Scientists find ecosystem early warning alarm

A three-year experiment conducted on a Wisconsin lake is offering important clues to scientists looking for early warning signs against pending ecosystem collapses.

The test, carried out by a team of ecologists, involved manipulating the food supply of Peter Lake, in Wisconsin, by adding largemouth bass into waters previously populated by smaller algae-eating fish. It was not long before the newcomers destabilized the natural ecosystem by pushing aside their smaller rivals, which fled to shallower waters to escape the predators. That led to subsequent changes in the amount of algae in the lake, as well as a sharp increase in the population of water fleas, shifts that pushed the aquatic system toward a potential tipping point. The researchers say that this marks the first time that these early warning systems have been demonstrated to exist.

"For a long time, ecologists thought these changes couldn't be predicted," said research leader Stephen Carpenter from the University of Wisconsin in Madison. "But we've now shown that they can be foreseen. The early warning is clear; it is a strong signal."

The hope is that the findings can improve ecosystem management to to the point where it becomes more of a predictive science to preserve threatened habitats in other ecosystems.