'Barren underworld' - coral bleaching and the perilous forecast for Pacific reefs
Jamie Tahana, RNZ Pacific Journalist
When Kristine Zipfel jumped into the sea off Mo'orea, she expected to open her eyes to an underwater world teeming with life and colour.
After all, that's what the island's famous for. Described in brochures as a haven for divers who fall in love with the varied ecosystem and colourful mix of life.
But instead, the New Zealand-based freediver found a barren underworld. There was little life apart from seaweed, she said, and chalky silhouettes of a landscape sapped of colour.
This picture, from January 2019, shows a healthy reef off the coast of Tahiti, French Polynesia. Photo: Supplied / Coral Gardeners
Three months after the January picture, this one shows the bleached reef in April. The bleaching took hold within a matter of weeks, scientists say. Photo: Supplied / Coral Gardeners
"I only remember seeing one type of coral that had a lot of colour, this one that was just shining through this blanket of seaweed," the 25-year-old recalled. "It just looked like it was struggling to breathe. It looked like it was suffocating."
The reefs that ring the French Polynesian islands of Mo'orea and Tahiti are in the grip of a massive coral bleaching event, described by both locals and scientists as one of the most devastating they've encountered. The bleaching only took a few weeks to set in, they said, transforming one of the world's most colourful environments into a whitewashed wasteland.
Researchers at the Centre for Research and Environmental Observatory, or CRIOBE, a French environmental observatory on Mo'orea, estimate that as much as 60 percent of the coral around the Society Islands have been affected by this year's bleaching.
While Mo'orea is no stranger to bleaching events - the last one happened in 2016 - they usually occur in the presence of an El Niño, a climate cycle that increases water temperatures in parts of the Pacific, including French Polynesia.
But this year it didn't need one.
What's most worrying, said Andrew Thurber, an associate professor of ocean ecology at the University of Oregon, is that nobody saw this year's event coming.
"We didn't expect it, we didn't predict it," Dr Thurber said. "The models didn't predict this to be a bleaching year. Mo'orea wasn't supposed to bleach and yet all of a sudden something's shifted and it's an incredibly widespread event."
Coral bleaching happens when the sea temperature rises to a point that puts coral under intense stress, causing them to separate from the plant-like organisms that give their colours, as well as their oxygen, waste filtration and up to 90 percent of their energy.
Climate and marine scientists are worried that as ocean temperatures continue to rise at a pace that far exceeds coral's ability to adapt, bleaching is going to become far too common. Coral takes years to recover from a bleaching, so if they happen frequently - as has been happening in the Great Barrier Reef off Australia - then they die.
That could prove fatal for Pacific communities like Mo'orea, where livelihoods depend on the reefs that surround them.
'A Beautiful reef'
Titouan Bernicot's life has always been tied to the sea. His parents were oyster farmers in the remote Tuamotu archipelago when he was born 21 years ago. "I was born literally on a little house on the water," he said.
His family then moved to Mo'orea, where he lives today. When he wasn't in school, he and his friends were surfing on the waves generated by the reef. When they weren't surfing, they were diving in the reef, frolicking with the fish amongst the coral.
"For us, as locals, [the corals] are everything," Mr Bernicot said. "The place where we can learn. Where we can find the food."
That beauty is also what draws Dr Thurber from Oregon to Mo'orea several times a year.
"One of the things I love about Mo'orea is the corals there are beautiful, they're healthy and, in general, it's one of these refugia for incredibly healthy coral reefs for a variety of different parts of the reef," he said.
"It's a perfect place to understand how a healthy coral reef works, essentially."
Dr Thurber said there were several factors that made this so. Part of it was the isolation of the Society Islands, and the relatively few people who live there.
But, geographically, it's also largely shielded from the climactic, annual and inter-annual variability in conditions which can add stress to coral in other places.
"In general, Mo'orea has avoided many of the worst bleaching events," Dr Thurber said. "Until this year."
One recent morning, Titouan Bernicot took his small boat out from his home on the sandy shore of Mo'orea's palm-fringed coast, in the shadow of the island's towering, rainforest-coated peaks.
"We saw some white corals and we were shocked," Mr Bernicot recalled. "This year, everyone is concerned."
Dr Thurber arrived in Mo'orea not long after, in May, for routine sampling. He was stunned by what he saw. "The entire reef was starting to turn white," he said. "And the other thing that was really surprising, the water wasn't clear."
"Normally this is really one of the most beautiful oceans on the planet, it's just bright blue and vibrant. And here, the water was just milky," Dr Thurber said. "It was the signs that something wasn't going right."
From there, the descent was rapid. In little more than a few weeks, as much as 60 percent of the reef around Mo'orea and Tahiti was bleached, some beyond repair.
"We returned about three weeks later and the reef essentially turned into this white, not pavement, but it looked like a sort of a white drawing of what a coral reef used to look like, but you haven't coloured it in yet," Dr Thurber said.
"We could actually watch it get worse over two weeks. It was like a different planet that we'd somehow visited."
The Society Islands are no stranger to coral damage. In 2005, the reef faced an invasion by crown-of-thorn sea stars, which decimated the coral polyps. And in 2016, there was another major coral bleaching. A study in the wake of that event, by the US National Science Foundation, found that the reef had bounced back remarkably.
But Dr Thurber, who was there for the 2016 bleaching, said those events paled in comparison to what's happening now.
"There were a few bleaching corals around," he said, referring to 2016. "In a sea of otherwise healthy coral, you'd see a little white coral head here or there, but still it was a surprisingly healthy reef."
