But the lake is similar in most respects to lakes anywhere in the world, Carpenter says, and the results of the new study are generally applicable to lakes anywhere.
"The global pattern is the same," he says. "We are releasing far more phosphorus to the soil than would be released by weathering." Restoring water quality is unlikely unless soil erosion is greatly reduced, phosphorus inputs are checked, and new technologies are developed for reducing phosphorus content of over-enriched soils, the report says.
"This type of eutrophication is not reversible unless there are substantial changes in soil management," Carpenter writes in PNAS. The amount of phosphorus that runs into the lake in any given year is small, the Wisconsin scientist notes, but a little bit of the nutrient is all that is needed to send aquatic ecosystems into overdrive.
Carpenter's model also shows that, unchecked, phosphorus pollution could put Lake Mendota on a fast track to extreme degradation. "There is a potential shift to an extremely degraded state that could occur even if we shut off the phosphorus tomorrow. It would have water quality as bad as the worst lakes in the world."
Lakes that are that highly eutrophic, Carpenter notes, have a higher incidence of toxic algae blooms, which would make the lake unfit for swimming or exposure to domestic animals and pets.
"And the odor cannot be underestimated. Lake Mendota has a certain smell about it on some summer days now," Carpenter explains, "but we're going to smell a lot more of that."
Steps that can be taken immediately, Carpenter says, include eliminating the impor
Source:University of Wisconsin-Madison