SUPERIOR NATIONAL FOREST— Forest planners here are taking steps now to help the national forest adapt to the changing climate through a new pilot project that includes a wide range of partners. …
SUPERIOR NATIONAL FOREST— Forest planners here are taking steps now to help the national forest adapt to the changing climate through a new pilot project that includes a wide range of partners.
It’s known as an Assisted Migration Pilot Plan and it’s the first of its kind on a U.S. national forest. Yet the 3.9 million-acre Superior National Forest sits at a unique location at the transition zone at the southern edge of the boreal forest, which means it could see some of the most dramatic forest changes of any national forest over the next several decades as the climate continues to warm.
Modeling on the impact of climate change has consistently projected that boreal tree species that currently dominate the Superior National Forest, such as balsam fir, white and black spruce, paper birch, and quaking aspen will decline. What will take their place is the key question being asked by forest planners on the Superior. According to the forest service, the new assisted migration pilot plan is an effort to ensure that its efforts are scientifically-based and implemented in a consistent and coordinated manner on the national forest.
As part of their ongoing reforestation efforts, forest planners here oversee the planting of about 1.2 million trees annually, which is enough to affect changes in the future makeup of the forest simply by changing where some of its seed stock comes from.
“Our policy has long been that local sources [of seed] are best for reforesting work,” said Kyle Stover, chief forester on the Tofte District. But as part of its new assisted migration plan, foresters are beginning to seek seed sources from more southerly locations, where the genetic makeup of the seeds may be more amenable to warmer conditions.
For the next 15 years or so, that means seed sources from places like Carlton and Pine counties in Minnesota, or Douglas County in northwestern Wisconsin. After 2040, forest planners are likely to look even further south, such as central Wisconsin, for seed sources for the species of trees, such as red and white pine, paper birch, and aspen, found in both locations.
The change in seed sourcing isn’t intended to fully replace local seed sources, which will still remain on the landscape for decades to come. Rather, said Stover, “it’s intended to inject those more southerly genetics into the population.” Natural selection, which will be heavily influenced by climatic changes, will help determine which genetics survive in the longer term.
But shifting seed sourcing to more southerly locations is just one tool in the toolbox when it comes to assisted migration, notes Stover. Forest planners are also beginning to look at favoring several tree species that are currently on the northern fringes of their range on the Superior. That’s species such as white and bur oak, basswood, and silver maple, all of which are currently uncommon to rare on the Superior but are much more common just to the south.
These species could begin to become components in future tree planting operations on the Superior, which would help to gradually expand their ranges to the north as the climate warms. While trees can naturally expand their ranges over time in response to climate fluctuations, the warming as a result of the buildup of carbon in the atmosphere from the burning of fossil fuels is happening on a much shorter time scale than natural fluctuations seen in the past, making it less likely that trees will be able move across the landscape quickly enough.
For now, forest planners on the Superior are not proposing the most dramatic method of assisted migration, planting tree species not currently found in the region. “We’re not looking at that,” said Stover.
The assisted migration pilot plan has involved participation from two dozen distinct entities, including the Bois Forte, Fond du Lac, and Grand Portage Ojibwe bands, as well as other tribal entities, such as the 1854 Treaty Authority and the Great Lakes Indian Fish and Wildlife Commission.
The Chippewa, Ottawa, and Chequamegon-Nicolet national forests as well as other research arms of the forest service, along with Departments of Natural Resources from Minnesota, Michigan, and Wisconsin, timber industry groups, the University of Minnesota, and the Nature Conservancy, were all involved in the development of the plan.
“During the development of the plan, it has been fully demonstrated that a cross-disciplinary team is crucial,” says Katie Frerker, a climate adaptation specialist who has spearheaded much of the work. “We have over 20 organizations and over 100 individuals involved on our voluntary team. The integration of scientific, social, operational, and cultural considerations and discussion has been amazing.”
The partnerships will also assist staff of the Superior to access seed sources that they normally would have gathered locally. In the future, the Superior could be relying on national forests or tribal entities in places like northern Wisconsin, or the DNR central portions of Minnesota, for seeds from more southerly locations.
Risks vs benefits
Officials on the Superior acknowledge that their plan does pose some risks. Many of the changes they’re seeking to implement are based on climatic projections decades in the future and while those projections are becoming more accurate as time goes on, future climatic conditions could be impacted by other factors. “There certainly are risks,” acknowledged Stover. “And that’s amplified by the fact that trees are relatively long-lived. The climate could be much different 60-80 years down the road.
Bringing seeds or seedlings from outside the forest also heightens the risk of new diseases or insects. “Moving seeds can also introduce invasives,” said Stover.
Yet, there are risks in doing nothing as well. “It’s a matter of weighing the risks with the benefits,” said Stover. “For a silviculturist like me the objective is to plant trees that are best adapted to the site.”
Determining that in an era of rapid climate change makes that determination a bigger challenge than ever.