[Coral-List] Poor terminology in coral reef research 5: Phase shifts

Thomas Goreau goreau at bestweb.net
Sun Nov 5 12:03:33 EST 2006

For some odd reason all changes in coral reefs are described these  
days as "Phase shifts",  yet few people seem to have looked at what  
this phrase really means or implies.

Phase shifts have a very precise meaning in all of mathematics,  
physics, and engineering. It refers to variables or parameters that  
oscillate with well defined periodicities in which the different  
variables lag behind, or lead, each other at well defined  
frequencies. So one can then try to infer which is the forcing  
variable and which is passively responding to the other, allowing  
inferences about potential mechanistic linkages between them from  
phase shifted correlations.

But the term is now being widely misused in coral reef ecology in a  
way that has no meaning in these well defined terms. Every time there  
is an ecological change it is called a phase shift these days. Part  
of this comes from the theoretical paradigm emerging from the Lotka- 
Volterra equation in which populations are linked to each other by  
interactive coefficients (such as eating each other, or messing up  
their reproductive efforts by showing up at the wrong time). But I'm  
not aware that there is any data showing coral reef populations  
following this equation because reality is so much more complex than  
the mathematics. Those who confuse nice models for reality love it  
because it has the nice feature of multiple mathematical solutions,  
so they can say that any change is just a jump between "natural  
stable states" driven by random stochastic fluctuations. This blinds  
us to the real explanation of the causes of the changes we are seeing.

The danger of this is that its devotees believe that the changes are  
natural, and can reverse themselves spontaneously. It avoids any  
understanding of the actual mechanisms causing the changes. So when  
we dump sewage on reefs and the algae kill the corals, this is  
described as a "phase shift" (that it surely is not by any  
mathematical definition of the term), which is supposedly natural,  
and that the dead algae covered reef will one day suddenly jump back  
to another stable coral dominated state if a butterfly flaps its  
wings hard enough in the Amazon. And nutrients are let off the hook  
entirely! Bad science causes worse public policy when it fails to  
properly identify the causes of the changes we are seeing, such as  
trying to control eutrophication by stopping poor fishermen from  
eating instead of treating sewage.

Let's use the term "phase shifts" only in a correct scientific sense  
and let's stop fooling ourselves about mechanisms by getting rid of  
misleading and inaccurate jargon uses entirely!

Thomas J. Goreau, PhD
Global Coral Reef Alliance
37 Pleasant Street, Cambridge MA 02139
goreau at bestweb.net

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