SPA takes the coastal zone as a demonstrator, because marine and coastal SES are complex systems emblematic of global change where there is ample evidence of environmental degradation and its persistence; and this despite multiple political attempts to solve the problems. The environmental impact assessment (EIA) policy is particularly crucial there and deserves to be investigated in an interdisciplinary manner. To do this, SPA combines analyzes of different modes of impact management in several strategic areas of the CNRS where new modes of science / society / policy relations are put to the test in the field. The social sciences of politics and in particular the new political sociology of science will be mobilized to study the decision-making process, in different political and cultural contexts, with regard to the types of knowledge used in this process. The ethnographic data collection carried out by researchers in HSS will be informed by specialists in natural sciences and by experts from EI. The ethnographic fieldwork will include in-depth observations and semi-structured interviews. A sample of stakeholders involved in the decision-making process will be selected for each site. From there, a mapping of social positions and relationships will be carried out, in a horizontal and multi-level manner, at different decision-making levels, from local to supranational. Participatory workshops will be organized with EIA experts to outline avenues and move towards better sustainable management of environmental impact – thanks to the reinforced integration of scientific recommendations and warnings but also of the values and representations of users of socio-ecosystems. For this, ecologists and biologists will carry out two types of modeling whose political and socio-economic uses will be questioned in workshops bringing together researchers, engineers and stakeholders in the management of the EIA studied.