Threats to Marine Turtles
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All species of marine turtles are threatened with extinction. This page summarizes the common threats they face. It is based primarily, but not entirely, on material gathered from the various Sea Turtle Recovery Plans adopted by the U.S. National Marine Fisheries Service and the U.S. Fish and Wildlife Service.
Fibropapilloma tumors (FP) are lobe-shaped tumors that can infect all soft portions of a turtle's body. Tumors grow primarily on the skin, but they can also appear between scales and scutes, in the mouth, on the eyes, and on internal organs. These tumors often increase in size and number until the turtle is seriously debilitated. Death is a common outcome.
While there have been isolated reports of FP in turtles that date back as far as the 1930s, it was only in the early 80s that the disease began to reach epidemic proportions. For unknown reasons, FP began infecting green turtles in large numbers simultaneously in several geographically discrete areas, such as Hawaii, Florida, and Australia. By the mid-90s, the single greatest threat to the green turtle was FP.
While much research has been and continues to be done to find the causes and remedies for FP, there is a new and alarming development. Fibropapilloma tumors are starting to show up on other sea turtle species in increasing numbers! If the same pattern of infection occurs as was seen with green turtles, it will not be long before FP outstrips even homo sapiens as the single greatest threat to marine turtles.
A major reason why marine turtles throughout the world are in danger is the continuing loss of nesting habitat. It is believed that marine turtles have an extremely high affinity for their nesting beaches, and therefore the loss or reduction of even a single nesting beach can have serious effects.
Residential and tourist use of beaches can result in disturbance to nesting turtles. The most serious threat is cause by increased human presence on beaches, especially at night. This results in nesting females shifting their nesting sites, sometimes being forced to use less suitable beaches. Egg laying can be aborted or delayed as well.
Recreational use discourages nesting activity on beaches that have been used for millennia. The introduction of recreational equipment such as lounge chairs, umbrellas, small boats, and beach cycles (to name a few) can further reduce the usefulness of a beach for nesting, and can seriously damage or destroy any existing nests.
Unfortunately for sea turtles, their eggs are still considered highly desirable for a number of reasons. For example, turtle eggs are supposed to be superior to chicken eggs for use in baking. The theft of turtle eggs continues to be a serious problem everywhere turtles nest, including within the United States.
Baby turtles find their way to the sea by the light reflected off the ocean. Artificial lighting from buildings, streetlights, and beachfront properties has a disorienting effect on little turtles. The problem of beachfront lighting is not just limited to the baby turtles. Adult turtles can mistakenly move inland after egg laying, and females tend to avoid areas where beachfront lighting is most intense. Turtles also abort nesting attempts more often in lighted areas. Artificial lighting has had profound negative effects on nesting behaviour and success.
Beach armouring includes the building of sea walls, sandbag installations, groins and jetties. Such practices save structures and property from erosion, but ultimately result in environmental damage and loss of a dry nesting beach.
Beach nourishment is the practice of adding sand onto a beach to rebuild what has been lost through erosion. Beach nourishment affects turtles by direct burial of nests, or by disturbing nesting activity during the nesting season. Heavy equipment on beaches can pack the sand, making it impossible for turtles to dig proper nests. For example, significant reductions in loggerhead nesting success have been documented on severely compacted nourished beaches, and probably affects leatherbacks as well.
Erosion of nesting beaches results in the loss of nesting habitat. Human interference has hastened erosion in many places. Even attempts to halt erosion can have negative effects on nesting beaches, as described in Beach Armouring above.
Human use of nesting beaches sometimes prompts beach cleaning activity, such as raking and the use of mechanical equipment. Not only can existing nests be disturbed by beach cleaning, it can also result in compacted beaches that are difficult or impossible to use for nesting.
Turtle eggs are particularly vulnerable to predators. Many animals seem to be aware of the nesting cycle of marine turtles, and eagerly gather to ravish nests once the turtles have made them. For example, raccoons have been known to destroy as much as 90% of all nests on a beach.
