11/8/2007 - The challenges of sea turtle conservation

WEEKEND FEATURE: The challenges of sea turtle conservation

WORLDWIDE
Friday, August 10, 2007, 23:50 (GMT + 9)


Turtles have created fortunes for some, and losses for others. They are for the most part a protected species, and seen as a problem by the commercial fishing fleet. Tundi Agardy at the World Ocean Observatory places into perspective the actions taken to protect dwindling turtle stocks.

What is it about sea turtles? How are they able to move us so deeply, perhaps more than any other marine creature? And why has the compassion that they have managed to generate not translated into effective conservation of marine turtle species throughout the world?

Sea turtles have touched the lives of so many people, in diverse and sometimes paradoxical ways. Unlike many other charismatic but less accessible marine animals like dolphins, whales, manta rays and whale sharks, a great number of people -- young and old, rich and less so, urbanites and farmers, environmentalists and naysayers -- have had the opportunity to interact with turtles in the wild.

Whether we encounter a large lumbering nesting female or a small helpless hatchling, sea turtles manage to convert even the most unsentimental among us into ardent conservationists.

There are seven recognized species of marine turtles, including the leatherback Dermochelys coriacea, the loggerhead Caretta caretta, the hawksbill Eretmochelys imbricata, green turtle Chelonia mydas, flatback turtle Natator depressus, olive ridley Lepidochelys olivacea, and the Kemps ridley Lepidochelys kempii.

All are either endangered or threatened. Leatherbacks, hawksbills, and Kemps ridleys are considered critically endangered – holding on to their existence by the skin of their teeth1.

Perhaps because of their increasing rarity, in many parts of the world, encountering sea turtles at sea or on a nesting beach is cause for great excitement. Some tourism operators cater specifically to those who want to witness a turtle laying its eggs (and some, like Earthwatch based in the United States and Frontier based in the United Kingdom, can arrange expeditions for those willing to volunteer their time and energy for sea turtle conservation and research projects).

At the same time, sea turtle eggs or meat represent an important (and often free) source of protein in most tropical developing countries – this and the lack of alternative protein sources have made conservation of turtles in the poorest countries a difficult endeavor. The challenges of saving sea turtles from extinction are a microcosm of marine conservation challenges everywhere – representing both huge obstacles to success and reasons for hope.

Sea Turtles as Metaphor

Marine turtles are at once emblematic flagships for the oceans, and umbrella species whose management must be directed at a series of linked ecosystems. People connect with sea turtles in different ways, viewing them a symbol of all enigmatic ocean creatures, or as the face of an ageless cautionary tale about man versus nature.

The strange attraction that people feel towards sea turtles makes them symbols of something bigger -- clear candidates for flagship status. Their story is indeed the story of all the ocean’s inhabitants, though saving them from extirpation involves a suite of conservation tools and policies. Sea turtles have been around a long time, some sixty million years, and for this reason they hold our fascination as ancients.

They are charismatic megavertebrates, ever so graceful as adults swimming through the water and oh-so-cute crawling out of the nest. And they share some traits with us – needing to breathe at the surface, returning to land to reproduce, struggling to survive and keep their evolutionary lineages going in a rapidly changing world. Perhaps it is these traits that make it so sea turtles in harm’s way conjure up such pathos – whether it is the sight of the turtle drowned in the fishing net, of feral dogs attacking a stalwart nesting female, or of tiny hatchlings undertaking the mad scramble down the beach.

Marine turtles are arguably the most logical organisms to denote as umbrella species. Their conservation requires the preservation of intact habitats ranging from tropical nesting beaches to sub-Arctic foraging grounds. Although this is also true for highly migratory species of fish and for most marine mammals, sea turtles are unique in that they rely not only on ocean habitat but also on terrestrial habitat.

Nesting beaches must remain open and secure for sea turtles to utilize them, access to these beaches must be maintained, and the nesting beach environment must be almost pristine to successfully support sea turtle reproduction. The more disturbance on the beach, the greater the chance that the female will abort her eggs in the water or unsuccessfully attempt to make her nest, known in the turtle lingo as a “false crawl”. Light contamination on the nesting beach – a common occurrence on most beautiful wide sandy beaches in the tropics where sea turtles lay their eggs – dooms both adults and young, as light from behind the beach fatally draws turtles away from the sea.

Once the hatchlings leave the safety of their underground nest on the sandy beach, they scurry to the ocean to escape the innumerable dangers of land and find relatively safe nursery habitats in which to grow. Just where these nursery grounds are is still a mystery – in the Atlantic Ocean the Sargasso Sea has been fingered as the most probable place where small turtles can both find food and escape predation by hiding in the drifting sargassum weed.

