Great Barrier Reef suffering ‘unprecedented’ damage

Global warming has severely damaged huge sections of Australia’s Great Barrier Reef, according to a new paper published Wednesday in the journal Nature.

The paper’s authors warn that the resilience of the planet’s largest living structure is waning rapidly.

Data from a series of aerial and underwater surveys shows that a heatwave in summer 2016, which saw sea temperatures in Australia reach record levels, triggered the most damaging and widespread coral bleaching event on record.

Extensive coral bleaching in the Kimberley Region of the Great Barrier Reef as seen in early 2017.

Almost 50% of the reef is now “extremely” bleached and 91% shows at least some signs of bleaching, Sean Connolly, program leader of a government-funded coral reef center at James Cook University, Queensland and the paper’s co-author told CNN.

“Coral cover [on the Great Barrier Reef] has halved over the last 27 years,” Connolly said.

“[In the last three decades] coral cover went from 28% to 13%. Preliminary estimates [from last year’s disaster] are saying we’ve lost half that amount again. To have that kind of mortality on that kind of scale is unprecedented,” said Connolly.

Bleached staghorn coral on the Great Barrier Reef in photo taken in 2016.

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Rising temperatures, diminished responsibility

Coral bleaching happens when an increase in sea temperatures causes the expulsion of algae that grow inside coral, turning the reefs white and eliminating their main energy source. It’s directly linked to global warming.

Sustained bleaching will result in coral death. The bleaching during last year’s heatwave was worse than expected and the episode’s severity has raised serious concern for the future of the reef ecosystem.

The study pointed to the bleaching of hardy, century-old reefs as a particular red flag.

“The severity and frequency of these [bleaching] events means slow-growing corals won’t have time to come back,” said Connolly.

“If all the coral bleaches and dies, it’s no longer a coral reef. The coral skeletons are quickly colonized by algae which turns them dark in color,” said David Baker, assistant professor at the University of Hong Kong’s Swire Institute of Marine Sciences.

There are 'winners' and 'losers' among corals as they respond to the accumulating impacts of climate change.

There are variations in the appearance of severely bleached corals. Here, the coral displays pink fluorescing tissue signalling heat stress.

The different color morphs of Acropora millepora, each exhibiting a bleaching response during mass coral bleaching event.

A bleached Acropora colony.

A severely bleached branching coral amongst the minimally bleached boulder coral.

Dramatic coral bleaching, seen in Australia's Great Barrier Reef from March 2016.

Some of the bleaching of reefs in the northern section has been described as "extreme."

Bleaching occurs when the marine algae that live inside corals die. Of the reefs surveyed in the northern third of the Great Barrier Reef, 81% are characterized as "severely bleached."

"At some reefs, the final death toll is likely to exceed 90%," Andrew Baird, of the ARC Center of Excellence for Coral Reef Studies, says.

A photo taken on September 22, 2014, shows bleached coral on the Reef, a key Australian tourist attraction.

Tourism on the Great Barrier Reef generates an annual income of A$5 billion ($3.9 billion) and employs nearly 70,000 people.

Of the reefs surveyed in the northern third of the Reef, 81% are characterized as "severely bleached."

Driven by ocean temperatures that have been 1-2 degrees Celsius (1.8-3.6° F) above average, the bleaching event has left large sections of coral drained of all color and fighting for survival.

The Reef has suffered two mass bleaching events, in 1998 and 2002, but the extent of the bleaching in these years was less severe than in 2016.

Australia's Great Barrier Reef suffers 'extreme' coral bleaching

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Eventually those skeletons collapse, he added, and the natural habitat for fish and other marine life is completely lost.

The paper’s authors also concluded, whether bleached or not, the reef had not acclimatized or adapted to high temperatures over time.

Connolly said that, as temperatures increase, reefs would eventually die off and be replaced with more stress-tolerant species such as seaweeds.

“We have known that things would go in this way for decades and unfortunately … our international system of government and policy has utterly failed to take relatively inexpensive action to head off what could be potentially catastrophic climate change – not just on reefs, but on other ecosystems we depend on.”

Around 275 million people globally directly rely on reefs for livelihood and sustenance, and globally reefs form the nurseries for around a quarter of the world’s fish, according to the UN.

The Great Barrier Reef is worth $3.7 billion annually to the Australian economy through fishing and tourism, and provides around 70,000 jobs, Connolly said.

“You’re looking at some potentially unfolding human tragedy over the decades if reefs cannot provide the same source of livelihood,” he added.

Many reef fishes depend on the habitat provided by healthy coral.

Ongoing damage

Last year’s disaster was the third major mass coral bleaching of the Great Barrier Reef on record, and scientists suspect that – less than a year on – a fourth is already underway.

The Great Barrier Marine Park Authority is currently conducting aerial surveys of the reef and, last week, Greenpeace released photos and video footage highlighting the ongoing damage.

“Greenpeace has just been on the Great Barrier Reef with a marine biologist to document the situation and it is heartbreaking,” said Alix Foster Vander Elst, Campaigner for Greenpeace Australia Pacific.

“We should know in the coming days or weeks the exact impact of this year’s disaster.”