Because human activities significantly impact even the remotest areas of the planet, developing a global-scale approach to ecological inquiry is perhaps the most important current challenge for ecologists this decade. Alterations such as introduction and extirpation of species, and increased availability of nutrients in natural systems influence species interactions and ecosystem functioning in myriad ways. Learning to predict the trajectories of these changes at the global scale is critical for future conservation and management of Earth’s biological diversity. Examining systems under perturbation also allows us to test fundamental paradigms of ecology: the relationship between productivity and species richness, resource and consumer controls on biodiversity and productivity, and the role of non-native species in ecosystems. This session will synthesize a broad diversity of results from a unique collaborative global experiment replicated in grasslands at 65 sites on 6 continents. Covering a third of the Earth’s land surface, grasslands represent a particularly important biome for producing food, fuel, and fiber as well as critical ecosystem services, therefore a predictive understanding of the response of these systems to global anthropogenic changes is particularly pressing. The work highlighted in this session is based on 4 years of identically collected data from each site including plant species composition, productivity, traits, and ecosystem rates in response to replicated nutrient and herbivory treatments. Speakers in this session use this unprecedented ecological dataset to examine critical current issues in population, community, and ecosystem ecology. Their work reveals truly general ecological dynamics in some cases, and debunks long-held paradigms in others, propelling our knowledge of ecological systems forward. The work presented in this session will touch on biological diversity of traits, species, ecosystems, and ecosystem functions and will address pressing basic and applied ecological issues. A short session summary will synthesize the advances and current ecological challenges arising from this work.