Barbara La Porta

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.

Mediterranean seagrass meadows, particularly Posidonia oceanica and Cymodocea nodosa, are among the most ecologically significant marine habitats in Europe. They provide multiple ecosystem services, including long-term carbon sequestration, biodiversity maintenance, sediment stabilisation, coastal protection, water quality regulation and nursery habitat provision. Despite their ecological and socio-economic relevance, these ecosystems continue to decline under the combined pressure of coastal development, anchoring, eutrophication, aquaculture impacts, sedimentation and climate change. Their degradation represents not only an ecological loss, but also a depreciation of natural capital that remains largely invisible in conventional economic and financial accounts.This article presents a Natural Capital Accounting framework for Mediterranean seagrass restoration developed within the INTERREG EuroMed ARTEMIS project and applied to four pilot sites: Atzikiari Bay in Crete, Cala Blanca in Menorca, Capo Testa-Punta Falcone in Sardinia, and the Bay of Panzano in Monfalcone. The framework is aligned with the United Nations System of Environmental-Economic Accounting - Ecosystem Accounting (SEEA EA; United Nations et al., 2021) and integrates elements of Corporate Natural Capital Accounting. It compiles ecosystem extent and condition accounts, physical and monetary ecosystem service flow accounts, Impact Statement accounts, and Natural Capital Balance Sheets for each pilot site. Two ecosystem services are valued: Global Climate Regulation, through blue carbon sequestration and storage, and Biodiversity Preservation, through a defensive cost approach.Results show substantial site-specific variation in natural capital values. Biodiversity Preservation dominates total asset values across all sites, while Blue Carbon is particularly relevant in Sardinia because of its exceptional carbon stock and accumulation rate. A passive restoration scenario developed for Sardinia shows much larger aggregate values, demonstrating the strategic importance of pressure reduction and eco-mooring infrastructure at landscape scale.The findings demonstrate that seagrass restoration should be understood not only as an ecological intervention, but also as an investment in measurable natural capital. The proposed framework provides a replicable basis for marine ecosystem accounting, nature-positive investment, seagrass credit development, and policy implementation under the EU Nature Restoration Regulation and related sustainability reporting frameworks. It also contributes to the process initiated by the European Commission through the Nature Credits Roadmap, particularly with regard to measurement, reporting and verification (MRV), natural capital accounting integration, and the definition of transparent price signals in emerging nature markets.

Anthropogenic impacts on Posidonia oceanica meadows have led to a decline of this ecosystem throughout the Mediterranean. Transplantations have often been prescribed as a compensation measure to mitigate the impacts caused by coastal maritime works. Here a Q methodology approach was used to investigate the stakeholders’ attitudes in four case studies of P. oceanica transplants realized in Italian waters. Twenty-two respondents were asked to score 37 statements, and the resultant Q-sorting was analyzed via an inverse PCA using the KADE software. Four discourses, corresponding to the significant axes in the factorial analysis were identified: science and conservation (F1), oriented at a rigorous scientific approach; engineering and industry (F2), oriented at the economic development; environmentalism and participation (F3), oriented at the conservation of seagrass meadows; and transplantation-oriented (F4), oriented at the realization of transplants as compensation measures. The main conflicts and agreements between discourses are assessed and discussed, based on the analysis of the distinguishing statements that contributed to consensus or disagreement among discourses. The benefits of the Q methodology in the identification and mediation of conflicts in the four case studies are discussed, and its potential as a powerful aid in the development of a good environmental governance is acknowledged.

Data from several research and monitoring projects carried out between 1999 and 2009, for a total of 26 study areas located along the Italian continental shelf (Mediterranean Sea), were extracted from ISPRA's data set, to revise and update the existing information on the ecology and spatial distribution of 20 selected soft-sediment polychaete species. The species were selected taking into account their spatial distribution and ecological role in the benthic assemblages and the existence of voucher specimens deposited in ISPRA's reference collection. Samplings were taken at 872 stations on soft sediments, at depths ranging from 1 to 155 m. Surface sediment composition data were available at each site. The number of specimens from the selected species was extracted at each site, and relative abundance (%)calculated. The spatial distribution of each species was investigated according to the biogeographical zones identified in the Italian Seas. The distribution of five species (Aponuphis bilineata, A. brementi, A. fauveli, Nothria conchylega, and Onuphis eremita) was updated. Several species that were previously considered to be characteristic of a specific biocenosis, sensu Pérès & Picard ( 1964 Pérès, JM and Picard, J. 1964. Nouveau manuel de bionomie benthique de la Mer Méditérranée. Recueil des travaux de la Station Marine d'Endoume, 31: 137 [Google Scholar] ), e.g. Diopatra neapolitana, Ditrupa arietina, Notria conchylega and Sternaspis scutata, were found to be distributed over a wider bathymetric and granulometric range of surface sediments. Indicator Species Analysis highlights that the distribution of 17 selected species depends on definite granulometric characteristics of the sediment. This new relevant information outlines the important contribution of environmental monitoring programmes to scientific knowledge.