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CAPTION: Human and buffalo skulls in a Mandan village, Karl Bodmer, 1833


Perhaps no exploration in American history has more famously combined intrepidity with scientific enterprise than the two-year expedition of Lewis and Clark from the Mississippi to the Pacific two centuries ago. The ecologist Daniel B. Botkin, in a 1995 book, called it “the greatest wilderness trip ever recorded.”

But how pristine was that Western wilderness of 1804 to 1806? The answer depends on how one conceives of the nature of nature, and it has basic implications for present-day conservation policy.

Fond tradition pictures the plains and mountains of the Lewis and Clark era as a nature untouched by humans and apart from them: a sort of original realm of the wild, undisturbed and eternal.

Many experts, however, have long since abandoned that vision. Today they see humans as longtime major players in nature’s grand drama, and American Indians among the main ecological actors of the old West — not only in the days of Lewis and Clark but for thousands of years before that.

Now, citing as evidence the marvelously detailed journals of Captains Meriwether Lewis and William Clark, some scientists are proposing that even Indian warfare played a critical ecological role, by regulating and maintaining both the numbers and distribution of bison and other big animals of the West before descendants of Europeans settled it.

Basically, according to this “war zone” theory, Indian hunters were so proficient that in an individual tribe’s homeland, populations of big game like bison and elk seriously declined and in some cases disappeared.

But in several big buffer zones between warring tribes, where hunters were loath to spend much time lest their enemies attack them, big game found more safety and flourished.

These no-man’s-lands functioned, in effect, as game preserves and may have kept the plains bison and other big animals from being hunted to extinction well before Europeans arrived.

Not everyone agrees wholly with the theory.

But the spotlight it casts on humans’ impact on the pre-Columbian landscape also highlights one of the major conceptual problems facing present-day efforts to restore and conserve “natural” ecosystems: What target should be aimed at? Should the goal be to maintain nature as nearly as possible in the state it was in before the ancestors of the Indians came to America many millenniums ago? Or to its state just before Europeans appeared on the continent? Or to some other state altogether?

The war-zone theory is laid out in the February issue of the journal Conservation Biology by Paul S. Martin, a paleoecologist at the University of Arizona, and Christine R. Szuter, editor in chief of the University of Arizona Press.

Dr. Martin says the theory could partly explain why bison, elk, deer and bears escaped the fate of other, even bigger North American animal species that became extinct 13,000 years ago. These included, among others, mammoths, mastodons, camels, giant sloths, tapirs and predators that depended on them, like giant short-faced bears, a giant wolf called the dire wolf and the saber-toothed cat.

The bison is the largest surviving life form in North America, and Dr. Martin is the chief advocate of the view that the earlier vanished species of megafauna, as they are called, were hunted to extinction in a continentwide “blitzkrieg” lasting several centuries by human hunters who had migrated to North America from Siberia 15,000 years ago or more.

“The land had been stripped of most of its native megafauna through human influence” long before Lewis and Clark appeared on the scene, Dr. Martin and Dr. Szuter write.

And except for the influence of humans, they say, much larger populations of the surviving bison, elk and deer would have greeted the white explorers.

Other scientists contend that the ancient megafauna were extinguished by climatic change or disease, or by a combination of factors. Be that as it may, it is abundantly clear that Indians and their ancestors, called paleo-Indians by scientists, transformed the landscape and ecological relationships of the Western Hemisphere, with both positive and negative effects.

Indians rearranged the land with earthworks, farm fields, houses, towns and trails.

As top predators, the impact of their hunting on many species rippled through pre-Columbian ecosystems.

Indians also set frequent fires for one reason or another, and many pre-Columbian forests were more open and parklike as a result.

In the West, the Indians’ fires helped create, renew and maintain grassland ecosystems.

Grasses with deep roots flourished, and the tender new shoots that sprang from them after the fires provided ideal forage for bison. The ecological loop came full circle when the Indians killed the bison, the underpinning of their hunter’s way of life.

The idea that Indian warfare created game sanctuaries in buffer zones between tribes has been proposed by a number of authorities.

In the 1960’s, Harold Hickerson, an anthropologist, found that in the18th and 19th centuries, a contested zone varying from 15,000 to 35,000 square miles separated the Chippewa and Lakota in Wisconsin and Minnesota.

