Costs and benefits of ecosystem services provisioning. A donor-side evaluation in marine protected areas

Over the past few decades, efforts were addressed to the understanding of the link between ecosystems and human well-being. Gradually, humans began to perceive that changes imposed to nature by their activities provoke effects, direct or indirect, on all components of well-being. From this perception, the concepts of Ecosystem Services (ES) and natural capital arose and it became urgent the definition and application of metrics and assessment frameworks able to define and quantify ES provided by nature. This is even more important where a protection regime is established (such as in marine protected areas - MPA) in order to evaluate the efficacy of undertaken measures. Nonetheless a reliable evaluation of ES lays on the estimate of natural capital value since only if natural capital is preserved the providing of services in the future at the actual level can be ensured. In this framework authors developed an integrated methodology, based on emergy analysis, specifically addressed to the evaluation of (1) the value of Marine Protected Areas natural capital, (2) the benefits in terms of ecosystems services provided and (3) the costs associated to the ecosystem services enjoyment. The methodology was applied to the Asinara MPA (Sardinia Region, Italy) in the context of a national project financed by Italian Ministry and aimed at the MPAs environmental accounting. The Asinara MPA occupies a total surface of 10920 ha and is subdivided in zones with different protection degree. The calculation of surfaces occupied by each habitat composing the MPA together with the evaluation of the biomass stocked in each habitat represent the basis for the assessment of MPA natural capital value. These information allow modelling the trophic network of each habitat to obtain the values of productivity amounts that both generated the biomass and keep annual fluxes. From productivity values, all resources required to feed the system, representing the item of emergy table, are calculated. Once expressed in emergy terms items can be summed up and translated in monerary units. From the application of this approach it is possible to: 1) identify the role played by different habitats in a system perspective; 2) recognize more valuable habitats; 3) to analyse the MPA self sufficiency or the need of external resources and, as a consequence, 4) develop management strategies about MPA structure and size. Together with the analysis of natural capital, emergy analysis is applied also to the evaluation of human activities associated with ecosystem services enjoyment aiming at the assessment of direct and indirect environmental costs (e.g. resources intake, resources consumption) and in turn introduce a sort of ecological balance for the evaluation of management strategies and limitations.