The Neurobiology of Nature vs. Culture

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It’s been over eight months since my last post (for shame!), but hey, we’re well into a new year, right? Now, this piece doesn’t exactly have much to do with watery landscapes, per se. Rather, it’s about our ideas of nature and the categories we use to understand all that non-human “stuff” out there and the relationship those ideas might have to our own physiology.

What might that have to do with my work on water and soggy places in southern Louisiana? Well, my post back in June, 2012 was about wetlands as in-between spaces, as borderlands, not just ecologically speaking, but also culturally and socially. While these ideas lie directly at the heart of my research, they’re motivated in turn by a fascination with the various boundaries—both physical and conceptual— that humans establish between themselves and the environment/natural world. Which brings me back to this post.

Nature/Society

Clarence Glacken's "Traces on the Rhodian Shore

Glacken’s “Traces on the Rhodian Shore” (Berkeley: UC Press, 1967).

What is nature? What counts as natural? Where do humans and their works fit into those categories? And how have the terms of these debates around nature and society changed over time?

These are foundational questions for a number of scholarly fields these days—geography, environmental history, anthropology, sociology, conservation biology, restoration ecology, philosophy, and so on—but they’re also far from new.

Enlightenment philosophers like Rousseau and Hobbes were preoccupied with somewhat similar questions and their implications for a functioning society. But reaching back to the Enlightenment only scratches the surface here. Clarence Glackens’s magnificent Traces on the Rhodian Shore follows these concerns all the way back to antiquity.1 The further one digs, it can sometimes seem like humanity’s relationship to nature is one of the oldest questions of all….

Nature-separation anxiety? Thomas Cole, "Expulsion from the Garden of Eden," 1828.

“Original sin” or just (nature) separation anxiety? Thomas Cole, “Expulsion from the Garden of Eden,” 1828. Note Adam and Eve fleeing the gates of Eden in the left-middle ground of the painting. Click to enlarge.

Semantic Space

So I was particularly struck when I saw a recent post up at Ed Yong’s Not Exactly Rocket Science blog for National Geographic. Yong writes about a neurobiology study at UC-Berkeley (Huth et al., 2012) that used fMRI scans to create a low-resolution map of the brain’s “semantic space.” The researchers charted, in Yong’s words, “the where of what,” the locations in the brain that were particularly active in response to images of buildings, animals, humans, faces, automobiles, plants, etc.. Yong is a far better science writer than I, so here’s his description of the paper:

“Huth made his maps by asking five volunteers to watch two hours of video clips. He later labelled the objects and actions in the clips using the 1,705 most common nouns and verbs from WordNet, a hierarchy of English words. As the volunteers watched, Huth used an fMRI scanner to measure the blood flow in 30,000 different sections of the brain. (Blood flow is an imperfect but widely used stand-in for brain activity.) The result: a giant matrix showing how all 30,000 points on the brain respond to all 1,705 categories.”

Semantic spaces of the brain.

Mapping the “semantic space” of the brain. Image from Huth et al. 2012. “A Continuous Semantic Space Describes the Representation of Thousands of Object and Action Categories across the Human Brain.” Click to enlarge.

The maps produced by the study are strange, beautiful things that Huth et al. suggest are revealing of the ways our descriptive categories of things in the world (our “semantic categories”) depend on an interconnected, continuous physical space in the brain.

Which is to say, the many thousands upon thousands of objects in the world we can recognize are not represented in distinct regions of the brain. We don’t dedicate specific parcels of gray matter to every single object we’ve ever encountered. My brain hasn’t carved out picket-fenced real estate for each of, say, chocolate ice cream, bourbon, and Wallander (just to name a few winter indulgences here at Porous Places).

Instead, the brain organizes large swathes of “stuff” out there in the world along continuous conceptual gradients. Rapidly moving objects might all be represented more or less in one area of the brain while stationary objects might be more or less represented in another. The space between those two regions might be organized to represent things according to how much they move, hence: the “continuous semantic space” described in the paper.

Tobler’s First Law of… Brains

Now although that was the study’s primary conclusion, that’s not what got me interested in it in the first place. While the researchers showed that the brain doesn’t have a filing system based on a near-infinite slew of unique categories (a place for every thing and every thing in its place), that doesn’t mean there aren’t any categories involved whatsoever.

Huth et al. found that there’s a geography of similarity when it comes to where things get represented in the brain: like things got filed in like places (sort of like Tobler’s First Law of Geography). I already mentioned moving objects, but here are more examples: all wheeled things (cars, buses, bicycles, etc.) might be represented more in one area of the brain, while buildings and structures might crop up more in another, and animals in still yet another.