Indians did sometimes steal in to hunt there, but usually, Mr. Hickerson wrote, “in constant dread of being surprised by enemies.” Deer were abundant in this tract until the two Indian nations made peace and hunting intensified in the zone.

In 1995, Elliott West, a historian at the University of Arkansas, identified contested zones of the central Plains that in the early and mid-1800’s covered huge stretches of what are now Colorado, Kansas and Nebraska. There, he wrote in a 1995 book, “The Way to the West” (University of New Mexico Press), bison were “spared the full devotion” of Indians who were occupied contending with each other.

“The buffalo, in short, got a break,” he wrote.

Similar zones have been identified, Dr. Martin and Dr. Szuter report in the article in Conservation Biology, between the Iroquois and Algonquins around Lake Champlain and in the upper Amazon River basin between forest tribes.

Now, citing the Lewis and Clark journals, Dr. Martin suggests that in their era, a great wedge of territory stretching for 46,000 square miles across the eastern two-thirds of what is now Montana, between the Missouri and Yellowstone Rivers, was an important war zone.

This region, he and Dr. Szuter wrote, “is commonly regarded by historians, biologists and TV producers alike as the very essence of ‘wild’ America.” But in fact, they wrote, the plenitude of bison and other game there “reflected the status of the area as a buffer zone,” where “war parties of various tribes or nations were ever at hand, and anyone hunting, processing and drying meat” might be killed by enemies.

The abundance of game in that region was clearly detailed by Lewis and Clark, says Dr. Martin.

And Clark, in one journal passage, writes, “I have observed that in the country between the nations which are at war with each other the greatest numbers of wild animals are to be found.”

By contrast, there were no comparable buffer zones west of the Rockies — and little big game, even though there was plenty of food for bison, elk and deer.

Dr. Martin’s interpretation is that the trans-Rockies Indians simply hunted the big game until it disappeared. Consequently, the Indians there lived mainly on fish and roots.

Lewis and Clark’s men found these unsatisfactory; unable to find enough big game to sustain themselves, they cooked and ate horses and dogs that they bought from the Indians.

The upshot, wrote Dr. Martin and Dr. Szuter, is that neither the scarcity of game west of the Rockies nor the abundance of it in the war zone to the east was “truly natural, that is, falling outside human influence or control.” The meaning for conservation efforts, they wrote, is that “the West in the time of Lewis and Clark was long past any purely ‘natural’ condition that might serve as an absolute benchmark for planners.”

For his part, Dr. Martin advocates the establishment of some nature preserves where the pre-Indian natural world might be re-created as closely as possible.

African or Asian elephants, for instance, might stand in for the extinct mammoths, enabling scientists to see something of how the pre-human North American landscape functioned ecologically.

One dissenter from the Martin-Szuter view is Dr. Botkin, an ecologist at George Mason University in northern Virginia and president of the Center for the Study of the Environment, a nonprofit research organization in Santa Barbara, Calif.

He wrote the 1995 book, “Our Natural History: The Lessons of Lewis and Clark” (Grossett/Putnam).

While there may have been more bison in war zones than elsewhere, Dr. Botkin said, Dr. Martin seems to assume that the ecology of the plains remained static.

In fact, said Dr. Botkin, the bison were highly migratory, and would probably have migrated in and out of war zones.

On a more fundamental level, he says, the Martin-Szuter paper implies that humans are a force outside nature, that their impact is unnatural and therefore undesirable. On the contrary, Dr. Botkin says, humans are an integral part of nature, one of many forces that have long kept the natural world in a constant state of flux.

There have been many states of nature in the past; for instance, many parts of North America have been covered by forests, grasslands or ice in different eras, and the assemblages of animals living there have varied accordingly.

The transformations wrought by Indians created yet other versions of nature.

Varying states of nature, said Dr. Botkin, constitute a “set of designs” from which today’s conservation planners can choose in deciding what model to use as a standard for conservation and restoration projects. The durability of a particular design is not necessarily relevant, he said: If one wanted to pick the most durable design of the last few hundred thousand years in North America, “you go back to ice.”

Therefore, he said, the state of nature encountered by Lewis and Clark is as valid a model as any of a number of other versions that have come and gone over the eons — and is probably the one most Americans today would prefer.

The larger point, he said, is that “there is not a single truth about what’s natural.” The main value of the Martin-Szuter view, he said, is that it “points up that the discussion of what is natural is alive and well, and that it’s not yet resolved.”

1999 The New York Times Company