Phosphorus pollution in Chinese lakes declined by over one-third between 2006 and 2014, according to a paper published online in Nature Geoscience this week. The study finds that the Chinese government’s introduction of policies to reduce water pollution in 2000 has helped to lower the risk of excessive algal blooms from phosphorus pollution in urban regions, though phosphorus concentrations have increased in lakes in some undeveloped regions.
Eutrophication - the excessive growth of algae as a consequence of increased nutrient availability - can occur naturally in lakes. However, the release of nutrients into water bodies as a consequence of human activity has broadly expanded eutrophication across the world, contributing to reductions in water quality, fish die-off, and declines in biodiversity.
Yan Lin and colleagues analysed water chemistry data from 862 lakes across China, along with provincial data on phosphorus sources and flows, between 2006 and 2014. They find that median phosphorus levels declined roughly to the concentration threshold at which phosphorus leads to eutrophication, and the number of extremely polluted lakes was reduced by two-thirds. Improved sanitation and reduction in sewage wastes were major drivers of the reduction; the cause of increasing phosphorus levels in some more remote lakes was less certain, but may be influenced by forest degradation and erosion.
In an accompanying News & Views, Jessica Corman writes that: “the analysis of Lin and colleagues has revealed that China has made some good progress in protecting its lakes."