Nature Conservancy Magazine: Summer 2009 - Circuit Theory: Rewiring Nature

Go Deeper

The Nature Conservancy in Washington
The Nature Conservancy has helped protect more than 550,000 acres of Washington’s irreplaceable natural lands since 1974.

It can be common for folks living in the U.S. West to see coyotes roaming through residential subdivisions. But these same people would probably be surprised to see native mountain lions wandering through their yards. Big cats don’t frequently travel through urban areas. In fact, mountain lions and countless other species depend on corridors of undeveloped land, and paving over a crucial link in the landscape can have big implications for their survival.

While protecting wildlife corridors is a high priority for conservation, identifying critical lands can be difficult. To address this problem, Nature Conservancy ecologist Brad McRae and his colleague Viral Shah have created a technique that uses computers to locate wildlife corridors. Their work has appeared in recent scientific journals, including Ecology.

Borrowing from engineering models that predict electricity flows through circuits, the researchers create maps that pinpoint obstacles—roads, mountain peaks, housing tracts — impeding the movement of species. The maps make it possible to see why populations of mountain lions, say, are becoming isolated by new developments and freeways. This, in turn, has the potential to change the way ecologists approach ecosystem management. McRae tells us how.

What are these wild-looking maps telling us?
We’re looking for new ways to sum up connectivity across a landscape. We can look at how well-connected one habitat patch is to another and how easily animals can move between them.

How does the approach play out in conservation work?
In Washington state, we’re part of a group of government agencies and nonprofits working to identify where connectivity between habitats is most vulnerable. We’ll see where there is a lot of redundancy — places where we could lose habitat and not lose connectivity — but also choke points, where if you lose one piece of connective habitat to a wildfire, say, you might disconnect the whole system. We’re also working to predict how climate change will affect habitat by 2100.

You can help us brace for climate change?
Some predictions say we’re going to lose an enormous amount of sagebrush habitat in the West and that some of the only remaining habitat in the future will be in eastern Washington. Right now, sagebrush goes down into Nevada, Arizona and New Mexico. If sagebrush starts shifting northward, the species that depend on it will need well-connected landscapes if they’re going to keep up.

I’ve seen a number of wildlife underpasses on freeways. Is that thanks to you?
[Laughs.] Actually, it’s the other way around. I was working on a project in Washington state, looking at areas that might be suitable for freeway over- and underpasses, and that got me thinking about circuits.

Has the conservation community been receptive to this approach?
I think there’s real consensus that we need tools like this to identify where to build redundancy in pathways between habitats. It could be a thin strip of grassland or a patch of forest or even a highway underpass.

— Oakley Brooks