Earth is approaching environmental thresholds that, if crossed, will create serious disruptions to ecosystems, economies, and society. To avoid the devastating effects of climate change and biodiversity loss, humanity must protect and restore native ecosystems. International conventions and organizations support forest restoration as a method for mitigating hazardous environmental shifts, but questions remain as to where and how to focus such restoration efforts. On page 76 of this issue, Bastin et al. describe a new approach that advances our understanding of global tree distribution.