|Coral feeding at night. Credit: Laszlo Ilyes via Wikipedia
Annual coral bleaching will probably happen fairly soon
Using statistically downscaled models to get a picture of what is likely to happen in particular areas, the authors found that before this century is out, practically all coral reefs will suffer severe bleaching every year. That's if we continue on the current emissions path. Given that it takes five years or more to recover from a severe bleaching, that means that coral reefs are in dire danger - which you knew already, I expect.
As a caveat, not only am I not an expert in coral reef science, I know very little about it. My experience is pretty well limited to a scuba dive and some snorkelling. However unlike WUWT fans who think a scuba dive makes them experts on coral reef science, this article is based on what I've gleaned from reading scientific papers and articles on the subject. In other words, this article reports some of the science that I have picked up by reading what scientific researchers have found.
In the paper, the authors give some background:
Reef-building corals bleach when warmer than normal sea temperatures disrupt their mutualistic relationship with the algal symbionts, called zooxanthellae, that reside within their tissues. Corals can either regain their zooxanthellae and survive or die if temperature stress persists. Currently, we are in the middle of the longest global coral bleaching event on record. Unprecedented and prolonged ocean warming triggered a global coral bleaching event that started in 2014 and may extend well into 2017. The length of the event means corals in some parts of the world had no time to recover in 2014 or 2015 prior to experiencing bleaching the following year.
Annual bleaching starts in 24 years in some areas
From the press release at ScienceDaily:
It takes at least 5 years for a reef to recover from a single bleaching event. "Bleaching that takes place every year will invariably cause major changes in the ecological function of coral reef ecosystems," said study leader Dr. van Hooidonk of NOAA and the University of Miami. "Further, annual bleaching will greatly reduce the capacity of coral reefs to provide goods and services, such as fisheries and coastal protection, to human communities."...Coral reefs aren't just important for tourism and our entertainment, they are important for marine life in general, and for the fishing industry. Reefs won't have time to recover where there is annual bleaching.
...The new study shows that, on average, the world's reefs will start suffering annual bleaching in 2043. About 5 per cent of them will be hit a decade or more earlier, while about 11 per cent will suffer annual bleaching a decade or more later than this date.
The above prognosis is if we continue to follow RCP8.5, which is the emissions pathway we are currently on. If we succeed in reducing emissions quickly enough to shift to RCP4.5, then it will delay things a bit, but not by much. From the paper:
RCP4.5 adds 11 years to the global average ASB timing when compared to RCP8.5; however, 75% of reefs still experience ASB before 2070 under RCP4.5.Not all reefs will suffer this annual bleaching at the same time. As the authors wrote:
Coral reef futures clearly vary greatly among and within countries, indicating the projections warrant consideration in most reef areas during conservation and management planning.
Eric Worrall's disinformation and pseudoscience
Eric thinks, wrongly of course, that he knows stuff that coral reef specialists don't (archived here). Eric isn't a scientist. He's not a marine biologist. He's not a climate scientist. He's a denier and science disinforming blogger. He doesn't just want the world to burn, he wants to bring back smog and shorten the lives of people in less developed countries and developed countries.
Eric first showed his ignorance on the subject by writing this bit of nonsense:
Coral survived the Cretaceous / Paleogene extinction event which wiped out the dinosaurs, when a 6 mile wide Asteroid crashed into the Gulf of Mexico 66 million years ago. Coral survived the Permian–Triassic extinction event 252 million years ago, when the Siberian Traps were formed, a colossal series of volcanic eruptions which covered almost three million square miles in lava, contaminating the entire world with toxic fumes and volcanic ash. But apparently its all going to come to an end, if we add a few hundred ppm more CO2 to the atmosphere.
Eric has been misled or is deliberately misleading. Corals and coral reefs didn't survive the Permian Triassic extinction event, they re-emerged several million years after they'd been made extinct. (A recent paper in Nature suggests reefs emerged much sooner, only 1.5 million years later, but these were from "various sponges and serpulids" rather than corals.)
In regard to the Cretaceous/Paleogene event, this is what is reported at Wikipedia (with references), showing that the impact was greatest on corals that form reefs, particularly in the tropics.
Approximately 60% of late-Cretaceous Scleractinia coral genera failed to cross the K–Pg boundary into the Paleocene. Further analysis of the coral extinctions shows that approximately 98% of colonial species, ones that inhabit warm, shallow tropical waters, became extinct. The solitary corals, which generally do not form reefs and inhabit colder and deeper (below the photic zone) areas of the ocean were less impacted by the K–Pg boundary. Colonial coral species rely upon symbiosis with photosynthetic algae, which collapsed due to the events surrounding the K–Pg boundary. However, the use of data from coral fossils to support K–Pg extinction and subsequent Paleocene recovery must be weighed against the changes that occurred in coral ecosystems through the K–Pg boundary.