Richard Scarry's "Cars and Trucks and Things That Go"

According to Huth et al. (2012), the brain might organize things with wheels more in one area of the brain compared with, say, buildings. Now, is this an innate biological tendency, or just something our brains grow into thanks to, say, Richard Scarry?

Their data suggested four main characteristics, or “dimensions,” by which visual stimuli were organized into this cerebral geography of similarity and difference: moving vs. stationary; social communication vs. everything else; “civilization” vs. “nature”; and biological vs. non-biological.

The Neurobiology of Nature vs. Culture

It’s that third continuum that grabbed my attention, a dimension that, in the authors’ words, “contrasts categories associated with civilization (people, man-made objects, and vehicles) with categories associated with nature (nonhuman animals)” (Huth et al. 2012, p. 1215). That is, images associated with human activity tended to provoke blood flow in one particular region of the brain, while images associated with “nature” induced blood flow to a distinctly different region.

Now, I should acknowledge there are a whole bunch of methodological reasons why we can’t just take these “dimensions”—in this case, the apparently neurobiological distinction between nature and society—at face value.

Methodological Interlude

The imaging technology, fMRI, has poor resolution (both visually and in terms of the time intervals between brain scans) and is prone to inconsistencies. Still more problematic is the fact that just because a machine detects blood flow to a particular region of the brain in response to visual stimulus, we don’t actually know what is going on in that part of the brain. Yes, fMRI imaging of blood flow gives us a proxy of brain activity, but one that is profoundly indirect. For example, if a test subject was shown a video of someone speaking, does the brain activity lighting up the scan signify a response to a mouth? A face? The act of talking? The concept of communication? All of the above? If all, then in what proportions? And so on.

Meanwhile, the WordNet library of 1705 words that Huth et al. used to label “stuff” depicted in the video clips offers its own source of bias, as does the labeling process itself. After all, can you imagine perfectly labeling and categorizing every possible thing appearing in 2 hours of video footage? Click to any random spot in Baraka, embedded below, watch just a minute of footage, and see how much there is to label and categorize in just a minute of moving pictures. And that’s aside from any preconceptions we bring to the material. Again, how do we know that brain blood flow observed in test subjects was actually in response to what the researchers categorized and labeled?

Finally, while statistical analysis yielded the four “dimensions” or qualities described in the paper, there’s good reason to be suspicious of that statistical analysis. If the labels and concepts fed into the model were biased in the first place, whether by the WordNet dictionary, the video content, the labeling process, or even the researchers themselves, then those statistical calculations will yield biased results.

Ok, now that that’s out of the way…. So what?

Nature vs. Culture, Reprise

Over the last two decades, one of the central themes in geography and environmental history (as well as numerous other fields in the humanities and social sciences) has been “hybridity.”

It’s a perspective that sees hard distinctions between nature and society/culture/humanity as not only deeply mistaken, but also profoundly destructive. From Donna Haraway and Bruno Latour, to William Cronon and Richard White, to Michael Pollan and Jenny Price (among countless others), writers and thinkers have been advocating ways of seeing the “cyborgs,” “monsters,” “organic machines,” and “gardens” that permeate our world.

Instead of pure nature or wilderness opposed to human civilization, these intellectuals argue that the two categories are thoroughly interconnected; if we  simply take the time to look closely enough, we’ll find that nature and culture continuously bleed into one another (and always have).

Even our bodies (and what could be more human than our own biology?) are a thorough melding of wild nature and civilization. Just think about the complex ecosystems that make up the bacterial flora in your gut, or—if you dare—about the organisms that inhabit your urethra.

Likewise, we regularly forget that even the computer on which you’re reading this is thoroughly a part of nature, a forgetting that has significant consequences. In one of my favorite books about the complicated intertwining of nature and society, Jenny Price suggests that things like computers—along with pretty much anything in your field of vision right now—embody “the nature we lose track of.”2 The rare-earth minerals that make up its hardware; the petroleum in its plastic keys; the hydrocarbons in its finishes; the (likely coal-powered) energy needed to cool data centers housing the thousands of servers that grant your web-surfing whims; the carbon footprint of it ALL, from mining to manufacture to transportation, and so on.

Servers and nature

Racks full of servers (and nature). “The Centaur server room,” by VIA Gallery, 2008.

Follow even the most “unnatural” things that we humans produce in this world back to their source and you’d be hard-pressed not to see the ways nature permeates even our most urban and technologically dependent lives.

