Northern Minnesota tree plantings anticipate a warming climate
By Stephanie Hemphill / Minnesota Public Radio
Superior National Forest -- A few miles from Lake Superior, near the Caribou Trail, members of a tree-planting crew seem to hit rock wherever they aim their long-bladed hoedads.
"We're just trying to find soil in between all these nice rocks, where the roots of these little oak trees are going to be able to grow down and survive," crew leader Kira Reoh said.
Reoh's crew is planting little red oaks on land in the Superior National Forest that has long largely supported the spruce, pine, birch and aspen trees typical to the northlands. They're planting trees that should do well as the climate continues to change in Minnesota's north woods.
As growing seasons become longer and winters are warmer, researchers are seeing more southerly tree species creeping northward into the boreal forest. They're worried about what climate change could mean for the existing ecosystem, and they are predicting big changes that could make the Boundary Waters Canoe Area Wilderness more like southern Minnesota or Iowa by the end of the century.
Planting such trees slightly outside of their current range may help ensure that the forest can continue to provide the like clean water, wildlife habitat, wood products and recreational opportunities that Minnesotans have come to depend on, said Mark White, a forest ecologist for the Nature Conservancy, an environmental group that is spearheading the experiment.
"If we just let things go, there's the possibility they'll start to lose those functions as we have these boreal species decreasing and we don't have other things that can take their place," White said. "We're in danger of losing some of those things that we value from forests."
White and his team are using seedlings from areas west and south of the northlands to create greater genetic diversity. In the next two years, they'll plant 60,000 trees during the experiment, funded by the Doris Duke Foundation and the Minnesota Outdoor Heritage Fund. Over the next few years, the team will measure the survival and growth of the red oaks and share the results with other natural resource managers.
Minnesota is at high risk for climate-related changes partly because it marks the border of three major natural systems: tallgrass prairie, eastern forest and coniferous forest. The transition zones are expected to see huge changes as the climate warms and rainfall becomes more erratic. That could spark a suite of other dangers, among them more fires, insect pests, diseases, and invasive weeds -- all of which put natural systems at greater risk.
In the last couple of years, officials at the state Department of Natural Resources have begun factoring climate change into their forest planning. The agency will watch the Nature Conservancy experiment with great interest, said DNR forester Paul Dubuque, a member of a climate adaptation team.
Meanwhile, the agency is taking a more cautious approach.
"If we were to retool our nurseries to produce, say, more red oak species, and we made major efforts to plant red oak in areas where we haven't normally seen it develop, there's some uncertainty to that," Dubuque said. "There's a bit of a risk to that."
If the trees don't thrive, he said, the DNR would have lost its investment of time and resources.
"However, I would say that a lot of our forest management plans really try to get at managing the forest for a mixed composition, making them more resilient to these potential changes in climate," Dubuque said.
Toward that end, Dubuque and his team developed a list of 40 different strategies to deal with climate change, which they will present to foresters around the state later this summer. They also added climate change factors to a tree planting guide that foresters use to help them decide what trees to plant where.
The greater variety of trees on a landscape, they say, the more likely that some of them will benefit from climate change and will help create a healthy forest.
The DNR relies on the forest industry to help keep forests healthy. Most logging is done in winter, and winters are getting shorter. Experts agree the industry will need to adapt and find ways to use the trees that do well as the climate warms.
Some hope that biomass -- burning trees for heat or electricity -- will be one answer.
Although many people likely would find if difficult to picture a Boundary Waters Wilderness that looks like southern Minnesota, such changes are part of the broad sweep of nature, said Lee Frelich, director of the University of Minnesota's Center for Forest Ecology. He said over thousands of years the boreal forest in northern Minnesota has moved from Hudson's Bay to Tennessee and back a dozen times.
"It resides in Minnesota for a few thousand years each way as it migrates north and south, and we take that to be normal," he said. "But actually northern Minnesota has been under a mile of ice much more often than it's had boreal forest. It's also had prairie. So this has happened before and it will happen again."
The difference now is the speed of the change and the frequency of extreme weather events such as the 1999 blowdown, when high winds toppled thousands of trees. Some models predict more intense changes will come around the middle of this century, 40 to 50 years from now.
Frelich said the best thing to do would be to cut carbon emissions to reduce the degree of climate change. He said it will be a lot easier for everyone -- trees and forests and people -- to adapt to a warmer climate than to a hotter one.