[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
President
Global Coral Reef Alliance
37 Pleasant Street, Cambridge MA 02139
617-864-4226
goreau at bestweb.net
http://www.globalcoral.org
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