Moreover, following that trail of breadcrumbs usually forces us to confront the full environmental and human cost of our daily habits as producers and consumers. When we strive to see the nature entangled in society, we reveal not only the real transformations humans have wrought in the world, but also the labor and inequality that often underwrites such transformations.

Finally, I should say hybridity doesn’t have to be one big bummer. When we acknowledge that humans and society are endlessly entangled with the natural world, we also allow for the possibility of better ways of relating to all that nonhuman “stuff” out there. We might find surprises in our own backyards, embrace the staggering ecological potential of human-made places, or even come to better care for some of our most neglected social landscapes in ways that could dramatically improve the lives of both human and non-human beings.

So, hybridity (or the gardens/cyborg/organic machine/”the nature we lose track of”) offers a lot of potential and it’s no wonder that humanists and social scientists who care about the environment would advocate such a perspective.

But consistently remembering these things, regularly paying attention to the hybrids that make up our world is difficult enough for scholars embroiled in the all this commentary, let alone for the general public. Most lay people tend to think of nature as that capital “N” Nature found wherever humans are least present.

Bierstadt, Yosemite Valley

Big “N” Nature, wherever humans are least present. Albert Bierstadt, “Looking Down Yosemite Valley,” 1865. Click to enlarge.

Hybridity, Social Values, and Cultural Neuroscience

Now, for as long as I’ve been exposed to these ideas, I’ve believed that this conceptual gulf people tend to carve out between nature and society, or between themselves and the environment, was completely learned. The separation was just a human invention (albeit, perhaps one with some very deep historical roots), and challenging that invention was simply a matter of popularizing some of these hybridity-type perspectives.

But Huth et al.’s study raises the possibility that the whole nature-vs.-culture problem isn’t just a matter of displacing old ideas. Maybe it’s also a matter of changing our brain tissue. Is it possible that such distinctions between nature and humanity have such a deep history, seem to be so stubbornly persistent, because they’re actually engrained in our biology? Could these ideas about nature be—shudder—natural?

So, I only say that to be provocative. As a humanist educated during the last decade of the twentieth century, I’m actually deeply suspicious of ideas and social conventions being branded as natural, and therefore immutable, correct, proper, etc.. All that popular evolutionary psychology stuff out there is just way too suspicious in the ways it tends to suggest some of our species’ most regressive and unjust social conventions—particularly when it comes to gender and race—are innately human.

Michel Foucault, 1975.

Michel Foucault, one of the late-twentieth century’s most influential thinkers when it comes to cultural constructions (particularly around the human body). Photo by Bruce Jackson, 1975.

And yet, notice how when I refuse to entertain the notion that ideas, cultural values, social constructions, etc. might have some grounding in nature, I’m just reproducing that same old nature/culture divide? This is where Huth et al.’s study got me really interested.

Let’s assume that their research was 100% correct in its findings: that its methodologies were unbiased and that there is in fact a biological basis for people’s distinguishing between nature and culture. That assumption about methodological perfection is, of course, ridiculous, but it’s useful.

Now, we could go the evolutionary-psych route and leap to the conclusion that the tendency for human brains to keep representations of “natural” things separate from “man-made” things is so fundamentally engrained in our biology that there’s no use changing it. We could argue that this is part of our evolutionary essence, hearkening back to some idealized existence on the African savannah in which those who could clearly separate human creation from the rest of the environment were at an advantage for survival.

Or, instead we could think about the ways learned cultural/social behaviors and values actually get entangled in our biology. When we’re raised by families and educated in schools that all together insist on distinguishing between nature and culture, well, all of that affects our brain chemistry, structure, and function. Our ideas about nature, while certainly a product of society and culture, might in fact be rendered natural in certain ways by being integrated into the physiology of our minds. If that sounds like a stretch, then check out the growing field of cultural neuroscience (Tanya Marie Luhrmann’s piece on changing treatment paradigms around schizophrenia is also suggestive here).

Which isn’t to say that makes such ideas normative in any sense. Just because social values and learned behaviors might manifest physically in our brains’ geographies, that doesn’t mean such values have to be natural in any sense that justifies, normalizes, or makes such ideas a permanent, essential feature of humanity.

Rather, our ideas and values might be just as entangled with physical nature as our computers.

Veluw, Landscape I

Levi van Veluw, “Landscape I,” 2008.

And of course, this raises all sorts of questions around the findings in Huth et al.’s research.

How would an environmental historian’s brain respond in such a study when the subject was shown something she knew unequivocally to be a thorough hybrid (something like the Salton Sea, perhaps).

Might Jenny Price’s brain, trained for many years to see the complicated ways nature and society are intertwined, look very different from those Huth et al. examined?

