuses, it seems that its population has not changed significantly in recent years; however, the impacts they suffer, as well as the low global population, make this species one of the most endangered turtles.
The importance of research
If there is any unknown to science when it comes to sea turtles, it is the case of the flatback turtle ( Natator depressus ). In 1994 it was listed as vulnerable, but after the IUCN changed its evaluation criteria —more strict and precise—, the data available to catalog this species were not enough, and it remained as an integral part of the uncomfortable list of deficient data. .
The very few data available on this species make the uncertainty about its situation, its population or the trend it suffers too high, preventing solid scientific conclusions from being drawn. In this case, then, the importance of increasing resources in scientific research can only be highlighted, providing enough rigorous and verifiable data to be able to assess its status and act accordingly.
Impacts on sea turtles
Biological hazards include the fibropapilloma virus, which can cause serious health problems. However, most of the impacts suffered by sea turtles are of human origin. These include certain fishing gear , which often capture specimens, by accident, that fail to recover. Pollution , whether by solid waste or toxic substances, can also have fatal effects. Nets or lines abandoned in the sea, as well as solid waste, can cause mechanical damage that sometimes leads to amputation of limbs, or suffocation if they try to eat it, mistaking, for example, a plastic bag for a jellyfish.
The massive urbanization of the coasts reduces the space for spawning —turtles lay their eggs on land, on the beaches—; climate change can alter their behavior, as well as the distribution and availability of food or their predators —particularly dangerous during the hatching of the eggs—. And among the most serious impacts is the human consumption of its eggs and meat .
References:
IUCN. 2022. The IUCN Red List of Threatened Species. Version 2021-3.
