David Higgins on the fragile ecology of one of the world's most remote islands.
To the US government it’s a giant listening station, tapping into the world’s secrets. To the US and UK militaries, it’s a strategic staging post. The BBC relays global services between continents from here. But for wildlife enthusiasts, Ascension Island is more important still.
This volcanic island was spat from the mid-Atlantic ridge two million years ago. Since then it has drifted westward by eighteen millimetres per year towards Brazil. At its present rate it will reach the Americas by the year 129643614 AD.
The most recent volcanic activity was less than 700 years ago. Solidified lava flows appear to be anger, frozen in time. The land is full of jagged shapes and twisted rock. Where bubbles of air escaped, the lava has become a rigid froth. Careless steps result in the thinner shards snapping under foot. The sharp edges make light work of skin.
The land is steep, stretching from the sea to a high point of 859 metres on Green Mountain. Up there a human-created cloud forest captures moisture from the air.
Lower down the orange hues are overtaken by the green of invasive Mexican thorn bushes. Here feral donkeys find shade. Everywhere parasitic volcanoes emerge in perfect conical forms. The flatter coastal reaches are lined with yellow-sand beaches which are pitted and dipped.
To the east of the capital, Georgetown, Long Beach appears to be a miniature Somme. It’s as though war games have been played out by an old general. I can picture him, a handlebar moustache, liver-spotted hands moving figures here and there. The wasted eggs of green turtles akin to dead men. Broken shells scavenged away by a harsh ecology. The sea adding its own madness. A metronome rhythm shanking the sands into steep banks that reptiles haul themselves up in the night and back down as the dark passes.
During the evening I join a green turtle tour run by Emily, Daniel, Maddie, and Maria, four British interns. We walk through the poor-lit streets of Georgetown, passing a thorn tree where a lone donkey stood all day watching the few cars come and go. With only red light to guide us we move down the track. The sea is oscillating with each wave. There’s no moon but a vivid milky way offers a tight strip of distant stars. The Southern Cross hangs above the peak of Cross Hill where HMS Hood’s guns point out to sea.
We stand still in the warm air as we wait for Daniel to radio back. He’s searching for a turtle in the near catatonic egg-laying stage. These green turtles are the largest of their kind. On Ascension Island the world’s second largest nesting occurrence of this species lasts between December and April. This is a small and young island. The green turtle is an old species. Yet they improbably met across an ocean. These turtles turn up each year to breed and lay their eggs in pits they dig with their flippers. The female adults will have been returning every three years for decades. Adult males will return every year. They expend less energy than the females.
When the call comes we tread carefully round the pits, following red light from head torches. And there she is, hauled up on a beach miles from anything else, except the sea where she lives, mates and travels between coastal plains.
Open wounds along her midriff show where males have clung on during sex. The deep lacerations are the marks of inconsiderate lovers. She will have stored the sperm to release it on her own terms. The females drag themselves up these steeply shelved beaches over several egg-laying sessions. At the start of the season fat rolls out from their shells. By the end of the season they’re emaciated. In this fat-reduced state they still need to swim to the coastal waters of Brazil.
As we watch her I sense she’s lost in the moment. Part exhausted, perhaps a little elated at dropping her offspring into this carefully dug pit. With each convulsive tremor journeying across her body another egg is deposited. Egg after egg descends as we listen to wave after wave lapping. The Milky Way sparkles like a universal bioluminescence.
We watch this ritual that’s travelled before us through evolutionary time. There is a privilege in being beside her. We wait till she begins pushing sand across her eggs. Then we leave her be.
The same night I’m lucky enough to watch turtle hatchlings emerge. Out of the sands they swarm. The slap-patter of tiny flippers mimicking the noise of an insect colony. Once orientated they rush towards the sea. Little clockwork bodies scampering across the sand. On Long Beach they’re relatively safe, but on more rocky stretches Sally-lightfoot crabs scurry to capture them. Once caught they pick their living bodies apart. Land crabs will do the same, tearing at the young turtles as their flippers try to drag some friction from the air.
I visited North-East Bay with Dr Sam Weber, a turtle specialist and his wife Dr Nicola Weber, Ascension Islands head of conservation. We were joined by two RSPB staff, Jonathan Hall and Clare Stringer. This is one of the places land crabs deposit eggs after migrating down from the cooler slopes of Green Mountain.
Along the shore and from the vantage of rocks they drop dark egg masses into the sea. As they do, hundreds of small sand crabs, or mole crabs as they’re known on Ascension Island, emerge to ingest them. As the waves recede a mole crab burrows into a gap in my shoes. I retrieve it and drop it into the next incoming wave.
