Claudine Schmidt-Lainé

Environnement : modélisation et modèles pour comprendre, agir ou décider dans un contexte interdisciplinaire

Abstract If the physical sciences were the cradle of modelling approaches, now almost all disciplines are concerned by this methodology. First based on mathematical language, the modelling formalisms become more and more diverse. Computer sciences contribute widely to the extension of the methodology at two levels : the first to make easier the use of mathematical models, the second to develop new formalisms, such as cellular automata or neural networks. The fields of basic and applied research on the environment and related technological developments give good examples of applications of this methodology, from global modelling at the planet level, for example for the study of climate changes, to local and specialised models, for example in population dynamics or water transfers in soils. Models are also developed to reach various goals : in basic research, to understand how environmental systems work, in technological development, to design adapted techniques, and in decision making process, as an argument, among others, to elaborate a decision. The recent expansion of modelling, to almost all disciplines implied in environmental research, makes it also a tool in interdisciplinary dialog. The model becomes a link between disciplines, for example between natural and social sciences, by combining dynamics of ecological and social systems. But the use of models is not exempt of hazards. Used in bad conditions, off its limits of validity, or running with a deficient simulator, it may lead to incorrect results. It may also be a screen to hide an insufficient knowledge. It such cases, it can be a wrong decisive argument in decision process or to lead to a bad technical device or protocol. Anyway, built and used carefully it is a precious and efficient tool. So, the state of the art and actual methodological problems and applications in environmental basic and technical research are presented. The foreseeable advances and endeavours are also envisaged. The text is essentially illustrated by examples developed by scientists and engineers of the Cemagref. Finally, the environment is an example of a complex system. Modelling is a good tool for complexity analysis and methodological advances in environmental research would be useful for other systems which are qualified “complex”, and then have a larger range of application than studies on environment.