Written By:




By Norman Christensen, Ph.D.


Norman Christensen was the Founding Dean of the Nicholas School of the Environment at Duke University where he continues to work as a research professor. He is also past President of the Ecological Society of America. The text below was given as a speech at United Church of Chapel Hill in January 2013.

I was attracted to Duke University nearly 40 years ago, and chief among the attractions was the opportunity to focus my research in the university’s 8,000 acre research forest. As a doctoral student, I had been admonished often by my major professor to study nature and nature only; meaning, avoid places influenced by the activities of humans, in part because they inevitably confounded ecological patterns, and in part because human activities were considered irrelevant to the construction of proper ecological theory. I imagined that the Duke Forest would provide ample opportunity to follow my professors’ admonitions. Soon after my arrival, I was mightily disappointed to learn that nature absent of human influence was not to be found anywhere on this landscape.

But, it was worse than that; nothing in the character and distribution of these forests made an ounce of sense without first understanding the impacts of people over time scales of decades, centuries and millennia. With time, however, my disappointment gave way to a fascination with the factors shaping the interactions between people and the land, and that fascination has motivated and informed much of my research since.

I was blessed with wonderful graduate advisors, but I now know that on this matter, they had it wrong. In a world of seven billion human souls, there is no such thing as nature untrammeled by humans, and ecological theory that does not embrace this truth is of little use.

I would like to share with you now the major lessons of this 40-year journey.

I’m rather certain that great many of you have walked through the woods in places like Duke Forest, the North Carolina Botanical Garden or Umstead State Park. One such walk in Duke Forest is a favorite of mine. It begins in uplands along Mt Sinai Road and descends to a wooden bridge crossing New Hope Creek. Most who use this heavily traveled trail give little thought to the origin of the woods that surround them; most of those who do, assume from the large size of the pines and various hardwoods that these are ancient woods, primeval perhaps.

But, 140 years ago, standing on a hilltop at the midpoint of this trail, you would have been surrounded by abandoned, and badly eroded cotton and corn fields reminiscent of some of the sorriest deforested landscapes on our planet; like places you might see today in Haiti and Madagascar.

The history of this hilltop and the lands that surround it is representative of the history for lands across this region, and many other regions. It has much to teach us about the ethics of sustainable land use.

This land was first settled and farmed by Europeans in the middle of the 18th century, and this particular property was first privately owned in about 1750 by a gentleman named John Patterson. It came to him a rather generous grant of several thousand acres from Lord Granville, the colonial governor. Looking from the top of this hill, it was Patterson land almost as far as the eye could see.

But, the Pattersons were by no means the first people to make a living off this land; over 10,000 years of human activity preceded them. The first humans arrived here sometime between ten and twelve thousand years ago. The impacts of these hunter-gatherers on the land were disproportionate to their relatively small numbers.

They hunted with great efficiency, and they were the primary cause for the extinction of much of the once abundant megafauna mammoths, giant sloths, camel-like ungulates and saber-tooth cats. At least as important, these people brought fire to this landscape and used it with great purpose to create and maintain open forest conditions that supported the plants and animals that sustained them.

Even more people populated this landscape 4,000 years ago. The so-called Woodland people of this time were semi-nomadic, cultivating crops such as squash and tomatoes in floodplains (such as along nearby creeks and rivers) and hunting white-tailed deer, elk and woodland bison. They, too, managed their landscape with fire.

Mississippian people, the first fully sedentary and agricultural Native Americans, appeared here about 1,500 years ago. These were the mound building people who established towns and cultivated crops in low lying areas such as along New Hope Creek and the Eno River. They coexisted and likely traded goods with Woodland people up to the time of the first European contact.

These were not scattered bands of people on a wilderness landscape. What we today call North Carolina was, in 1491, home to as many as a million people.

So, John Patterson may have been the first human to have formal title to this land, but he was by no means the first to manage it and depend on it.

By the mid-18th century, disease had reduced the numbers of indigenous people ten-fold, but their historic impacts still echoed across the landscape. For sure, what the Pattersons saw as they traversed their estate for the first time were forests and bottomlands shaped by the actions of hundreds of human generations.

That the Industrial Revolution was just beginning was of little consequence to the Patterson family in 1750. They cleared and prepared land for cultivation with little more than axes, plows, oxen and their own hard work. We don’t know the details of their particular practices, but we do understand most land in this region was being farmed in the context of a subsistence economy. People farmed only small portions of their large ownerships, growing to meet their needs, with surplus enough to trade in nearby towns, such as Hillsborough, for things they couldn’t grow themselves.

