Climate-driven spatial reorganization of cropland nitrogen pollution hotspots toward arid and semi-arid regions.

Cropland nitrogen (N) runoff contributes over 40% of riverine N loads globally, driving widespread aquatic eutrophication. The severity of this pollution is governed by the balance between N runoff and aquatic retention, yet how climate change will redistribute this risk across regions remains unclear. By integrating 1485 field observations into spatially explicit models across China, we show that climate change is creating new N pollution hotspots in arid and semi-arid regions. China's humid South currently dominates riverine cropland N export (0.31 vs. 0.16 Tg in arid regions). However, under SSP2-4.5 and SSP5-8.5 scenarios, humid regions demonstrate hydrological resilience by 2050, with exports declining by ∼5% due to warming-enhanced aquatic retention. In contrast, cropland N export from dryland-dominated North surges by 18.8%-53.2%, driven by a nonlinear amplification of N runoff. These hydroclimatic shifts necessitate spatially adaptive strategies that prioritize cropland source reduction in the newly emerging arid and semi-arid hotspots.