Local biodiversity of species - the scale on which humans feel contributions from biodiversity - is being rapidly reorganized, according to a new global analysis of biodiversity data from more than 200 studies, together representing all major biomes. The findings are important as historically, "it has been surprisingly difficult and controversial to find signals of ... global trends in biodiversity in the context of local ecosystems," write Brita Eriksson and Helmut Hillebrand in a related Perspective. The report also shows that changes to biodiversity are greatest and most variable in the oceans - particularly in tropical marine biomes - which are hotspots of species richness loss. These results may help inform conservation prioritization. While there is little doubt that the impacts of climate change and other human activities are causing unprecedented alterations to biodiversity worldwide, recognizing the global trends of decline in the context of local ecosystems has been challenging. Global biodiversity projections are often at odds with the highly variable trends observed at local levels, which suggests a possibility that current biodiversity change has geographic foundations. To explore the geography of biodiversity change, Shane Blowes and colleagues mapped trends in the richness and composition of biodiversity across marine, terrestrial and freshwater realms worldwide using the BioTIME database, the largest collection of local biodiversity time series data to date. In their analysis, Blowes et al. did not identify an overall trend of global species loss but instead showed that the composition of local species assemblages is rapidly being reorganized on a global scale. This restructuring, too, can have severe consequences on ecosystem functioning. The findings suggest that our understanding of biodiversity loss - as well as our efforts to stem the tides of change - needs to be conditional on context and location, the authors say. "Blowes et al. thus highlight that the global biodiversity crisis, at least for now, isn't primarily about decline, but about large-scale reorganization," write Eriksson and Hillebrand.