There are turtles here too. Sam tells me the majority hatching on Ascension Island are female. The sex of a turtle is temperature controlled. In sands below 28 degrees Celsius it is predominantly males that hatch; above this temperature it is females that predominate. This temperature-controlled sexual dimorphism results in a high proportion of females hatching on Ascension Island. It doesn’t alter the hazards they face. At North-East Bay non-native rats predate on hatchlings. We find a dozen eaten through to their innards, hearts still beating.
I take photographs for Clare and Jonathan. They’ll act as another piece of data showing how damaging rats can be to small island ecologies. It’s more evidence to mobilise rat control or eradication. Whilst I agree with this I can’t help feeling bad for animals that suffer because of human error. The rats could never have found this island alone.
Any turtle hatchlings that mistakenly emerge in daylight have frigate birds to evade. These primordial hunters swoop down like middle-earth ringwraiths taking hapless hatchlings into their bills. Sea predators await those that make it across the sands. All this attention means that less than one percent survive to adulthood. For the survivors it will be at least thirty years before they return to these same beaches to breed.
Sam has worked with the turtles on Ascension Island for several years now. He did his PhD on them. Recently he’s tagged two hawksbill turtles to decipher their movements. They haven’t yet analysed the data but it’s encouraging to see funds being made available for such work.
Later in the week Dr. Eliza Leat, the island’s seabird specialist, allows me to join her as she visits the sooty tern colonies at Mars Bay. We drive round the US airbase and continue as far as we’re allowed before walking down towards the birds. The number is phenomenal. Eliza tells me the seabird colonies once numbered in the millions, not the tens of thousands of today. Still, the sight staggers me.
The first colony we find isn’t quite settled. Only a few birds tend eggs. So Eliza sets off over the lava flows towards Shelley Beach. The sun is high, the temperature well in the thirties. People have reported terns nesting on the track but we don’t find the signs. Perhaps they’ve hatched. Perhaps mynah birds or rats have taken the eggs.
Eliza checks the area through binoculars. There are pockets of sooty terns in all directions. In the distance she spots the largest group she’s yet seen. We leaves the track and traverse the old lava flow. We try to keep a marker in the landscape but have to keep correcting ourselves as we walk up and down the twisted mass of rocks.
The sound and smell of this large colony is fascinating and oppressive. Terns break from the crowd, flying over to check us out. They come within a few metres before veering off. Eliza gives the colony a quick assessment then we move a little distance to eat lunch.
On another day I join a group of conservationists from the UK, Falkland Islands and St Helena. In Land Rovers we follow a steep gravel track down a valley before parking in a barren location surrounded by a sun-bleached landscape. Fairy terns hover in front of us and follow our progress as Sam and Nicola lead us across a hill-slope to the high cliffs of Letter Box. Here we pass by masked booby nests as we move to where endemic Ascension frigate birds glide along the cliff edges. Opposite us, Boatswain Bird Island juts from the sea. The sky is heaving with birds. On the cliff top the RSPB have funded frigate bird decoys that sit motionless in the heat. The idea is to encourage the birds to nest back on land. The removal of feral cats from Ascension Island has made this a possibility. However, the first frigate bird to nest successfully on the mainland is still a long walk from here.
We follow Nicola across a harsh plain lacking all but a meagre vegetation. Despite the paucity of plants a few rabbits run from us and no doubt that other hazard, the rat, is close by. At the far end of the plateau a series of lower cliffs are passed by yellow billed tropic birds, sooty terns, brown and masked booby as well as brown noddys. A heavy swell is rolling in, crashing against protruding rock pinnacles.
Down amongst the rock-face a single frigate bird nestling watches us through blue-rimmed, coal-black eyes. This bird has become an icon of conservation. It shows that things can improve when resources match the will of conservationists.
Towards the end of my stay I visit Nicola and Sam’s house, located among a small series of terraces grandly called Chinatown. The evening has passed beyond a brief twilight. The night is barely lit by an infinity of stars. In the yard a black bag covers a dead hawksbill turtle. It was found at Comfortless Cove, a little sandy bay where fevered sailors were once left to die. A group of scuba divers noted the concreted GPS data-logger on its shell so retrieved the dead animal and brought it here. Sam removes it from the bag. Putrified guts and blood leak from its hawk-like bill. The smell is strong. After an initial inspection Sam picks up the limp animal. Its innards wobble as he places it in a more robust sack for burial.
The red light on the tracker glows in mockery of its death. Somewhere above us a circling satellite receives the signal.
David Higgins' previous article for The Island Review, about St Helena, can be found here.