Most coral reefs are at risk unless climate change is drastically limited

Sep 16, 2012
Plate coral (Fungia sp.). The picture was taken in Papua New Guinea. Credit: Wikipedia.

Coral reefs face severe challenges even if global warming is restricted to the two degrees Celsius commonly perceived as safe for many natural and man-made systems. Warmer sea surface temperatures are likely to trigger more frequent and more intense mass coral bleaching events.

Only under a scenario with strong action on mitigating greenhouse-gas emissions and the assumption that corals can adapt at extremely rapid rates, could two thirds of them be safe, shows a study now published in Nature Climate Change. Otherwise all coral reefs are expected to be subject to severe degradation.

Coral reefs house almost a quarter of the species in the oceans and provide critical services – including , tourism and fishing – to millions of people worldwide. and , both driven by human-caused CO2 emissions, pose a major threat to these ecosystems.

"Our findings show that under current assumptions regarding thermal sensitivity, coral reefs might no longer be prominent if global mean temperatures actually exceed 2 degrees Celsius above the pre-industrial level," says lead author Katja Frieler from the Potsdam Institute for Climate Impact Research. "Without a yet uncertain process of adaptation or acclimation, however, already about 70% of corals are projected to suffer from long-term degradation by 2030 even under an ambitious scenario." Thus, the threshold to protect at least half of the coral reefs worldwide is estimated to be below 1.5 degrees Celsius mean temperature increase.

A more comprehensive and robust representation than in previous studies

This study is the first comprehensive global survey of coral bleaching to express results in terms of global mean . It has been conducted by scientists from Potsdam, the University of British Columbia in Canada and the Universities of Melbourne and Queensland in Australia. To project the cumulative heat stress at 2160 reef locations worldwide, they used an extensive set of 19 global climate models. By applying different emission scenarios covering the 21st century and multiple climate model simulations, a total of more than 32,000 simulation years was diagnosed. This allows for a more robust representation of uncertainty than any previous study.

Corals derive most of their energy, as well as most of their famous color, from a close symbiotic relationship with a special type of microalgae. The vital symbiosis between coral and algae can break down when stressed by warm water temperatures, making the coral "bleach" or turn pale. Though corals can survive this, if the persists long enough the corals can die in great numbers. "This happened in 1998, when an estimated 16% of corals were lost in a single, prolonged period of warmth worldwide," says Frieler.

Adaptation is uncertain and ocean acidification means even more stress

To account for a possible acclimation or adaptation of corals to thermal stress, like shifts to symbiont algae with a higher thermal tolerance, rather optimistic assumptions have been included in the study. "However, corals themselves have all the wrong characteristics to be able to rapidly evolve new thermal tolerances," says co-author Ove Hoegh-Guldberg, a marine biologist at the University of Queensland in Australia. "They have long lifecycles of 5-100 years and they show low levels of diversity due to the fact that corals can reproduce by cloning themselves. They are not like fruit flies which can evolve much faster."

Previous analyses estimated the effect of thermal adaptation on bleaching thresholds, but not the possible opposing effect of ocean acidification. Seawater gets more acidic when taking up CO2 from the atmosphere. This is likely to act to the detriment of the calcification processes crucial for the corals' growth and might also reduce their thermal resilience. The new study investigates the potential implications of this ocean acidification effect, finding that, as Hoegh-Guldberg says: "The current assumptions on thermal sensitivity might underestimate, not overestimate, the future impact of on corals."

This comprehensive analysis highlights how close we are to a world without coral reefs as we know them. "The window of opportunity to preserve the majority of , part of the world's natural heritage, is small," summarizes Malte Meinshausen, co-author at the Potsdam Institute for Climate Impact Research and the University of Melbourne. "We close this window, if we follow another decade of ballooning global greenhouse-gas emissions."

Explore further: Conservation scientists asking wrong questions on climate change impacts on wildlife

More information: Frieler, K., Meinshausen, M., Golly, A., Mengel, M., Lebek, K., Donner, S., Hoegh-Guldberg, O. (2012): Limiting global warming to 2°C is unlikely to save most coral reefs. Nature Climate Change, DOI: 10.1038/NCLIMATE1674

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User comments : 22

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jonnyboy
1 / 5 (8) Sep 16, 2012
stop having babies or AGW will accelerate, there is no other option.
NotParker
1.9 / 5 (13) Sep 16, 2012
Ocean temperatures in the Pacific fluctuate as much as 8C in 4 months.

http://www.bom.go...C007.gif

I think coral adapted to the Little Ice Age cold and the warming after the LIA ended.

They can adapt. If they can't, they aren't the fittest.
Shootist
1.9 / 5 (13) Sep 16, 2012
The climate has never changed in the 400 million years there have been coral?

