WASHINGTON, DC, May 22, 2002 (ENS) - Rising water temperatures caused by global warming could drive trout and salmon from many U.S. waterways, warns a new report from two environmental groups. Their study of eight species of fish suggests that the cold water habitat required by these species could shrink by more than 40 percent over the next century if steps are not taken to curb emissions of greenhouse gases.
Salmon and trout are cold water species, acutely sensitive to stream temperature. In many areas, the fish are already living at the margin of their temperature tolerance, meaning even modest warming could render a stream uninhabitable.
Habitats for some of these species could shrink as much as 17 percent by 2030, 34 percent by 2060, and 42 percent by 2090, finds the study released Tuesday by Defenders of Wildlife and the Natural Resources Defense Council (NRDC).
"Rising temperatures are increasingly going to curtail the range of trout and salmon in the U.S. That means more and more of our favorite fishing holes will come up empty," said Dr. Daniel Lashof, science director of the NRDC climate center. "The reason is pollution from cars and power plants. Fortunately, there are measures we can take now to start solving the problem."
The groups' analysis covers four species of trout - brook, cutthroat, rainbow and brown - and four species of salmon - pink, coho, chinook and chum. Researchers looked at air and water temperature data from more than 2,000 sites across the U.S.
Using three internationally recognized climate models, they estimated changes in stream temperature under a variety of pollution scenarios.
Projected increases in water temperature vary by location, but average 0.7 - 1.4 degrees Fahrenheit by 2030, 1.3 -3.2°F by 2060, and 2.2 -4.9°F by 2090, depending on future emissions of greenhouse gases such as carbon dioxide and which climate model is used. The models also show that the timing of summertime high temperatures could change in some cases, sometimes by as much as four weeks.
The report predicts widespread habitat losses that vary by region. For trout, the most severe losses appear in the south, southwest and northeast. For salmon, significant losses are seen throughout their current range, with the biggest impact likely in California.
The extent of predicted habitat loss also varies somewhat by species. For example, if emissions continue to increase at current rates, rainbow trout habitat would shrink by eight to 11 percent by 2030, 14 to 24 percent by 2060, and 24 to 38 percent by 2090. For coho salmon, by comparison, six to 14 percent of habitat could be lost by 2030, 16 to 30 percent by 2060, and 23 to 41 percent by 2090.
For many of the fish species, the effects of global warming come on top of a battery of existing problems. Cutthroat trout, native to the western U.S., have been reduced to less than five percent of their original range and several subspecies are listed as threatened.
Wild pacific salmon have disappeared from almost 40 percent of their historic range in the northwest, and populations are down more than 90 percent in the Columbia River system. Chinook salmon have been listed under the Endangered Species Act, and several populations of coho are listed as threatened.
"Wild trout and salmon populations are already stressed by factors such as loss of habitat to development, competition with hatchery fish, invasive exotic species, and more. Now we must add climate change to the list of challenges they face," said Mark Shaffer, senior vice president for programs at Defenders of Wildlife. "If we don't address the cumulative impact of all these factors, we will see more of these populations switching from a recreational resource to being listed as threatened or endangered."
A report released this week by the U.S. Fish and Wildlife Service showed that 34 million recreational anglers went fishing in 2001, spending an average of 16 days and more than $1,000 on their sport or hobby. Anglers spent more than $35 billion on trips, equipment and other fishing items last year.
Many of the species covered by the study are also regional icons with cultural significance that rivals their recreational and economic value.
"This report warns us not only of losses to natural resources and family traditions, but also that the future of jobs that depend on healthy recreation are at risk," said Steve Moyer, vice president for conservation for the group Trout Unlimited. "Our grandchildren and their families may not have the pleasure of fishing for these magnificent creatures in many areas that we know and love today. Billions of dollars per year spent on recreational fishing equipment, guides and resorts may be hit too."
The study covers direct thermal effects on the stream habitats only, and does not examine indirect impacts of global warming such as changes in precipitation or evaporation. It does not include Alaska or Hawaii. Nor does it look at global warming on ocean environments where salmon and some trout species spend much of their lives.
"For many of us, cold water fisheries are one of the things that make life worth living. This data rich report asks some sobering questions about yet another area of our lives that may be significantly impacted by global warming," said Paul Hansen, executive director of the Izaak Walton League of America. "Many of the early actions needed to address this problem are very cost effective, even before we consider the impact on trout and salmon, and can be taken immediately."
Although natural causes may be playing a role in global warming, most experts believe heat trapping pollution from cars, power plants and other sources is the main culprit. These emissions collect in the atmosphere, preventing excess heat from escaping, and increasing temperatures on the ground.
The Intergovernmental Panel on Climate Change (IPCC) - a 2,500 member body representing international scientific consensus on the subject - concluded in 1995 and again in 2001 that human made pollution from fossil fuel combustion and deforestation is driving temperature increases.
Asked by President George W. Bush to review the panel's scientific findings, the National Academy of Sciences reconfirmed in June 2001 that heat trapping pollution is causing both surface and ocean temperatures to rise. The IPCC estimates temperatures will rise five to 10°F over the next century.
Despite the evidence, President Bush has withdrawn the U.S. from one of the most powerful tools available to combat global warming: the international Kyoto Protocol, which would require mandatory reductions of greenhouse gas emissions. Several other nations, including the entire European Union, have voted to ratify the agreement before the World Summit on Sustainable Development in Johannesburg this September.
Meanwhile, the U.S. Congress is currently considering legislation called the Clean Power Act that would require power companies to reduce carbon dioxide pollution, along with several other pollutants that contribute to the decline of fish populations.
The full report on the effects of warming streams on salmon and trout is available at: http://www.defenders.org/publications/fishreport.pdf
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