The final two years of the 20th century mark a vital pair of anniversaries for anyone committed to wilderness and to the struggle to help human beings live more gently and sustainably on this precious planet. One of these anniversaries, even 50 years after the event it commemorates, remains an occasion for mourning; the other, an undiminished cause for celebration. Together, they signal an end and a beginning for the extraordinary career of one of America's greatest ecologists, conservationists, and nature writers - and a founder of The Wilderness Society: Aldo Leopold.

A Fire and a Phoenix

On the morning of April 21, 1948, Aldo Leopold and his family learned that a trash fire on their neighbor's property was burning out of control. When they went to investigate, they were disturbed to discover that the fire was heading downhill toward their own land, the once worn-out and abandoned farm property surrounding the old chicken shed they called "The Shack."

For the past 13 years, they had made this weekend retreat by the side of the Wisconsin River into a pioneering experiment in ecological restoration, one of the first in the United States. Now, a careless fire threatened a grove of pines they had planted as part of that project.

Leopold grabbed a water pump and disappeared into the marsh to wet down the back edges of the burn. No one ever saw him alive again. He suffered a massive heart attack while fighting the fire, lay down on the ground with his head resting on a clump of grass, and died as the fire swept lightly over his body. He was 61 years old, and at the peak of his creative powers. We mark the 50th anniversary of his death in 1998.

Fortunately, Leopold left behind the almost-completed manuscript for a book-originally entitled Great Possessions, which Oxford University Press had already accepted for publication. Modestly revised and copy-edited by Aldo's son Luna, it finally arrived in bookstores in the fall of 1949. Responding to Oxford's fear that the original title sounded too much like Charles Dickens, Luna chose another: A Sand County Almanac.

It will see its 50th anniversary in 1999, and in the book's 226 pages its author cheated death by leaving a legacy that would carry on his conservationist work literally for generations. Although the book enjoyed only modest sales in the years immediately following Leopold's death, a new Ballantine Books paperback edition two decades later catapulted it to bestseller status and made it a bible of the new environmental movement. There is little reason to doubt that we will still be celebrating and learning from its wisdom a hundred years hence.

A Quiet Catalyst

A Sand County Almanac is by any estimation one of the three most important and influential books in the history of American conservation. Only two other volumes can be said to have had comparable impacts: George Perkins Marsh's Man and Nature in 1864, which helped spur forest - and watershed - protection efforts in the decades following the Civil War, and Rachel Carson's Silent Spring in 1962, which launched the modern environmental movement with its attack on DDT and other pesticides. All three books literally made history by defining environmental agendas for generations of Americans committed to protecting the natural resources and ecosystems of their native land.

But Sand County is surely the most unlikely of these three as a history-making tome. Few reading it in 1949 could have anticipated that it would play such a pivotal role in the political and intellectual history of the 20th century. Man and Nature and Silent Spring were intended by their authors very explicitly as political broadsides, books crafted as polemical interventions and meant to make controversial claims on behalf of the causes they defended. They have the feel of books whose authors' ambition was to change the course of history in their own time, and for that very reason they feel a little dated when we read them today.

Sand County is very different, which is probably why it feels as fresh today as it did when it was written-the mark of a true classic. To the first-time reader, it presents itself as an unprepossessing collection of nature writings, brief essays offering reminiscences of landscapes and encounters in natural places, all cast in a spare, lucid prose that is far more elegant and literary than polemical.

Only as one reads more deeply into the book does one begin to recognize the arguments and insights that lie almost between the lines, or appreciate the quiet passion that informs its call for a new human sense of moral responsibility toward the natural world. The voice is that of a first-rate scientist and naturalist, a cool-eyed observer not just of nature but of the human condition, and the tone is far more meditative and ironic than polemical or belligerent. One gets the sense that the author would be much happier getting out into the woods with his dog than finding himself mounting the barricades on behalf of a political cause.

And yet these little essays bespeak nothing less than a revolution in ways of thinking about the human place in nature - a revolution as yet unfinished, but very near the heart of environmental politics in the second half of the 20th century and beyond. By putting into words the deep questions and concerns that would persuade millions of Americans to join the environmental movement in the years after its author's death, A Sand County Almanac earned itself an indelible place in history.

Celebrating Wilderness

What are the lessons of this profound little book? Among the most compelling are the powerful arguments it mounts on behalf of wilderness. No one has ever written more movingly about the value of protecting wild land and the creatures that inhabit it-including people. The book is both a lament for the world we have lost, and a plea to preserve its remnants.