The threat does not end when the egg is hatched. Hatchlings must escape the clutches of animals such as foxes and gulls as they try to reach the water, and even when they reaches the ocean, predators such as sharks await them.
Of course, the most dangerous predator of all is Homo sapiens.
With the exception of the leatherback, marine turtles live most of their lives in fairly shallow coastal waters. This makes them terribly vulnerable to the excesses and carelessness of the human species.
The most serious marine environment threat to turtles is commercial fishing. In some parts of the world, turtles are still hunted, both for food and for their shells. In places where turtle hunting is banned, the incidental taking of turtles during other fishing operations remains a major threat.
For example, shrimp trawlers without turtle excluder devices trap and drown sea turtles. Gill nets also snare turtles, and frequently are not pulled soon enough to free the turtles before they drown. Although turtles can remain underwater for long periods, they need to breathe. A trapped turtle will struggle, significantly reducing its oxygen supply and shortening the time it has before it needs to reach air. Shrimp and gill nets simply are not removed from the water soon enough to save most trapped turtles.
Human attempts to exploit offshore oil and gas reserves pose a serious threat to marine turtles for several reasons.
Activities associated with developing offshore oil and gas resources can destroy or seriously disrupt foraging habitat and nesting habitat. Dredging not only destroys habitat, it also results in the incidental injuring or killing of sea turtles. The presence of offshore structures alters the characteristics of nesting areas in ways that could well affect nesting habits.
The exploitation of offshore oil and gas reserves also leads to oil spills and the presence of tar in the water. Both of these pollutants have serious effects on marine turtles. Oil on the skin and shell of a marine turtle can affect respiration and salt gland functions, as well as the turtle's blood chemistry. The ingestion of tar pellets is also a major concern. In a 1985 review of available information, George Balazs reported that tar balls were the second most common type of ingested debris.
We humans are terribly irresponsible when it comes to garbage thrown into the ocean or allowed to find its way there through neglect. This has numerous effects on the marine environment, but one particularly gruesome aspect of this problem is the ingestion of marine debris by turtles.
It is widely assumed--and available evidence supports this theory--that hatchling turtles spend their "lost years" drifting with sargassum and other sea grasses. Unfortunately, drifting garbage collects in the same places as the seaweeds do. Young turtles inevitably attempt to eat some of this material, with devastating consequences.
Plastic resembles food closely enough to fool even a mature turtle. Ingested plastic is not only toxic, it also obstructs the stomach and prevents the turtle from receiving nutrition from real food. This can often lead to a lingering death.
During the 104th Congress, amendments to the US Endangered Species Act (ESA) were proposed that would have virtually destroyed the protection given to endangered species. If they had passed, the Kemp's ridley would have had absolutely no chance of survival. The Kemp's ridley turtle is endangered and is especially vulnerable, since it has only one known nesting beach and lives its life in a particularly hostile environment. Its habitat is heavily fished with shrimp trawls and gill nets, posing the single largest threat to the Kemp's. Amendments to Section 403 of the ESA would have meant that turtle excluder devices would no longer be required.
All marine species in the coastal waters of the United States would have suffered, particularly all species of marine turtles. These amendments could easily have resulted in altering the status of the loggerhead turtle from its present "threatened" status to "endangered"--if they didn't wipe out the Gulf and southwestern Atlantic population first.
Fortunately, these amendments were not passed before the 104th Congress ended. Unfortunately, support for such amendments comes from Republicans, who now dominate both the House and the Senate. It is only a matter of time before the assaults on the ESA are renewed.
No, of course not. We have listed just the most serious threats. For more information, refer to the sources listed in The Library.
It wouldn't hurt to review the list of threats provided here, and then ponder how many of them are the direct result of humans and their activities. We like to think of ourselves as the only intelligent species, but anyone looking over a list like this should immediately question just how smart we really are. It is not a question of compassion, a trait not all of us share. It is a question of survival, for if we callously allow ourselves to destroy other species, there is no reason why our destructive behaviour will not ultimately eliminate us too.
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Last modified 05/02/12
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