To face the new challenges of dairy farming in North-Western Europe, an innovative dairy system was redesigned to produce milk in a context of climate change while saving scarce resources (water, fossil energy) and contributing to a sustainable agriculture. This system, called OasYs, is based on the diversification of forage resources, the development of grazing, larger use of legumes and on a consistent strategy for the livestock system (Novak et al., 2015). The main research hypothesis is that the increase of diversity allows to conciliate production levels and environmental performance, this way improving system resilience.