Multiple global change factors amplify nitrogen loss and croplands are at the highest risk

Microbial-driven processes, particularly denitrification and anaerobic ammonium oxidation (anammox), convert inorganic nitrogen (N) in soils into gaseous forms, causing substantial N losses. However, their responses to global change across ecosystem types remain unclear. Here, we synthesized global data on denitrification and anammox from experiments examining major global change factors (GCFs), including elevated CO2, N addition, warming, and altered precipitation. Our analysis shows that N addition markedly stimulated both processes, and warming enhanced denitrification. On average, multiple GCFs exerted stronger effects on N-loss processes than single or two GCFs. These effects are ecosystem dependent, with croplands being the most affected, particularly under N addition. Furthermore, the sensitivity of N-loss processes to each GCF varies greatly among ecosystems and is largely explained by local climate and soil conditions. Our findings reveal accelerated soil N losses under multifactor global change and offer insights for improving future N-cycle predictions and sustainable N management. Multiple factors, such as warming, precipitation, and nitrogen addition, exert stronger effects on nitrogen loss processes than single or two factors, and the effects are ecosystem-dependent, with croplands being the most affected, according to a synthesis of experimental data.