More hogwash science that a school boy could pick apart. Logic people.

And don't tell me, "Shootist, temperatures have never changed more rapidly". More hogwash. The southern coast of England went from deciduous forest to tundra in something less than 100 years (lesser Dryas). Iceland went from ice bound year round to ice free in something less than 50, and that in historical times (1350-1400).

What scares me is the correlation between believers and leftists. And they complain about the Conservatives being anti-science.
MikPetter
not rated yet Sep 16, 2012
"The evolution of modern corals and their early history " G.D. Stanley Jr. / Earth-Science Reviews 60 (2003) "A setback in coral diversity, brought on by a mass extinction at the end of the Triassic, abruptly severed the adaptive radiation underway in tropical reefs of the Tethys, causing the collapse of reefs (Hallam and Goodfellow, 1990). There ensued a 5 – 8 million year interval during much of the Early Jurassic (Hettangian to Sinemurian) when reefs were depressed globally and diversity of surviving scleractinian species was low." and guess what caused all the stress? Extract from Wikipedia on end of Triassic Extinction "....the correlation suggests that the end-Triassic extinction event began at the same time in marine and terrestrial environments, slightly before the oldest basalts in eastern North America but simultaneous with the eruption of the oldest flows in Morocco ...., with both a critical CO2 greenhouse and a marine biocalcification crisis"
Franko
1 / 5 (6) Sep 16, 2012
OK, here's a drastic measure for ya.... How about stopping chemtrails, which are the cause of all of this? Oh no, we couldn't do that....we need to control the weather and conduct our little experiments. F you and this stupid article. Get real you gullible brain dead idiots.
jyro
2.1 / 5 (7) Sep 16, 2012
If the globe warms enough there won't be chemtrails (frozen water at high altitude from jet exhaust) and I suppose H2o IS a chemical.
VendicarD
4 / 5 (4) Sep 16, 2012
ParkerTard presents a modern time series in which coral are under stress and portrays it as if it is normal, when it is actually very unusual.

"Ocean temperatures in the Pacific fluctuate as much as 8C in 4 months." - ParkerTard

Further ParkerTard doesn't seem to realize that his own data disagrees with his assertion, since the depth at which corals are found are very much smaller than 50 meters.

Corals are virtually at the surface of the ocean, and there ocean temperatures vary by 2 to 3'C at most.

Poor ParkerTard. Reality never seems to agree with him.

Not even his own sources of data.

He is mentally diseased.
ScooterG
1.4 / 5 (11) Sep 16, 2012
The pro-AGW crowd, and liberals in general, remind me in a lot of ways of radical muzzlims - vicious, illogical, driven purely by emotion. They are so angry and vile that it's impossibly hard to take any of them (or their claims and data) seriously any more.

Physorg, by faithfully promoting the questionable science of AGW, places their own credibility in question. Seems like three or four pro-AGW articles per week, with zero non-AGW articles.

My impression is that Physorg ain't interested in presenting credible science, they are only interested in furthering the AGW agenda. But that's their prerogative I suppose, no-one is holding a gun to my head and forcing me to visit this site. :)
ScooterG
1.4 / 5 (9) Sep 17, 2012
I think what brings me back to physorg is that chick on the snorgtees ad - pretty, happy, stacked.

At the risk of sounding shallow, what more can you realistically ask for in a woman?
rubberman
2.8 / 5 (9) Sep 17, 2012
Thanks for the science Mike.
Nice try at science PT, but if your position is out of bounds from the start it's hard to get in the game.
Vendi, well done at reading and understanding the data. (a novel concept if you are going to comment on a science site)
The other guys....educate yourselves
But Scooter is 100% correct on the snorgtees girls. You should try examining the IR absorbtion capabilities of CO2 with the same passion, you might understand climate science a bit better.
PaxAeterna
5 / 5 (1) Sep 17, 2012
Long live snorgtees girl.
rockwolf1000
5 / 5 (2) Sep 17, 2012
The pro-AGW crowd, and liberals in general, remind me in a lot of ways of radical muzzlims - vicious, illogical, driven purely by emotion. They are so angry and vile that it's impossibly hard to take any of them (or their claims and data) seriously any more.
Physorg, by faithfully promoting the questionable science of AGW, places their own credibility in question. Seems like three or four pro-AGW articles per week, with zero non-AGW articles.

My impression is that Physorg ain't interested in presenting credible science, they are only interested in furthering the AGW agenda. But that's their prerogative I suppose, no-one is holding a gun to my head and forcing me to visit this site. :)

Well... F@#$ off then!
ScooterG
1.4 / 5 (9) Sep 17, 2012
You should try examining the IR absorbtion capabilities of CO2 with the same passion, you might understand climate science a bit better.