How might subjects from another society, one much less insistent on such nature-vs.-culture distinctions, respond to this study?

Or what might the natural/man-made semantic space Huth et al. found look like when studying the brains of Baining people of Papua New Guinea, a group so rigid in their distinctions between humans and non-humans that they forbid their children from play (something they believe to be solely an animal activity)?

So these questions around Huth et al. aside, let me pull back a little.

What do humanists and social scientists think about this? Might we understand culture, ideologies, etc. as being both socially constructed and ”natural,” albeit not in any unchanging/essential way? Instead of wholly rejecting the notion that values have anything to do with nature (in this case our biology), can we accept some degree of hybridity here as well?

If Huth et al. AND the cultural neuroscientists are right, then surely together their work would suggest a lot for environmental historians, geographers, philosophers, etc. to talk about without necessarily conceding the uglier claims of evolutionary psychology (or of the countless others who’ve used both Darwin and “nature” to justify inequalities of race, class, gender, and sexuality).

Footnotes

  1. Though long and, for some, a little “old-fashioned,” Traces on the Rhodian Shore is unlike anything else out there in its scope and synthesis. Take a glance for its humbling effect, if nothing else. ↩
  2. Jennifer Price, Flight Maps: Adventures With Nature in Modern America (NY: Basic Books, 1999), pg. 164. Also be sure to check out her fantastic two-part essay tackling similar ideas in The Believer: “Thirteen Ways of Seeing Nature in L.A.” ↩

Wetlands as Borderlands: Where Land and Water Meet

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Moving water connects these places, weaving the threads of the landscape together. The places where water and land combine—the riparian zones—mediate these connections, and what happens in these zones affects areas far beyond their boundaries.
— Nancy Langston, Where Land and Water Meet

Although it only describes riparian wetlands, this passage from Nancy Langston applies to pretty much any soggy ecosystem. For me, it has long suggested that wetlands might be usefully thought of as borderlands, albeit not in the conventional terms of state or political boundaries. Rather, wetlands are borderlands in that they are fundamentally “in-between” places—whether in terms of ecology, geography, or even culture and society—that have wide-ranging impacts.

Where land and water meet: physical borderlands

Wetlands exist simultaneously as both boundary and intersection. Which is to say, they mark the edges of terrestrial and aquatic ecosystems while also embodying thorough hybrids of land and water. As such ”liminal” (or borderline) places, they gain a truly unique identity of their own.

A home along Bayou Manchac

A home in the marshes along Bayou Manchac, Louisiana. Photo by author, October, 2011.

For both geographic and temporal reasons, the in-betweenness of wetlands also makes them a kind of borderland that can be particularly difficult to consistently define.

Geographically, wetlands rarely have distinct edges and exist instead as part of a continuous gradient between dry land and open water. How far into an estuary must I venture before I’ve left the wetlands at its edges? And if I find floating mats of grass and other plants scattered throughout that open water, what then? Meanwhile, depending on changes in topography, hydrology, climate, and resident animal and plant communities, the wettest parts of a wetland can even shift across a given landscape (the Tijuana Estuary’s river mouth, for example).

Temporally, wetlands might be continuously, seasonally, or only infrequently wet. How often and how persistently must a place flood (or drain) to be defined a wetland (or not)? Similarly, wetlands can come and go quite easily over time, emerging or receding into the terrestrial and aquatic worlds at their edges through sinking soils, ecological succession, climate change, or even through biotic activity (the building or collapse of beaver dams, for example).

Bald cypress forest in dry season

A bald cypress wetland near Weston, North Carolina during the dry season. Note the high-water marks on the trees running midway through the image. Photo by Duane Burdick, June19, 2010.

Now, it’s worth noting that if the “moving water” of Langston’s passage doesn’t seem to apply to the so-called stagnant swamps or bogs of the imagination, well that’s only because our imaginations have wrongly equated wetlands with stagnation. Though its movement might be so sluggish as to be imperceptible, water in even the boggiest of bogs is always moving, whether percolating through underlying soils, migrating in surface flows, or even simply evaporating into the air.

While our language and cultural references often suggest otherwise—think: “bogged down”; being “swamped with work”; the doldrums scene in the animated version of The Phantom Tollbooth; or the Swamps of Sadness in the Neverending Story—wetlands, in their borderland in-betweenness, are in fact very dynamic landscapes.

What makes them so dynamic? Well, all that slow-moving water makes for a host of very distinctive ecosystem functions. For a start, wetlands serve as critical habitat for a variety of mammals, fish and shellfish, amphibians, and birds, many of which might be endangered or threatened. It also probably goes without saying that wetlands harbor very distinctive plant communities, from spanish-moss-draped bald cypress and tupelo gums to carnivores like venus flytraps and pitcher plants.

