Benefits of adapting to sea level rise: the importance of ecosystem services in the French Mediterranean sandy coastline

International audience12 This article proposes an innovative approach to assess the benefits of adapting to sea level rise (SLR) in a coastal 13 area on a regional scale. The valuation framework integrates coastal ecosystem services, together with urban and 14 agricultural assets. We simulate the impacts of a progressive 1 m rise in sea level in the 21 st century and an extreme 15 flooding event in 2100 for four contrasted adaptation scenarios (Denial, " Laissez-faire " , Protection and Retreat). 16 The assessment involves coupling the results of hazard-modelling approaches with different economic valuation 17 methods, including direct damage functions and methods used in environmental economics. The framework is 18 applied to the French Mediterranean sandy coastline. SLR will result in major land-use changes at the 2100 time 19 horizon: relocation or densification of urban areas, loss of agricultural land, increase in lagoon areas and 20 modification of wetlands (losses, migration or extension of ecosystems). Total benefits of public adaptation options 21 planned in advance could reach €31.2 billion for the period 2010-2100, i.e. €69,000 per inhabitant (in the study 22 area) in 2010 or €135 million/km of coastline. Our results highlight the importance of (i) raising awareness to 23 ensure that public services and coastal managers can anticipate the consequences of SLR and (ii) incorporating 24 coastal ecosystems into the assessment of the adaptation options. Our findings could provide a basis for 25 participatory foresight approaches to build coastline adaptation pathways. 26 2