The COST Action ES0805, titled “The Terrestrial Biosphere in the Earth System (TERRABITES),” was a collaborative research initiative that ran from June 12, 2009, to March 11, 2014. Its primary objective was to conduct a cross-disciplinary assessment of the terrestrial biosphere within the context of the Earth system, aiming to enhance the accuracy of future climate projections by integrating climate-biosphere interactions into simulations. The Action focused on key areas such as Earth system modeling, terrestrial biosphere dynamics, climate projections, remote sensing technologies, and global change phenomena. By fostering collaboration among experts in these fields, TERRABITES sought to improve the reliability of coupled climate-biosphere models, thereby contributing to a more comprehensive understanding of the Earth’s climate system.