For Lakes and Rivers Trouble Comes From Far Away

Since humans began mining and farming on a large scale, the annual accumulation of phosphorus in the environment has almost quadrupled, causing increasingly serious problems for the world’s lakes and rivers, reports a study in the March/April edition of the World Watch magazine. According to its authors, University of Wisconsin scientists Elena Bennett and Steve Carpenter, most of this pollution originates far from the freshwater systems it affects. “That patch of algae in the pond at your feet may be affected by changes in the soil hundreds or thousands of miles away,” say the authors.
Most direct sources of phosphorus, such as sewage and outflows from specific farms, were greatly reduced by the 1990s. But runoff from surrounding and upstream lands persists. When farm runoff containing phosphorus-laden fertilizer travels downhill and enters aquatic ecosystems, it causes patches of algae to expand prolifically, ultimately stifling all life underneath. But we don’t have to wait until fish die off. “Studying phosphorus increase in soils can be an effective preventive measure,” say Bennett and Carpenter.
They suggest closer monitoring of phosphorus in upstream soils, supplemented with international markets for phosphorus runoff permits in order to curb the movement of excessive nutrients from one place to another. Their strategy would protect watersheds from being overwhelmed by excess nutrients, conserving fertilizer, stabilizing soils and improving water quality.