Alarming nutrient pollution of Chinese rivers as a result of agricultural transitions

Transitions inChinese agriculture resulted in industrial animal production systems, disconnected from crop production.We analyzed side-effects of these transitions on total dissolved nitrogen (TDN) and phosphorus (TDP) inputs to rivers. In 2000, when transitionswere ongoing, 30%–70%of the manurewas directly discharged to rivers (range for sub-basins). Before the transition (1970) this was only 5%.Meanwhile, animal numbersmore than doubled. As a result, TDN andTDP inputs to rivers increased 2to 45-fold (range for sub-basins) during 1970–2000. Directmanure discharge accounts for over two-thirds of nutrients in the northern rivers and for 20%–95%of nutrients in the central and southern rivers. Environmental concern is growing inChina.However, in the future, directmanure inputsmay increase. Animal production is the largest cause of aquatic eutrophication. Our study is a warning signal and an urgent call for action to recycle animalmanure in arable farming.