 Many scientists believe multiple factors caused the salmon decline. Some are studying how to more precisely understand the cumulative effect of human and natural factors. |
By Andy Duncan If Jay Nicholas wanted to point fingers in the salmon crisis, he'd need millions. "The way I look at it, it's not anybody's fault, it's everybody's. We all get the benefits of our society. Every one of us," says Nicholas, a technical advisor to Gov. John Kitzhaber for the Oregon Plan for Salmon and Watersheds. "But this is America. We have an incredible diversity of opinions and objectives," adds Nicholas. "We want food (including salmon) and wood and electricity and shopping centers and good roads. "We want wild salmon. We even want wildness in our neighborhoods--until the coyotes start having our pets for dinner. It's a dilemma. Our society wants everything, and finding reasonable compromises is a tremendous challenge." |
Where Nicholas is headed with these observations is a discussion of cumulative effects, a theory that's a relatively young area of scientific study.
"One way to think of cumulative effects is to think of all the little actions that happen in a watershed that can have an impact," says Keith Kirkendall, a Portland-based fisheries biologist with the National Marine Fisheries Service.
"In a watershed there may be a gold mining operation. You may have gravel extraction, timber cuts and road construction to get to the timber cuts, a campground for the public, and so on," says Kirkendall. "By themselves none of these may be all that big of a deal, but when you start adding them up you say, hey, where'd all this sediment come from? Why is the water temperature rising?"
There are a couple of ways to look at cumulative effects, adds Spencer Hovekamp, another National Marine Fisheries Service fisheries biologist.
One way is "additive," he says. This is when you simply sum up the effects of all the individual human activities in a watershed. The more accurate way to look at the concept is "interactive," he says. This is when the effect of one activity interacts with the effect of another activity, or several activities, in a way that makes the impact more than just the sum.
For example, the forest canopy catches rain. Part of the water drips slowly to the ground. Some sinks in, reaching the stream gradually. This reduces the chances of erosion and helps keep the stream cool. When you remove timber, more of the water runs into the stream right away. Additional sun also heats the stream. If there's a campground, the earth probably is compacted from people walking and driving. With compaction, even more water will run into the stream immediately. Irrigation downstream, if done in certain ways, may warm the stream more. And so on.
"All the little interactions combine," says Kirkendall. "In an urban area, it's things like the black, hardened surfaces in parking lots that absorb sunlight and heat rainwater and promote runoff. It's cars in the parking lots leaking oil and antifreeze that run into streams. It's sewer outfalls and storm drain runoff into streams. It's de-icing chemicals from the airport, fertilizers from people's lawns, and so on.
"And streams in urban areas usually have been cut off from floodplains and stripped of the shallow edgewaters and wetlands that provide habitat for young salmon and filter out pollutants that enter the stream," he adds.
Estuaries, where fresh and ocean water meet, and where many young migrating salmon pause to get their bodies used to the saltwater, are "great places to build up cumulative effects," adds Hovekamp. Also, little is know about cumulative effects in the ocean.
"There's no cookbook on the shelf on how to get a handle on cumulative effects," he says. However, Kirkendall notes that "science in this area has progressed more in the last 10 years than it did during the previous 50 years."
"The state is developing an assessment manual that watershed councils around the state will be able to use to evaluate the order of magnitude of cumulative effects in their watershed," says Ken Bierly, program manager of the Governor's Watershed Enhancement Board.
Bill Krueger, the head of Oregon State University's Department of Rangeland Resources, says there is a danger that the theory of cumulative effects could confuse nonscientists.
"Everything does not add up to a cumulative effect," he says. "Thresholds and compensation [in natural systems] are well-accepted scientific principles. So some impacts are site and situation specific."
Compensation, he goes on to explain, refers to the ability of natural systems (a stream, for example) to cope with a certain level of disruption. If the threshold level is not exceeded, the system can compensate.
"I see broad recognition that cumulative effects are a matter of concern we need to look at," says Jay Nicholas. "But how we do that is not at all clear. We're trying to find a way to co-exist with nature, but we don't know how, precisely enough.
"Society wants a prosperous economy--jobs in fishing, agriculture and forestry, cheap electricity, new housing and so on. On the other hand, individual scientists might tell us we have too many roads, and parking lots and sources of effluents. Too many clearcuts and acres of pasture land and dams. But there's no formula that shows decision makers exactly how everything is connected. How much asphalt is too much? Cumulative effects is more of an art than a science at this time, in my opinion."
He reemphasizes the importance of learning more:
"Allowing the demise of salmon would be like throwing part of our historical identity in the trash can. But this is about more than salmon. We don't know how it all fits together. If watersheds are not healthy enough to support salmon, they're probably not healthy enough to support people in the long term."