Rain forests in the sea??

John Ware jware at erols.com
Fri Jun 2 14:08:57 EDT 2000

Dear List,

Well, I wasn't sure the topic was controversial but it obviously is and
it has even stirred up the old question: "what is a reef?".  Since I
started this, maybe I should add a couple of comments.

As the analogy is commonly used, the term 'coral reefs' clearly is
meant to apply to tropical reefs built primarily by zooxanthellate
corals.  Not meaning to degrade or deny the importance of deep water
corals and reefs, just trying to focus the discussion.  

- It appears that the comparison between reefs (tropical coral reefs)
and rain forests traces back to the paper by Joe Connell in Science
(1978: 199:1302-1310) 'Diversity in tropical rain forests and coral
reefs'.  The two ecosystems were brought into the same paper because of
(1) their high diversity and (2) by the mechanism that Connell proposed
to explain the high diversity.  Connell's Intermediate Disturbance
Hypothesis (IDH) became an immediate hit.  (But see Mackey and Currie
2000; Oikos (88):483-493.)

Connell was careful to limit his comparisons to corals and trees and
commented that whether his arguments "might apply to mobile species, ...
remains to be seen".  

Even limiting the comparisons to coral and trees may be misleading. 
Trees by the common definition are large, woody plants and so are
separated from other plant types (bushes, etc.).  However, Connell (and
others) did not distinguish between big corals and little corals.

(Out of curiousity, I would be very interested to know who or what group
was the first to expand Connell's comparison and state "coral reefs are
the rain forests of the sea".)

- It would appear that most coral reef workers feel that claiming that
coral reefs and rain forests are highly similar is a misleading
analogy.  However, others may feel that the analogy is justified on the
basis of high diversity arguments alone, even though the diversity is
due to very different taxa.

- There were some respondents who felt that the comparison was valid on
less than technical grounds: They are both threatened ecosystems; 
Linking the two will raise public awareness of reefs;  Both have high
potential for ecotourism; etc.

- Thus far it appears that no one on the coral list that has responded
has sufficient knowledge of rain forests to make a really valid
comparison.  For example, probably all the people on the coral list
could make a reasonable guess as to the the number of reef building
coral species (or at least how many zooxanthellate scleractinia there
are).  How many of us know how many species of trees there are in rain
forests world wide within an order of magnitude?  What would really be
useful is for someone knowledgeable about coral reefs to get together
with someone knowledgeable about rain forests and start a list
similarities and differences.  This could most easily be done by someone
in an academic environment.

As an interesting piece of trivia, the record for the highest number of
tree species on a single hectare is 487.  What is the record for reef
building coral diversity at a similar scale?  (Keeping in mind that some
corals are more analogous to bushes or something like that than to

Dive safe,
     *                                                           *
     *                       John R. Ware, PhD                   *
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