Story & photo Mary Gardner
Because the massive proportions of the declines of sea turtles occurred so long ago [3–500 years ago], they are now viewed by many as charming anachronisms or quaint archaic relics. Their past roles as major marine consumers… have been forgotten (K Bjorndal and J Jackson 2002).
Experience some history. Imagine great numbers of sea turtles like flocks of emus or herds of elephants or American bison. Instead of inhabiting vast landscapes, they occupy the seascapes from the tropics to the subpolar. Now fast-track from AD1500 to now and watch region by region as the global herds decline to approximately five per cent of their original numbers. What does this mean for the seascapes of the world?
These great marine herds, as did their terrestrial counterparts, shaped the underwater gardens as they chomped on their favourite sponges, algae, jellyfish and seagrass.
Seagrass meadows are underwater plants that grow better by being munched down. Long blades get slimy and diseased. Trimming sponges gives coral reefs more space. Eating jellyfish helps balance marine dynamics.
In the season, both sexes of turtles moved towards the shores of their birth. One captain writes in his ship log that he found his way sailing in a dense fog through the Caribbean by following the clamour of thousands such turtles heading to shore.
Turtle cleaning stations
The turtles shaped these near-shore communities in unexpected ways. Shrimps and fish would set up cleaning stations for grooming turtles. Some creatures, like crabs, dropped off and started new populations. Barnacles on the turtle shell would spawn and the young would settle in this new location.
Tens of thousands of females enriched sandy shores as in great groups, they clambered onto selected beaches and left nests of eggs.
In Mexico, 40,000 Ridley’s turtles were filmed plodding on a single shore at the same time as late as 1947. Per nest, some 20 per cent of eggs don’t hatch. The vegetation was nourished by these nutrients.
Before the young hatch, the embryos coordinate by calling to each other. When the night chorus builds up to include most of the young, the hatching begins. Celestial lights guide the little ones into the sea. Half these hatchlings would be eaten before reaching the sea. Life giving life.
Since the time of the dinosaurs, the turtle lifecycle has provided generously to other forms of life. A thousand eggs laid would realise twenty mature adults. Since 1500, that figure has reduced to two adults.
Over-harvesting of adults and eggs as human food was the first blow. Turtles for sailors’ meat. Oxley took seven off what is now Cooks Island near the Tweed. Each was ‘four hundred weight’. They named the spot Turtle Island so other sailors would know they could find such food there.
Turtles were caught for global markets and soup factories. This was one of the first industries in the Great Barrier Reef, until banned in 1950. Through the early 20th century, turtles caught in NSW were quick food or a cash bonus from the Sydney Fish Market.
Many of today’s marine ecosystems are still adjusting to life without an abundance of sea turtles. Most people do not realise how much is different or how many animals are missing.
The loss is often trivialised in NSW, where both state and Commonwealth governments don’t identify any part of our state as critical habitat for sea turtles.
Commercial fishers in NSW aren’t required to use turtle excluders on their nets, though they are in Qld. Commonwealth and NSW governments collude to change laws allowing shark nets in protected waters, killing and traumatizing sea turtles.
NSW nesting sites
See, these marine animals are still with us in NSW. Rochelle Ferris, of Seabird Rescue and now completing her PhD on turtles, is preparing maps with confirmed sightings of five species and nests for at least three of those species. She also found some evidence that at least one species is shifting here because of global warming.
To rescue degraded marine ecosystems, there are projects to restore wild oyster beds. Unexpectedly, these benefit existing sea-grass meadows. They also enhance restoration plantings, which up till now have been slow to take root and thrive. More shellfish mean more sea-grass for certain sea turtles, also helping dugong, fish and prawn.
This history ends with a small glimpse of a long ecological tangle. There’s a sense of entire marine ecosystems teetering. Will they collapse or revive? For luck and inspiration, I rub the head of my stone turtle. It lives on the back deck, a daily reminder of these marine connections.