Emergy analysis, a methodology able to analyze the overall functioning of a system or a process has been applied to estimate the value of main ecosystem services provided by P. oceanica meadows, a fragile Mediterranean ecosystem widely recognized as an high value habitat. Estimates, based on calculation of resources employed by nature to provide considered services, leaded to an economic value of P. oceanica equal to 172 € m 2 a 1. The value of ecosystem services provided by P. oceanica is almost completely associated with sediment retained by the meadow and is notably greater (nearly 2 orders of magnitude) for seagrasses in general. The suggested procedure, even if preliminary, represents an effective and operative tool to provide a synthetic monetary measure of ecosystem services value to be employed when natural capital must be compared human and financial capitals in a substitutability perspective. It become evident from results that preservation actions and research activities addressed to system conservation and damages limitation (or even avoidance) are to be preferred in a precautionary approach: appraisals have been made about the high intrinsic value owned by P. oceanica, the high cost of restoration and mitigation procedures as well as the uncertainty about their success, the great investment devoted to monitoring after intervention and the fact that research about ecosystem services evaluation is still in progress. Such evaluations should be always taken into account in decisional process as, for example, when evaluating whether a recovery intervention should be applied or protective measures fostered, carefully evaluating costs to incur in or to avoid.