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Minnesota's forests are slow adapting to climate change. These scientists are giving trees a head start

Innovative research in the Superior National Forest may serve as a template for forest resiliency nation-wide.

Minnesota's forests are slow adapting to climate change. These scientists are giving trees a head start
(Andi Lynn Arnold for Project Optimist)

Climate change is happening remarkably fast in Minnesota's northeastern region called the Arrowhead, threatening the trees and other species that define its coniferous forest. Rapidly warming temperatures have prompted foresters, scientists, community representatives and tribal leaders to launch an ambitious plan to save the iconic trees of Superior National Forest (SNF).

The Superior National Forest Assisted Migration Plan directs foresters to retrieve seeds of native species from the southern edge of their range, propagate those seeds into one-year-old seedlings and get them into the more northerly SNF dirt, where the climate is predicted to be similar to the seedlings’ natal home in just a few years.

“Trees don’t have legs,” said Katie Frerker, who was the ecologist and climate change coordinator for SNF through mid-July and now works for the Northern Institute of Applied Climate Science. “ Assisted migration gives the trees the ability to keep up."

Frerker said trees migrate on their own about two kilometers a decade in good conditions.

"Right now, those trees would have to migrate 20 to 50 kilometers a decade to keep up with the warming climate,” she said.

Assisted migration is not without controversy, but in many ways it’s nothing new. People have carried seeds for millennia, as have animals and birds. This kind of migration, however, uses climate data and research to choose which seeds to move within the 3-million-acre forest, in hopes of retaining a forest similar to what we see now.

This is the first assisted migration program of its kind for the National Forest system, although several national forests have been experimenting in smaller ways. The individualized plan for SNF, to be finalized by late summer, is also serving as a template to be fast-tracked to Washington and subsequently made available to all national forest managers within the year. SNF was chosen to go first, out of all the national forests, as the challenges facing this forest are immediate and well-documented.

The plan is notable in another way. Tribal leaders, whose cultural and spiritual roots are embedded in the forest itself, brought unique concerns and considerations to the table, significantly shaping the three years of discussion leading to the final plan. This information exchange between tribes and the United States Forest Service represents a new effort to bring a diversity of voices from the forest forward.

The end product, a plan that is both forward-thinking and traditional, is a unique experiment in a time of unknowns.

One type of assisted migration called "assisted species migration" involves moving a species beyond its historic range and beyond the area of natural seed dispersal. (Courtesy of the U.S. Forest Service)

The race for answers

The SNF is home to roughly 325,000 Minnesotans, and intrinsically drives the core northern economies of mining, logging and tourism. It reaches into the Boundary Waters Canoe Area Wilderness and holds much of the rugged North Shore within its boundaries. Postcard picture clear lakes, tall pines and rocky outcroppings shape our identity as Minnesotans.

It’s a forest scientists say is disappearing more quickly than previously understood. The boreal forest, a high-latitude biome that barely dips south from Canada into northeastern Minnesota, is particularly at risk.

The Northeastern Minnesota climate is changing faster than in other parts of the country, at what the Washington Post estimated at twice the global average.

In northern Minnesota, daily average minimum temperatures, December to February, have increased 7.3 degrees from 1895 to 2021. The frequency of -35° F readings in northern Minnesota has fallen by up to 90%.

Dr. Julie Etterson, biology professor at the University of Minnesota-Duluth and director of Institute on the Environment-Duluth, studies the evolution of plants and trees in this region.

“The forest is not doing well. The rate of adaptation is too slow,” Etterson said. “Trees are not regenerating. Even the trees that traditionally do well, such as aspen, are affected.”

In a 2020 study, Etterson and fellow researchers demonstrated that seedlings sourced from southern Minnesota flourished in northerly zones, with better survival and growth rates, as compared to seedlings sourced from the north. In short, natural selection favored seedlings that expressed traits characteristic of trees sourced from more southerly forests, where the climate compares to the changes felt in Northeastern Minnesota. Her work in the boreal forest was an instrumental influence on the decision to pursue assisted migration in SNF.

(Andi Lynn Arnold for Project Optimist)

Lee Frelich is watching closely and has been for decades. As director of the University of Minnesota’s Center for Forest Ecology, Frelich is a leading expert on forestry, frequently called upon to testify to the Legislature and occasionally Congress. Frelich speaks clearly and with great concern, predicting that by 2070, SNF will “look like Nebraska.”

“If warming trends continue, and there’s no reason to think they won’t,” he said, “we will have a very different landscape.”

Frelich, nonetheless, is not without hope. Trees sequester carbon, and the more trees planted, the better.

“If we have a reduced emission scenario, and we plant millions of trees, Minnesota won’t change so dramatically. It’s still going to warm up, and we’ll have to make some adjustments, but it could be done,” he said. “These initiatives are like betting on what’s good.”

Etterson and her students are expanding their studies to determine how far seeds of certain species can be moved, exploring the boundaries of adaptation and migration. “We are also designing studies to determine whether seedlings will be more successful if they are planted with inoculated soil,” Etterson said. “Trees have relationships with soil microorganisms, particularly mycorrhizal material. We know there are webs of life, but the question is whether it’s the right one for any particular set of trees.”

(Andi Lynn Arnold for Project Optimist)

Seeing the forest for its trees

Hannah Panci, a climate change scientist, speaks of the forest in terms that reflect both her training in biology and her growing understanding of Native views. Panci was part of the 100-person Superior National Forest advisory group that created the assisted migration plan. She attended as a scientist from the Great Lakes Indian Fish & Wildlife Commission, which represents the interests of 11 Ojibwe tribes’ treaty-reserved hunting, fishing and gathering rights.

“The way the tribes look at the forest is very different from seeing it as a crop with a monetary value,” Panci said. “From a tribal perspective, trees are beings that have connections to other beings in the forest and to beings in the tribes. Trees are beings that have connections to other beings in the forest and have their own agency.”

How climate change affects the forest may depend on who is viewing the change. And assisting the tree nation, as Panci said, depends very much on how you view the forest.

“Change is predicted to happen really quickly, and we have models to show us where these beings might be in the future,” Panci said. “There’s much to be learned from observing and seeing how the beings withstand changes. There’s a lot we don’t know.”

Katie Frerker (Courtesy of Katie Frerker)

Frerker, recent lead of the Superior National Forest’s assisted migration plan, said this Native viewpoint lent itself to a more conservative approach, in which only the species native to SNF will be included, as opposed to introducing species not native to SNF. Importantly, the assisted migration program will work within the current Forest Management Plan, serving the same management objectives.

“The aim we all share is to keep the forest forested. One thing we know we can do right now is get our seed from a location that is similar to what we are seeing,” Frerker said. “Working across fields of study, and attempting to gain perspective from all of the people who live and work and recreate in this forest [is] what we’re after in helping these trees make it.”

This article was originally published in the Project Optimist newsletter on Aug. 2, 2023.

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