Feeling Minnesota, Looking Nebraska

The latest models for global climate change predict a doubling of carbon dioxide, the primary greenhouse gas, in the atmosphere by 2100, to be accompanied by an increase of 2 to 10 degrees in average temperatures globally. According to Peter Ciborowski of the Minnesota Pollution Control Agency, Minnesota’s temperature increase could be significantly more than the change in the global average. One big question is how much temperatures will rise here (and what time of year will they increase). The second question is very much related to the first: Will we be a warm and wet climate closer to that of Ohio, or a warm and dry climate like Nebraska?

In the Great Lakes, a 1997 study predicted, a warmer climate caused by a doubling of carbon dioxide in the atmosphere could lead to a drop in lake levels of 6.5 to 8 feet. That same study predicted differential drying effects on smaller lakes and streams, but predicted significant warming at all lake depths, from two degrees at the surface to 14 degrees at greater depths. John Tester says a sample of things to come might lie in the droughts Minnesota suffered in the 1930s, where many shrinking lakes in the state were surrounded by vast mud flats.

The modeling of global warming relies on many complicated factors that will keep graduate students busy for years to come in fields like climatology, ecology, hydrology, and botany. Soil types, for example, will likely have a profound effect on landscape. John Pastor and his colleagues studied the sandy forest soils around the Boundary Waters, north of Duluth and around Brainerd. From his research, he predicts that with a two-degree temperature increase and boosted carbon dioxide levels, the pines, birch, and aspen would be replaced by brushland and oak savannah—a landscape characterized by open fields, smaller oaks, and stunted pines. In the heavier, clay-based soils that also dot the northern landscape, Pastor guesses that the maple and basswood forests of northern Wisconsin and Michigan’s Upper Peninsula will creep into northern Minnesota. Forest researcher Lee Frelich believes that if the climate dries out significantly, “Minnesota could end up being a state without much of any forests at all.”

Other scientists have studied whether or not trees will be able to “migrate” fast enough under rapid warming conditions. Instead of setting up new colonies in cooler, more northerly areas, they may not adapt to changing conditions fast enough and will possibly just die in place.

Julie Etterson has looked at similar issues affecting prairie plants. The Duluth biologist took partridge pea plants from Minnesota and planted them in areas of Kansas and Oklahoma, where the plant is also native. She found that the Minnesota species suffered an 84 percent reduction in seed output—a major indicator of plant fitness—in Kansas and a 94 percent decrease in Oklahoma. She also determined that if our prairie climate changed to that of either of the other states within 25 to 35 years, the plant would not be able to adapt quickly enough to the new climate through evolution. Because the prairie landscape is fragmented and dominated by farm fields, roads and towns, she believes that prairie preserve managers should begin moving plants gradually to more northern environments.

Of course, animals are profoundly affected by vegetation. Their range and habitat would be affected by climate change, too. The American Bird Conservation Society estimates that 36 bird species might exclude Minnesota in their summer range under global warming scenarios. The boreal chickadee, the evening grosbeak, 14 species of warblers, and several other north-woods species might spend their summers in the pines of Canada. Other birds may see their range increase to include bigger parts of the state, depending on what vegetation and food is available.

Waterfowl may face dire consequences under any extended drought that could accompany warming. The number of wetland potholes in the western part of the state, which are part of a vast network of duck breeding wetlands (“the continent’s duck factory”) that stretch into central Canada, may decrease. One South Dakota researcher predicts that if temperatures increase between 3.6 and 7 degrees, precipitation would have to increase 10 to 25 percent in order for wetlands to retain the water they currently hold. Another study projects that half of the potholes could dry up by 2060, and the duck population would experience a corresponding decimation.

The effect on animals is harder to predict, although some would head north like so many suburban cabin owners on a Friday afternoon. White tail deer, for example, range throughout the lower 48 states, although they tend to be smaller in hotter climates. Bears, too, are highly adaptable as long as forest areas are available. But boreal-forest animals such as the pine marten, fisher, and moose are sensitive to heat. They would likely migrate to cooler areas in Canada.

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