[Coral-List] Thoughts on coral decline and the future.

Risk, Michael riskmj at mcmaster.ca
Mon May 8 11:49:03 EDT 2017

   It is raining, firewood stacking is on hold, so I thought I would add some
   more to this mix. This has been a generally excellent exchange, with some
   important and insightful comments from smart people. I think I am summing-up
   here, but I may just be rambling.

   First of all: I learned early on not to waste time in exchanges with those
   who resort to insults and invective. John Bruno, telling your colleagues
   that they are “denying reality” and “peddling nonsense” is outside the
   bounds of professional debate. I suggest you lift your game.

   At the centre of this debate is what has happened to our ecosystem, and what
   we can do about it. John has been very forceful in his statements that the
   Caribbean decline has been driven by temperature changes, whereas I think
   that viewpoint is myopic. Using data in the references John has been kind
   enough  to  provide,  we could estimate that from say 1960 to 1980 the
   Caribbean warmed less than 0.5°C, during which we lost about half the corals
   in the Caribbean-and those corals were still under their thermal limit. John
   accuses me of pandering to the deniers, a comment which would be annoying
   were it not so amusing, but I hope WUWT doesn’t get hold of his stuff. We
   could be treated to postings ridiculing us along the lines of “scientist
   says all Caribbean corals already killed by half a degree.”

   I spent much of my professional career working in the developing world at
   the sharp end of “coral reef decline”, where that means your kids might not
   eat. It seems to me that focusing on future developments and ignoring local
   stresses is a viewpoint driven by white Western privilege. If you don’t
   really care what happens out there to off-white people, it’s much easier to
   arm-wave about the future.

   John maintains that reefs far from habitation are not “healthier” than reefs
   close to shore. This is obviously incorrect for the general planet, but
   there have been reports of isolated reefs suffering damage (the less said
   about Bruno and Valdivia the better, in my opinion). I think we should
   consider these critically, for several reasons. First of all, it may no
   longer  be  possible to consider ANY reef as being isolated from human
   impacts. Twenty (argh! Thirty!) years ago, our crude techniques were able to
   trace terrestrial influence >100km offshore on the GBR. Secondly, we may
   need to look closely at the science, especially as some of the “inverted
   biomass pyramids” should be re-examined (Ward-Paige et al., 2010, PLoS
   ONE).  A few years ago, I received a manuscript to review from one of these
   “isolated” reefs. In the supplementary data, I discovered that between the 2
   regions, Affected and Comparison, there was a difference in the ratios of
   stable  isotopes of nitrogen of 2 per mille (there was a small village
   there). Oh goody, said I, there’s the answer-in a much older paper, I had
   suggested that this level of difference indicated significant sewage stress
   and should trigger enforcement. Nope. The authors forged ahead with their
   conclusion, that it was all due to overfishing.

   Tom Tomascik has pointed us to a volume which should be widely read in the
   biological community. It contains many examples of reefs that were simply
   obliterated by terrestrial stress, including his own description of the
   disappearance of reefs offshore Jakarta. I think his paper comes as close to
   poetry as science allows, but it is ineffably sad. “The unrivalled splendour
   and wealth of forms” in 1928 of a reef that no longer exists…In that same
   volume, Terry Scoffin (RIP) describes the decline of the iconic Bellairs
   Reef on Barbados as due to eutrophication and sedimentation in the 80’s-and
   of course Tom’s own papers on eutrophication and corals are classics.

    I hope we can all agree that reefs are facing land-based stress AND global
   change stress: one started when the first Neanderthal washed her face in the
   Mediterranean,  and  the  other when the first oil well was drilled at
   Petrolia,  Ontario.  There  is a large body of research supporting the
   contention that land-based stress dominated until late in the 20^th century,
   but global warming is gaining quickly in a race we would rather not watch.
   We need to figure out what our responses should be, and perhaps for the
   first time speak with one voice.

   I was delighted to see the Earth scientists chime in, because knowledge of
   that field seems to be notably lacking in many of our biological colleagues.
   We  need  to  learn  from  history.  We are in the early phases of the
   Anthropocene Transgression, and to prepare for the future we should study
   the Holocene Transgression.  Sea-level rise during the Holocene was not
   gentle and steady, but likely proceeded through a series of “jokelhaups”, or
   catastrophic meltwater releases.  Ulf feels that some of the 35-meter rises
   in sea level cited earlier could have come in one day!  Water velocities
   during meltwater drainage off Eastern North America transported boulders 2 m
   in diameter out onto the continental shelf. Melting of Greenland will play
   havoc with thermohaline circulation, as it did in the past. This is what’s

   This may not be a “slow-moving” catastrophe after all. Human populations
   will be displaced, perhaps suddenly, by unpredictable rises in sea level.
   The time may come when society as a whole may not have the resources to save
   coral reefs, because people come first. Triage in action. If we wish to
   prepare for this, we should be listening to the Pleistocene geologists.

