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Abstract Global trends in river nitrogen yields reflect human distortion of the global nitrogen cycle. Climate change and increasing agricultural intensity are projected to enhance river nitrogen yields in temperate watersheds and impair downstream water quality. However, little is known about the environmental drivers of nitrogen yields in major Arctic rivers, which have experienced rapid climatic changes and are important conduits of nutrients and organic matter to the Arctic Ocean. Here we analyze trends in nitrogen yields in the six largest Arctic rivers between 2003 and 2023 and develop generalized additive models to elucidate the watershed characteristics and climatic processes associated with observed spatial and interannual variability. We found significant increases in dissolved organic nitrogen yield and/or declines in dissolved inorganic nitrogen yield in four of the six rivers. While temperature and precipitation, via their relationships to discharge, enhance dissolved nitrogen yields, we attribute the diverging trends to the responses of inorganic and organic nitrogen to temperature via effects on permafrost free extent. Spatially, we attribute differences in nitrogen yields across watersheds to differences in land cover and temperature. Shifts in the amount and composition of river nitrogen yields will impact the balance between primary productivity and heterotrophy in nitrogen limited coastal Arctic Ocean ecosystems. Results from this work highlight the importance of climate‐driven changes in temperature and precipitation on river nitrogen yields in large Arctic rivers and motivate further investigation into how permafrost loss and hydrological shifts interact to drive water quality and biogeochemical cycling in the region. 

Agriculture’s global environmental impacts are widely expected to continue expanding, driven by population and economic growth and dietary changes. This Review highlights climate change as an additional amplifier of agriculture’s environmental impacts, by reducing agricultural productivity, reducing the efficacy of agrochemicals, increasing soil erosion, accelerating the growth and expanding the range of crop diseases and pests, and increasing land clearing. We identify multiple pathways through which climate change intensifies agricultural greenhouse gas emissions, creating a potentially powerful climate change–reinforcing feedback loop. The challenges raised by climate change underscore the urgent need to transition to sustainable, climate-resilient agricultural systems. This requires investments that both accelerate adoption of proven solutions that provide multiple benefits, and that discover and scale new beneficial processes and food products. 

Van Meter et al . (Reports, 27 April 2018, p. 427) warn that achieving nitrogen reduction goals in the Gulf of Mexico will take decades as a result of legacy nitrogen effects. We discuss limitations of the modeling approach and demonstrate that legacy effects ranging from a few years to decades are equally consistent with observations. The presented time scales for system recovery are therefore highly uncertain.