Meta-analysis and mapping of the monetary value of Mediterranean seagrass ecosystem services

• We used a meta-regression model to quantify the value of seagrass ecosystem services in the Mediterranean • Mediterranean seagrass ecosystem services are valued at 11.6 billion Int$/year, with an average of 8,712 Int$/hectare/year. • Monaco has the highest unit value at 95,767 Int$/ha/yr, while Morocco has the lowest at 1,588 $/ha/yr. • Gross Domestic Product (GDP) significantly influences seagrass valuation across Mediterranean countries. Seagrass meadows in the Mediterranean Sea deliver a broad range of services that benefit the economy and human welfare, yet they remain substantially undervalued in policy decisions. This study systematically reviewed 511 publications, with 17 qualifying for meta-analysis, providing 91 observations (predominantly in the northwestern Mediterranean) across eight ecosystem services (coastal protection, water purification, food provision, climate regulation, biotic materials and biofuels, life cycle maintenance, recreation and tourism, and cognitive effects). Employing a meta-regression model and standardizing values to International dollars (Int.$) per hectare per year (with 2020 as the reference year), the economic value of these services was quantified. A key factor influencing the values of seagrass ecosystem services was the Gross Domestic Product (GDP) per capita. The model projected the total annual value of Mediterranean seagrass ecosystem services at approximately 11.6 billion Int.$/yr, with substantial country-specific variations. Italy had the highest valuation, while Slovenia the lowest. The average per hectare value of seagrass ecosystem services was estimated at 8,712 Int.$/ha/yr. This research highlights the utility of meta-analysis and benefit transfer in shaping policy, especially where direct valuation studies are lacking, and emphasizes the need for further seagrass valuation research, particularly in underrepresented Mediterranean regions and less-studied ecosystem services.