The day of conferences organised by IFREMER at IHP on 7 October 2013 focused attention on the need to build models by involving all the actors concerned.

Faced with complex systems that behave in a non-intuitive manner, decision-makers need to be able to estimate the impact of different management scenarios. However, it is not sufficient to provide them with estimates of uncertainties of each scenario to gain their confidence! From the outset, it is important to involve them in discussions and to work with them in constructing models. Co-construction contributes to a better understanding of the results of models by the decision-makers and also makes it possible to better integrate decision-makers’ objectives and needs as well as the capacities of anticipation or feedback based on local knowledge.

Similarly, it is vital to model new processes, such as complex fluids, by associating mathematicians, physicists, and computational scientists in co-construction (see Proposal 4).