by evan larson

22 Minnesota Conservation Volunteer

March–April 2017 23

Wilderness is a poignant word that conjures up images of sweep-ing tundra, rugged mountains, and primeval forests broken only by lakes and winding rivers. The common feature shared by these images is the absence of human influence. This perspective was codified in the 1964 federal Wilderness Act, which defined wilderness as land “untrammeled by man, where man himself is a visitor who does not remain.”

What would it mean if landscapes we now consider wilderness were, at least in part, the legacies of human activity?

As an associate professor of geography at the University of Wisconsin–Platteville and a dendrochronologist, or tree-ring scientist, I am pursuing

Tom Wilding, a researcher at the University of Wisconsin–Platteville, takes notes about a scarred 300-year-old red pine near Lac La Croix in the Boundary Waters Canoe Area Wilderness.

By Evan Larson

Examining tree rings,

researchers reconsider the

history of human influence in

the Boundary Waters.

Wilderness?What Is

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answers to such questions. Over the past five years, I have collaborated with professor Kurt Kipfmueller and research specialist Lane Johnson from the University of Minnesota, as well as students from both of our institutions,

on research to seek a more complete and nu-anced understanding of wilderness. Funded by the National Science Foundation, this re-search may help guide the management of the Boundary Waters Canoe Area Wilder-ness—an iconic Minnesota landscape—by considering the role of people in its history.

My own perspective on wilderness in the BWCAW was transformed on day four of a late August trip to Lac La Croix, a massive island-studded lake along the border of the United States and Canada. The winds had picked up and the water was growing choppy as my research crew and I neared a site that Johnson had urged me to visit. We paddled around a small point, spotted a landing, and

Lac La Croix (above) has been used as a paddling route for centuries. Here researchers have found red pines bearing peel scars (below left) made by Ojibwe people to release resin used for sealing birch-bark canoes. A peel scar on a dead red pine (center) shows ancient ax marks and unharvested resin. Large living pines (right) show evidence of at least eight low-severity fires. Now fire-free for more than a century, these pine stands are vulnerable to the next fire.

pulled up our canoes in the shade of tower-ing pines. The landing was directly along the Border Route, once a primary fur-trade cor-ridor from Lake Superior to Rainy Lake.

The trees at this site had stories to tell. Near-by, the trunk of a fire-scarred, wind-thrown red pine displayed a long, vertical wound. Upon closer inspection, marks from an ax were evident, but barely, as centuries of heal-ing wood curled over the wound. The injury was intentional. At one time, this injury ran thick with resin. When combined with wood ash and animal fat, this resin created the gum used to seal the seams of birch-bark canoes. Scanning the forest, we noted that nearly every large red pine within sight bore a similar scar.

By examining annual growth rings in core samples taken from tree trunks, we found that many pines at this site were more than 250 years old. Distinct injuries recorded within their rings denoted the passage of multiple low-severity surface fires that dam-aged but did not kill many of these trees. In all, 16 fires burned here between 1660 and 1909, after which fires abruptly ceased.

Lightning certainly caused wildfires in the area, but the abundance of past fires seems too great to have been the product of light-

ning alone. And if lightning had been the cause, why were so many fires limited to this one stand?

In pursuit of answers to these questions, our research group has studied tree rings at 75 sites across the BWCAW. From these studies, we’ve developed an environmental narrative that helps us explore the meaning of wilderness.

Forest Sanctuary. Protected by the BWCA Wilderness Act of 1978, this million-plus-acre landscape harbors some of the last pine forests spared during the logging era. Since then, the BWCAW has become a vital natu-ral laboratory for scientists to understand the dynamics of northern ecosystems. With more than 150,000 visitors each year, the area has also become an integral part of many Minnesotans’ cultural identity through out-door adventures and the search for wilder-ness experience.

Clear waters and deep forests convey a sense of the primeval, yet this landscape has a rich human history that spans thousands of years. In the 1700s Ojibwe settled in the area following a westward migration over the pre-ceding decades. After the arrival of early Eu-ropean explorers during the 1700s and early


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1800s, the area became a hub of trade among the Ojibwe and French-Canadian voyageurs. The journals of explorers and voyageurs in-clude numerous mentions of trade relation-ships and locations of Ojibwe settlements.

Oral traditions and ethnographic research

tell of the Ojibwe people using fire to clear en-campments and trails and to promote plants such as blueberries, a highly valued food that grows vigorously on recently burned land. The intensity of land use varied from place to place, depending on local conditions and

This map shows where visitors to the Boundary Waters Canoe Area Wilderness can expect to encounter old-growth forest that is at least 120 years old and predates 19th- and 20th-century logging. In other areas they will find second-growth forest, some of which has been disturbed by more recent fires or wind events, including the 1999 blowdown. Before European settlers arrived in the region, Ojibwe people selectively set smaller, more frequent fires to clear land for encampments and trails and to promote growth of beneficial plants. This also promoted the growth of scenic stands of large pines. Created by University of Minnesota researcher Lane Johnson, the map is based on information from Miron “Bud” Heinselman, the U.S. Forest Service, and the Minnesota Department of Natural Resources.

Remnant Old-Growth Forest and Area Burned Since 1919 in the BWCAW


proximity to travel routes, resources, and settlements, yet people were clearly a part of the landscape.

Working with historical documents and the advice of U.S. Department of Agriculture For-est Service archaeologists, our research team identified red pine stands on and off the his-toric Border Route. At each site we used tree rings to reconstruct historical patterns of fire.

