Water rushes over large boulders in a river lined by evergreens and trees yellow with fall color
Bad River: The Bad River starts at Caroline Lake, where the forest filters the clean, clear water that contributes to the high water quality of the Kakagon/Bad River Sloughs downstream. © Mario Quintana

Stories in Wisconsin

Shaping Future Forests at Caroline Lake

We adapted our forest management at Caroline Lake Preserve to keep these Great Lakes forests healthy and productive in the face of climate change.

Home to migratory warblers, wolves and the rare pine martin, the Caroline Lake Preserve in Iron County is a great place to experience the serenity and beauty of the forests and wild lakes that epitomize Wisconsin’s Northwoods.

The forests at Caroline Lake are located in the Great Lakes basin and are part of one of the largest remaining swaths of unbroken hardwood forest in the United States.

Like other Northwoods forests, however, the forests at Caroline Lake face an uncertain future due to an increasing trend toward hotter, drier summers, unpredictable storm events and milder winters.

We recently caught up with Matt Dallman, Wisconsin Deputy State Director, to see how The Nature Conservancy is changing its forest management at Caroline Lake to help keep the forests healthy and productive for generations to come as conditions change in the Northwoods.

Nature.org:

Tell us about the Caroline Lake Preserve. Why is it special?

Matt Dallman:

Despite the logging in Wisconsin’s Northwoods from the late 1800s to the 1930s, the forest at Caroline Lake still has all the tree species it once did—hemlock, sugar maple, basswood and large white cedars to name a few. But the forest has changed. The larger, older trees are missing, and the way the tree species are distributed across the forest is different. There is also an increasing abundance of red oak on the property.

The forest provides important habitat for a diversity of birds, especially neotropical migrants like the black-throated blue warbler, northern parula and Canada warbler.

And perhaps, most importantly, the Bad River starts at Caroline Lake, where the forest filters the clean, clear water that contributes to the high water quality of the Kakagon/Bad River Sloughs —16,000 acres of wild rice, wetlands, streams and open water along the southern shore of Lake Superior.

Nature.org:

What are climate scientists telling us the future might look like in the Northwoods?

Matt Dallman:

The Wisconsin Initiative on Climate Change Impacts (WICCI), which has done extensive research to understand how Wisconsin’s climate has already changed and how it might change in the future, anticipates an increasing trend toward warmer summers, more severe and unpredictable weather, and milder winters in the Northwoods in the future.

Warmer temperatures in winter could mean less lake-effect snow, leading to increased potential for deer browsing on vegetation. Conditions in the future could be less hospitable to some tree species, like aspen, paper birch, black spruce and balsam fir, while favoring others like red oak.

An American pine marten perches in the branches of a moss-covered pine tree
Pine Marten: An American pine marten perches in the branches of a tree. © Bill Silliker Jr.

Nature.org:

So, are you saying there could be winners and losers as the climate changes in northern Wisconsin?

Matt Dallman:

We think it’s likely that some tree species will fare better in the future than others—red oaks, for example. Right now, they occur at Caroline Lake Preserve but in smaller numbers. In a warmer, periodically drier future, they could become a more dominant part of the forest, while the populations of other species like sugar maple, yellow birch and aspen—which dominate the forest today—could decline.

Another example is the rare pine marten, which needs good snow cover to survive. In the future, if there is more rain than snow, which is possible, then the fisher (another member of the weasel family that directly competes with pine martens) could gain a competitive edge, and we could lose pine martens in northern Wisconsin.

Nature.org:

What is TNC doing to help the forests at Caroline Lake adapt to climate change?

Matt Dallman:

We are working with the U.S. Forest Service’s Northern Institute of Applied Climate Science (NIACS), the Wisconsin Department of Natural Resources (WDNR), and other partners to use the best available climate science to modify our forest management at Caroline Lake in a way that we believe will help keep the forests healthy and productive in the anticipated warmer, less predictable future.

Our goal is to create a more diverse forest in terms of tree species, age and structure, because a more diverse forest will be more resilient to changing conditions, including climate. So, we’re not just managing for a few desirable tree species, young or old trees, big or little trees, but a mix of all types. We will continue to manage for the hemlock and yellow birch that characterize this northern hemlock-hardwood forest, but we’ll also manage for species like red oak that we believe will do better in a warmer future.

Forest manager Jon Fosgitt holds a measuring tape wrapped around the trunk of a small tree and reads the measurement.
Jon Fosgitt: Forest manager Jon Fosgitt measures the trunk of a tree in the Two Hearted Forest Reserve in Michigan’s Upper Peninsula. © Drew Kelly

Nature.org:

What have you done so far?

Matt Dallman:

With our partners, we completed a forest inventory of the Caroline Lake Preserve, and then we used a computer model to evaluate the risks the forest could face in the future under different climate scenarios. Using that information, we developed a variety of actions we are taking to enhance forest resilience under a wide range of future climate conditions.

Our forest consultant, Jon Fosgitt with Compass Land Consultants, is working with us to incorporate selected actions from this list into a revised plan that will guide our forest management in the future. The management actions we take will vary in different parts of the forest, and in some places, we may choose to take no action.

For example, our standard management in the northern hardwoods has been removing the poorest quality trees in the stand. This usually entails removing single trees, leaving a mostly shaded forest. As we look to promote a diversity of tree species and especially oak, climate-informed forestry suggests we create larger gaps in the forest canopy, increasing sunlight to the forest floor and benefiting species that thrive in full sun.

Nature.org:

How will TNC know if it is successful and how long will it take?

Matt Dallman:

Before we started this process, we gathered baseline data on the composition and condition of the forest. And we have established permanent forest inventory plots so we can monitor change over time and evaluate if we are achieving our goals.

Change won’t happen overnight, however, because trees grow on generational time, not human time. And we’re not taking drastic steps. We’re using traditional forestry methods but looking 50 to 100 years ahead so we can slowly move the forest at Caroline Lake from its current composition to one that can withstand a range of potential future conditions from warm and dry to wet and cool.

Nature.org:

Will the work TNC is doing at Caroline Lake be used elsewhere?

Matt Dallman:

Our Caroline Lake project is part of a larger effort to help forest managers take the available information on forest vulnerability to climate change and use it to meet their specific, on-the-ground forest management needs. Caroline Lake is one of several demonstration projects that provide real-world examples for forest managers of how climate change information has been integrated into forest management.

We are sharing information about the Caroline Lake project with forest managers in Wisconsin, the Great Lakes region and beyond in The Journal of Forestry and other forestry publications and through presentations at numerous meetings with groups, including the Society of American Foresters and the Great Lakes Timber Professionals. The Silviculture Guidance Team for the Wisconsin Department of Natural Resources visited the property and discussed the project as part of a field tour focused on climate change impacts. With the US Forest Service we have published the Climate Change Field Guide for Northern Wisconsin Forests: Site-level considerations and adaptation. (Download the field guide here.)

Longer term, we are working with NIACS and the WDNR to incorporate a climate risk assessment application into current forest management software. If forest managers can click a “climate risk” button that produces a map of stands that are at risk of decline or regeneration failure due to climate impacts, then we believe they will be better able to look beyond the next harvest and promote more climate resilient tree species.

You can find a summary of the Caroline Lake adaptation demonstration project on the NIACS Climate Change Response Framework website.