Extinction events of the past 550 million years
For people who never studied (or can't remember) extinction events, here is a timeline for events that occurred over the past 550 million years or so. The ones shaded in pink were mass extinctions. It may be too soon to know if the current one (shaded yellow) is a mass extinction, though many people fear the worst:
|Figure 1 | Extinction events over time. Mass extinction events are highlighted in pink. The current extinction event is highlighted in yellow. Data source: Wikipedia.
Extinction, evolution and re-emergence of corals over time
I went to the website of the Australian Institute of Marine Science and learnt some things about coral reefs. Way back in the Paleozoic era (541 to 252 million years ago) reef-like carbonate structures first formed, not from coral but from cyanobacteria. The first reef-like structures formed from animals were built in the lower Cambrian, 530 to 520 million years ago. They were built by archaeocyath sponges. In the Ordovician (448 to 443 million years ago), there were tabulate and rugose corals that formed reefs in shallow waters, with other organisms. By the late Devonian (382 to 372 years ago) there were some massive reefs that were wave resistant.
All corals became extinct in the end-Permian extinctions, together with 80% to 95% of all species. You can read more about these early reefs here. There's also the 2003 paper by George D Stanley Jr, which has a diagram (Fig 4 p 202) showing how at the end of the late Permian, there was extinction of all Paleozoic corals and reef collapse.
It took another 12 to 14 million years before reef-like structures appeared again, in the Middle Triassic (247 to 237 million years ago). The end of the Triassic extinction (201 million years ago) once again caused the collapse of reefs. There was no recovery of reef-building for another six to eight million years. In the early Cretaceous (146 to 100 million years ago), molluscs largely displace corals as the dominant species in reefs. There were events during later periods that affected corals and reefs, which you can read about here.
AIMS has a page on modern corals, but it doesn't describe the emergence of modern coral reefs over time. There is a paper by G. D. Stanley Jr in Earth Science Reviews, in which he discusses some hypotheses about the evolution of corals through to modern times, including the idea the modern corals may have had "several different kinds of soft-bodied ancestors - ephemeral ancestors, capable at critical points in earth history, of transforming between calcified and soft-bodied forms".
Coral reefs today, and coral bleaching
In April 2014, coral expert Dr. Ove Hoegh-Guldberg from The University of Queensland had a paper in the journal Current Opinion in Environmental Sustainability. That was partly in response to a paper by Cheryl A Logan et al, published in Global Change Biology in October 2013, in which the authors had suggested that corals may be able to adapt to thermal stress, and delay the demise of coral reefs caused by frequent bleaching events. Around the same time (May 2014) there was another paper, this time in Science, in which the authors stated they had identified some corals that acclimatised to heat fairly quickly.
Ove Hoegh-Guldberg wasn't writing about short term acclimatisation and increased heat tolerance as such. What he was arguing was that there is scant evidence for evolutionary adaptation, whereas there is "abundant evidence of rapidly declining coral populations and associated coral reef ecosystems". He wrote:
In Southeast Asia and the Western Pacific, coral reefs have declined by 50% since the early 1980s [13,14]. In the Caribbean, dramatic declines of well over 90% since the 1970’s have been documented for coral cover on Jamaican reefs  and the wider Caribbean [16,17]. Similar reports exist for the Indian Ocean and other sites .
In that paper, Hoegh-Guldberg explained about the two main types of coral reefs. He wrote:
Coral reefs are found throughout the world’s tropics and can be separated into two broad categories based on whether or not their calcium carbonate skeletons build up over time to create the complex three-dimensional structures that typify carbonate coral reefs. Carbonate coral reefs are found in the region from 30° north or south of the equator where local physical and chemical conditions are favourable . At the fringe of this distribution (in addition to regions affected by equatorial upwelling), there are often dense populations of reef-building corals that don’t build carbonate reef structures . While both coral reef ecosystems are typified by high levels of biological diversity, carbonate coral reefs are among the most diverse ecosystems on the planet with an estimated 1 – 9 million species . Both types of reef systems provide ecosystem goods and services to human populations through support of fisheries, tourism and broader benefits such as the protection of coastal areas from waves and storm impacts [5,6].