Cypress swamp

Bald cypress, spanish moss, and water lilies in a swamp near Breaux Bridge, Louisiana. Photo by author, June 21, 2010.

Additionally, in gathering and retaining slow-moving water, they help recharge aquifers and provide crucial buffers for flood and storm-surge mitigation. At much larger regional and global scales, wetlands perform valuable ecosystem services by acting as sites for carbon sequestration, de-ntirification of agricultural runoff, and balancing global sulfur cycles. In a related fashion, wetlands, often described as the “kidneys” of watersheds, play important filtering roles for the waters that, no matter how sluggishly, move through them. Wetland biology, topography, geochemistry, and hydrology all uniquely combine to render these landscapes crucial sinks for excess nutrients and toxic chemicals.

How wetlands work

This diagram illustrates some of the "kidney" functions of wetlands in a watershed. Image courtesy of the City of Caspar, Wyoming.

And again, that sluggish water is really important. It’s not only the critical condition for sustaining these water/land hybrids, it also transforms wetlands into a very particular kind of node in a watershed’s network of streams. I’ve often thought of watersheds as collapsing distance. Which is to say, whatever happens upstream often leaves its signature somewhere downstream. Wetlands—as places in the watershed where land and water are in close, prolonged contact—are where that upstream signature often gets rendered a little more visible. Whether in the form of eroded upland sediments, fertilizers from agricultural runoff, industrial toxics, or even pharmaceuticals in urban wastewater, upstream detritus accumulates in wetlands thanks to the combined forces of slack water, ecology, and topography. As places so thoroughly in between land and water, I imagine wetlands to be almost like the connective tissues of watersheds.

Landscapes on the periphery?

Riparian meadows and backswamps, estuaries and deltas, coastal marshes and inland bogs, and so on aren’t just dynamic ecological and geographical borderlands, however, they’re also fundamentally cultural and social ones as well. I’ve mentioned before that Ann Vileisis’s watershed (see what I did there?) book, Discovering the Unknown Landscape, highlights the ways the Europeans and their descendants that occupied North America have long scorned watery landscapes. Her work is revelatory for its insights around the intersecting ways culture, politics, and ecology have played out in the history of American wetlands, frequently with depressingly destructive results. Indeed, Vileisis points to what seems to be a trend wherever western modernity has taken root: the draining and dredging of watery landscapes. Wetlands around the world are increasingly threatened, if not disappearing entirely.

If you want to get rid of mosquitos, drain the swamp that breeds them

Udo Keppler, "If you want to get rid of mosquitos, drain the swamp that breeds them," 1909. Though actually a political cartoon commenting on early twentieth-century U.S. economic policy, it illustrates the widespread Euro-American perception of wetlands as dire nuisances. Image courtesy of Library of Congress, call number: AP101.P7 1909 (Case X) P&P. Click to enlarge.

Yet, as I’ve also mentioned before, Vilesis’s narrative, aside from discussing Native American use and occupation of wetlands, also obscures some of the fundamentally human histories of these places. At the very least, though wetlands may have been anathema to Euro-Americans, that still leaves the long, if not always intensive, histories of human occupation in other watery landscapes around the world.

Wilfred Patrick Thesiger, Marsh Arabs, 1950

Marsh Arabs photographed in 1950 by Wilfred Patrick Thesiger. Photo courtesy of Pitt Rivers Museum, accession number 2004.130.29267.1. Note the livestock in the far-left background of the image. Click to enlarge.

Landscapes of encounter

But, even if we were to focus only on North America (as my research does), I don’t think a narrative of derision, resource extraction, and destruction—followed by snippets of redemption in the environmentalist late-twentieth century—tells the entire story. For one, even if the majority of Euro-Americans shunned wetlands, watery landscapes often acted as refuges for marginalized peoples in the New World, from displaced Native Americans and Cajuns to escaped slaves and other fugitives. Though these histories might on the surface justify the claim that North American wetlands were “landscapes on the periphery,” that phrase doesn’t do much to reveal the ways such landscapes also served as sites of encounter between the margins and the core.

Imagining wetlands as borderlands instead of peripheries—that is, as places that imply encounter and exchange, rather than marginality and obscurity—allows much more room for moving them to the center of historical and geographical questions about nature and society. Rather than simply being wild places on the edges, edges that have receded with ever greater human transformations of the environment, wetlands as borderlands become busy places full of deeply human questions.

