Med iterranea n mari ne biodi versity has recei ved only a
fract ion of the atte ntion accorde d to its terr estrial coun-terpa rt, despite the great cult ural and economic impor-tance that the sea has been having for the Medit errane an
countr ies. A rough estimate of more than 850 0 species of
macr oscopi c marine organi sms should live in the Medi-terr anean Sea, correspon ding to somewh at b etween 4%
and 18% of the world marine speci es. This is a conspi c-uous ®gure if one consi ders that the Medit erranean Sea is
only 0.82% in surface area and 0.32% in volume as
compa red to the world ocean. The high biodiversi ty of the
Med iterranea n Sea may be exp lained by histori cal (its
tradi tion of study dates older than for a lmost any other
sea), paleog eograph ic (its torment ed geolog ical history
throu gh the last 5 my has been deter mining the occurr ence
of distinct biogeo graphi c c ategories ), and ecolog ical (its
varie ty of c limatic and hydrol ogic sit uations within a
singl e basin has probably no e quals in the world) reason s.
Present -day Medit errane an biodi versity is undergo ing
rapid alterati on under the combined press ure of climat e
change and human impact, but protec tion meas ures, eith er
for speci es or ecosys tems, are still scarce . To unders tand the
role and pa tterns of Medit erranean mari ne biodi versity,
mari ne ecolog ical research should: ®rst, re-va lue those
scien ti®c areas curren tly unfashiona ble with fundi ng
agenci es (systemati cs, biogeo graphy and taxonom y); sec-ond, start moni toring biodive rsity with a long- term ap-proach at a who le M editerran ean scale , possibly throu gh an
inte rnational ly co-or dinated network of mari ne prote cted
areas. Ó 2000 Elsevi er Science Ltd. All right s reser ved.