As sub-adults, sea turtles often congregate in nutrient rich shallow waters to continue their slow growth to adulthood (most species take a decade or more to mature and will live for several.) These critical areas vary according to the species – for herbivorous green turtles, seagrass meadows and areas of algal-encrusted rock reef are preferred; for the sponge-eating hawksbills, diverse and healthy coral reefs are the only habitat where they can survive; for leatherbacks, cold and rich upwelling areas in temperate zones provide large quantities of the jellyfish they consume with vigour, and for the others that are omnivores, areas that support large populations of benthic fish and crustaceans are the coastal habitats of choice.

Adult turtles may go to different feeding grounds altogether, and when sexually mature will travel to breeding areas to mate. Gravid females come ashore on tropical nesting beaches to lay their eggs – a hundred or more at a time, in nest pits that they painstakingly excavate with their hind flippers. The process of finding access to the beach, hauling a huge body built for aquatic life onto gravity-encumbered land, then crawling with flippers made for water across wide swaths of sand, rock, and berms, is extraordinarily difficult.

Finding a suitable nesting spot (like all reptiles, turtles do not incubate their eggs but rather let the warm sand of tropical beaches do it for them – the temperature and moisture level must be just so…), digging the nest, laying the eggs, then carefully covering the nest and disguising it takes hours, by which time the mother turtle is spent – and highly vulnerable to a host of predators, including man.

So, the need to meet the ecological requirements of these far-ranging species is huge. Yet in addition to protecting these disparate critical habitats on land and in the sea, conservation of sea turtles requires maintaining connections between these places. Migration corridors link tropical nesting beaches with temperate feeding grounds, sometimes thousands of miles away.

Sea turtles are considered other sorts of symbols as well, beyond flagships or umbrella species. Some view sea turtles as canaries in the coalmine, reminding us of how our impacts on the oceans are reaching critical thresholds. A good example is provided by the hawksbill, which frequents coral reefs in all the world’s tropical seas. The hawksbill turtle could be considered a keystone species of sorts: its grazing on a wide assortment of sponge species on the reef prevents any one sponge from dominating the reef and thereby reducing biodiversity and productivity. When hawksbills disappear from large reef tracts, they may well signal the decline of these delicately balanced ecosystems.

To other people, sea turtles are a highly valuable commodity. Sea turtle meat is considered an important food source; sea turtle eggs, though widely protected, are coveted not only as food but as aphrodisiacs in some places. The beautiful shell of the hawksbill, known as beko in the trade, is still being used to make expensive bracelets, combs, eyeglass frames, and other curios. Sea turtle bones, fat, and oil are used for medicinal purposes (though their curative value has never been scientifically demonstrated). Then there are the non-market values attached to these marine icons. Sea turtles are revered in some religions. Tourists speak of life-changing experiences when interacting with them.

For all the ways that we value sea turtles, one hopes that the most appropriate analogy is not that of the passenger pigeon, a species whose great value spelled its ultimate doom.

Saving Sea Turtles
Conservation of sea turtles is clearly no easy feat. Their reliance on diverse habitats, ranging from unsullied and open access tropical beaches, to offshore nursery grounds, to unrestricted migration corridors across whole ocean basins, to productive feeding grounds on coral reefs, seagrass meadows, and cold open ocean areas, means that cooperation among countries is essential.

Marine and coastal protected areas are an indisputably important tool in the sea turtle conservation toolkit. But these protected areas must be strategically linked throughout the chain – weak protections at any of the necessary habitats can undermine even the strongest conservation efforts at the nesting beach or in coastal habitats frequented by adults. High seas protected areas are needed, even though these are difficult to establish and even more difficult to enforce2.

Pelagic protected areas will have to address fishing, shipping, and even contamination by debris – plastic bags, balloons, polypropalene pellets, and other trash constitute an insidious threat to all turtle species. And even protected beaches are difficult to maintain in a way suitable for maintaining or recovering sea turtle populations: introduced species such as dogs, cats, pigs, goats, raccoons, mongoose, etc. are difficult to eradicate from the beach, and there is only so much manpower available to guard nesting females and clutches of eggs through their two month long incubation periods.

While important nesting beaches can be and often are protected as parks or reserves, in many cases the very existence of the beach is at risk from human activities, sometimes far from the coast. With worldwide use of freshwater for irrigation, consumption, and hydroelectric power, estuaries around the world are showing signs of massive sediment starvation (decreases of freshwater limiting the delivery of sediment to the coast)3. This affects the maintenance of shorelines and some beaches.

Others are formed by sands produced through a combination of coralline animal and coralline algae remains. When coastal development or blast fishing destroys part of the reef system, beach formation can cease and beaches erode away. And increasingly frequent tropical storms and the occasional tsunami can instantly erase nesting beaches from the face of the earth.

