Humanity is facing massive global challenges, as highlighted in the global sustainable development goals (SDGs). One of the most challenging is the looming, increasing risk of strong future climate change. We see this as one of the biggest future ecological risks, and while subject to much work and discussion, we think the scope is constantly underestimated. At the same time, our ability to forecast the consequences for biodiversity and ecosystems remains limited. Linking to theme 1 (Fundamental Biodiversity Dynamics), we aim to: (1) Strengthen our predictive capacity by developing forecasting models that robustly capture the likely widespread disequilibrial transient dynamics and assembly of novel ecosystems and are able to predict the impacts on ecosystem functioning and services, as well as (2) develop methods for society to optimize its responses to these dynamics.