Proceedings of the Second Mediterranean Symposium on Marine

to be built up, this disappearance must be considered irreversible from <strong>the</strong> human point
<strong>of</strong> view (even when <strong>the</strong> causes <strong>of</strong> death are believed to have been removed).
Lithophyllum byssoides trottoirs are also threatened by constant treading: <strong>the</strong> platform <strong>of</strong>
Cala Litizia (Scandola nature Reserve, Corsica), well publicised as a high value natural
monument, was visited by growing numbers <strong>of</strong> tourists who arrived <strong>the</strong>re in rubber
dinghies. Lithophyllum byssoides dies if it is walked over too <strong>of</strong>ten. In addition, at <strong>the</strong> side
<strong>of</strong> <strong>the</strong> platform, rope marks could be observed (dinghy moorings) (Verlaque, 1996). For
<strong>the</strong>se reasons, at <strong>the</strong> request <strong>of</strong> <strong>the</strong> Scientific Committee <strong>of</strong> <strong>the</strong> Scandola Nature
Reserve, access to <strong>the</strong> Cala Litizia L. byssoides trottoir is now prohibited.
Finally, <strong>the</strong> expected relative rising <strong>of</strong> <strong>the</strong> mean sea-level, rapid in terms <strong>of</strong> geological
scale, resulting from global warming (Pernetta and Elder, 1992), threatens in <strong>the</strong> long
term <strong>the</strong> L. byssoides rims and trottoirs. The building up <strong>of</strong> this bio-construction is linked
to a stable or very slowly rising sea-level (see above).
CONCLUSIONS
Researchers' attention with regard to anthropogenic impact on marine vegetation has
been mainly focused on pollution although, in <strong>the</strong> long term, this is far from being <strong>the</strong>
greatest cause for concern. The <strong>Mediterranean</strong> marine vegetation is mainly threatened
by coastal development, species introduction and global warming, which are irreversible
events, at least at human scale. In addition, <strong>the</strong> regression <strong>of</strong> long-lived species, such as
Cystoseira ssp, and <strong>of</strong> Lithophyllum byssoides trottoirs, whose construction takes several
centuries, jeopardizes present day nature conservation policy.
Unfortunately, scientific knowledge <strong>of</strong> <strong>the</strong> consequences <strong>of</strong> <strong>the</strong>se threats is ra<strong>the</strong>r sparse
and, above all, policy makers and stakeholders still ingenuously consider that reducing
pollution will solve all environmental problems.
ACKNOWLEDGEMENTS
The authors are indebted to Michael Paul for improving <strong>the</strong> English text.
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