“They say, reluctantly, that a time may come to stop trying to save
certain salmon runs because their home streams will be too warm.”
The Oregonian (Portland, Oregon, US0
Sunday, January 06, 2008
Warming could fry salmon
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
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
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
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
“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
“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
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
Rising temperatures are likely to alter the life
cycle of salmon in several crucial ways,
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
Earlier melting of snow will leave rivers and
streams warmer and shallower as summer and fall
Diseases and parasites probably will flourish in
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
He said federal agencies responsible for salmon
protection are not planning for such dramatic
“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
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
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.”
Michael Milstein: 503-294-7689; michaelmilstein@
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