Assessing biophysical and economic changes in Posidonia oceanica carbon sequestration under climate change scenarios

Marine ecosystems act as carbon sinks, particularly through vegetated habitats such as seagrass meadows. In the Mediterranean Sea, the endemic Posidonia oceanica is one of the most important seagrass species for climate change mitigation due to its high capacity to store large amounts of carbon dioxide over long periods of time. To assess and monitor changes in environmental conditions and the economic value of natural resources, this study aims to estimate the effects of climate change on the carbon sequestration capacity of P. oceanica under different detailed climate change scenarios. Carbon fixation and storage capacity (carbon sequestration) were investigated from both biophysical and economic perspectives at different projections of sea surface temperature and salinity in the Mediterranean Sea based on the various Representative Concentration Pathways scenarios. The results highlight the sensitivity of P. oceanica to specific physical variables closely linked to climate change. Considering linear and logarithmic models, and according to the four climate change scenarios analyzed, the Mediterranean Sea would experience a loss of carbon storage capacity ranging from 0.55% to 1.70%, with a consequent loss of monetary value estimated applying the market price and social cost of carbon. The findings emphasize the importance of sub-regional division for carbon fixation and sequestration of P. oceanica, enabling long term planning and management of ecosystem services.