For example, what was life in Louisiana swamp or marsh communities actually like and how did places like New Orleans, or the reclamation efforts of planters and other entrepreneurs, intrude on their lives? Or, how did wetlands facilitate the establishment of fugitive “maroon” societies of escaped slaves? How did these colonies participate in clandestine slave communication networks that tied “civilized” plantations to unruly marsh and backswamp? Similarly, how did they manage encounters with bounty hunters, loggers, and other emissaries of of the metropolitan core?

James L. Langridge, "Negroes Hiding in the Swamps of Louisiana," 1873

African Americans hide in a Louisiana swamp after the Colfax Massacre of 1873. White militias had killed dozens of freedmen in the wake of a contested Louisiana gubernatorial election. James L. Langridge, "Negroes Hiding in the Swamps of Louisiana," 1873, "Harper's Weekly," May 10, 1873, pg. 396. Click to enlarge.

All of this is to say nothing of the succeeding waves of colonization—each accompanied by their own explorers, resource harvesters, and traders—that  spread over southern Louisiana. From French to Spanish, back to French, and finally to the Americans, the watery landscapes of the Mississippi River’s lowest reaches were fundamentally sites of knowledge exchange, cultural encounter, and both conflict and accommodation.

Of course, the region was distinguished by political boundaries for some time, making Louisiana a much more conventional borderland. But the cultural and economic exchanges that distinguished the colonial period also persisted long after those political boundaries dissolved. Those succeeding waves of colonial occupation and their creole (or hybrid) cultural legacies took place largely because of the Mississippi River watershed’s role as a vital transportation network that spanned over two-thirds of the continent.

Given that crucial role of the river delta, it’s hard for me to imagine southern Louisiana’s borderlands history (in the more conventional sense of the term) wasn’t just as profoundly shaped in some way by its wetlands as by its shifting national boundaries.

Wetland frontiers: natural resources, land reclamation, and human bodies

Besides being borderlands of encounter between the marginal and the powerful or between vastly different cultures and economies, wetlands in my research area were also important resource frontiers. Logging in Louisiana swamps at one time counted for a majority of cypress lumber extracted in North America, while logged-over swamps and treeless marshes also saw a variety of aggressive attempts at being “reclaimed” or otherwise developed for agriculture, oil and gas extraction, and even residential communities. Certainly, scholars like Ann Vileisis have told these stories of extraction and drainage in great detail. Yet the ways logging, oil and gas development, and wetland reclamation also represented an ever-shifting borderland between wild and improved land receives little attention.

Floating sawmill in Louisiana swamp

A floating sawmill in a Louisiana swamp. Photo by George François Mugnier, taken sometime between 1880 and 1920. Image courtesy of the Collections of the Louisiana State Museum.

How did these industries and their laborers adapt to working in these watery landscapes? What happened culturally, economically, environmentally when a new logging town sprung up in the midst of a Louisiana swamp only to be abandoned and recede back into “wilderness” (albeit a dramatically altered one)? What new technologies did logging or petroleum industries bring to wetlands that enabled them to do their extractive work and how did those new technologies transform wetland ecosystems into new, part-humanized, part-wild landscapes? These are just a handful of questions that arise when we consider wetland resource frontiers as landscapes of adaptation and hybridity rather than simply as sites for disappearing wilderness.

Finally, and I might be pushing the borderland metaphor here, all of these stories necessitated deeply visceral encounters between human bodies and an inhospitable environment. People are, by nature, not so well-adapted to watery places. To state the painfully obvious, we lack the right kind of eyes and skin, to say nothing of fins, webbed appendages, or gills to comfortably navigate and inhabit soggy places. Swamps and marshes present some of the most challenging environmental conditions for human beings. Though they might have rarely risked starvation, people living and working in wetlands faced water and vector-borne diseases, hostile wildlife, exposure, and even drowning on a daily basis. Compound those dangers with the facts of being a hunted fugitive or the risks of operating temperamental floating sawmills, logging equipment, or dredges and other machinery, and wetlands inevitably became dramatic sites of confrontation between a fragile human body and a decidedly “other” landscape.

Laying a Standard Oil pipeline in Louisiana swamp.

Laying a Standard Oil pipeline in Louisiana's swampy environment was a challenge for both industry and its laborers. Image courtesy of "Fuel Oil Journal," December, 1914. Click to enlarge.

Porous places: boundary crossings in watery places

In bringing this post to a close, a disclaimer/apology is in order: I’ve tended toward more abstract, imprecise concepts and hand-waving than I would like. Of course, that fulfills one of the original goals of this blog: a means of thinking (out loud) through dissertation ideas and questions as they evolve. And this particularly idea is definitely one in progress.

