Understanding the rules that generate the common patterns of biodiversity is a grand challenge in ecology, a goal that spans levels of ecological organization and is fundamental to effectively responding to the ongoing biodiversity crisis. One of the central obstacles to explaining and forecasting biodiversity is the translation from the local scales at which process can be measured—the birth and death of individual plants—to the larger, landscape scales at which many key questions remain open. In this seminar, I will present research that highlights how a demographic approach can resolve this scaling problem and, when integrated with theory and field experiments, reveal the processes controlling common patterns of plant biodiversity. I’ll begin by showing how demographic tools can forecast the fates of plant populations and shifts in species ranges under climate change by integrating across the diverse responses of different types of individuals. Then I’ll generalize these demographic approaches beyond the population to reveal the controls over multispecies coexistence in heterogeneous landscapes. In closing, I’ll summarize my ongoing work that seeks to identify the climatic drivers of future biodiversity change and to generalize biodiversity forecasts beyond simplified systems to complex communities.