Warming Could Fry Salmon
by Michael Milstein
The Oregonian, January 6, 2008
The region's signature fish can't survive in warm waters; they're already feeling the heat
Salmon survived massive dams and fishing fleets, but now they're feeling the heat of global warming -- and it's likely to hammer them as hard as anything they've faced.
Although the government has spent billions to save salmon, warming will probably force even more extreme measures in coming years at the expense of water and power for people.
Biologists who have spent their careers watching over the fish said temperatures expected to rise an average of 0.2 to 1 degree per decade over the next century will probably wipe out some fragile runs of salmon. Snow will fall as rain instead, feeding floods that flush away their eggs. Heat waves will multiply, leaving less refuge to which they can retreat.
The region's signature fish needs cool water the way people need air. But temperatures in the Columbia River, their critical conduit to the sea, are rising toward lethal levels. The coolest years now are often warmer than the hottest years of the 1950s, according to temperature gauges near Bonneville Dam.
The climate is not the only thing driving that trend. Dams that slow water flow, allowing it to warm, and the loss of plants that once shaded tributary streams, keeping them cool, also play a part.
But climate is growing more dominant and is expected to push river temperatures about 2 degrees higher on average by 2040, according to the Independent Scientific Advisory Board, a panel of top fish and wildlife researchers who advise federal agencies.
Already, some steelhead going home to the Snake River divert into the cooler Deschutes River to escape the warm Columbia, said Bob Heinith, a biologist at the Columbia River Intertribal Fish Commission.
Days of unusually scorching heat and meager river flows killed more than 100 salmon last July in the Middle Fork of the John Day River, a tributary of the Columbia. That wiped out a large piece of the river's remaining salmon run.
"We've had some fish kills, but they've never been this extensive," said Tim Unterwegner, a state biologist who helped survey the dead fish. "It did not cool off at night like it usually does."
On its own, the fish kill might have seemed like a freak event. But it's the kind of event that global warming makes more likely as it fuels longer heat waves and shrinks rivers in summer -- two trends that weather records show are already under way.
"With a warming climate, these are the sorts of things we will probably see more of," said Robert Bilby, an aquatic ecologist with timber company Weyerhaeuser and a lead author of a new scientific assessment of how global warming will affect salmon.
"We're talking about the survival of a cold-water fish in warming conditions," he said. Rising temperatures "potentially will make large areas of the Columbia Basin uninhabitable to these species in the not-too-distant future."
Climate projections suggest that within the next 25 years, up to 10 percent of all trout habitat in the Northwest will be too warm for trout to survive. Salmon, which dams often hold to lower and warmer elevations, will feel the heat even more severely.
Warming by the 2040s will turn rivers and streams across 20 percent of the Northwest, including much of the main Columbia and Snake rivers, lethal for salmon in summer, according to the University of Washington's Climate Impacts Group.
About 80 years from now, up to 40 percent of salmon habitat in Oregon, and 20 percent in Washington, will be too warm for salmon to survive, projections show.
Scientists who marvel at the resiliency of salmon say global warming combined with a ballooning human population in the Northwest poses as great a challenge to the fish as the construction of hydroelectric dams across their rivers decades ago. They say, reluctantly, that a time may come to stop trying to save certain salmon runs because their home streams will be too warm.
Nearly half of the John Day Basin, for instance, is at especially high risk of losing much of the winter snow that feeds cool water into streams as it melts through summer, according to an analysis by the Columbia River Intertribal Fish Commission.
"We may have to identify areas that are totally uninhabitable and not spend resources there," said Bilby, a member of the Independent Scientific Advisory Board, which issued the assessment of salmon.
The scientific panel usually examines issues at the request of federal agencies. But the scientists decided that climate change and population growth pose serious challenges to Northwest fish and wildlife that agencies have usually overlooked. So they moved on their own to assess the implications.
Bilby said that as much as he already knew about climate change, he was startled by how quickly and widely salmon are likely to feel it. "Once you get into the literature, it is pretty frightening."
Rising temperatures are likely to alter the life cycle of salmon in several crucial ways, scientists say:
Winter floods, increasing as more precipitation falls as rain instead of snow, might scour away salmon eggs incubating in the streambed.
Warmer water will lead eggs to hatch earlier in the year, and the young salmon will be smaller and more vulnerable to predators.
Warmer conditions accelerate the metabolism of the fish, taking energy away from growth. Higher metabolism will force fish to find more food, but earlier hatching of eggs could put them out of sync with the natural cycles of food sources such as insects.
Earlier melting of snow will leave rivers and streams warmer and shallower as summer and fall roll around.
Diseases and parasites probably will flourish in warmer water.
Shifting ocean temperatures, circulation and chemistry might reduce food supplies for salmon during the time they spend at sea.
"It just truly scares the pants off you if you're a fisheries biologist," said Jim Martin, former head of fisheries for the Oregon Department of Fish and Wildlife who now works with conservation groups.
He said federal agencies responsible for salmon protection are not planning for such dramatic change.
"We're preparing for the status quo when change is rocketing towards us," he said.
By stressing salmon, such fallout is likely to push them closer toward an extinction threshold where there are too few adults to find each other so they can reproduce.
"The likelihood of hitting that floor goes way up as climate puts more pressure on them," said John Ferguson, director of the fish ecology division at the federal Northwest Fisheries Science Center in Seattle.
Researchers who examined salmon in the Snohomish River near Seattle found that climate change will make salmon recovery goals, which the region is already struggling to meet, more difficult. They found flooding that destroys eggs will cause some of the most severe damage to fish.
But they said aggressive efforts to repair salmon habitat -- by restoring trees and plants that shade streams, for instance -- should offset many of the climate threats, at least in some lower elevation areas. Habitat repair in the John Day drainage might help salmon there. Biologist Unterwegner hopes so.
"With global warming, my hope is that we can hold the lines with all the improvements that have occurred, so that we're not losing ground," he said.
One of the wild cards in the way salmon handle climate change is their ability to adapt to it.
The fish are resourceful: Biologists have found some in the Yakima Valley spawning in irrigation canals because they were cooler than the rivers. That adaptability is tough to predict but makes biologists ultimately hopeful.
"If they weren't tough," Bilby said, "they wouldn't still be around."
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