CONCORD (CBS) – What would Henry David Thoreau think?

A new study of the conditions at Walden Pond calls for swimmers to stop using the well-known waters as a bathroom.

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The study published in the PLOS journal says water clarity in the pond declined significantly in 1900s due to shoreline development and human waste, and the pond has not returned to the pristine conditions described by Thoreau in his famous book.

In fact, more than half of the phosphorous in the lake may be from swimmers’ urine. Phosphorous supports algae growth, making the water murkier.

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“Swimmers are probably the largest source of such nutrients now, and demand for the beach facilities is likely to increase in a warmer future,” the researchers stated. “Swimmer-education programs or construction of a separate swimming pool facility nearby to relieve pressure on the lake might therefore be advisable.”

A warming climate will only attract more swimmers who could relieve themselves in the pond, researchers say. Paul Smith’s College professor Curt Stager, who led the study, told The Boston Globe banning swimming there might be the solution.

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“That would be ideal for the sake of the lake. I think it would be a tough sell for the public,” he said.