[Coral-List] Evidence that ocean warming has caused most Caribbean coral loss

Peter Sale sale at uwindsor.ca
Thu May 4 14:02:27 EDT 2017

I've been watching and reading.  Multiple posts on 'Evidence that ocean warming has caused most Caribbean coral loss", many of them long and thoughtful, but people are starting to talk past one another.  There are really three questions being thought about (at least three): 1) What factors have been responsible for the dramatic loss of corals on Caribbean reefs in recent years (last 50 or so) and how do they interact? 2) What are the consequences if the current trend continues? And 3) What should we do about it (if we assume what is happening is 'bad' and 'needs fixing')?  Additional questions come to mind and have likely been alluded to in some of the numerous posts on the topic.  Such as a) Is the Caribbean similar to, or different from the Indo-Pacific in how coral loss has occurred? b) When did serious coral loss start?  And so on.

The first question about causes and their interactions is intrinsically interesting to scientists, but perhaps of less interest to others.  As scientists we 'need' to understand the details, and knowing the details can be very helpful in devising management solutions.  Most of the posts have centered predominantly on this question.  May I humbly suggest that the discussion has been generating a lot more smoke and less light than it would have if we had begun by recognizing a) that it is quite unlikely that a single factor has been overwhelmingly important as the cause of coral loss, and b) that the relative importance of factors, and probably also the nature of their interactions will vary in space and in time -- and the Caribbean is plenty large enough to include some of this heterogeneity.  If we want to answer this first question, we have got to consider it at specific times and places, and not seek a single answer applicable across the Caribbean and across all times.  (Having said that, I remain persuaded by John Bruno's original blog post that warming has been 'a major factor' in coral decline 'for some time' across the Caribbean.)

If we need to point fingers, we could pick on John Bruno, whose initial post with this subject line seemed to be arguing that ocean warming was 'the prime cause' across the Caribbean.  As the discussion has gone on, there has been a progressive increase in the apparent desire to find a Caribbean-wide causal pattern.  It may, but it probably does not exist because the Florida Keys are not Bonaire, Barbados, or Bimini (forgive me the urge to be alliterative).

The second question has hardly been addressed in any posts, presumably because we all agree that coral loss is bad for reefs and for coastal communities.  But frankly, I'd love to learn how much less effective are today's Caribbean reefs at providing fishery resources or protecting coastlines than were the reefs of 50 or 100 years ago.  And also, what will be the trajectory in ecological 'value' of reefs if they continue to lose coral (on human timescales, please).

The third question, the one most non-scientists might identify as most important, does depend on how we answer the first question.  If warming now appears to be becoming substantially important as a cause (whether or not it was important in the past), we need to address that issue.  We cannot stop el Nino (so far as I know), but we can stop increasing the concentration of GHGs in the atmosphere, and could start to reduce them if the effort to curtail emissions was aggressive enough.  I doubt we can do anything locally on ocean temperature, although I suspect some crazy engineers will want to try.

If we decide that pollution (of specified kinds, please) is important everywhere, or even in just some locations, we will need to control/reduce that pollution.  If overfishing is a chief culprit, we will need to start fishing sustainably.  And so on.  Just as I suspect the particular mix of currently important causes of coral loss will vary spatially, the particular mix of efforts to correct the situation must also vary.  Working globally to cut GHG emissions does not preclude simultaneously working locally on specific mixes of other factors.  What we need to avoid is the presumption that there is a silver bullet -- a single, easy-to-understand solution that will solve the problem of coral loss in all locations, preferably overnight with no substantial costs.

Two final thoughts:  1) If some of us 'have to' conclude that pollution is the (or an) important cause of coral loss,  GHG emissions are a form of pollution and ocean warming is currently a consequence of this pollution.  Yes, pollution really is the major causal factor.  (On the other hand, to pretend pollution is 'unimportant' simply in order to make 'warming' overwhelmingly important, suggests people have been closing their eyes when near centers of human activity.)  And 2) CO2 is implicated both as a GHG causing warming, and as the cause of ocean acidification.  While I think the evidence for any significant coral loss having already occurred due to OA is slim to nonexistent, drawing a distinction between CO2 and warming as putative causes of coral loss is disingenuous and will convey a confused message to the public.

Peter Sale

-----Original Message-----
From: coral-list-bounces at coral.aoml.noaa.gov [mailto:coral-list-bounces at coral.aoml.noaa.gov] On Behalf Of coral-list-request at coral.aoml.noaa.gov
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Today's Topics:

   1. Re: Evidence that ocean warming has caused most	Caribbean
      coral loss (Ulf Erlingsson)
   2. Re: Evidence that ocean warming has caused most	Caribbean
      coral loss (Bruno, John)
   3. Re: Evidence that ocean warming has caused most Caribbean
      coral loss (Pedro M Alcolado)
      (Robin T Smith PhD)
   5. Re: Evidence that ocean warming has caused most	Caribbean
      coral loss (Dennis Hubbard)

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