Coral bleaching and its effects
Getting back to the paper that prompted Eric Worrall to write his nonsense, as the authors wrote, coral reefs all over have been subjected to an increasing frequency of coral bleaching. The current bleaching has been happening since 2014, and is being monitored and reported via the NOAA coral reef watch website.
The open access paper, van Hooidonk16, has figures and charts showing how soon annual bleaching is likely to dominate in different parts of the world. In some places it is likely to happen sooner than other places.
More weirdness from Eric Worrall - corals are "a weed species"
As well as his misinformation about coral survival, Eric wrote how he thinks that the collapse and demise of coral reefs "deserves utter ridicule". From what he's written he couldn't give a damn if coral reefs collapse and it takes several million years to re-emerge. (Maybe he gave up fish and chips when he left the mother country, so he wouldn't care about the devastating impact on the marine environment and fisheries). The other thing is that he is under the false impression that coral is a plant species and an undesirable one at that, saying "Coral is the weed species". He's wrong. Corals are animals, not plants, and are critically important:
If there is one aspect of the climate scare which deserves utter ridicule, it is the continuous bad news claims about Coral. Coral is the weed species which will survive the end of the world, because it has already survived multiple global extinction events which killed most other life. There is nothing we could do to the planet which would be worse than the series of world wrecking natural disasters which coral has already shrugged off.
Ted talk on coral reef conservation by Ruben van Hooidonk
Below is a Ted talk by the lead author of the paper in Scientific Reports, Ruben van Hooidonk. I hesitate to include it because I can't hear a word. That might be just because it's pouring rain on a warm tin roof right now. Let me know if you have better luck.
From the WUWT comments
At WUWT there was a mix of people who think they know better than scientists, tropical tank owners, scientific illiterati, and utter nutters. Brian j in UK can't cope with science at all, and wrote:
January 6, 2017 at 7:52 amJoe Crawford wouldn't know a GCM if it bit him in the butt. He probably doesn't believe that there are aeroplanes that fly:
The moment I read “models” my eyes glazed over and my brain refused to read on.
January 6, 2017 at 1:05 pm
I strongly suspect you can get a Doctorate in ‘Climate Science’ today by just running the GCMs and coming up with innovative and creative ways of (statistically) interpreting the results but only so long as those results toe the party line.
Dodgy Geezer thinks that 24 years is a "long timescale". He must be no more than ten years old:
January 6, 2017 at 7:59 am
I like these papers with nice long timescales.
I predict that Unicorns will be discovered shitting diamonds in 100 years from now, and would like a grant to study the effect of this on de Beers….
Kip Hansen presents himself as an expert on coral. It doesn't take much research to see that he's not, unlike people who are doing research on deep water coral. He wrote:
January 6, 2017 at 8:18 amCoral bleaching only occurs with near-surface coral reefs. Near-surface reefs do not make up 99% of the world’s coral reefs. In fact, the vast majority of reefs are deeper and are not affected by sea surface temperatures, and there is no physical possibility that waters at 10-20 meters will reach bleaching temperatures, this or any century soon.
Any one who has explored the coral reefs of the Caribbean knows this from personal experience — diving reefs at 30 to 60 feet for more than a few minutes requires a wet suit for comfort and to prevent hypothermia. Its [relatively] cold down there!
This is from Wikipedia:
While there are nearly as many species of deep-water corals as shallow-water species, only a few deep-water species develop traditional reefs. Instead, they form aggregations called patches, banks, bioherms, massifs, thickets or groves. These aggregations are often referred to as "reefs," but differ structurally and functionally. Deep sea reefs are sometimes referred to as "mounds," which more accurately describes the large calcium carbonate skeleton that is left behind as a reef grows and corals below die off, rather than the living habitat and refuge that deep sea corals provide for fish and invertebrates. Mounds may or may not contain living deep sea reefs.
Sage Vals says not to worry if corals die off, there'll be other organisms to take their place - or so he or she hypothesises:
January 6, 2017 at 8:20 am
A bit more complicated than this. Reef building species change considerably over geological time. Modern corals are relatively recent as main reef building animals. However, even if warmist’s predictions true, other reef building species will reasonably quickly replace any removed from that environmental niche.
jclarke341 got one thing right. The stupid it hurts. Seriously - he or she thinks that this current warming is "gradual". It's on pace to be ten times faster than any period in the last 65 million years. (And modern coral hasn't been around for hundreds of millions of years. It takes millions of years to re-emerge after a major extinction event.)
January 6, 2017 at 9:18 am
The stupid…it hurts!