So, yes, wetlands are clearly redolent of many kinds of historical boundary crossings, though I’ve only suggested a handful here: aquatic/terrestrial, periphery/core, marginal/powerful, other/familiar, body/environment. But there are also onceptual risks in gathering these boundary-crossings under one wetland roof, from Jay Taylor’s concern over imprecision (see his “Boundary Terminology” article listed below for more on this), to producing unhelpful dualisms.

One of our capacities as creative, thinking creatures is analogy and, really, it’s possible to analogize pretty much any one thing to any other. If I start seeing borderlands everywhere, they cease to become useful explanatory metaphors. The same goes for other concepts that have been bubbling away as I undertake my research: permeability, porosity, membranes, etc..

That said, I’ve also already been rewarded a few times in the archives by keeping these concepts at the forefront of my thinking (more on those rewards in future posts). The trick will ultimately be to make sure that—whether I’m speaking of borderlands, porous places, or permeable membranes—each of my arguments actually gains analytical traction from those metaphors, rather than just conceptual window-dressing.

So, if you have thoughts on wetlands as borderlands, or on thinking about non-national, non-political borderlands in environmental history or geographical scholarship, drop me a comment. And thanks for reading.

Further Reading

Buchanan, Thomas. Black Life on the Mississippi: Slaves, Free Blacks, and the Western Steamboat World. Chapel Hill: University of North Carolina Press, 2004.

Campanella, Richard. Bienville’s Dilemma: A Historical Geography of New Orleans. Lafayette, LA: University of Louisiana, 2008.

Colten, Craig. An Unnatural Metropolis: Wresting New Orleans from Nature. Baton Rouge: Louisiana State University Press, 2006.

Davis, Donald. Washed Away?: The Invisible Peoples of Louisiana’s Wetlands. Lafayette, LA: University of Louisiana, 2010.

Hall, Gwendolyn Midlow. Africans in Colonial Louisiana: The Development of Afro-Creole Culture in the Eighteenth Century. Baton Rouge: Louisiana State University Press, 1992.

Langston, Nancy. Where Land and Water Meet: A Western Landscape Transformed. University of Washington Press, 2003.

Lockley, Timothy James. Maroon Communities in South Carolina: A Documentary Record. Columbia: University of South Carolina Press, 2009.

Mancil, Ervin. An Historical Geography of Industrial Cypress Lumbering in Louisiana. PhD Dissertation, Louisiana State University, 1972.

Mitsch, William and James Gosselink. Wetlands. New York: Wiley, 2000.

Sellers, Christopher. “Thoreau’s Body: Towards an Embodied Environmental History.” Environmental History 4, 4 (1999): 486-514

Taylor, Joseph. “Boundary Terminology.” Environmental History 13, 3 (2008): 454-481.

Theriot, Jason. Building America’s Energy Corridor: Oil & Gas Development and Louisiana’s Wetlands. PhD Dissertation, University of Houston, 2011.

Vileisis, Ann. Discovering the Unknown Landscape: A History of America’s Wetlands. Washington, DC: Island Press, 1997.

Deltas and Human History

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A few posts back, I flagged an 1856 map showing major mountains and rivers of the world arranged by size. One of the reasons I like that map is that it lays out dozens of river mouths side-by-side. As you scan the lineup, you’re reminded just how many major centers of human history have in fact been located in the watery landscapes of river mouths, whether delta or estuary.

But what exactly is the story behind human occupation of deltas? How far back does it go? And what precipitated it in the first place? Ann Vileisis’s Discovering the Unknown Landscape: A History of America’s Wetlands would suggest that extensive human occupation of deltas, estuaries, and other dynamic, watery places only happened through draining, filling, and otherwise drying these landscapes. Vileisis convincingly argues that, at least for Euro-Americans, “wetlands have long been a landscape on the periphery,” a landscape “long despised and avoided.”

But what about the rest of the world? Euro-Americans only settled in places like southern Louisiana in the last three hundred years. On other continents people have been living in and around wetlands for millennia, and often without attempting to so aggressively dry the landscape. What accounts for this opposing and rich history of human settlement in estuaries and deltaic plains (here’s a particularly striking example) around the globe?

Wilfred Patrick Thesiger, Marsh Arabs, 1950

"Marsh Arabs" photographed by Wilfred Patrick Thesiger in the Tigris-Euphrates marshlands of Iraq, 1950. Photo courtesy of Pitt Rivers Museum, accession number 2004.130.29267.1. Note the livestock in the far-left background of the image. Click to enlarge.

