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Figure 5. Surface isotherms of February (traced every 0.25°C) of the Mediterranean Sea
(climatological means from the historical data set 1906–1995). The 14°C and the 15°C isotherms are
highlighted by a thicker tract (Bianchi, 2007).

Climate change combines with Atlantic influx, lessepsian migration and the
introduction of exotic species by humans to favour the occurrence and
establishment of warm-water species, whether exotic or native, in the
Mediterranean Sea. Climate change has been suggested for the expansion of the
biogeographical range of benthic and nektobenthic marine species, as recorded in
the last decade in the western Mediterranean (Francour et al., 1994; Vacchi et al.,
1999; Bianchi and Morri, 2000; Laubier et al., 2004) as well as in other areas (Bianchi,
1997).
The consequences of climate-mediated biological invasions are far-reaching
and more controversial than those of past invasions not affected by climate change,
where species typically originate from habitats with similar climatic conditions
(D’Antonio and Meyerson, 2002; Kowarik, 2003).
Mediterranean marine ecosystems are certainly heading towards a climate-
induced revolution in their functioning. Their resilience to such changes remains to
be determined since other disturbances (biotic and abiotic) combine and interact.
For example, the arrival of new species in these ecosystems (through natural range
shifts or human-induced introductions) might be a major disruptive force for
ecosystem functioning. The arrival of new key species, sometimes acting as
ecosystem engineers, could alter competition patterns between native species,
and/or transform current ecosystems into new ones.
The effects that climate change will have on this region should serve as an
example of what could happen globally. Among the uncertainties, it is not known
whether all parts of the Mediterranean will be equally affected by global change.
Different climatic conditions are involved in the Mediterranean basin, so responses
are expected to vary.

Impact of Invasive species
Man is greatly altering marine biodiversity in many ways, ranging from the
overexploitation of biological resources and habitat modification to the introduction
of exotic species (Cognetti and Curini-Galletti, 1993; Castilla, 1999; Connell and
Glasby, 1999; Leppakoski et al., 1999). Habitat modification and introduction of