Drylands cover 41% of the world’s total land area and are home to greater than 38% of the human population. A variety of global change drivers -- such as increasing temperatures, altered precipitation regimes, increased species introductions, and land-use conversion -- are leading to degradation and instability of key ecosystem services from drylands. Such changes in these ecosystems services can have impacts ranging from altered global biogeochemical cycles to increased food insecurity of local pastoral communities. Given their spatial extent and importance for global to local ecosystem services, we must improve our understanding of the dominant global change threats to dryland ecosystems. In this session, we have invited experts in dryland ecology, who study different ecosystems and scales, and given them the challenging task of selecting the one dominant global change driver that they believe poses the greatest threat to drylands. Following the presentations, moderators will set up a debate-style discussion among speakers and the audience, with each speaker encouraged to take a strong position in favor of their perceived risk to drylands. From the discussion we will determine if there is consensus on the dominant threat to dryland ecosystems or if experts’ assessments are largely dependent on scale and dryland ecosystem type.