The environment is changing at an alarming pace, resulting in changes in the number, identity and abundances of species in communities, but mechanisms underlying community dynamics are poorly known. This presents novel challenges for scientists and managers to identify solutions and mitigate the consequences of biodiversity change. Specifically, it requires moving beyond commonly done evaluations of taxonomic richness to more robust assessments of temporal dynamics. We are exploring mechanisms influencing diversity dynamics in aquatic (e.g., lake, stream, flooded grassland) and terrestrial ecosystems (e.g., forest, shrubland, grassland). Our aims are to (1) test for differences in temporal dynamics between aquatic and terrestrial ecosystems using existing and newly compiled global and Swiss data, and (2) evaluate environmental factors likely influencing these temporal dynamics, paying particular attention to those that might represent system inter-connectedness.