An economic assessment of carbon sequestration of Posidonia oceanica in the marine protected area of the Tremiti Islands

The ocean ecosystem has a central role in achieving climate neutrality, both through its carbon sequestration capacity and its potential for providing offshore renewable energy. Marine ecosystems absorb approximately one-quarter of annual anthropogenic CO2 emissions, thereby significantly contributing to climate change mitigation. In the context of limiting global warming, the seagrass Posidonia oceanica (L.) gained the centrality of several international climate change mitigation projects being the most effective carbon storage sink among Mediterranean seagrasses. This study provides a broad overview of marine ecosystem services, ranging from a review of international literature on the factors influencing their valuation, to a case study on the biophysical and monetary valuation of carbon sequestration capacity, and concluding with an applied assessment of biophysical and monetary valuation under different climate change scenarios at the Mediterranean Sea scale. In particular, the first chapter investigates potential drivers of the marine and coastal ES value at global level using a meta-regression analysis. A panel of 1423 observations from 296 studies was analyzed, with a span time from 1974 to 2021. The second chapter suggests, for accounting purposes, a driver to link the ecosystem condition to the ESs provided by P. oceanica meadows in the Mediterranean Sea, particularly at the Tremiti Islands Marine Protected Area (MPA). It highlights the value added by an ecosystem-condition- based approach to assess the monetary value of P. oceanica compared to a baseline scenario. The third chapter offers an estimation of the effects, in biophysical and economic terms, on the provision of ecosystem services by P. oceanica, under different climate change scenarios proposed by the Intergovernmental Panel on Climate Change (IPCC). Carbon fixation and storage capacity of P. oceanica were investigated as pilot ecosystem service. The chapter presents different projections of the increase in Sea Surface Temperature (SST) and salinity of the Mediterranean Sea, based on the different IPCC scenarios.