Proceedings of the Second Mediterranean Symposium on Marine

Here, we will firstly delineate what encompasses <strong>the</strong> popular notion <strong>of</strong> plant. Then we will
define biodiversity, especially alpha and gamma species diversity, since some forms <strong>of</strong>
impact may increase alpha diversity while reducing gamma diversity. We will rank human
impacts according to <strong>the</strong> time necessary for <strong>the</strong> impact to become reversible. Clearly,
those forms <strong>of</strong> impact which are irrever-sible at human scale (e.g. coastal development,
species introduction, species extinction and global warming) are a much greater cause for
concern than those which are reversible within a few years (e.g. most types <strong>of</strong> pollution
and oil spills). Here, we will only address three forms <strong>of</strong> human irreversible impact:
coastal development, introduced species and global warming. Finally, we will leave aside
<strong>the</strong> well known decline <strong>of</strong> <strong>the</strong> Posidonia oceanica seagrass and poorly documented
problems such as <strong>the</strong> decline <strong>of</strong> epiflora <strong>of</strong> <strong>the</strong> coastal detritic community, to focus on
two case studies, Cystoseira forests and Lithophyllum byssoides rims.
THE NOTION OF VEGETATION
The notion <strong>of</strong> plant kingdom versus animal kingdom dates back to Karl von Linnaeus, two
and a half centuries ago. He empirically ga<strong>the</strong>red within his plant kingdom flowering
plants (Phanerogama, now Magnoliophyta) and Cryptogama (ferns, mosses, fungi and
algae). Scientific findings in <strong>the</strong> fields <strong>of</strong> anatomy, cytology, biochemistry, biology and
finally molecular biology invalidated this classification between <strong>the</strong> end <strong>of</strong> <strong>the</strong> 19th
century and <strong>the</strong> 1980s. Surprisingly, this customary classification is still in use in many
text books and is still taught in most universities in <strong>Mediterranean</strong> countries.
Teachers ei<strong>the</strong>r actually ignore a one century suite <strong>of</strong> discoveries, or are aware that some
changes happened but claim that "new classification is too complicated and <strong>the</strong>refore
cannot be understood by students" (by students? or by <strong>the</strong>mselves?) and that "it is
changing over time, so that it is preferable to wait until it is would be stabilized before
teaching it". The latter argument is <strong>of</strong> course irrelevant. Firstly, <strong>the</strong> main features <strong>of</strong> <strong>the</strong>
modern classification have been more or less stabilized for at least two decades.
<strong>Second</strong>ly, changing likely hypo<strong>the</strong>ses into more likely hypo<strong>the</strong>ses constitutes a general
characteristic <strong>of</strong> Science: stabilization will never occur. Do geneticists wait decades to
teach new notions on <strong>the</strong> plea that <strong>the</strong>y will continue to be improved over time?
ACTES DU DEUXIEME SYMPOSIUM MEDITERRANEEN SUR LA VEGETATION MARINE (ATHENES, 12-13 DECEMBRE 2003)
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