Changing Assemblages: Although the rate of species extinction has increased markedly as a result of human activity across the biosphere, conservation has focused on endangered species rather than on shifts in assemblages. Dornelas et al. (p. 296 ; see the Perspective by Pandolfi and Lovelock ), using an extensive set of biodiversity time series of species occurrences in both marine and terrestrial habitats from the past 150 years, find species turnover above expected but do not find evidence of systematic biodiversity loss. This result could be caused by homogenization of species assemblages by invasive species, shifting distributions induced by climate change, and asynchronous change across the planet. All of which indicates that it is time to review conservation priorities.

Spatial structure of species change: Biodiversity is undergoing rapid change driven by climate change and other human influences. Blowes et al. analyze the global patterns in temporal change in biodiversity using a large quantity of time-series data from different regions (see the Perspective by Eriksson and Hillebrand). Their findings reveal clear spatial patterns in richness and composition change, where marine taxa exhibit the highest rates of change. The marine tropics, in particular, emerge as hotspots of species richness losses. Given that human activities are affecting biodiversity in magnitudes and directions that differ across the planet, these findings will provide a much needed biogeographic understanding of biodiversity change that can help inform conservation prioritization. Science , this issue p. 339 ; see also p. 308