This paper presents an ongoing project funded by the FRB (Foundation for Research on Biodiversity) that aimed at understanding the changes of a biodiversity hotspot in the Amazon floodplain under climatic change. One of the objectives is to explore how global warming induce changes in human activities and conversely, how changes in human activities may have impact on the local ecosystem. The Amazonian floodplain of our study (Lago Grande of Curuai, in Santarem) is among the most productive and diversified ecosystems in the world. The moving littoral in the aquatic terrestrial transitional zone prevents from stagnation and enables a rapid organic matter and nutrients recycling, thereby explaining the large productivity of the system. Attracted by such favourable conditions for agricultural activities and fishing, populations have settled in the floodplains and have learned to cope with important variations in their environment, between the flood season and the dry season. They have adapted their livelihoods to these variations, by developing complementary activities between seasons. However, the rhythm of these floodplains seems to have changed in the past decades, obliging the actors to deal with great uncertainty. These changes occur across different spatial scales, from the whole Amazonian basin to the local lake, making it very difficult to understand locally why they are happening. This pluri-disciplinary project attempts to understand the reasons of these changes, through hydrological and biochemical models, as well as their impact on aquatic biodiversity (plankton and fish). Can the results about the dynamics of these floodplains help local populations better anticipate the future fluctuations of the river and adapt their activities to be less vulnerable to such change? Our challenge is to develop a process that will enable to confront the scientific models with the perceptions of local populations. Based on a Companion Modelling approach, which will combine t