Humans are overloading the world’s freshwater bodies with phosphorus

Poorly treated sewage and fertilizer runoff are main sources of the nutrient

algal bloom

FEELING GREEN  Freshwater bodies on more than a third of Earth’s land area (excluding Antarctica) are maxed out on phosphorus, which can help create algal blooms such as this one.

Felix Andrews (Floybix)/Wikimedia Commons (CC BY-SA 3.0)

Human activities are driving phosphorus levels in the world’s lakes, rivers and other freshwater bodies to a critical point. The freshwater bodies on 38 percent of Earth’s land area (not including Antarctica) are overly enriched with phosphorus, leading to potentially toxic algal blooms and less available drinking water, researchers report January 24 in Water Resources Research.

Sewage, agriculture and other human sources add about 1.5 teragrams of phosphorus to freshwaters each year, the study estimates. That’s roughly equivalent to about four times the weight of the Empire State Building. The scientists tracked human phosphorus inputs from 2002 to 2010 from domestic, industrial and agricultural sources. Phosphorus in human waste was responsible for about 54 percent of the global load, while agricultural fertilizer use contributed about 38 percent. By country, China contributed 30 percent of the global total, India 8 percent and the United States 7 percent.

Carolyn Gramling is the earth & climate writer. She has bachelor’s degrees in geology and European history and a Ph.D. in marine geochemistry from MIT and the Woods Hole Oceanographic Institution.

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