Dry Climate Aggravates Riverine Nitrogen Pollution in Australia by Water Volume Reduction

Freshwater is a scarce resource, and maintaining water quality is of great importance in dryland Australia. How water quality is affected by the dry climate and socio-economic influences in Australia remains widely unknown. Here, we find that agriculture activity dominates reactive nitrogen (N_r) emissions to water bodies. Such emissions not only contribute to deteriorating water quality in Southeastern Australia but also harm marine ecosystems, including the Great Barrier Reef, a World Natural Heritage site. A dry and warm climate reduces the share of N_r emitted directly to water bodies; however, it increases the N_r concentration in surface water due to reduced water volume, leading to a 3-fold higher water N_r concentration compared to major rivers globally, e.g., in the US or China. Business-as-usual socioeconomic development would increase the total N_r emitted to surface water by at least 43% by 2050, while effective mitigation measures could reduce N runoff by about 27%. Advanced agricultural management strategies should be considered to reduce future environmental pressures due to N runoff in Australia.