Climate change is predicted to reduce global belowground ecosystem multifunctionality.

Although climate change is known to abruptly shift ecosystem functions in drylands worldwide, the global response of belowground ecosystem multifunctionality (BEMF) to future climate change remains largely unknown. Herein, we use fifteen indicators associated with key ecosystem functions (e.g., belowground productivity, nutrient pools and cycling) to evaluate global BEMF by averaging, principal component analysis, and single-threshold approaches. Our results reveal marked spatial variation in functionality across Köppen climate biomes, indicating that BEMF is higher in polar and continental biomes compared to dry and tropical biomes. We further identify an abrupt shift in global BEMF at a mean annual temperature (MAT) threshold of approximately 16.4 °C. Globally, temperature and soil pH generate strong negative effects on BEMF in MAT ≤ 16.4 °C regions, whereas precipitation and plant species richness positively dominate the dynamics of BEMF in regions where MAT > 16.4 °C. Importantly, we predict ongoing climate change to result in a 20.8% loss of global BEMF under SSP585 by 2100, particularly in temperate and continental biomes. As future climate change is projected to increase, integrating in situ experiments and Earth system models into BEMF-climate studies is critical to the conservation and sustainability of ecosystem functions.