Mission and Aims. Human welfare ultimately depends in many ways on ecosystem functioning. Most ecosystems on earth are under the influence of physical and chemical stressors, and face a steady change of concentrations and effects of a whole suite of polluting substances. All ecosystems are exposed to considerable climate change, now and in the near future. The mission of Core 2 is to contribute significantly to the analysis of environmental change and ecosystem dynamics, and to contribute to possible solutions for connected environmental problems. The research is aiming at improvement of our understanding of the main forces that drive the dynamics of human societies, biological communities and the environment as one interactive complex system. Core programme 2 focuses on the interaction of ecosystems and their components with chemical and physical stressors on the one hand, and global climate change on the other. Considering the level of integration in this Core, most research projects focus on specific local and regional problems. The scientific position of Core programme 2 is in between Core 1 and Core 3. The small-scale behaviour, effects and fate of micro-pollutants is the domain of Core 1. Ecotoxicology in Core 1 is mainly concerned with small-scale aspects of ecosystems (single organisms; environmental chemistry; microbiology). Core 2 is dedicated to processes and effects on a larger scale, both geographically (e.g. region; forest area; watershed) as well as ecologically (e.g. populations, communities; ecosystems; landscapes). In Core programme 3 an even larger scale is pursued, concerning global change in general, continental and global hydrological cycles, large scale greenhouse gas fluxes and global biogeochemical cycles. Research priorities. In the SENSE Research Programme 2002 2006 a list of Research Priorities of Core 2 has been included. In this Midterm review we present an updated description of the Core programme, which can also be tracked in the main results presented. The research activities of the Core 2 research programme are centred around three main themes. (In the re-accreditation report only two foci are mentioned, but since that time the SENSE Research School has widened its membership): (1) Fate of substances and their role in ecosystem functioning; (2) Structure and functioning of populations, communities and ecosystems; (3) A-biotic and biotic regulation of ecosystems.