Environment

Great Barrier Reef has "died" five times already – but this might be the last straw

Great Barrier Reef has "died" ...
A new study has found that the Great Barrier Reef has persisted through five major "death events" in the past – but the current problems could be happening too fast for the coral to keep up
A new study has found that the Great Barrier Reef has persisted through five major "death events" in the past – but the current problems could be happening too fast for the coral to keep up
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A new study has found that the Great Barrier Reef has persisted through five major "death events" in the past – but the current problems could be happening too fast for the coral to keep up
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A new study has found that the Great Barrier Reef has persisted through five major "death events" in the past – but the current problems could be happening too fast for the coral to keep up
A graphic representation of the mechanisms behind the Great Barrier Reef's adaptations to changing climate in the past
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A graphic representation of the mechanisms behind the Great Barrier Reef's adaptations to changing climate in the past
University of Sydney Associate Professor Jody Webster, with a fossil reef core
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University of Sydney Associate Professor Jody Webster, with a fossil reef core

The Great Barrier Reef is not doing so well. In 2016 it was hit with the worst coral bleaching event in its history, and it didn't help that another one struck the following year. As the fate of the reef remains uncertain, a new study has examined the health of the Great Barrier Reef over the last 30,000 years, and found that it has suffered five "death events" in the past – but its current woes could be the last straw.

The study was conducted over 10 years by an international team of scientists, who drilled fossil reef cores from 16 sites along the northeastern Australian coast, and analyzed the dating, geomorphic, sedimentological and biological data from them. In doing so, the team was able to piece together the evolution of the Great Barrier Reef over the last 30,000 years, and, in particular, how well it bounced back from past environmental upheavals.

University of Sydney Associate Professor Jody Webster, with a fossil reef core
University of Sydney Associate Professor Jody Webster, with a fossil reef core

The researchers found evidence of five distinct death events during that time, mostly as a result of changes in sea level. The first two large scale deaths occurred about 30,000 and 22,000 years ago, as the sea level drastically dropped, bottoming out at 118 m (387 ft) lower than it currently is. This left parts of the reef exposed to the open air.

As the last ice age ended, melting glaciers caused the sea level to rise again, triggering another two reef-death events, about 17,000 and 13,000 years ago. In these cases, large sections of coral effectively "drowned" as deeper waters deprived them of sunlight.

The final event occurred about 10,000 years ago, but wasn't accompanied by any known sea level change. Instead, the team found that the death may have been the result of a huge increase in sediment, which reduced the water quality.

The fact that the reef persisted through these events showed the researchers that it's more resilient in the face of danger than was previously thought. The scientists suggest that this is because the coral is able to spread at a rate of 0.2 to 1.5 m (0.7 to 4.9 ft) per year, meaning some parts of the reef are saved as they migrate into safer territory. During sea level drops, for instance, the Great Barrier Reef as a whole survived by migrating towards deeper waters, and marching back towards land as the level rose again.

A graphic representation of the mechanisms behind the Great Barrier Reef's adaptations to changing climate in the past
A graphic representation of the mechanisms behind the Great Barrier Reef's adaptations to changing climate in the past

As resilient as it is, unfortunately the researchers don't believe that defense mechanism will be enough to save the reef this time around. Those natural shifts occur slowly, over hundreds or thousands of years, giving the coral plenty of time to adapt and migrate. But it's now being destroyed it at an unprecedented rate, with a recent report concluding that human influences cut the coral cover in half between 1985 and 2012.

"I have grave concerns about the ability of the reef in its current form to survive the pace of change caused by the many current stresses and those projected into the near future," says Jody Webster, lead researcher on the project. "Our study shows that as well as responding to sea-level changes, the reef has been particularly sensitive to sediment fluxes in the past and that means, in the current period, we need to understand how practices from primary industry are affecting sediment input and water quality on the reef."

The research was published in the journal Nature Geoscience.

Source: University of Sydney

5 comments
SimonClarke
I am confused by there results. the last major sea level even was from around 10,000 years ago until 6,000 years ago when we came out of the last ice age. at that point the sea level was nearly 500 feet lower then today. the coral polyps by that time had been dead for several thousand years. Only once the sea level had risen to it's current level could new coral start to form once the soil, grass and trees that had been growing there been washed away. this is not there last chance, they will sort themselves out once the water temperatures level out.
piperTom
"...but its current woes could be the last..." There is nothing in the article to support this hypothesis. Is it important that we not lose our sense of panic?
ljaques
What does this study give us? 1) Proof that the reef reestablishes when conditions are right. 2) Proof that these die-offs are a natural cycle and aren't an anthropomorphic globular swarming kumbaya thing. but 3) that man can stop disturbing the sand upstream of the coral so it doesn't suffer from sediments. and 4) that man can likely flush the sediments and help restore the coral more quickly. Now would the alarmists kindly get off the world's back? Every soul onboard is aware of the effects man can have on the world (which aren't nearly as bad as alarmists would have us think by 1000x) and most are trying to tread more lightly on Mother Earth, and it is definitely having a good effect. The alarmists can't allow the "sense of panic" to ebb or they'll lose their funding, as facts overtake their many lies.
bwana4swahili
"it has suffered five "death events" in the past" The reef will persist if conditions are right regardless of the "human factor". It may die as the result of us but will return when we are extinct. The Earth will continue to exist regardless of homo sapiens being around and will probably do far better without us!!
b@man
Hilarious:) Fear and hope... don't be manipulated, this is strictly BS:)