The impact of land use on N2O emissions from watersheds draining into the Northeastern Atlantic Ocean and European Seas

This paper focuses on the impact of land use on biogenic (both terrestrial and aquatic) nitrous oxide (N2O) emissions from watersheds draining into the Northeastern Atlantic Ocean, the Baltic Sea, the Black Sea and the Mediterranean Sea. While these watersheds cover about 10% of the global land area draining into oceans, nitrogen (N) inputs to soils (40 Tg N year−1) in these watersheds include about 25% of worldwide fertilizer use, and about 20% of worldwide atmospheric NOy deposition and N excretion by livestock. Total biogenic N2O emissions from this region are calculated to be 1.8 Tg N year−1. This includes 0.8 Tg N year−1 from background emissions from soils, 0.6 Tg N year−1 from soil emissions induced by additional N inputs, and 0.3 Tg N year−1 from aquatic emissions. Our results indicate that human activities have at least doubled biogenic N2O emissions from this region.