Climate change threatens river flows, trout streams, ducks

By Duane Hovorka

Climate change may be a global problem, but the risks to natural resources on the Great Plains were brought home at a Sportsmen’s Forum on Climate Change and Nebraska Fish and Wildlife, on Dec. 1, 2009, in Lincoln, Neb.

More than 50 people attended the forum, held on the East Campus of the University of Nebraska. They heard warnings from climate and wildlife experts about the potential impacts of climate change and the need to adopt sound adaptation conservation strategies. They heard about the science behind climate change projections, and about the specific risks to Platte River flows, duck populations, trout streams and migratory birds on the Great Plains.

“We have a lot of studies showing that the rise in greenhouse gases is related to the increase in temperatures,” said Rick Schneider of the Nebraska Game and Parks Commission. “According to average of several models, Nebraska is looking at a 6 degree F temperature rise by 2050 if we do nothing to address our carbon emissions.”

If that happens, “We’ll reach a global temperature in the next 50 to 100 years that most species haven’t seen before,” continued Schneider. “This is going to have an impact on species and ecosystems.”

Platte River flows

Dr. Bob Oglesby, a professor of climate modeling at the University of Nebraska’s School of Natural Resources, explained that Platte River flows depend on snow that falls in the Rocky Mountain headwaters of the North Platte and South Platte rivers in Wyoming and Colorado.

As the snow gradually melts, it provides base flows in the Platte that often last well into summer.

“Slow melting of the mountain snowpack is essential to maintaining flows in the Platte River,” said Dr. Oglesby. He noted that current climate models are global in scale and not well suited to predicting changes at a watershed scale. That makes it difficult to predict whether climate change will result in less or more rainfall in the Platte River Basin.

However, he said, “Every scenario includes significant warming and reduced snowmelt. Some more extreme scenarios suggest potentially catastrophic effects on the Platte River.”

“I’d be concerned,” continued Oglesby. “And I’d start planning now.”

Wetlands and waterfowl

Most of the ducks that fly through Nebraska every spring and fall are hatched in the shallow wetlands of the Prairie Pothole region, which stretches from southern Canada across Montana, North and South Dakota, and into western Minnesota and Iowa. Ducks Unlimited calls the Prairie Pothole region “North America’s Duck Factory,” because the region produces more than half of North America’s migratory ducks.

Ducks Unlimited also warns that in some regions 50 to 90 percent of the Prairie Pothole wetlands have been drained or destroyed, and it warns that unchecked climate change could make the situation worse.

Many of those ducks and geese use the Platte River or the shallow wetlands of Nebraska’s Rainwater Basin as a stopover in their annual migratory trek in the spring and fall —making this part of south-central Nebraska “America’s waterfowl hotel.”

“Climate change is another threat to sustaining wildlife populations at target levels,” said Andy Bishop of the Rainwater Basin Joint Venture, a partnership of conservation organizations and agencies that is working to restore and protect wetlands in the Rainwater Basin.

Bishop told the forum audience that Joint Venture partners are already building climate change scenarios into their planning and conservation decisions. “By restoring the ecological system we are hoping to build resiliency and thereby protect the wetlands of the Rainwater Basin.”

Research by Dr. Carter Johnson at South Dakota State University has highlighted the risks that climate change poses to North America’s duck populations. The research he and colleagues have done shows that even modest increases in average temperature could seriously degrade half or more of the Prairie Pothole wetlands, especially those in the western part of the region.

According to Dr. Johnson’s studies, “Only a substantial increase in precipitation would counterbalance the effects of a warmer climate.” In addition, “The most productive wetlands, currently centrally located in the Prairie Pothole Region, may become marginally productive in a warmer, drier future climate.”

Too warm for trout?

Dr. Craig Allen, director of the Nebraska Cooperative Fish & Wildlife Research Unit, explained the importance of resilience in ecological systems, and talked about the importance of tipping points. He noted that gradual changes, like a gradual increase in air temperature, can lead to sudden, nonlinear changes.

“Lakes can be clear or algae-dominated. That flip from a clear state to algae-dominated can be quite sudden, usually as a result of the slow input of increasing nutrients, like phosphorus,” said Dr. Allen. He said that once the flip occurs, it can be very difficult to reverse the process —another reason to be concerned about gradually rising global temperatures.

Aquatic biologists say an example of that is the change from a cold-water stream to a warm-water stream. When the summer temperature of a stream stays below about 72 degrees F, the stream can support cold-water fish like trout. When maximum summer temperatures rise above 72 degrees F, species like trout can no longer survive, and catfish, bass and sunfish take over.

Nebraska has a number of trout streams in northern and western Nebraska, where average summer air temperatures are now around 71 or 72 degrees F. Climate models suggest average summer air temperatures in that region could reach 76 to 78 degrees F in the next 40 years, and that could be enough to raise stream water temperatures enough to eliminate or substantially reduce available trout habitat.

The Environmental Protection Agency estimates that Nebraska will lose 50 to 100 percent of its current trout stream habitat if climate change continues unchecked. According to Frank Rahel at the University of Wyoming, even mountain states like Colorado and Wyoming are likely to lose trout habitat as a result of warming stream temperatures. The change would also result in increased extinction rates of cold-water fish species confined to smaller, more isolated habitat areas higher in the mountains.

Dr. T. J. Fontaine of the Nebraska Cooperative Fish and Wildlife Research Unit spoke about the adjustments in the timing of annual bird migrations caused by the changes in plant behavior due to the changing climate.

“The world is warming,” Dr. Fontaine said. “One of the major effects is change in seasonality—earlier springs and later falls. Many plants are flowering earlier, especially in the more northern latitudes, and migrating birds are adjusting their movements because of it.”

Those changes could disrupt the predictability of food resources for migrating birds, according to Dr. Fontaine.

The forum highlighted the need to begin to take action now to reduce greenhouse gases globally and to put in place adaptation strategies.

“We have a very short time, a couple of decades, to turn things around before they really get out of hand,” said Rick Schneider.

Sponsors of the Sportsmen Forum were the National Wildlife Federation, the Nebraska Wildlife Federation, Audubon Nebraska, Ducks Unlimited, the Izaak Walton League, Nebraska League of Conservation Voters, the Rainwater Basin Joint Venture, the Nebraska Cooperative Fish and Wildlife Research Unit and the Nebraska Game and Parks Commission.

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