Perhaps even more important than habitat protections are international agreements, regulations, and enforcement of laws concerning commercial fishing in areas frequented by turtles – either those resident or those migrating through. Longline fisheries have decimated leatherback turtle populations, especially in the eastern Pacific4. Gillnets are devastating to all marine turtle species. And bottom trawls routinely drown loggerhead, ridley, and other species – since sea turtles commonly feed on the very things we wish to catch, such as shrimp or prawns. Since so many sea turtles are killed incidentally in commercial fishing operations, their protection means restructuring how and where we fish -- something that is notoriously difficult to do when highly lucrative fishing interests are at stake.

We cannot forget that on the other end of the economic spectrum, sea turtle eggs and adults represent an important source of protein to impoverished and marginalized people the world over, who continue to harvest adult turtle products even when the practice is illegal, because of lack of economic or subsistence alternatives. For such people the choice is considered one between “us and them”, and conservation commonly takes a back seat to human survival.

Turtle Excluder helps

This is not to say that marine turtle conservation has not made great headway in the last 50 years. Some populations of sea turtles are stable or recovering, thanks to intensive efforts to protect nesting beaches, equip the most damaging fishing gear with Turtle Excluder Devices (TEDs), establish voluntary ordinances to shield nesting beaches from artificial light, and create strict regulations on take (as exists, at least on paper, in most coastal countries in the world). And there are innovative approaches being adopted as well. In the U.S., temporary closures are instituted in the mid-Atlantic when northwardly migrating leatherback turtle numbers reach a critical threshold. In the Pacific, many fishing fleets have instituted the use of circle hooks on longlines, to reduce turtle by-catch, and that of other highly valued but not targeted species5.


However, for every step forward we seem to falter, and even take some steps back. The Pacific populations of the leatherback turtle are plummeting so drastically that some predict their imminent extirpation6. The Kemp's ridley is barely holding on despite many decades of head-starting and a strong focus on getting all shrimp trawlers in the Gulf of Mexico where they occur equipped with TEDs. And many coastal species, such as loggerheads and green turtles, show signs of disease, such as extensive fibropapillomas. Fibropapillomatosis has been called the most important health problem affecting sea turtles in the wild7. There seems to be a clear link between water quality and the aetiology of this disease, such that outbreaks are occurring in more and more new places as coastal habitats become increasingly degraded.

There are also bigger forces at play. Climate change threatens to send some species over the brink, not only by affecting habitat or food availability, but also because higher than normal sand temperatures at nesting beaches will produce only one gender of hatchling (usually all males).

Thus, despite turtles having touched so many humans, we seem somehow incapable of securing their futures alongside our own. As a metaphor, then, the continued decline of something so thoroughly cherished around the world is a sobering one indeed.


By Tundi Agardy, PhD
World Ocean Observatory

Endnotes

1. People wishing to get more detailed information about the extant sea turtle species should visit the following websites: www.seaturtlestatus.org and www.seaturtle.org. A compendium of scientific descriptions of natural history, behaviour, and conservation is available in K. Bjorndal [ed.] 1995. Biology and Conservation of Sea Turtles. Smithsonian Institution Press, Washington DC. The late Archie Carr wrote many popular accounts of sea turtles, including his famous So Excellent a Fishe. 1967. Charles Scribner and Sons, NY; decades later Jack Rudloe wrote Time of the Turtle. 1979. E.P. Dutton, NY. Most recently, O.G. Davidson wrote Fire in the Turtle House: the Green Turtle and the Fate of the Ocean. Perseus Books Group, Cambridge, MA. There have been hundreds of other publications about sea turtles in the past decades.

2. See D. Hyrenbach, K. Forney and P. Dayton. 2000.Marine protected areas and ocean basin management. Aquatic Conservation: Marine and Freshwater Ecosystems 10:437-458.

3. Millennium Ecosystem Assessment. 2005. Vol. 1 Current State and Trends. Island Press, Washington DC

4. Spotila et al. 1996. Worldwide population decline of Dermochelys coriacea: are leatherbacks going extinct? Chelonian Conservation Biology 2:209-222.

5. See for example Watson, J.W. and D.W. Kerstetter. 2006. Pelagic longline fishing gear: A brief history and review of research efforts to improve selectivity. Marine Technology Society Journal 40:6-11.

6. Spotila, J.R., R.D. Reina, A.C. Steyermark, P.T. Plotkin and F.V. Paladino. 2000. Pacific leatherbacks face extinction. Nature 405:529-530.

7. Herbst 1994 and George 1997, cited in Formina, A. et al.. 2007. Fibropapillomatosis confirmed in Chelonia mydas in the Gulf of Guinea, West Africa. Marine Turtles Newsletter 116:20-22