Shell shock

Life's a bitch, but it's particularly bitchy if you're a baby sea turtle. Baby sea turtles are born buried beneath 60 centimetres of sand, in a nest packed with up to 120 of their siblings. Provided they have not already been eaten by ghost crabs or snakes or dug up by dogs, dingoes or foxes, the hatchlings emerge from their eggs and head to the surface, burrowing up and out, crawling over the top of one another in a process that can take up to a week. Once at the top, they wipe the sand from their eyes with their front flippers, then make a beeline for the ocean. They are so small, just 4.5 centimetres long, that almost anything they encounter - shells, sticks - can represent a virtually insurmountable obstacle.

Recently, on a dark, windswept Mon Repos Beach in Queensland, I saw a hatchling immobilised by a strand of grass that had become tangled around its hind flipper. (Our guide unhooked it.)

Mon Repos, about a 15-minute drive from Bundaberg, is the most important loggerhead rookery in the South Pacific. About 140,000 turtles are laid here every season, a handful of which I watched charging seaward, chasing the glow on the horizon. To be a baby sea turtle is not only to be born beneath 60 centimetres of sand, but to be repeatedly smacked in the face by walls of water. Just when they appeared to have made it, the hatchlings would be hit by another wave and washed right back up the beach. Only once they penetrate the shorebreak can they embark on what zoologists call their "swim frenzy", heading for open ocean, where their mortal risks expand to include birds, fish, sharks, moray eels, seals, fishing nets, killer whales and boat propellers. Not surprisingly, only one in 1000 hatchlings reach adulthood.

Now they face another threat: climate change. Climate change is already affecting sea turtles, with tidal surges soaking their nests (the porous eggs are spoiled by water) and increased storm activity damaging their rookeries.

Yet other effects are more insidious, not to mention bizarre. "Successful embryonic development with sea turtles only occurs in a limited temperature range," says zoologist Dr David Booth, a lecturer at The University of Queensland. "That range is from 27 to 32 degrees. Much below 26 degrees can be lethal to the eggs. Above 36 degrees can also be lethal: the eggs just cook in the sand. Even at 34 degrees, the hatchlings may be smaller and weaker, slower at running and swimming."

Temperature also determines the turtle's gender: below 27 and almost all of the hatchlings will be male. Above 32 produces almost all females. In the middle and you get a mix. "If temperatures continue to rise as projected, then by 2070 we will get total feminisation of the Mon Repos rookery or even non-viability," says Booth.

Sea turtles are among the earth's oldest creatures. They have been around in various forms for 110 million years, since the age of the dinosaurs. During this time they have, of course, dealt with several changes in climate. The difference with today's climate change is its speed. "Compared to the past," says Booth, "this change is happening lightning fast." This is bad news for sea turtles, which are slow-growing and long-living (between 50 and 70 years), meaning they pass on adaptive traits only gradually. "Basically, if the turtles can't adapt fast enough, if they can't move rookeries or change breeding seasons, then they're doomed."

Sea turtles have been nesting at Mon Repos for at least 5000 years. They are philopatric animals (from the Greek for "home loving"), meaning they return to nest at the beach where they were born. Considering the career of the average sea turtle, this is no small feat. The tiny loggerheads I saw skittering down the beach would soon be on their way across the Pacific to the coast of Chile, where for the next five to 10 years they eat plankton and floating seaweed. They then swim back across to the east coast of Australia, settling down for another 15 years in an inshore feeding ground. Around 30 years of age they start their first breeding season, zeroing in to lay their eggs on the very same beach where they themselves were born three decades before.

They are able to do this thanks to having what amounts to a miniature compass in their nose - tiny particles of an iron oxide, known as magnetite, that are thought to provide the turtle with a finely calibrated sense of magnetic location. "As the hatchlings make their way down the sand, they imprint with the beach's magnetic signature," says Cathy Gately, head ranger at Mon Repos. "They then use that to make their way back 30 years later."

In the past, sea turtles have adapted to temperature changes by moving their rookeries north or south. But that was when potential nesting spots were virtually unlimited. The spread of human settlement down the eastern seaboard now severely constrains where turtles can viably lay their eggs. Hatchlings, for instance, are drawn down to the water at night by the glow of the stars on the horizon. Artificial light sources can therefore prove disastrous. Recently, Gately discovered that even the ambient night haze from the nearby township of Bargara was luring the Mon Repos hatchlings south, away from the ocean. This resulted in a government campaign called Cut the Glow to Help Turtles Go, which suggests, among other things, that residents close their curtains and face any lights away from the beach.

Last year, however, Gately was horrified to discover groups of people carrying lanterns down the beaches at twilight. "It turned out they were part of Light the Night, a cancer charity," she says. "So I couldn't really rouse on them."

One of the best places to see adult sea turtles is on Lady Elliot Island, a flat, lonely speck of land about 85 kilometres north-east of Bundaberg, on the southernmost tip of the Great Barrier Reef. Lady Elliot is a coral cay, less than half a kilometre square in area; flying in, it seems barely big enough to land on. "It's a Green Zone," says Peter Gash, our pilot, who also owns the eco-resort here. "No fishing, no spearing, no nothing. Great for the fish, but we recently had some poachers come out here on a boat; when one of our guys told them to leave, they pulled a gun on him."

Gash is tall and lean, a former Team Yamaha motorcross rider turned eco-maniac who has made it his mission to turn Lady Elliot into a beacon of sustainability, complete with a reforestation program, composting pits and a $600,000 bank of solar panels that has reduced the island's emissions by 70 per cent (or 340 tonnes a year).

Lady Elliot is intriguing not only for its sea life but its short, brutal history, which perfectly encapsulates the extractive nature of Australia's land management since white settlement. Having popped up 3500 years ago, the island served as a pit-stop for seabirds, whose droppings, or guano, provided nutrients for thick, glistening forests of pisonia trees. In the 1860s, however, Chinese workers mined the guano, both for fertiliser and gunpowder, some of which was used in the American Civil War. Within a few short years, 20,000 tonnes were removed, reducing Lady Elliot to a windswept rock. Adding insult to injury, authorities then left goats here as a food source for shipwrecked sailors.

The island has since been rehabilitated by successive caretakers, starting in 1969 with a pilot, named Don Adams, who won a lease to start a resort here. Adams broke up the soil by planting casuarinas, which were the only trees tough enough to take root. Now, Gash, who took over in 2005, is replacing those casuarinas with native pisonias. "The trees are back, which brings in the birds, which poop on the ground, which fertilise the soil," he says. "It's like I say: you look after nature and nature looks after you."

Nowadays, most visitors come here for the diving and snorkelling. The reefs that ring the beach - shallow bomboras and dog-legged coral canyons - swarm with fish with funky names and funkier colours: humbugs, scissortails, dotted sweetlips and parrotfish, which glow like hazard vests and have the ability to change gender from male to female. Turtles are here, too, adults the size of car doors.

One afternoon I went snorkelling with them, wading out just off the beach. I couldn't tell if they were loggerheads or hawksbills, but whatever they were, they were remarkably unfussed by me. The photographer and I swam right beside them, studying them at leisure, marvelling at their gnarled necks and big brown eyes. I longed to feel their shells, which you're not really meant to do, though everyone does. So I followed one old turtle down towards the bottom, deeper and deeper, and, as the creature nibbled absently on some coral, I reached out and felt the shell. It was smooth and slippery and oddly inert, like a mossy old cobblestone.

Tim Elliott travelled courtesy of Earth Hour, which commences tonight at 8:30PM.

Smartphone
Tablet - Narrow
Tablet - Wide
Desktop