Leatherback Turtles Near Extinction, Experts Say
for National Geographic News
|February 24, 2003|
They are the longest-living marine species to ever ply the world's
oceans. They survived catastrophic asteroid impacts and outlived the
dinosaurs. But the leatherback sea turtle, the largest turtle in the
world, is on the brink of extinction, and scientists question whether
the animal will survive into the next decade.
"Over the last 22 years their numbers have declined in excess of 95 percent," said Larry Crowder, a marine scientist at Duke University in Durham, North Carolina. Crowder detailed the plight of the turtle during last week's annual meeting of the American Association for the Advancement of Science in Denver, Colorado.
Leatherback turtles roam tropical and sub-tropical waters of the Pacific, Atlantic, and Indian Oceans. They are found as far north as the British Isles to as far south as Australia. The turtles grow as large as nine feet (2.7 meters) long, six feet (1.8 meters) wide and weigh over 1,000 pounds (454 kilograms). Leatherback turtles are covered in a namesake rubbery shell and can dive 4,922 feet (1,500 meters) deep in search of soft-bodied prey like jellyfish.
Leatherback sea turtles have lived for 150 million years. If the species is allowed to vanish, scientists believe it will foreshadow the extinction of a host of other marine species. Scientists estimate there are less than 5,000 nesting female leatherbacks in the Pacific Ocean today, down from 91,000 in 1980.
Crowder has joined more than 400 international scientistsincluding marine biologist and National Geographic Society Explorer-in-Residence Sylvia Earlein calling on the United Nations to issue a moratorium on destructive fishing practices in order to save the turtle.
"Recent studies warn that unless immediate and significant steps are taken, the world's largest and most wide-ranging sea turtle will soon become extinct," signatory scientists said in a statement issued last week in advance of a meeting by UN's Food and Agriculture Organization's Committee on Fisheries which begins today in Rome, Italy.
Hooked, Tangled, Harvested
Leatherback sea turtle populations have been decimated by a fishing technique known as longlining, in which fishing vessels lay out 40- to 60-mile-long (64- to 97-kilometer) lines of vertically hanging baited hooks.
"An individual vessel will put out 3,000 hooks at a time. It is a curtain of baited hooks," said Todd Steiner, director of the Save the Leatherback Campaign for the Sea Turtle Restoration Project in San Francisco, California.
Leatherback sea turtles get caught up and tangled in these hooks, causing them to drown. Scientists are uncertain as to what attracts the leatherbacks to the hooks, which are used primarily to catch swordfish and tuna.
According to a recent study conducted by the Pew Charitable Trusts (a non-profit philanthropic organization based in Washington, D.C. and Philadelphia, Pennsylvania), longline fishing fleets set on the order of 1.5 billion baited hooks in the world's oceans each year. "That's 4.5 million hooks per night," said Crowder. A number, he adds, which is too high to sustain.
To help remedy this problem, U.S. longline fisheries already have been restricted or closed in areas where leatherback sea turtles are known to swim. But scientists believe that this will not be enough to save the leatherbacks from extinction.
More than 90 percent of longline fishing conducted in international waters originates from international fleets, primarily from Japan, Taiwan, Korea, and China. Saving the leatherbacks will require the cooperation of these countries, said Steiner.
Compounding the population toll caused by longline fishing, leatherback sea turtle eggs are considered a delicacy in many parts of the world. Eggs are actively harvested in parts of Latin America and Asia.
Most nations, however, have taken steps to protect leatherback sea turtle nesting beaches over the past few decades. Costa Rica has turned a major nesting beach into a national park, and the turtles have had legal protection in Mexico for over a decade. "One of the key things to understand is harvesting an adult has a much bigger effect on population than an egg," said Crowder. Many of the eggs may not make it to reproductive age, whereas an adult can actively reproduce.
To save leatherback turtles from extinction, scientists say the most important step is to place an immediate ban on longline and gillnet fishing until alternate, turtle-safe methods can be developed.
This is not an easy task, said Steiner. Turtle excluder devices developed for trawl net fishing fleets allowed the Kemp's Ridley sea turtle to recover from the brink of extinction in the 1980s. But no such technology presently exists for longline fishing.
The world's appetite for swordfish has a significant impact on leatherback turtle populations. According the Pew Charitable Trusts study, longlines set out to catch swordfish are ten times more likely to entangle a leatherback than a longline set for tuna.
Steiner's Save the Leatherback Campaign is actively targeting supermarkets in California to post warnings about the high level of mercury found in swordfish, which he says is much higher than the levels advised as safe by the U.S. Food and Drug Administration.
Additionally, the scientists are asking that all beaches where leatherback sea turtles are known to nest and lay eggs be protected and all egg harvesting be banned.
"Things are dire for the leatherbacks in the Pacific right now," said Steiner. "We need to do everything at once."
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