With extinction continuously altering the fates of plants and animals, the researchers say it may be extremely difficult to predict which organisms will be the next to cease existing and that the wisest conservation plan is one that reaches beyond a particular species to protect entire communities.

A pair of researchers from the University of Wisconsin-Madison, interested in understanding what happens when species go extinct, developed mathematical models looking at changes in a community's tolerance to a particular environmental condition, such as global warming or acid rain.

They found that, as individual species start to disappear, two forces begin to act upon a community, making it either more or less tolerant to the environmental condition.

One of these forces occurs when species disappear in order of their sensitivity to a particular environmental factor, with the least tolerant ones going extinct first. "We know that some species are more sensitive to environmental stressors," says Anthony Ives, a UW-Madison zoology professor and co-author of the Nature paper. "And they often go extinct in order of their sensitivity."

With the disappearance of organisms most vulnerable to a certain condition, such as the increase of nutrients in lake water, the species best suited for that condition are left behind. This ordered extinction, notes Ives, makes the community as a whole more resistant to that environmental pressure and, in a sense, protects it from future degradation.

"One important message is that if we're going to understand the consequences of extinction, we need to pay attention to order," says Bradley Cardinale, a UW-Madiso
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Contact: Tony Ives
arives@wisc.edu
608-262-1519
University of Wisconsin-Madison
12-May-2004