Natural Capital Accounting for Mediterranean Seagrass Restoration Across Pilot Sites

Mediterranean seagrass meadows, particularly Posidonia oceanica and Cymodocea nodosa, provide important ecosystem services including blue carbon storage, biodiversity support, sediment stabilization, and coastal protection, yet they continue to decline under multiple anthropogenic pressures. This article presents a SEEA EA-aligned natural capital accounting framework for seagrass restoration, developed within the INTERREG EuroMed ARTEMIS project and applied to four pilot sites in Crete, Menorca, Sardinia, and Monfalcone. The sites were selected to represent heterogeneous Mediterranean restoration contexts, including different seagrass species, degradation histories, pressure regimes, and restoration strategies. The methodology applies a seven-step marine natural capital accounting cycle combining ecosystem extent and condition accounts, physical blue carbon accounts, monetary ecosystem service accounts, impact statement accounts, and natural capital balance sheets. Two ecosystem service components are valued: global climate regulation, through blue carbon sequestration and storage, and biodiversity preservation, through a defensive cost approach. Results show strong site-specific variation. Biodiversity preservation dominates total asset values across all sites, while blue carbon is particularly relevant in Sardinia because of its high accumulation rate and carbon stock. A passive restoration scenario for Sardinia shows that pressure reduction and eco-mooring infrastructure can generate substantially larger aggregate values than small-scale active transplantation, mainly because of the larger area addressed. Compared with previous service-specific or broad-scale seagrass valuation studies, this article contributes by linking site-specific ecological monitoring, SEEA EA-compatible accounting outputs, and natural capital balance sheet values within a single framework relevant to marine restoration finance and future nature credit design.