An ecological-economic approach to the valuation of ecosystem services to support biodiversity policy. A case study for nitrogen retention by Mediterranean rivers and lakes

Several international initiatives have highlighted the need to prove the relevance of ecosystem services in monetary terms in order to make a comprehensive and compelling case for conservation of biodiversity. The different approaches and frameworks used so far have shown that there is no economic or monetary estimate of ecosystems or ecosystem services with absolute validity: any valuation exercise is always context-related and the theoretical rationale behind the applied valuation technique does matter. This study presents an approach for assessing ecosystem services in monetary terms to support conservation policies at the regional and continental scale. First we briefly review the foundation of environmental and ecological economics, second we explore the differences between economic models and the application of valuation techniques, third we try to pick the difference between the mainstream economic valuation approach and the translation of biophysical models' outcomes in monetary terms. Then we present and discuss a methodology suitable for associating a monetary cost to ecosystem services when the purpose addresses conservation policies. In order to provide a contribution, we show a practical case study on water purification in the northern Mediterranean region.