Our work builds on the groundbreaking research of Miron “Bud” Heinselman, a pre-eminent scientist and strong advocate for the BWCAW until his death in 1993. As a U.S. Forest Service researcher during the 1960s

and 1970s, Heinselman documented the role of fire in Boundary Waters forests. To do so, he used the ages of trees established af-ter severe fires and fire scars recorded in the growth rings of living trees.

Heinselman’s research was fundamental to developing the field of fire ecology. He pioneered the concept of a “shifting forest mosaic” shaped by landscape-scale fires. Despite his remarkable efforts, questions re-mained. In a landmark 1973 publication, he wrote, “In the Boundary Waters, people were primarily an added source of ignitions until about 1910. … A relevant question, then, is M

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how much burning would have taken place prior to 1910 if only lightning ignitions had occurred? A direct answer is unobtainable.”

The rings of long-dead pines may now bring an answer within reach. Our research uses a technique known as crossdating, which provides us access to information hid-den from Heinselman. Through previous re-

search, we know that the amount of moisture available to red pine trees during the growing season influences the relative width of each annual growth ring. Wide rings correspond to wet summers, and narrow rings to dry ones. As weather and climate vary, uniform patterns emerge in the rings of trees across the region. Distinct as fingerprints, the pat-terns can be read to assign calendar dates to the rings of dead trees with absolute certain-ty. Through crossdating, we used fire scars in remnant stumps to produce a network of sites with fire history that spans the wilder-ness and tells a detailed story of fire activity over the last 400 years.

Clockwise from top left: A cross section from a tree at Upper Pauness Lake shows that the tree started growing in 1756 and has peel scars in 1802 and 1816. Ben Matthys and Liz Schneider use a crosscut saw to gather a sample. Chris Crawford (left) and Kurt Kipfmueller survey Little Saganaga Lake from a 2006 burn site.

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Cultural History. The fire patterns illustrat-ed by our data are stark. Fires were most com-mon along the Border Route. In some places, the open stands of red pine we see today expe-rienced fires every five to six years during the 1700s and 1800s—the period when fur-trade networks were expanding across the region. Our data make a strong case that many of these spectacular red pine stands are, in part, legacies of the region’s cultural history.

In The Boundary Waters Wilderness Eco-system, Heinselman stated that “old-growth red and white pine groves of the Boundary Waters reserves are among the most en-dangered forest communities of the entire Great Lakes region of the United States and Canada. They are an irreplaceable element in the biodiversity of the region.” Our data suggest that at least some of these pine stands took root and flourished in the presence of frequent surface fires, many of which were likely set by people. By burning away tree seedlings and underbrush, these fires created the open, parklike forest structure prized by people in the past and today.

The more complete understanding of BWCAW forests emerging from our work poses challenging questions for managing the nation’s most visited wilderness area,

particularly in an era of profound environ-mental changes.

How then does the legal definition of wil-derness square with stands of red pine that are quite possibly a product of historical land use? Should managers take a hands-off ap-proach based on the idea of “untrammeled wilderness”—even while once-open pine stands grow denser and more susceptible to conflagrations? The severe effects of the recent fires such as Pagami Creek, Ham Lake, and Cavity Lake, which reduced many groves of old-growth pines to ashes and charred snags, illustrate the likely outcome.

Alternatively, do we identify heritage stands of ancient pines that represent the confluence of human and ecological processes and then actively manage them with prescribed fire? The aim would be to increase their resilience to the impacts of severe wildfires, provide opportunities for future regeneration of red pine, and maintain a vital component of the region’s ecological diversity.

These are difficult questions that require

Lane Johnson (left) uses a borer to collect a core sample from a centuries-old red pine on Saganaga Lake. The author (right) labels a peel scar sample he’s collecting from a log near Lac La Croix.


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careful thought and reflection, but with the long absence of forest fires enabling a build-up of fuels, answers cannot wait long.

Wilderness Views. In his essay “The Loons of Lac la Croix,” Sigurd Olson evoked a long-ing for the deep connections between people and wilderness through his lyrical descrip-tions of pictographs on granite cliffs and a hill challenged by Ojibwe runners.

Olson wrote about a pine stand along the Border Route “as perfect as any we had seen” where a trapper’s cabin had “seemed a part

of that scene, its quiet serenity part of the tall, smooth trunks and the silences.” As research-ers, we have been to this stand and docu-mented peeled trees that tell of human land use in the 1790s and early 1800s. From the tree rings of charred stumps, we now know that fires passed through in 1739, 1757, 1764, 1867, 1875, 1892, and 1915. Fires stopped burning here as the traditional lifeways of the Ojibwe were constrained. The pines Ol-son refers to remain on the landscape today, though the forest around them is changing.

In the end, people decide the definition and designation of wilderness. Today, public land managers are charged with the difficult task of preserving the beauty, function, and biodiversity of wilderness areas in the face of changing climate conditions and increasing human use. A growing body of evidence sug-gests that active management that includes the use of prescribed fire can help maintain resilient forest communities. Wild places that were profoundly impacted by the actions of people in the past need not devalue the wil-derness concept. Rather, this knowledge can make them richer through tangible connec-tions to our human history.

The stands of ancient pines on Lac La Croix embody the ideal of wilderness, yet they have felt the tread of moccasins and boots on their roots for centuries. Recognizing the role of past human influences in creating these mag-nificent stands may help people learn how to be better stewards of wilderness today. nV

Left, from top: Lane Johnson documents a peel scar sample that still shows the resin Ojibwe people gathered from such scars. Dendrochronology, the study of tree rings, allows scientists to precisely date peel scar samples. Right: Without frequent fires, smaller conifers create “ladders” that will allow fire to climb to the canopy.

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by evan larson

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