To develop an integrated approach to study the response and robustness of ecosystems in a context of global change. The overall challenge of each ecosystem modeller, ie the scaling from individual to ecosystem, is considered an opportunity for innovation in this project. The aim is to develop theoretical and numerical tools to analyze data and to predict how biological systems react and adapt to external disruptions. Describing 'leaderless' collective behavior can not be done solely on the basis of correlations. A reactive system must be able to propagate information throughout the group. The tools will be developed in this project for both homogeneous and heterogeneous systems.