News

Warm wind blowing in big changes

Minnesota natural resources officials say global warming appears real to them. And they say a changing climate will have a major impact on the state's fish and wildlife.

By Doug Smith, Star Tribune

January 9, 2007

 

Ducks swim where anglers should be strolling. Deer browse northern forests frosted with just an inch or so of snow. Pheasants peck at food on a snow-free brown landscape.

Meanwhile, snowmobiles and cross-country skis gather dust, and their owners grumble. And anglers use extra caution traveling on some ice-covered lakes.

 

It's another weird winter in Minnesota. Mild temperatures and a lack of snow and ice have frustrated those who love winter sports. It's been 10 years since the state was smacked with a good old-fashioned winter of cold and snow.

 

Though some still question whether the string of mild winters is just a quirk of nature or temporary aberration, others, including leaders at the Department of Natural Resources, say they believe we're starting to see the beginnings of global warming caused by greenhouse gases. And the ramifications for the state's natural resources could go beyond significant changes to winter recreation. They say Minnesota's fish and wildlife are being affected now and will be affected in the years ahead -- both positively and negatively.

 

"Some species will prosper under a warmer climate, and some won't do as well," said Don Pereira, a senior research biologist at the DNR.

 

He and DNR colleagues say the evidence is compelling that serious climate change is occurring, and that temperatures are likely to continue warming for the next 50 years even if we reduce the greenhouse gases blamed for the phenomenon.

 

"I don't think there's any doubt about it," said Dave Schad, director of the DNR's Fish and Wildlife Division. The DNR asked Pereira to give a presentation on climate change to the 220 people attending the DNR's annual roundtable meeting in St. Cloud last weekend "to bring hunters and anglers into the debate," Schad said.

 

Everything from deer and pheasants to ducks and walleyes will be affected -- or already is.

 

Walleyes and tullibee

 

Pereira said some Minnesota lakes have experienced more frequent summer dieoffs of tullibees -- also called ciscos -- a cold-water species that serves as food for gamefish such as walleyes, northerns and lake trout. Tullibees die when the water gets too warm.

 

"It was a natural event that always happened in Minnesota, but now it's happening with increased frequency," Pereira said. Tullibee numbers in some lakes -- including Lake of the Woods, Winnibigoshish, Leech and Mille Lacs - have been declining for 20 years, he said.

 

"Which tells us that tullibees ... are in peril and may not persist into the future," Pereira said.

They are an important food for walleyes late in the year, he said. "Walleyes aren't going to die off because tullibees are gone, but their productivity is going to decline."

 

Pereira said walleye growth in southern Minnesota has been hurt by recent warm summers.

"It's getting too warm for them," he said. Walleyes in the Arrowhead region might actually benefit from the warming temperatures, Pereira said. But in other areas walleyes might lose their dominance to warm-water species, such as bass and panfish.

 

A warmer climate could spell trouble for lake trout, another cold-water species. "The future doesn't look very good at all for them," Pereira said. And stream trout need cold, clear water.

 

"Bass and panfish will prosper and expand, because they do better in warmer climates," he said.

All of this has implications for anglers and fisheries managers. For example, it would be fruitless to stock walleyes in a lake that is no longer hospitable to them.

 

Freeze-outs and ducks

 

Minnows, carp and other undesirable fish have fouled wetlands and shallow lakes used by waterfowl. Carp stir sediments and root up vegetation, causing degraded water. Cold temperatures and heavy snows normally "freeze out" these shallow waters, killing the undesirable fish and improving habitat.

"In the early 1980s, it was a rare year we didn't get a winterkill," said the DNR's Jack Wingate. "Now it's becoming the rare year we do get a winterkill."

 

Said Pereira: "We want those systems to produce ducks, not fish. If you're going to decrease the frequency of winterkill, it's going to make it more difficult to manage those systems to produce ducks."

An example is Swan Lake, one of the state's premier waterfowl lakes, where carp were discovered a couple of years ago. Officials lowered the water level in hopes of spurring a winter kill. But last winter was too mild, so officials used rotenone to kill the fish last fall. The cost: $160,000.

 

Deer, pheasants prospering

 

Whitetails have been thriving of late, aided by mild winters. The DNR keeps a "winter severity index" to gauge winter severity, and all but one winter in the past 10 have been rated "mild." None since 1996-97 have been "severe." The deer population, estimated at 1.3 million last fall, has flourished.

 

"We have a generation of hunters who have grown accustomed to high deer numbers," said Schad.

Wildlife mangers used to be able to count on occasional severe winters to help keep the deer population in check. With the recent mild winters, officials have liberalized deer hunting regulations to encourage higher harvests. That trend will continue as the DNR tries to reduce deer densities in some areas.

If the state's climate continues to warm, deer probably will prosper, forcing more management changes.

 

Meanwhile, pheasants also have been thriving with the mild winters, and Minnesota hunters have had banner seasons of late. Those could become the norm.

 

Other wildlife suffers

 

But other species could have problems with a warmer climate.

 

"We have a bunch of boreal forest species on the southern end of their range -- moose, lynx, fisher and martin," Schad said. "We may lose some of those species."

 

Already moose numbers have declined dramatically in northwestern Minnesota, and studies have said temperature changes might be responsible.

 

And climate change could change the makeup of our forests and farmlands, officials say.

Pereira said there is strong evidence that even if we reduce greenhouse emissions, the climate will continue to warm significantly over the next 30 to 40 years.

 

"We are going to have changes in the future that will make life more challenging. We need to get our act together," he said. " There's a lot we can do, and we need to move quickly to minimize the impacts if we care about what we are passing on to our kids and grandkids."

 

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