   It  is  highly  unlikely  reefs  will  be  able to adapt by colonizing
   newly-flooded landmasses. Walter Adey has shown that, during the Holocene
   Transgression, there was a lag time, generally on the order of 1000 years,
   before corals colonized the new substrate. Presumably this was to allow time
   for waves and currents to rework and clean the bottom. The water that will
   flood the continents during the coming transgression will be much filthier
   than  the  Holocene water. In addition, the landmass will be much more
   difficult to colonize: all those condos, highways, abandoned Hummers…

   It would be wonderful to study a reef that had survived through the Younger
   Dryas, but as Hal has pointed (hi, Hal), the critical outcrops are all under
   water now. Of course, the oceans wouldn’t be as high now if it weren’t for
   all those whales in them…

   Hal has also been kind enough (?) to point out to us that many of the major
   extinction  events  of the past have been driven by CO2 increases. The
   terminal  Permian event killed 80% of life on the planet. As this fact
   becomes more generally absorbed and as the urgency grows, it may be possible
   to reverse the warming trend. We have to hope so. Our job now will be to
   protect  those reefs that have a chance. We can’t do much about global
   change, other than to contact our legislators and lead by example. What we
   can do is try our utmost to reduce land-based sources. This bears repeating:
   we as individuals can do relatively little about atmospheric CO2, but we CAN
   as individuals do a lot to control land-based sources. Start with sunscreen.
   All  of  our  friends  now avoid oxybenzone sunscreens. They also quiz
   prospective  resort  destinations on how they treat their sewage. Most
   maritime countries routinely monitor E. coli in their coastal waters. In
   most  Caribbean  countries,  the  results  are  closely-guarded by the
   State-because they fear tourist dollars would vanish if people learned how
   filthy the waters were. We have immense influence, both as scientists and
   consumers. Just imagine: what would Florida’s reefs be like now if, 20 years
   ago, some of our reefy talking heads had said “I understand there is a
   problem with sewage stress. Until you fix this, I am going to recommend
   people go elsewhere for their holidays.” (I said this, but nobody listens to
   me…) So now the Keys reefs, at the northern end of the Caribbean, are dead
   as dodos, whereas Cuba, in the warmer centre of the Caribbean, still has
   good reefs.

   There are glimmers of hope. Paul Hawkens’ “Drawdown” outlines a reasonable
   approach  that  could  turn  things around in a couple of decades. Tim
   McClanahan’s new paper shows some (small) thermal adaptation in corals from

   Many years ago (some Coastal Conference, early 80’s) I proposed we apply
   “triage” to reefs. If we apply triage ruthlessly now, we can probably save
   some reefs for the next half-century. If we keep the water clean, it may
   even be possible to regenerate/restore some. We need to prioritize. One of
   the critical factors will be our ability to characterise and quantify the
   various threats/stresses, and this is an essential step in any reef-saving
   exercise. Fortunately, our assessment “toolbox” now contains the necessary
   techniques-from  cellular  diagnostics  to trace element profiles. The
   time-slice technique that has been used on gorgonians is especially powerful
   in places with spotty baseline data. It can just as easily use bivalve
   records  or even scleractinians (although corals are procedurally more
   difficult). It’s a useful technique that deserves wider usage. Trust me, it
   isn’t hard-if it were hard, I could not do it. (If you want to know how, I
   will walk you through off-line.)

   And finally, as Gene is wont to do, he points us to cool stuff: Yates et al.
   (2017). I strongly recommend listers read this, because it is a depressing
   tour de force. Major lowering of the sea floor in studied areas (Florida, US
   Virgin  Is.,  Maui)  such  that  erosion  rates far outstrip potential
   calcification rates. Authors are careful not to attribute causes-but we know
   what’s  probably  doing  this:  nutrient-driven  bioerosion. The fecal
   bioindicator Cliona delitrix is all over the Florida bottom, with colonies
   so large (it’s brick red) that they can be seen from a light plane.

   Sorry for the long post. The devil makes work for idle hands when it rains.
   Some ideas, some bad news, some good news. We need to hope, but we need to
   remember that “hope is the pretty mask of fear” (Buddha). We need also to be
   afraid-and we have reason to be.


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