Coral has been around for hundreds of millions of years. During most of that time, the CO2 concentrations in the atmosphere have been much higher than they are today. Temperatures have also been warmer and cooler than today. Bleaching is a reaction to short term stress, not long term, gradual changes, like those predicted by the climate models. From year to year, the predicted change would be imperceptible to the coral, therefore…not stressful.
So how does one make a model that predicts annual bleaching of all coral? One would have to completely ignore the obvious adaptability of coral. Come to think of it, the adaptability of all life forms is generally ignored in the climate scare models. If it wasn’t ignored, the models would not be scary!
There is just far too much wrong with this illogical "thought" from ristvan:
January 6, 2017 at 9:50 am
Annual bleaching? This makes no biological sense. Bleaching is a response to a long term (e.g. many months, as there is no observed seasonal bleaching–I use personal dive experience on the three tier coral reef off Fort Lauderdale for reference) temperature change on the order of >1C. Since corals live in many different water temperatures (3 off Fort Lauderdal), Bleaching gives them the ability to adopt new better adapted symbionts. It takes 1-2 years for polyps to starve to death if they are not recolonized with better symbionts; they can still filter feed. There are also egigenetic changes in the polyps; shallow corals are more adaptible than deeper corals when two populations of the same species have their locations swapped, as experiments in the Florida Keys have shown. That is because they are used to more seasonal water temperature and pH change. So annual bleaching implies delta ~1C per year at a specific reef. That cannot be monotonic temperature increases; the result soon becomes ridiculous. And if it is temperature rise followed by temperature fall, then there is no warming over time. Silly bad models.
If he'd read the paper he would have discovered that the researchers looked at specific regions, and he would also have found the following:
The onset of annual bleaching conditions is defined as the annual exceedance of >8 DHW [Degree Heating Weeks] accumulating during any 3-month period. The focus here is on spatiotemporal variability in the projections.
And about Degree Heating Weeks:
One DHW is equal to 1 °C above the maximum monthly mean (bleaching threshold) for one week. 8 DHWs is higher than the mean optimum bleaching predictor of 6.1 DHWs for the globe; i.e. at 8 DHWs we can have confidence thermal stress will be sufficiently great for bleaching to occur.
There are a lot more silly comments from pseudo-experts (who own a tropical marine aquarium or have snorkelled or scuba dived in coral reefs).
References and further reading
Ruben van Hooidonk, Jeffrey Maynard, Jerker Tamelander, Jamison Gove, Gabby Ahmadia, Laurie Raymundo, Gareth Williams, Scott F. Heron, Serge Planes. "Local-scale projections of coral reef futures and implications of the Paris Agreement." Scientific Reports, 2016; 6: 39666 DOI: 10.1038/srep39666
- Future of coral reefs under climate change predicted - press release at ScienceDaily.com
Stanley, George D. "The evolution of modern corals and their early history." Earth-Science Reviews 60, no. 3 (2003): 195-225. DOI: 10.1016/S0012-8252(02)00104-6 (pdf here)
Hoegh-Guldberg, Ove. "Coral reef sustainability through adaptation: glimmer of hope or persistent mirage?." Current Opinion in Environmental Sustainability 7 (2014): 127-133. doi: http://dx.doi.org/10.1016/j.cosust.2014.01.005
Logan, Cheryl A., John P. Dunne, C. Mark Eakin, and Simon D. Donner. "Incorporating adaptive responses into future projections of coral bleaching." Global Change Biology 20, no. 1 (2014): 125-139. DOI: 10.1111/gcb.12390 (pdf here)
Palumbi, Stephen R., Daniel J. Barshis, Nikki Traylor-Knowles, and Rachael A. Bay. "Mechanisms of reef coral resistance to future climate change." Science 344, no. 6186 (2014): 895-898. DOI: 10.1126/science.1251336 (pdf here)
About coral reefs from the Australian Institute of Marine Science (use the menu on the left).
Coral Reef Watch - a website of NOAA Satellite & Information Service
From the HotWhopper archives
- Bob Fernley-Jones' fixation on hot Marches toward coral bleaching - September 2016
- The Great Barrier Reef: an unmitigated disaster - if only the Australian public knew... - June 2016
- NASA three year CORAL mission - aerial and in-water surveys of the Great Barrier Reef and more - NASA press release at HotWhopper Chat
- Willis Eschenbach turns on the charm for NOAA's coral watch crew - July 2015
- Luddite Eric Worrall huffs and puffs and wants to bring back smog @wattsupwiththat - January 2017
- And lots more nonsense from Eric Worrall