Increasing numbers of global change stressors reduce soil carbon worldwide

Soils support a vast amount of carbon (C) that is vulnerable to climatic and anthropogenic global change stressors (for example, drought and human-induced nitrogen deposition). However, the simultaneous effects of an increasing number of global change stressors on soil C storage and persistence across ecosystems are virtually unknown. Here, using 1,880 surface soil samples from 68 countries across all continents, we show that increases in the number of global change stressors simultaneously exceeding medium-high levels of stress (that is, relative to their maximum levels observed in nature) are negatively and significantly correlated with soil C stocks and mineral association across global biomes. Soil C is particularly vulnerable in low-productivity ecosystems (for example, deserts), which are subjected to a greater number of global change stressors exceeding medium-high levels of stress simultaneously. Taken together, our work indicates that the number of global change stressors is a crucial factor for soil C storage and persistence worldwide.