This is a good moment to call attention to the fact that agriculture is inherently not a sustainable enterprise. When land is cleared, erosion rates increase ten to one hundred fold. Furthermore, the supply of essential soil nutrients, such as nitrogen and phosphorus, is rapidly depleted as these elements are incorporated into plant and animal tissues and then harvested and exported from the land. No surprise that, after land clearing, agricultural productivity declines by more than half within only a few growing seasons. This, by the way, is why nearly all Native American farming was confined to floodplain areas where seasonal flooding and siltation continually restored fertility.

In those early decades, the Pattersons and most of their neighbors practiced a form of shifting agriculture — a farming system that has at least the potential to be sustainable. The process was begun by clearing a 3-5 acre tract of land—an arduous process given limited human and technological resources. As productivity declined after a few years, they would let that tract go fallow (i.e., they would abandon it), and begin farming another. In our region, fallow land is very quickly re-vegetated by a succession of plant species. In the first year, annual weeds prevail. In the second and third years perennial grasses and herbs—broomsedge, asters, goldenrod and the like—take over along with the seedlings and samplings of young vines, shrubs and trees. After 4-5 years, those species and associated herbs form a diverse and impenetrable thicket. Importantly, over these 4-5 years, this succession of plants has the effect of restoring soil organic matter and stores of those nutrients essential to plant growth. Left to its own devices, this thicket would soon develop into a young forest. But here, the farmer intervenes, re-plows the land and begins another cycle of growth.

I say this farming system was potentially sustainable. Whether that potential was realized depended on the amount of land in production and whether fallow cycles were sufficiently long to ensure restoration.

John Patterson sold his property to William Robson in about 1790. Within a decade, the fallow system of agriculture was all but abandoned for several reasons. Populations and urban centers were growing, and rural barter markets were rapidly giving way to fully monetized economies. Worldwide demand for agricultural products—most particularly cotton, tobacco and dye stuffs like indigo—was growing exponentially. These crops grow especially well in this region. Furthermore, technologies such as the cotton gin and mechanized looms allowed the processing of these crops on very large scales.

Farm families like the Robsons were no longer growing things they themselves needed (you can’t eat cotton and you can only smoke so much tobacco). Rather, they were earning money and buying their needs at market.

This change from subsistence to market economy has, itself, important impacts on human behavior. Economists assure us that our utility or desire for things diminish as we acquire more and more of those things. After all, you can only use so much of any foodstuff, so many tools and so much clothing. But money is not a thing, it is an abstraction for things . . . and it seems the more we have, the more we desire. . . . You just can’t have enough.

Taken together, these developments vastly altered incentives for land use and stewardship, and they set in motion economic, social and ecological change that would prove to be truly unsustainable. Rather than allow land to lie fallow, Robson and his neighbors countered declining productivity by putting more and more land into production. The uncertainties associated with regional and global markets reinforced this behavior.

By 1820-1830, well over half, perhaps a 1,000 acres, of the Robson property was in cultivation. In 1750, this region was probably 90% forest; by 1830 it was less than 50% forest. By 1860, only 30% of the region’s forests remained, and these forest fragments had been severely degraded by livestock grazing and high-graded for fuel wood.

In 1830, the tractor was still nearly a century in the future. Then, a single family, no matter how large, could not by itself farm 1,000 acre. As we all know too well, they accomplished this with human chattel—slaves. Although it had been on the decline in the late 17th century, this transition to market agriculture greatly increased the demand for and dependence on slavery. We don’t know the specifics of the Robson’s holdings, but nearby ownerships of this size often depended on the labor of 100-200 slaves.

The impacts of continuous farming had devastating effects on this landscape. Studies indicate that between 1800 and 1860 erosion removed an average of 1-2 feet of soil from exposed cropland across this region. In the woods along the path to the Wooden Bridge you will see that deep erosion gullies still scar the hillside. By 1860, per acre productivity had been reduced many fold.

The impacts of this erosion extended well beyond individual farm fields as sediment polluted creeks and rivers, filled in mill ponds and caused the closure of water-driven mills on all but the largest streams.

The regional economy went through ups and downs, but mostly ratcheted down. The pattern of change has something of a modern ring to it. Variations in the markets encouraged widespread debt financing. By the mid-19th century, most ownerships, including the Robson’s, were heavily mortgaged. Produce buyers such as the large textile mills typically held the mortgages. In the case of Robson’s lands, that was Erwin Cotton Mill, honored today by naming the public road connecting Duke Forest to Chapel Hill “Erwin Road.”

