Farmers have the deeply ingrained belief that extra phosphorus aids in animal reproduction, he says, and it's still being used. But while phosphorus may be a necessary nutrient for animal health, when animals ingest more than they need, the excess becomes part of their waste, which is then used to fertilize crops. Heavy rains and spring melts then sweep these wastes into nearby rivers and lakes. But not all phosphorus pollution can be blamed on modern farming practices. An increase in construction around New York's Lake Champlain is the suspected cause for the symptoms of phosphorus pollution in some of the lake's bays.
Land development adds two times the phosphorus to water sources as agricultural land does.
Elena Bennett, a doctoral student of inland water conservation at the University of Wisconsin-Madison, recently led a research team that studied the state's Lake Mendota. Bennett calculated that even if phosphorus pollution halted immediately, almost three centuries would need to pass before the watershed would have the same healthy readings it did in the 1970s. All the more reason to take action now. Scientists are currently investigating more effective sewage treatments, including the use of enzymes that break down excess phosphorus while it's still in the animals' systems. With agricultural, urban and land expansion sources all contributing to surplus phosphorus, their program serves as a much-needed model for the nation.