Biodiversity is rapidly declining and the frequency and strength of environmental changes (e.g. climate and land-use change) is increasing. A diminished biodiversity may increase the sensitivity of ecological systems, such as individuals, populations, communities and food webs, to environmental changes, which may lead, in turn, to a further decline in biodiversity. The Priority Programme aims to improve our understanding of this important but severely understudied feedback loop by accounting for the biodiversity-related flexibility of ecological systems arising from, e.g., genetic, phenotypic, or species diversity, which enables them to adjust to altered conditions and thus influences their dynamics. Research proposals for the second three-year funding period are now invited.