For years wilderness preservationists and U.S. Forest Service staff who wanted to limit wilderness clashed over what was essentially a purity issue.

The Forest Service wilderness managers of the 1960s often opposed designating any area where the hand of man, except Indians, was obvious. The legal criteria specified by the 1964 Wilderness Act defined wilderness "as an area where the earth and its community of life are untrammeled by man, where man himself is a visitor who does not remain."

Changes made in the 1970s, especially the passage of the Eastern Wilderness Act, reduced the influence of the purity folks but didn’t eliminate the overall issue. The Forest Service removed old cabins and other signs of the miners and homesteaders who pioneered deep into what were designated in the the late 20th Century as federal wilderness.

Most of the wilderness in the United States has a deep and long human history that the authors of the Wilderness Act downplayed if not ignored. When Indians were considered, their own rich civilization was considered in tune with nature, natural in the eyes of the environmental thinkers of the time.

In fact scientists today recognize that Native American civilizations have had dramatic effects on the ecology of both North and South America. Those changed predated European settlement and only in the last two decades has this reality reached beyond academics.

But the discussion of wilderness has hardly caught up with these new historical works. One of wilderness thinkers who has addressed this issue is William Cronon, a historian at the University of Wisconsin. Cronon was the historian who first laid out the argument that wilderness is a human construct and that it is born out of the industrialized society it appears to reject.

He took a step further several years ago writing about one of my favorite places in the world, the Apostle Islands National Lakeshore in Wisconsin on Lake Superior. There Congress was considering designating part of its old growth forestlands and rocky shorelines as wilderness. Since his writing the Gaylord Nelson Wilderness has been approved in honor of the former Wisconsin Senator and founder of Earth Day.

Cronon urged people to place wilderness is a larger context that recognizes that the relationship between man and the land is ebbing and flowing. The Frank Church-River of No Return was once filled with miners seeking gold. They are gone and like the Apostles the area has gone through a “rewilding” as Cronon says.

.”To acknowledge past human impacts upon these islands is not to call into question their wildness; it is rather to celebrate, along with the human past, the robust ability of wild nature to sustain itself when people give it the freedom it needs to flourish in their midst,” he wrote in Orion, an environmental magazine in 2003.

Cronon’s concept is never more critical than now as the world faces climate change. Already there is no place in the world untouched by human pollution. Now scientists say its like that ecosystems all over the world are going to change and even disappear with extinctions over the next century of between 20 to 40 percent of known species.

These profound changes challenge the concept of wilderness that Henry David Thoreau, John Muir and others envisioned. Man and the land are inexorably tied together in this reality. Yet wilderness continues to have scientific values, restorative value, stillness value. Most of all the new reality of climate change does not eliminate the spiritual values of wilderness espoused by my own hero Sigurd Olson, the nature writer, wilderness guide and protector of Minnesota’s Boundary Waters.

“Spiritual values are values that affect your emotions, that affect your happiness, that affect your culture,” Olson explained.

He showed this connection in his book, "The Singing Wilderness" as he described the frog chorus in his beloved borderland:

“No matter where I listen to a bog at night, strange feelings stir within me,” he wrote.

As climate change transforms the places we love and forces us to make painful choices about what we can preserve and what we can’t we need to listen to the music of the bog.