Ecosystems are constantly facing numerous natural and human induced perturbations, occurring both over short time scales (e.g. extreme climate events) and long time scales (e.g. change in land use). Such perturbations often alter the dynamics of ecological communities and worsen the provision of ecosystem services to human populations. Ecological communities are key elements of the response of ecosystems to global change perturbations. To assess and mitigate ecosystem response to perturbations, we need to understand how perturbations affect the diversity of species as well as the complex interactions between them, and how these effects in turn determines ecosystem stability. However, knowledge on this issue is still largely lacking, partly because the different facets of the links between global changes, community structure and ecosystem stability have been mostly considered by disconnected ecological research pieces. The project ECOSTAB aims to bring the experimental, empirical and theoretical knowledge needed to assess and understand how different components of global changes affect community structure and ecosystem stability, in terms of both the variability of ecosystem properties over time and the resistance and resilience of ecosystem properties to extreme climate events. To achieve this ambitious objective, ECOSTAB brings together a consortium of researchers with highly complementary expertise on community ecology, food web structure, ecosystem functioning, aquatic and terrestrial ecosystems, large database analyses, ecological models and management of large experimental infrastructures, to combine: (1) A unique experimental test of the consequences of two major components of global changes (eutrophication and top predator loss) and their interaction on food web structure and stability of freshwater ecosystems at fine temporal resolution. (2) An unprecedented assessment on a large temporal and spatial scale of the effects of land use alterations and climatic variability on the trophic structure of terrestrial and aquatic communities, and on the stability of large functional groups having a commercial or patrimonial value (e.g. commercial fishes, birds, butterflies). (3) Novel models with predictions connected to the stability of natural ecosystems to understand the consequences of different components of global changes (e.g. climate variability, nutrient enrichment) on stability of ecosystem functioning in complex food webs. To our knowledge, ECOSTAB would be one of the first project to tackle the study of the consequences of multiple perturbations on different components of community and ecosystem stability (variability as well as resistance and resilience to extreme climate events). Furthermore, it would do so at very different temporal and spatial scales by exploiting the synergies between experimental, empirical and theoretical approaches. In addition to novel and important scientific results, we expect that ECOSTAB’s results would also bring important knowledge on how to manage ecosystems for conserving the structure of natural communities and to restore or improve the stability of important services such as water purification, primary or secondary productivity.