Natural capital accounting in marine protected areas: The case of the Islands of Ventotene and S. Stefano (Central Italy)

Marine ecosystems are exposed to significant anthropogenic pressure mainly due to the exploitation of biotic and abiotic marine resources. Marine protected areas (MPAs) are important tools to achieve local and global marine conservation targets. Marine ecosystems generate goods and services vital for human well-being. Their value can be explored not only from an economic viewpoint based on market and human preferences, but also using a biophysical perspective based on the accounting of environmental costs sustained for the generation of natural capital stocks and ecosystem services flows. In this study, the value of natural capital in the MPA “the Islands of Ventotene and S. Stefano” (Central Italy) was assessed applying a biophysical and trophodynamic environmental accounting model based on emergy accounting. The value of natural capital was estimated for the main habitats of the investigated MPA in terms of the work done by the biosphere for its generation and maintenance. Both the autotrophic and heterotrophic natural capital of the MPA was evaluated. The highest value of emergy density of 4.26∙1011 sej m−2was shown by the habitat “Posidonia oceanica seagrass bed” when investigating the autotrophic natural capital. The sciaphilic hard bottom habitat (coralligenous) showed the highest value of emergy density of 2.76∙1012 sej m−2when investigating the heterotrophic natural capital. The high emergy cost of coralligenous confirmed the importance of this habitat that represents one of the most important hot spot of species diversity in the Mediterranean Sea. The total emergy value of natural capital of the MPA was converted to monetary units by using the emergy-to-money ratio for Italy, resulting in 8.26 M€. Finally, a GIS tool was used to show the spatial distribution of natural capital values in relation to different habitats. The outcomes of this study highlighted the usefulness of the applied biophysical and trophodynamic environmental accounting model to explore the ecological value of natural capital in marine ecosystems while supporting local managers and policy makers for the sustainable development of MPAs.