A new approach to assess marine opportunity costs and monetary values-in-use for spatial planning and conservation; the case study of Gulf of Naples, Mediterranean Sea, Italy

Conservation actions (as Marine Protected Areas) are key tools to maintain coastal ecosystems. However, many reserves are characterized by several problems related to inadequate zonings that preclude important areas from economic activities, determining a strong hostility by local populations. Thus, estimations of marine economic values-in-use are needed for protection of marine ecosystem in order to find the best compromise between conservation priorities and local population needs. Algorithms to estimate monetary values of the main human activities in marine territories (large scale and small scale fishings, aquaculture, beach resorts, yachting, diving and commercial shipping) are here implemented using Gulf of Naples (centre Tyrrhenian sea, Italy) as study area example. These algorithms are based on different sources data (questionnaires, monitoring activities, official local authority reports, web and scientific literature). They can also be compared with each other being their outputs all expressed in the same measure unit. During the models development process a new flexible approach, called “Systematic Costs Assessment” (SCA), to assess opportunity costs in systematic conservation planning process was developed and applied. Results show that the total turnover in the Gulf of Naples is 3,950,753,487 € per year and 747,647,887 € per year excluding small scale fishing estimation, and one hectare of marine territory is worth 40,672 € and 7696 € per year excluding small scale fishing activity. In particular, excluding small scale fishing activity, beach resort and yachting show the highest values referred to one hectare of marine territories. In conclusion, SCA is a flexible approach where no long and costly sampling campaigns are always needed, provided that two assumptions have to be taken into account, in order to estimate credible values-in-use costs: i) do not use economic activities data and ecosystem services data in the same assessment layer, since it could lead to costs overestimation and ii) SCA method are efficient when used by operators with strong knowledge of the study area, since they are able to recognize parameters affecting economic activities of local population.