Sustainability is often likened to a three-legged stool, with the legs representing social, economic and environmental systems and the seat representing the inescapable linkages among these systems. Surely, the changes for Robson and his associates during this period—the inexorable downward spiral of increasing dependency on a despicable institution of slavery, the loss of essential ecosystem functions and services, and ever increasing fragility of the economic system—validate this metaphor.

The Civil War was a watershed moment. Slavery was abolished, although many the social injustices associated with it persist to this day. It inaugurated a period of regional economic depression that would extend up to World War II. The Robson estate, like those of the majority of his neighbors, was put into foreclosure and ownership passed to the mortgage holder, Erwin Cotton Mills. Indeed, it was from Erwin Cotton Mills that James B. Duke bought much of the land that he chose as the site for his eponymous university and forest.

And what about the land itself? Although tenant farming and share cropping continued in some places, much of the land was simply abandoned . . . at long last. Much of the land along the Wooden Bridge trail was abandoned in about 1870 and that fallow succession was repeated once again. Old field weeds were soon replaced with a dog-hair thicket of pines. Through time, that thicket thinned to a respectable forest as faster growing trees overtopped smaller competitors. When Duke Forest was formally established in 1931, those pines were about 60 years old and broadleaved trees—oaks, sweetgums, maples and hickories—were prominent beneath them. But, the very features that make pines such successful pioneers in open fields, limit their ability to persist beyond a single generation. Unable to grow in their own shade, the pines are today gradually being replaced by the hardwoods. Walk to the Wooden Bridge in 30 years, and the pines along that path will likely be gone altogether.

What happened on this hillside, was repeated on millions of acres of abandoned land across this region. Between 1870 and 1940, forest cover increased from 30 to over 70% of the landscape. Shortleaf and loblolly pine regenerating on this abandoned land now provide the raw resource—lumber and pulp—for one of the world’s most important timber economies. Much former crop land in this region is now central to that economy.

Whether managed for timber or not, rapid change continues on this landscape. Once rural land is rapidly becoming urban. Forest is being replaced by complex, impervious surfaces like roof tops and roads that greatly alter local climate, not to mention the quality, quantity and timing of water flows.

When Duke Forest was dedicated in 1931, its woods were part of a contiguous landscape of forest and open fields. Today, the Forest resemblessomething closer to New York’s Central Park. Individual forest tracts are losing their unique character as they are invaded by a welter of plants introduced from virtually every continent. As a consequence, the overall biological diversity of this landscape has diminished considerably since that dedication.

Exactly 30 years ago, I was invited to address a convocation of entering freshmen in the Duke Chapel. I chose to talk about the change that had occurred in the Duke area.  But I was then far less certain about the lessons to be derived from that change

I recall finishing the talk with a simple observation that folks like William Robson came, went and left their mark and I allowed as how all those freshmen would probably do the same. Today is my chance to provide a much more specific and meaningful interpretation of that history.

Several times in this talk, I have used the word sustainability. This is a term with its own long and somewhat confused history. In the late 19th century, people spoke of sustainability in terms of the ability to move and process natural resources to growing markets. The concept of sustainable yield management of croplands, forests and fisheries was focused on how best to extract, transport and process resources. It was all about meeting demand. And, why not? There was still prairie sod to be broken, wild forest to be harvested, and abundant un-fished waters.

By the time of the Great Depression, untapped virgin resources were becoming rare, and many scientists and resource managers seriously wondered whether croplands, forests and fisheries could be relied on to provide resources after repeated harvest. The concept of sustainable resource management—focusing on the capacity of ecosystems to supply resources through time—grew out of that concern.

With the subsequent explosive growth of our population, the concept of sustainable management was further enlarged to include the need to manage for multiple resources and competing interests in particular places. How do we grow crops and harvest wood fiber and still maintain abundant wildlife and biological diversity, clean water and aesthetic beauty? Sustainability in many places became synonymous with the concept of multiple use management.

The word “sustainability” is misleading. “To sustain” is defined in many dictionaries as “to keep in existence, to maintain.” This implies to some an idealistic endpoint, a destination. If we do X, Y and Z, we will achieve a sustainable future. But if history tells us anything, it is that sustainability cannot be static. It must be seen as a journey, not a destination. That journey always occurs in the context of change.

Any notion of sustainability must accommodate the inevitability of three kinds of change!

