Friday, December 7, 2007

Study: global warming threatens trout, salmon

Warmer earth will be harmful to native fish


By JASON KAUFFMAN
Express Staff Writer

Photo by Corey Fisher/Trout Unlimited Species of cold water fish such as salmon and trout, like this bull trout on the South Fork of the Flathead River in northwest Montana, face an increasingly uncertain future because of global warming. , A report released earlier this week indicates that migratory bull trout could decline by as much as 90 percent due to warming temperatures.

Salmon, trout and other species of cold water fish face an increasingly uncertain future in the streams and rivers of the Northern Rockies due to the effects of global warming, a report released this week by the conservation group Trout Unlimited indicates.

Furthermore, rising temperatures will likely impact these cold water species of fish across the broad range of areas they inhabit, from the west coast to the east coast of the United States, including the Appalachian Mountains and in the Wood River Valley.

The 12-page report, titled "Healing Troubled Waters," states that trout and salmon are especially vulnerable to global warming because of their dependence on clear, cold water. As cold water habitats warm, the rising temperatures will have negative impacts on the entire life history of these iconic fish—from eggs to juveniles to adults.

And the changes aren't just something that should be anticipated to take place in the years to come.

"Climate change is not some uncertain future problem. It is happening right now, and we see evidence in terms of reduced snowpack and earlier spring runoff," said Jack Williams, Trout Unlimited's senior scientist and one of the report's authors.

Increasingly, the discussion of global warming in the United States and throughout the world has gone from a debate over whether it's real to one of how impactful the climate changes will be, the Trout Unlimited report points out.

Although the reasons for global warming have been widely reported, the study makes sure to remind people why the changes are taking place. It notes that carbon dioxide—the primary greenhouse gas responsible for global warming—is at its highest concentration in the earth's atmosphere in the past 400,000 years, having risen 30 percent since the late 1800s, and is increasing at the fastest rate in recorded history.

The study cites widely reported figures indicating that global temperatures have already risen more than 1 degree Fahrenheit during the last century, and scientists project that temperatures will increase anywhere from 2 to 10 degrees Fahrenheit over the next 100 years.

All of this will increase the vulnerability of cold water fish, many of which are already imperiled by habitat degradation and other human-caused factors.

But the findings aren't all doom and gloom.

Based on research by the scientists working for Trout Unlimited, the report provides recommendations for what can be done to help fish and rivers withstand the rapid changes already taking place and those that are expected to continue taking place in the years and decades to come.

To be sure, the measures needed to counteract or limit the impacts of global warming on salmon and trout species won't be simple. What's needed is a massive effort looking at multiple variables related to the survival of cold water fish, the scientists say.

"Salmon and trout are among our most vulnerable species and their protection in the face of a rapidly changing climate demands strong actions," Williams said.

The report points to the potential that warming temperatures will contribute to dramatic declines in select species of cold water fish that occupy many of the streams and rivers in the Northern Rockies.

Numbers of migratory bull trout, which are listed as threatened under the federal Endangered Species Act, could decline by as much as 90 percent, the scientists warn. While bull trout don't inhabit the Big Wood River, the members of the char subgroup of the salmonid family are known to swim in nearby streams and rivers in the Salmon, Big and Little Lost and Snake river drainages.

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Similarly threatened are western trout populations like the Yellowstone cutthroat, which the U.S. Fish and Wildlife Service declined to grant an Endangered Species Act listing in early 2006 despite their numbers having fallen far below historic levels. For western trout populations, the report suggests the declines could exceed 60 percent in certain regions.

Outside of the West, the scientists estimate that up to 90 percent of wild brook trout living in the Appalachian Mountains region of the northeast U.S. could be lost due to global warming.

Many of the recommendations made by the Trout Unlimited scientists sound similar to actions taken in recent years by Hailey-based Wood River Land Trust. Among these are the report's recommendations that action be taken to place more in-stream woody debris and variable rock structure within streams and rivers.

Such projects help slow fast-moving floodwaters, provide shelter for fish and through the passage of water over top of them help scour out deeper downstream pools, whose cooler waters are excellent safe havens for fish when summer temperatures make shallower waters too warm for their survival.

A project completed on the Big Wood River in August 2006 by the land trust and supervised by the group's project coordinator Kathryn Goldman is an example of the kind of work the Trout Unlimited report states are needed.

As part of that demonstration project, a local heavy equipment contractor helped create a massive engineered logjam along the river in Bellevue's 12.57-acre Howard Preserve. Although most of the man-made structure was comprised of large cottonwood logs trucked in from various valley locations, a certain amount of large angular rock from the nearby Minnie Moore Mine was also used to lock the trees in place.

Mirroring some of the report's recommendations, the river enhancement project seeks to replicate the natural process of woody debris buildup. However, the land trust's goals weren't related to mitigating the impacts of global warming, but rather constituted a river health project, Goldman said.

As a whole, Goldman said that the land trust hasn't considered global warming when designing its restoration and land protection efforts. That said, she did say that organization's staff have been pleased to learn that recent findings about global warming have supported what they're doing.

"It lines up pretty well with the data that's coming out," she said.

The Trout Unlimited report also states that protecting riverside vegetation is a key to fighting the effects of global warming because green buffers help shade passing waters.

Goldman said river systems like the Big Wood that are protected from source to lower elevations allow cold water fish to migrate upstream to escape warming waters.

"It's so key," she said. "You have to keep the ecosystem as strong as you can so fish can adapt to changes."

In its list of recommended actions that are needed to combat global warming the report highlights four areas of focus. They are to protect remaining critical habitat areas, reconnect high quality habitats that have been cut off by human-caused actions, restore entire watersheds, not just individual streams and rivers, and, finally, sustain existing conservation and recovery efforts.

Another impact of global warming with potentially strong local ties is the effect warming temperatures may have to allow introduced brown trout to expand their current ranges and displace native species like cutthroat and redband rainbow trout, the last of which exist higher up in the Big Wood. Brown trout are much more adaptable to warm waters than other species of trout, the report notes.

The scientists stress that an expanded range for these fish of European descent will actually be a negative development.

To view the Trout Unlimited report, log on to www.tu.org.




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