Cross-scale management of ecosystem services in the Mediterranean Large Marine Ecosystem
Lead Author: Renato Casagrandi (PoliMi)
Contributors: Lorenzo Mari (PoliMi), Paco Melià (PoliMi), Marino Gatto (PoliMi)
The Mediterranean Sea (MS) constitutes roughly 0.32% of the whole ocean water volume, yet it is estimated to host between 4% and 18% of the macroscopic marine organisms of the planet. Such a biotic richness is complemented by an abiotic variety of diversified marine habitats. Taken together, these two facts make the MS a unique entity that really deserves a special care. Multiple stressors are acting on it nowadays. They range from a huge maritime traffic to overfishing, and from water pollution to invasion of alien species, just to mention a few. On top of all, climate change is adding uncertainty to the future of the ecosystem services provided by the MS.
The current societal response to activate protection of such a fragile and important Large Marine Ecosystem (LME) consisted in establishing Marine Protected Areas (MPAs), i.e. limited portions of the sea where anthropogenic activities (such as resource exploitation or habitat deterioration) are avoided or otherwise regulated. The “Status of MPAs in the Mediterranean” compiled by MedPAN in 2012  listed 170 MPAs: each of these areas is subject to country-specific management rules, because no homogeneous legislation has been established across the European, Asian and African countries overlooking the MS. However, one peculiarity of the marine environment is that it is by all means an intrinsically open and interconnected system, in both physical-chemical terms (circulation of currents and nutrients) and ecological terms (movement of living organisms). To make a complex subject simple, (i) no marine area (including existing MPAs) can be ecologically closed in itself by “fences”, and (ii) the movement of nutrients and organisms in the sea does not recognize any political barriers between countries. Connectivity shapes the patterns of marine biodiversity (a lesson learnt from the EU-FP7 CoCoNet project), which provides ecosystem services in the MS.
In order to design ecologically relevant protection for the entire MS without protecting it all, it is therefore important to first find which marine areas play key functional roles at the LME level. For instance, some areas may deserve protection not only because they produce many larvae or propagules of keystone species providing ecosystem services, but also because they successfully retain these propagules in situ. Other areas should be protected because they donate propagules to [or receive propagules from] other suitable areas in the MS. Protection should not be perceived as a cost for the society, because it contributes to generating ecosystem services that allow for important economic revenues (such as fisheries, which benefit from the spill-over of adults from reserves, or recreational activities). Quantifying with appropriate indicators these functional roles within the LME allows decision makers to prioritize areas and provides them with operational tools for a cross-scale management of ecosystem services in the Mediterranean.
 MEDPAN12 - The status of marine protected areas in the Mediterranean sea 2012, available online at www.medpan.org