Climate change threatens ecosystems worldwide, yet their potential future resilience remains largely unquantified. In recent years many studies have shown that biodiversity, and in particular functional diversity, can enhance ecosystem resilience by providing a higher response diversity. So far these insights have been mostly neglected in large-scale projections of ecosystem responses to climate change. Here we show that plant trait diversity, as a key component of functional diversity, can have a strikingly positive effect on the Amazon forests’ biomass under future climate change.