Too much data has been falsified, too many "scientists" have been discredited, too many studies rigged, too much scientific contradiction - and if that ain't enough, you have people like Al Gore, Bill Richardson, and Maurice Strong leading the movement for all the wrong reasons - best advice is to run like Hell!
ScooterG
1 / 5 (7) Sep 17, 2012
weird computer errors - sorry
djr
1 / 5 (1) Sep 17, 2012
"At the risk of sounding shallow, what more can you realistically ask for in a woman?"

Scooterg and others who joined in the joke - objectification of women is really ignorant - can we be better than that on a science web site? We understandably drive women away with that kind of crude ignorance...
rubberman
1 / 5 (4) Sep 18, 2012
DJR - A few things to consider - Physorg allowed the ads on their site. They could have used any human in the pictures, but advertising logic correctly says on a male dominated science site, a cute girl in a T-shirt will draw the most attention if you want to sell something...unless you can get Hawking into one of those shirts of course. His (ScooterG) observation of her qualities is 100% correct. The question after the observation is objectionable to an extent, however we cant tell how intelligent she is from the photograph and again, when posed this question, I would guess no less than 90% of single males would at least take her on a date.

"We understandably drive women away with that kind of crude ignorance..."
True, except all the intelligent women I know, good looking or not just laugh at the behaviour specifically because if it's shallow nature.
Scooter - You can't falsify an observed property, Ir absorbtion by CO2 is precisely that.
ScooterG
1 / 5 (7) Sep 18, 2012
Scooter - You can't falsify an observed property, Ir absorbtion by CO2 is precisely that.


Agreed.

Al Gore, Bill Richardson, and Maurice Strong also exhibit observable properties - properties I doubt any of you would approve of.

While I admire the dedication and passion of the genuinely concerned AGW proponents, I can't help but believe you've hitched your wagon to a fictitious bill of goods, presented and promoted by snake-oil salesmen who have one thing in mind - lining their pockets with your money.

The entire cost (plus 35%) of the AGW charade is/will be borne by you, the US consumer - especially troubling for me is that the vast majority of you don't even realize it.
rubberman
1.8 / 5 (5) Sep 18, 2012
Scooter - Since we have access to data and peer reviewed work by scientists that actually practice research in the places where the climate is changing the most, as well as access to satelite data regarding ice mass loss, temperatures (land, air, ocean) and solar variance. We actually didn't need Al Gore to tell us that the human race has contributed to the current warming we have witnessed. As far as the political/financial motivations of "figureheads" on either side of the debate, our society is based on money. It's a good barometer of someones character as to what they will do to make it....
ValeriaT
1.8 / 5 (5) Sep 18, 2012
They can adapt. If they can't, they aren't the fittest.

It doesn't help the biodiversity of coral reefs, which may lead in avalanche-like decay of whole ecosystems. Every organism which evolved for millions of years is a treasure of evolution. Maybe the corals contain the cancer cure of something similar - the fact, they're not adaptive enough will not help the people anyway: it may help in extinction of human civilization itself. Will you say, we aren't the fittest after then? Maybe we weren't smart enough.
NotParker
1 / 5 (8) Sep 18, 2012
They can adapt. If they can't, they aren't the fittest.

It doesn't help the biodiversity of coral reefs, which may lead in avalanche-like decay of whole ecosystems. Every organism which evolved for millions of years ....


You do realize that 20,000 years ago ice sheets 2 miles thick covered a lot of the northern hemisphere and the coral reefs adapted to that.

And 140,000 years ago in the Eemian interglacial it was 3C-6C warmer than it is now.

So in the last 140,000 years coral have survived a 12C minimum swing in temperature.

Howhot
3.7 / 5 (3) Sep 18, 2012
Nopark:
And 140,000 years ago in the Eemian interglacial it was 3C-6C warmer than it is now.


That is just pure BS. Speculation at best NP. I read on Wikipedia it was 1-2C colder than now. Look it up. It does depend on where you drill your core samples, doesn't it?

Are you Cherry picking again?

NotParker
1 / 5 (7) Sep 19, 2012
Nopark:
And 140,000 years ago in the Eemian interglacial it was 3C-6C warmer than it is now.


That is just pure BS. Speculation at best NP. I read on Wikipedia it was 1-2C colder than now. Look it up. It does depend on where you drill your core samples, doesn't it?

Are you Cherry picking again?



"So far the ice cores can only provide us a glimpse into the Eemian warm period. But we can already tell that Eemian climate was significantly warmer than the climate of the current Holocene interglacial - probably about 5°C warmer. "

http://www.iceand.../eemian/

"There's no doubt it was warm at this time. Eemian Britain, for instance, had a menagerie of hippos, elephants, rhinos and hyenas that roamed the island."

http://www.celsia...warming/