"Man always kills the thing he loves," Leopold wrote in one of his most famous and beautifully crafted passages, "and so we the pioneers have killed our wilderness. Some say we had to. Be that as it may, I am glad I shall never be young without wild country to be young in. Of what avail are 40 freedoms without a blank spot on the map?"

Piece by piece, Leopold assembled in A Sand County Almanac the collection of arguments on behalf of protecting wild nature that would eventually culminate in the great Wilderness Act of 1964. They have continued to serve as the mainstay for all subsequent wilderness preservation efforts in the United States, and activists have been relying on them ever since.

Why protect wilderness? Leopold leaves no doubt that, for him, the most compelling reason, wholly sufficient in and of itself, is aesthetic and spiritual: Wild lands are the places he most loves and that have touched his life most deeply, stretching all the way back to the small pothole lake in an Iowa field where he shot his first duck.

Sand County's most powerful prose more often than not narrates the very particular places and moments that best express the feelings of one who cannot "live without wild things." The experience of being in the presence of such places is so fundamental to Leopold's being that he does not even try to defend its value. "Either you know it in your bones," he says, "or you are very, very old."

Those who would fight for wilderness today on seemingly more scientific grounds like "biological diversity" would do well to ask whether that phrase can ever evoke the same passion that makes A Sand County Almanac feel so full of love for the land.

Persuading the Pragmatists

Not that biological diversity is absent from this prescient book. Knowing that "mere" aesthetics could hardly offer an adequate defense for the wild things he loved, Leopold mapped out arguments that might be persuasive to those of a more "practical" bent. Wilderness, he said, was a repository for wildlife and other resources that would not survive without its protection, and these had clear value, economic and otherwise, that more than justified their protection. Efforts to preserve individual species that ignored the larger natural context in which such species prospered or died would be doomed to failure.

On the human side, wilderness would increasingly be needed as a recreational resource in a world that was ever more urban and industrial, offering at least a remembrance of those 40 freedoms that had been such an important part of his own life. Finally, Leopold argued that wilderness was a necessary baseline against which ecologists and other scientists could measure the dynamics of ecological change in other systems: Without some sense of how nature functioned in the absence of human beings, it would be difficult to manage any ecosystems intelligently and responsibly.

In one way or another, virtually every argument that has been used to defend wild land in the United States over the past half-century is developed or at least anticipated somewhere in the pages of A Sand County Almanac. It remains a veritable handbook of the wilderness preservation movement.

A New Paradigm

But there is more. Leopold couples his love of wild nature with two other crucial qualities that set his book apart from run-of-the-mill nature writing: a deep sense of history on the one hand, and, on the other, a richly ironic and chastened sense of how difficult it is to live on and use the land in responsible ways. Having spent his entire life as a manager of land and wildlife, he knew all too well that wild nature will not long remain in the modern world without an active commitment on the part of human beings to manage it responsibly...and he knew that this task was far from easy.

Knowing that he himself was manipulating wildness in the very act of protecting it gave him a powerful sense of the paradoxes such work entailed, and he was clear-eyed and unblinking in acknowledging these paradoxes. "All conservation of wildness," he wrote, "is self-defeating, for to cherish we must see and fondle, and when enough have seen and fondled, there is no wilderness left to cherish."

But Leopold refused to despair in the face of such insights; instead, he argued for radically new ways of thinking about wildness and its place in human culture. Always pragmatic, he had no illusions that the land we inhabit could ever fail to carry our signature. Instead, he urged us to think very carefully about the kinds of signatures we prefer to leave.

A Sand County Almanac is filled with stories about wild places that nonetheless bear the mark of human history, whether for good or for ill. As such, the book helps lay a foundation for the new field of environmental history, which would not fully emerge as a discipline in its own right for another quarter century.

It is because Leopold cared as much for human history as he did for wild nature that he ultimately sought to describe a new "land ethic" that would enlarge the boundaries of human moral responsibility to include not just other people, but "soils, waters, plants, and animals, or collectively: the land."

He knew better than most that wildness would survive on the land only if people cared about it enough to reorganize and re-imagine their own lives to make a place for it in their midst. "We can be ethical," he wrote, "only in relation to something we can see, feel, understand, love, or otherwise have faith in."

His dream was for a world where large tracts of wilderness would be protected, but where wild things would thrive and be honored in many other places as well: in rural wood lots, in humble wetlands, in restored prairies, even in urban parks. Only so would people be reminded, regularly and in the most ordinary ways, of the larger community to which they belonged and on which their own lives depended.

These are the "Great Possessions" that A Sand County Almanac celebrates, great because we belong to them as much as they belong to us. As we celebrate the 50th anniversary of its publication and mourn the 50th anniversary of its author's death, we could hardly do better than to revisit the pages of this remarkable book.