Stephen Carpenter, limnologist and UW-Madison professor of zoology. (Photo: limnology.wisc.edu)
Early warning signs for ecosystem collapse can be detected: study
Monday, May 02, 2011, 03:20 (GMT + 9)
Researchers at the University of Wisconsin-Madison studying signals coming from an isolated Wisconsin lake have determined that its aquatic ecosystem is nearing collapse.
The findings comprise the first experimental evidence that dramatic shifts in an ecosystem can be detected in advance and potentially allow for the prevention of an ecological tragedy.
The results of the National Science Foundation-supported study were published in this week’s issue of Science by a team of researchers led by Stephen Carpenter, a limnologist and UW-Madison professor of zoology.
"For a long time, ecologists thought these changes couldn't be predicted," said Carpenter, one of the world's chief ecologists.
"But we've now shown that they can be foreseen. The early warning is clear. It is a strong signal," he declared.
He said the findings could revolutionise ecosystem management, as they suggest that proper monitoring could enable the tracking of any ecosystem’s vital signs and thus allow for a timely intervention to prevent irreversible environment damage.
"The concept has now been validated in a field experiment and the fact that it worked in this lake opens the door to testing it in rangelands, forests and marine ecosystems," Carpenter proclaimed.
The ability to perceive when an ecosystem is approaching a state of disaster could prevent the collapse of fisheries and other marine ecosystems.
In the study, the researchers looked at Peter and Paul lakes, two remote and undeveloped lakes in the north of the state. Peter’s biota was manipulated and Paul served as a control for three years.
Carpenter’s team gradually added predatory largemouth bass to Peter Lake, which was previously ruled by small fish that fed off water fleas, or zooplankton, to turn the lake into an ecosystem dominated by large predators.
"Almost immediately...the small fish begin to sense there is trouble and they stop going into the open water and instead hang around the shore and structure, things like sunken logs. They become risk averse," Carpenter explained.
The lake then became "water flea heaven" - as the water fleas’ preferred food, phytoplankton, became highly erratic.
The group first discovered telling signals in computer simulations of spruce budworm populations in boreal forests in Canada, where every few decades the insects’ burgeoning numbers caused extensive deforestation.
But the computer models experienced odd blips just before a virtual outbreak. William "Buz" Brock, a UW-Madison professor of economics who focuses on the mathematical connections of economics and ecology, figured out the problem by devising a way to notice subtle changes in the ecosystem's natural trends of variability.
Carpenter noted that the catch of the validated statistical early warning system for ecosystem collapse is that, for it to work, it requires intense and ongoing monitoring of an ecosystem's chemistry, physical properties and biota.
By Natalia Real