This manuscript investigates the vulnerability of food security in terms of floating rice production in the Inner Niger Delta to upstream water resources management (reservoir management) and population growth under climate change and variability in the time period 2011–2050. Reservoir management and climate change have large impacts on the inflow patterns into the Inner Niger Delta and thus on the extent and duration of the flooded surface area, which in turn is closely linked to ecological integrity, livelihoods, and food production within the delta region. A vulnerability assessment concept, developed in the framework of the WETwin project, is used to investigate the impacts of existing and planned upstream dams on food demands and supply in the Inner Niger Delta under different climate and population growth scenarios. The impacts on the water balance and inundation patterns were simulated using a process-based eco-hydrological modelling system equipped with an inundation module and a reservoir module. Both projected climate change and upstream reservoir management lead to a significant reduction of peak discharges during the rainy season and hence to serious losses of potential agricultural areas within the Inner Niger Delta. The effectiveness of the planned extension of irrigated rice areas within the Inner Niger Delta, in order to mitigate the losses of areas suitable for floating rice, was investigated as adaptive measure. This land use change fulfils increasing food demands under some scenarios, but at the expense of other ecosystem services and has thus to be critically questioned.