"This year it was not supposed to bleach."
A changing climate
The intensity of this year's bleaching and the climactic conditions that unleashed it has triggered a deep worry about the perilous state of coral in the Pacific as sea temperatures continue to rise.
There was not predicted to be an El Niño this year, Dr Thurber said, but conditions have gradually leaned towards one over the summer, albeit mild. But beyond that, the temperature in the waters around Mo'orea and Tahiti has been exceptional.
Gilles Siu, a collaborator with the CRIOBE on Mo'orea, said the models that forecast whether or not a bleaching would occur were wrong.
"The models are only models," he said. "Most of the time it's quite correct for cyclone seasons. But that's why we do the research, we need to improve the data for these models."
The temperature range that a coral can survive in before bleaching is narrow, but Dr Thurber said the ceiling is now being pushed with worrying regularity. This year, he said, the ocean temperature has been consistently high.
"We've been measuring the temperature of water at this site for a long time" he said. "The temperatures started to get warm a lot earlier than they have in the last nine years, and there's also some critical thresholds in temperature that were surpassed."
"The only time that it last hit those temperatures was 2016, when it hit for a few days," Dr Thurber said. "It's hit it numerous, numerous times this year."
While Dr Thurber added that it was too early to conclude whether this was a trend being seen at Mo'orea, studies from other parts of the world paint a dire picture for much of the planet - and especially the Pacific's - coral reefs , particularly as the oceans continue to warm rapidly, in some cases up to 40 percent more than previously forecast.
Coral, of course, can recover from bleaching. It did so in 2016, and often must in the wake of a cyclone or tsunami. But while it only takes a few weeks for a vibrant reef to be sapped of all colour, it can take years for that colour - and the associated life - to return.
Mr Siu said scientists were waiting to see how much of the coral around Mo'orea and Tahiti will have died because of this year's bleaching. But a recent bleaching in the nearby Tuamotu Islands killed a good portion of coral.
"We need to wait, they are not dead yet," said Mr Siu. "If the event is too long, then the coral dies and the algae comes and colonises the coral. You will notice that quite easily. But you need to wait, it can be four weeks, one month, maybe two months."
But with temperatures increasingly spiking past the threshold coral can withstand, and with research pointing towards an increased frequency of El Niño in the Pacific, that window for recovery is likely to grow narrower and narrower.
"If you stress them a little bit they can recover, if you stress them a lot it gets harder for them," said Dr Thurber. "And if you repeatedly stress them that's where things become a problem."
"The problem is everything we're doing in regards to the atmosphere is really pushing us to making events like this more common."
Last year's report by the Intergovernmental Panel on Climate Change said that if global warming was limited to 1.5 degrees celsius - the target set and signed up to by most governments under the Paris Agreement - coral reefs would still decline by between 70 and 90 percent.
And a study published in April by Australian scientists, which focussed on the Great Barrier Reef, found that global warming had hampered its ability to recover from large-scale bleaching in both 2016 and 2017. The researchers said the time between bleachings would shrink as global warming intensified.
"Dead corals don't make babies," said the study's lead author, Professor Terry Hughes from Australia's James Cook University, in a news release.
"We have noticed more events like that, high temperatures," Mr Siu said. "We've also seen more wave events coming from hurricanes."
"If they don't get back fast enough in between the events, that could be very bad," he said.
A Moorea Coral Gardener tends to one of their coral nurseries. Photo: Supplied / Coral Gardeners
The consequences of that could be dire.
Coral reefs effectively act as the lungs of the ocean, producing more than half of the oxygen that humans breathe and, in turn, regulating both air and water temperatures.
Their rigid shape also acts as a barrier, their friction slowing the force of waves and acting as a barrier against waves and erosion, both of which are increasing with climate change.
Reefs are also home to about a quarter of all marine life, ranging from microscopic plankton, through to colourful reef fish, sharks and giant whales. This life is critical for communities like Mo'orea and Tahiti, which depend on them for food, protection, recreation and livelihoods.
When an 18-year-old Titouan Bernicot first saw the coral bleaching of 2016, he was surfing with his school friends. Shocked by what he saw, he wasn't going to wait for either the territorial or the French government to act.
"We started to realise the coral reefs give us everything in our lives," he said. The waves they surfed on. The fish they ate when they returned to Mo'orea's white shores. The jobs their parents relied on - tourism, the pearl industry, fishing. "Everything is all connected," he said.
Motivated to act, Mr Bernicot and friends formed the Mo'orea Coral Gardeners, a group that set about trying to restore the island's reef. It started with them trying to replant coral cuttings in other parts of the reef.
Three years later, Mr Bernicot's movement is bigger than he ever imagined.
People from across Mo'orea had joined him, and now people from across the globe are too. He tours the world speaking about the reef, his group offers eco-tours, and Instagram pictures of Mr Bernicot free diving into the deep blue garner thousands of likes. They offer eco-tours on Mo'orea, as well as an 'adopt-a-coral' programme.
The team now is now backed by several organisations and a dedicated team of scientists. It's got an underwater coral nursery. A sort of greenhouse for coral, where bits broken off the reef are taken to a sort of bamboo table, where they're grown enough to be planted back into the reefs. A process similar to using cuttings from a plant in a garden.
Mr Bernicot said this year's bleaching has been disheartening. "This year, everyone is concerned," he said. But if anything, he added, it's given him further drive. His planting effort has intensified, and he's more motivated than ever.
"It's simple. If we do nothing, nothing is going to happen, and the reef will die."
"If we do nothing my children will ask me, 'why didn't you do something?'"