Reduce Variability At Your Peril

UW-Madison Center for Limnology:

We want robust harvests of crops, fish and fuel year after year. As a result, we try to manage the use of our resources in a way that minimizes their variability. We seek a predictable “status quo.”

But a new study says that managing our environment for predictable outcomes is risky. In fact, more often than not, it backfires...

[Dr.] Carpenter and his colleagues ran a series of simple computer models looking at three human endeavors – controlling nutrient pollution in lakes, maintaining cattle production on rangelands invaded by shrubs, and sustaining harvest in a fishery.

In all cases, when they tried to control variance – by tightly controlling fish harvest or shrubs in grasslands, for example – unexpected outcomes occurred. Fish stocks collapsed at lower harvest levels. Grasslands were replaced by shrubs with even light pressure from cattle grazing.

The results are counter-intuitive. How can reduced pressure on a resource end up being bad for business? Part of the explanation, Carpenter says, is that, “the minute humans try to manage the system, they become part of the system.” And our involvement may help explain some of these unintended outcomes.

“Living systems need a certain amount of stress,” Carpenter says, noting that, as they evolved “they continually got calibrated against variability.” Just as our immune systems rely on exposure to bacteria and viruses to sharpen their skills at responding to disease, natural systems also need that kind of stimulation.

Are there examples in your area? The building of levees for flood control in the article resonates. How about the Mille Lacs walleye population?