[Coral-List] Great Barrier Reef is rapidly losing coral

David Fisk davefisk at gmail.com
Fri Nov 2 09:15:52 EDT 2012

Apologies for the long-ish post. It seems that the original posting on the
GBR and Coral Loss has morphed into the Climate Change issue once again. I
don’t think this is coincidence, so I want to close the circle and return
to an early posting from Eugene Shinn as I think it is instructive for a
number of reasons. Eugene wrote: ‘Some geologists had ...found layers of
the distinctive skeletal parts of COTS indicating the infestation was
nothing new. Some biologists...refused to accept geological observations.
They opted for humans as the cause ... The division between anthropogenic
and natural causes seems little changed over the past 35 years.’  The
similarity of the divide between biology and geology professions should be
noted here wrt the CC debate. I am not sure why this is the case, but maybe
the two disciplines represent the extremes of the ability to accurately
define the frequency, intensity, and timing of major changes in natural

Back to my issue and correct me if I am wrong, I understood that the
presence of (a few) COTS spines in sediment samples was generally accepted
as evidence that COTS have existed on modern day reefs for a long time.
There was no conclusive evidence of aggregations in the past (though
chances are they did occur due to their biology). Eugene wrote: ‘Green
Island, was most instructive. COTS had decimated hard corals around the
island and the reef sand consisted almost exclusively of starfish fragments
and spines.’ I studied natural recovery processes at Green Island during
the 1980’s, after the next major COTS outbreak to the one Eugene described
from the 1960’s. I have never heard of, nor observed, any COTS spine
sediment layer during my time on Green Island, so I would really like to
hear from Eugene if he recalls where and when he saw this feature as it is
pivotal to his argument.

As with some sedimentary geologists at the time, Eugene links an
observation of high spine densities in present day sediments (or simply a
current COTS outbreak) at a single reef, and the presence of a few spines
in older sediments, as conclusive evidence of a natural phenomenon on a
multi reef scale. The predator removal - COTS outbreak hypothetis is just
as tenuous and impossible to directly prove but, as with the sediment
record argument, no doubt contains some degree of truth. The nutrient
enhancement-outbreak link is also a strong correlative argument, but no one
cause and effect will ever really be proven I suspect as all three
hypotheses probably are true for a reef system at different spatial and
temporal scales. That is, they all have some partial validity but one
cannot conclusively link one major cause with the effect (a major outbreak)..

As with the CC debate, the COTS-human causation debate is whether or not
humans are altering essential natural processes to cause responses outside
the normal range of system behaviour. Humans may be doing relatively very
little that is different to the normal range of system responses to
disturbances, so the effects of a relatively small alteration on the system
will be difficult to accurately measure, and impossible to reduce down to a
conclusive single cause and effect.

My thoughts are this: Univariate approaches to large system issues like
COTS outbreaks and Climate Change are a dead end in terms of determining
conclusive evidence of a single cause. The old adage applies – a model that
is highly predictive is by definition not broadly applicable in practical
terms. I am not saying give up on the subject(s), rather, we should be
aware of the pitfalls and the limitations of a reductionist approach when
discussing large system issues. Several hypotheses may be equally valid and
can coexist  over time – the world is not B&W, but dare I say it: Shades of

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