All the case studies that have been presented and discussed proved to be complex. The complexity relates to the situations scientists want to interact with. In all cases, one observe a multiplicity of stakeholders developing their strategies to produce, consume and manage their own resources as well as collective ones, a multiplicity of resources and a multiplicity of uses of the same that are inter-dependant. There is also a multiplicity of institutions that have a specific mandate and strategies and which actions is designed to impact at différent levels (local, regional, national, etc). It also relates to the approaches designed by scientists to address the objectives, both scientific and operational. The type of activities impIemented (research, research-development, research-action, etc) always relies on the integration of various disciplines, methods and tools. Dealing with this complexity both in terms of analysis and support for decision making therefore appears as a scientific challenge.