Don't Fence Me In: Managing ecosystems for predictable outcomes may backfire, new study warns

When it comes to ecosystem goods and services, we humans tend to want to know what we are going to get: We want to have clean water every time we turn on the tap, beaches free of algae and bacteria, and robust harvests of crops, fish and fuel year after year.

As a result, we try to manage the use of our ecosystems in ways that minimizes their variability.

But a study published in the Proceedings of the National Academy of Sciences concludes that managing ecosystems for predictable outcomes is risky. In fact, more often than not, it backfires.

At the heart of the problem is the fact that while we can reduce variability in the short frame, variability doesn’t go away, it just goes somewhere else.

Take for example our attempts at flood control on rivers:

By installing levees, engineers are able to constrain flow and curb the fluctuations in water levels that once led to routine flooding of low-lying areas. These levees work so well that whole communities now exist in what were once floodplains.

But, of course, the levees cannot remove all variability from the system. Sometimes a levee breaks or a river reaches levels higher than what the levee was built to withstand.

The end result is a flood that is much more destructive than before.

Steve Carpenter, lead author and director of the Center for Limnology at the University of Wisconsin-Madison explains:

"For many years the river stays in the levee and everything is fine. However, every once in a while, it goes out and everything is worse."

Folke, Carpenter and their colleagues ran a series of 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, for instance by tightly controlling fish harvest or shrubs in grasslands, unexpected outcomes occurred. Fish stocks collapsed at lower harvest levels. Grasslands were replaced by shrubs with even light pressure from cattle grazing.

Steve Carpenter says that living systems "need a certain amount of stress" 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.”

This does not mean we shouldn not try to manage our ecosystems responsibly and sustainably, it just means that we may need to redefine acceptable levels of change and variability.

Carl Folke concludes that we need more adaptive approaches that allow for greater natural variability in social-ecological systems and encourage a diverse set of management approaches:

"By exploring what does and doesn’t not work resource managers can better learn how to sustain ecosystems as they change over time”, says Folke.

Story highlights:
1. Managing ecosystems for predictable outcomes is risky. In fact, more often than not, it backfires.
2. Researchers ran a series of computer models on nutrient pollution in lakes, cattle production fishery harvesting.
3. More adaptive approaches that allow for greater natural variability is needed.

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