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The ongoing decline of ecosystems around the world is often described in terms of biodiversity loss. But exactly how much of this decline is the result of species loss in local communities (α diversity), and how much is due to shifts in species composition of these communities? On page 296 of this issue, Dornelas et al. (1) address this issue with a comprehensive analysis of changes in plant, mammal, bird, fish, and invertebrate diversity in a wide range of biomes. Contrary to expectation, loss of α diversity, though widespread, is not a systematic trend in ecological communities. Rather, communities appear to be undergoing massive turnover in the species that constitute them (β diversity), resulting in the global emergence of communities with novel species configurations.