A new paper published in Proceedings of the National Academy of Sciences presents the first geographically explicit and predictive modeling of the impact of river damming on the biogeochemical cycle of the nutrient element phosphorus.
Results show that the total mass of phosphorus being retained by sediments accumulating behind dams doubled between 1970 and 2000, and could increase by another 41% by 2030. The spatial analysis further indicates that the largest projected increases in phosphorus retention by dams will take place in Asia and South America, where most new dams are being built. According to the calculations, by 2030, the Yangtze River basin will overtake the Mississippi River basin as the world’s top location for phosphorus retention in dam reservoirs.
Despite the massive dam building activity now and in the coming decades, the global export of bioavailable phosphorus by rivers to the coastal ocean is expected to continue to increase – by 2030, it could be up to 21% higher than in 2000. The reason lies in the projected rise in fertilizer use and sewage discharges. Thus, unless measures are taken to curb anthropogenic phosphorus emissions, we can expect a worsening of harmful algal blooms in many coastal zones of the world.
The paper’s first author is Taylor Maavara. Her co-authors are Chris Parsons, Christine Ridenour, Severin Stojanovic, Hans Dürr, Helen Powley and Philippe Van Cappellen.
The paper is freely available online at:
http://www.pnas.org/content/early/2015/12/01/1511797112.abstract