Quantification of interdependencies between economic systems and ecosystem services : an input - output model applied to the Seine estuary

The aim of this paper is to test inside an input-output model, three precepts of the sustainability strategy of integrated coastal zone management and Post-Normal Sciences: developing decision support tools with holistic perspectives which lend themselves to public participation and handle high uncertainty degrees. Unsustainability is partly due to an inadequate use of “narrow-system-boundary” tools that fail to capture important ecosystem services and ignore interdependencies between them. To respect the three precepts, our method is first based on the monetization frontier and allows environmental assets to be assessed with multiple units and indicators. Second, it integrates results from recent researches in natural sciences. Both make possible interdependencies between ecosystem services to be covered. Interdependencies are essential because they make possible to enlarge inputoutput modeling from conventional ecosystem services of sink and provisioning to supporting ecosystem service, the most vital one. A numerical application to the Seine estuary addresses the impacts of maritime transportation on nursery habitats for fish. The ecosystem services covered are life support and resource provisioning. Our results show that the restoration of a total of 73,7 km of nursery areas on the period 2004-2015 would result in a stock of soles in 2015 which exceeds the business as usual scenario by 61,3%. In spite of high restoration costs, no negative macroeconomic impact is observed. However, at sector scale, a trade-off is observed between nursery restorations and harbor and mining sectors. The quantification of such trade-offs in our model is particularly useful to public participation in decision process.