OREGON STATE UNIVERSITY

Climate changes may have major impact on salmon

06/25/1997

CORVALLIS - Natural climate cycles and the advent of global warming could both have a dramatic impact on already-depleted stocks of Pacific Northwest salmon, one fisheries expert said today.

There's evidence of a natural 40-year cycle in weather patterns, and some people are hoping that conditions in the ocean will follow past patterns, soon improve and help solve the salmon fisheries conservation crisis.

But it's also possible that global warming caused by the greenhouse effect might negate any positive trends and create future conditions on both inland streams and in the ocean that are worse than ever, the researcher said.

A summary of these climatic, ocean, and precipitation trends was made today by Daniel Bottom in a meeting at Oregon State University of the Pacific Division of the American Association for the Advancement of Science.

"The focus in recent years has turned very strongly towards the impact of climate and ocean conditions on salmon growth and survival," Bottom said. "In the past we always emphasized hatcheries, dams, and fishing pressure as the only important factors in salmon conservation. That was shortsighted, this problem involved environmental changes literally Pacific Rim in scope."

Factors such as dams and riparian protection are still very important, Bottom said, but there's now more appreciation of the critical role that long-term climate change can play, as it dictates ocean upwelling and currents, marine food supply, terrestrial temperatures, snowpacks and stream flows.

And when looked at from that perspective, the news is not good.

"There's a lot of variability in the predictions for this region, but the latest climate models based upon a doubling of atmospheric carbon dioxide indicate that large interior basins like the Columbia River may shift from a spring to a winter peak period of flow," Bottom said. "More precipitation may fall as rain and less as snow, with serious impacts on summer stream flows."

And to complete the double whammy, ocean upwelling cycles and nutrient rich currents may continue to resemble those most often observed during recent "El Nino" events, which have been disastrous for salmon health and survival.

Bottom is a research biologist with the Oregon Department of Fisheries and Wildlife, and has managed the salmon conservation program with OSU's Center for the Analysis of Environmental Change.

He and other climatic experts have identified a significant "turning point" in 1976 which seemed to begin a long, downward spiral in the ocean conditions and onshore weather patterns salmon need to thrive in this region.

For about two decades now, a low-pressure system that forms over the Aleutian Islands each winter was often more intense than usual. That seemed, by mechanisms still not clearly understood, to enhance salmon fisheries in Alaska and British Columbia while those in the Pacific Northwest withered.

If historical trends were to continue, Bottom said, this trend might soon reverse itself and begin improving weather and ocean conditions in the Pacific Northwest. Whether that will actually happen is less clear.

"A lot of people don't seem to think that the one or two degree changes we talk about with climate change are a big deal," he said. "But global warming can have a profound ripple effect that changes entire ecosystems, including those necessary to support salmon. It's a very big deal."

As yet another El Nino looms this year, Bottom said, an unusually-frequent occurrence of this global weather phenomenon begins to raise still more questions about links to a changing global climate.

Many people also don't realize, Bottom said, that despite its historic association with salmon, California and the Pacific Northwest are actually on the southern fringe of the natural range of this cold-water fish species.

"Our salmon are already literally living on the edge," Bottom said. "And since future climatic conditions are impossible to predict with certainty, that makes it all the more important to preserve as many different stocks as possible to give us the best chance that some can adapt to new conditions."

The new facts that are being learned about climate, ocean conditions and weather impacts in no way lessen the need to improve salmon survival and habitat in other areas, Bottom said.

In fact, the dubious climatic conditions of the future make it all the more important to give the fish every possible advantage. And it's also important to better understand such climate mechanisms, so that other salmon restoration efforts are not inappropriately given credit for which they may not really be responsible.

"Too often in the past we've managed these fisheries from a perspective of the times always being good and production always high," he said. "Now we must quit deluding ourselves, and manage the fisheries for the lean years."