The world is changing. It always has and always will. The capacity for ecosystems to change is essential to their persistence. Forests are constantly being disturbed and constantly undergoing change. Over the long term, change is essential to adaptation and survival.

We are changing. We always have and always will. Each generation of human beings brings new technologies and values to the land. My interests and values are very different from my parents and grandparents, and the interests and values of my children and grandchildren are no less different from mine.

We are changing the world. This, too, we always have done. But today there are seven billion of us and our individual impacts are disproportionately magnified by the power of the technologies we employ to garner the things we need or think we need.

Ecological change shaped the landscape that greeted the first human occupants of this landscape. For better or worse, their activities altered the process of change in ways that influenced resource options for successive generations.

The land granted to the Patterson family in 1750 was the product of millennia of interactions between ecological and human change.

Over several generations, the Pattersons, Robsons and others inflicted unprecedented change on the land; change that, at least in the short term was clearly unsustainable. Yet, we can take heart in the amazing restorative capacity of ecosystems. Ecosystem change has repaired some of the impacts of those many years of unsustainable land use. But they are far from erased. No vestige of old-growth forest remains, and it will take many more decades, even centuries, to restore soils to their pre-agricultural productivity.

Today, we, too, are mighty agents of change. And surely we would like to believe that nature’s change processes will mitigate our impacts, too. But history provides no guarantee of this. Too often, we fail to recognize the unprecedented magnitude and character of our impacts. Our planet’s human population has increased 10-fold since the Robsons abandoned their land, and each of us individually consumes 5-10 times more energy and resources than did the Robsons and their peers. Furthermore, many of our impacts have no precedent in either historic or prehistoric times.

Environmental ethics aims to provide a framework or frameworks for making appropriate choices — for discerning right from wrong actions —on this sustainability journey. A review of the literature in this discipline, however, can be daunting and confusing.

Those of a utilitarian bent argue that an action is right if it provides the greatest benefit or utility to the greatest number. This majority rules ethic, however, has proven over and over to be myopic.

Those who focus on the importance of the functions and services provided by nature’s ecosystems repeat Aldo Leopold’s admonition that “a thing is right when it tends to preserve the integrity, stability and beauty of the biotic community. It is wrong when it tends otherwise.”

Those who are concerned with the well-being of human communities are apt to see strong connections between sustainability, equity and justice as suggested by the United Nations Commission on Sustainable Development. An action is right if it meets the needs of the present without compromising the ability of future generations to meet their own needs.

Many would expand this notion of intergenerational responsibility to include responsibility to all communities today and in the future.

What the history of this land tells us is that these visions of environmental right and wrong are intimately intertwined. Land management decisions ultimately provided benefit or not depending whether the ecosystems they impacted could continue to deliver essential resources and services over long periods of time—multiple generations. Historical actions that diminished the dignity and well-being of other peoplewere not sustainable in either economic or environmental terms.

My students sometimes find it disconcerting when I assert that sustainability is an inherently human concept—one that is necessarily anthropocentric. My point is simply this: For countless eons, Earth’s myriad ecosystems functioned wonderfully in our absence. No other single organism during those eons impacted our planet to the extent that we have.

Study nature and you will understand that, were we to disappear tomorrow, ecosystems would continue to change and life would continue to evolve. In a few millennia, the scars of our actions would be reduced to a thin, albeit messy, layer in Earth’s geologic strata. We are not an essential element to any of Earth’s ecosystems save for those we have created such as cities and farm fields.

I like to close out my undergraduate environmental science and policy course by sharing my favorite Gary Larson cartoon. A dinosaur stands at a lectern before an audience of other dinosaurs and says, “Friends the picture is bleak. Climates are changing, mammals are on the rise, and here we sit with brains the size of a walnut.”

Dinosaurs are, unfairly I think, often depicted as the metaphor for unsustainability — unable to adapt, they were merely a cul-de-sac in the history of life. But, consider that these remarkable beasts dominated Earth’s ecosystems for a couple hundred million years.

We humans measure our tenure on Earth only in the tens or hundreds of thousands of years. We are prone to believe that the history of life that preceded us occurred solely for our benefit. That belief supports denial among some that we actually have the capacity to alter our world in ways that might irreparably diminish its capacity to sustain us. There is nothing in our history of interaction with the land to support that sort of denial.

We are fond of calling attention to features—intelligence, self-awareness, empathy—that we believe set us apart from all the rest of creation; we have brains the size of a grapefruit. Sustainability is all about demonstrating that these features will truly ensure our tenure and the quality of our lives in the long term.

Copyright © Norman Christensen, 2013