Water movement across European landscapes will dramatically reshape how nitrogen pollution spreads as climate change alters rainfall and temperature patterns, according to research published in Science.
Scientists at the Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB) and the Helmholtz Center for Environmental Research (UFZ) found that both the volume and velocity of water flowing through soil and groundwater systems determine whether nitrogen from fertilizers becomes a persistent pollution threat.
The study examined how nitrate, a common form of nitrogen pollution from agricultural fertilizers, moves through European watersheds. Water velocity matters because faster-flowing water can transport nitrates before soil microbes break them down into harmless nitrogen gas. Slower water movement allows more time for natural degradation. Simultaneously, the total water volume available to dilute and transport contaminants affects pollution concentration in rivers and groundwater aquifers.
Climate change will shift both variables. Warmer temperatures alter evaporation rates and precipitation patterns across Europe. Some regions will experience increased winter rainfall and summer droughts, while others face the opposite. These changes will modify water velocity and volume in ways that differ regionally, creating unexpected pollution hotspots in some areas while reducing nitrogen risk in others.
The research carries practical implications for water management and agriculture policy. European nations relying on groundwater for drinking water supplies face particular vulnerability if climate-driven hydrological changes accelerate nitrate transport into aquifers. Conversely, regions where climate change slows water movement through landscapes may tolerate higher fertilizer application rates without exceeding pollution thresholds.
The findings suggest that blanket approaches to reducing nitrogen pollution across Europe will prove ineffective. Policy makers must account for region-specific climate trajectories and hydrogeological properties when setting fertilizer limits and wastewater treatment standards.