Takuro Uehara a , Mateo Cordier b, c , Bertrand Hamaide d and Jeffrey Weih e

1. An Input-Output/ System Dynamics Approach to Ecological Economic Modeling: An application to the Seine Estuary in France TakuroUeharaa, Mateo Cordierb, c, Bertrand Hamaided and Jeffrey Weihe aCollege of Policy Science, Ritsumeikan University, Kyoto, Japan b Centre Européen Arctique, Université de Versailles Saint-Quentin-en-Yvelines (CEARC-UVSQ), France. c Centre d’Etudes Economiques et Sociales de l’Environnement, Centre Emile Bernheim, Université Libre de Bruxelles, (CEESE-CEB-ULB), Brussels, Belgium. d Centre de Recherche en Economie, Université Saint-Louis (CEREC-FUSL), Brussels, Belgium. e Senior Adult Learning Center, Portland State University, USA.

2. Objectives • Build a model which links an Input-output (I-O) tableto a System Dynamics (SD) modelto capture the complexityof an ecological-economic system • Apply the method to the Seine Estuary, France • For this paper, policy implications for the restoration of the estuary are NOT the main focus • (we will address these in the next step!)

3. Motivation • We need modeling techniques which can capture the complexityof an ecological-economic system. • Environmentally Extended I-O • Well-developed; an I-O is often readily available • Captures detailed economic structures, but not dynamics • Constant technical coefficients; Lack of feedback loops • SD(a computer-aided approach to solving a system of nonlinear first-order differential equations) • Captures nonlinear dynamics and feedback loops, but not detailed (disaggregated) economic structures • It is technically possible to integrateI-O and SD. • SD can be synchronized with SAP, Oracle, Microsoft Excel, GIS, etc.

4. Study Area: The Seine Estuary • The nursery area for sole has been decreasing due to economic activities(Rochette et al, 2010; Culliviez et al, 2008). Nursery habitats have been continually destroyed since 1834 by the construction of dikes and harborextensions for maritime transport, and by the Normandy bridge. Evolution of nursery areas of the internal part of the Seine estuary Source: Rochette, S. (2010) Source: Cuvilliez (2008).

5. Ecological System Economic System (SD on Powersim ) (I - O on Excel) Fractional Nursery Area in the Destruction Rate Seine Estuary Destruction Rate Restoration Rate Total Output Initial Nursery Area Restoration Policy Maximum Number of Carrying Capacity of Sole per km2 of Sole Nursery Area Sole in the Seine Estuary Initial Stock of Sole Average Weight per Net Birth Catch Price of Sole per kg Intrinsic Growth Catch Rate Rate of Sole Fractional Catch Rate Weight of Caught Sole Final Demand for Sole Change in Total Output Final Demand for Total Output Sole Initial Total Output The Schematic Model • SD on Powersim® is synchronized with I-O on Excel®.

6. Simulation Results • Preliminary results with three scenarios. • 0% Restoration Every Year, from 2018 to 2028 (as a baseline) • 2% Restoration Every Year, from 2018 to 2028 • 10% Restoration Every 5 Years, from 2018 to 2028 Nursery area in the Seine Estuary Final demand for sole

7. Future Research Directions • Feedback loops between an economic system and an ecological system • E.g., impacts of economic activities on the destruction of the nursery • Delays • E.g., dike construction impacts that linger for several years (Cuvilliez, 2009) • Ecological System • Need natural scientists’ advice to sophisticate the structure of the ecological system model • Data Collection • Collect “soft data” through, for example, expert meetings • Scale Mismatch? • Is the economy too big (monetarily) relative to the size of the ecological system? • Boundary of Economic System? Adjust I-O using RAS method? • Optimal Restoration Policies • SD offers optimization techniques for analytically unsolvable models • SOPS (Stochastic Optimization in Policy Space)