Productivity and sea levels

One of the field of ecology’s most basic measures of an ecosystem is “productivity,” or the rate at which solar energy gets converted into living tissue (or biomass). Primary productivity refers to the rate at which plants convert solar energy directly into biomass. Secondary productivity refers to the rate at which organisms (mostly animals) convert other organisms into biomass. Which is to say, when animals (including humans) eat plants, fungi, and other animals to build tissues, they’re engaged in secondary productivity.

What does this have to do with river deltas? When sea levels began to stabilize about 7,000 years ago after a rapid rise at the end of the last ice age (about 18,000 years ago), they facilitated a huge burst of productivity along the coastal margins of the world’s landmasses. This happened largely because of the particular form continental edges take.

Rising sea levels pushed coastlines several kilometers inland, encroaching on continental shelves. Compared with the steep continental slopes where many coastlines had previously begun, continental shelves have much more gentle gradients. When sea levels stabilized at this higher elevation, they left these shelf areas inundated, creating much larger expanses of shallow water.

Continental Shelf

Note the steepness of continental slopes as compared with continental shelves. The more gentle gradient of continental shelf areas, inundated by rising sea levels, allowed for much larger areas of shallow waters. Image courtesy of Wikimedia Commons.

Shallow waters allow a great deal more light to reach the ocean floor. Since productivity depends ultimately on the conversion, by plants, of solar energy into biomass, it’s probably no surprise that shallow waters are a great deal more productive than deep ocean.

The productive river mouth

Because rivers deliver soil, nutrients, and organic matter to these areas while also stirring up nutrient-rich bottom waters. Deltas and estuaries, then, by virtue of being the meeting place of shallow ocean waters and nourishing rivers, are some of the most productive ecosystems in the world. Enriched by the combined pulses of seasonal flooding and marine tides, these landscapes rival tropical rainforests in their biological abundance. Indeed, a large portion of the world’s marine fisheries today depend fundamentally on the ecosystem services provided by deltas.

These dramatic increases in productivity along the world’s coasts, particularly wherever rivers encountered the ocean, produced a huge surge in the availability of large, nutrient-rich (think omega-3 fatty acids!) organisms. Without sounding too much like an environmental determinist (after all, human cultural practices and social institutions matter critically here), that abundance of high-quality food provided a set of conditions in which human communities could thrive.

"Miraculous" catch of fish

James Tissot, "The Miraculous Draught of Fishes," c.1886-1896. Of course, productivity is hardly a miracle in this sense. Tissot's painting is housed at the Brooklyn Museum.

Deltas and society

And indeed, in some places, they did. In one of my first posts, I described how stabilizing sea levels around 7,000 years also facilitated the formation of deltas and estuaries at river mouths. These new coastal landscapes were sites for some of the highest increases in productivity I’ve been describing. Within about 1000 years of sea levels stabilizing, early urban societies had begun to take hold in these new, highly productive environments all around the world. In the case of the Nile and Yangtze rivers, it only took about 500 years after sea levels stabilized for humans to expand settlement onto newly forming deltaic plains. River deltas globally became important sites for new developments in agriculture and hydraulic engineering, not to mention social organization and cultural exchange.

All that may seem like ancient history. But today deltas (to say nothing of estuaries) are still home to over half a billion people, including almost the entire population of Bangladesh. More than 200 million people live in the Ganges, Nile, and Mekong deltas alone. Meanwhile, several Asian megacities—Shanghai, Karachi, Kolkata (formerly Calcutta), Bangkok, and Ho Chi Minh City, to name just a few—are located on deltaic plains.

Lower Ganges-Brahmaputra Delta in Bangladesh

Almost all of Bangladesh's 150 million inhabitants live in the Ganges-Brahmaputra Delta. Pictured here is the very lowest part of the delta, which contains several large cities of over 1 million people. Offscreen to the north is the Bangladesh capital, Dhaka, also located on the delta. Note Kolkata, India lies on the delta to the east. Image courtesy of Google Earth. Click to enlarge.

That half a billion, then, though a fraction of the globe’s population, isn’t insignificant. After all, the planet’s combined coastal zones—of which deltas are just a tiny portion—make up only 5% of the earth’s land surface.

Which brings me to my main point. Deltas and estuaries aren’t just highly complex ecosystems. They’re also the epitome of porous places. Ann Vileisis may be right that at least Euro-Americans, having long despised wetlands, relegated them to the margins of cultural and social life. But I’d also say that story obscures the fundamentally human histories of these particular wetlands elsewhere in the world.

Can Tho Floating Market, Vietnam, October 15 2009

Cần Thơ Floating Market, Vietnam. Cần Thơ is the largest city in the Mekong Delta. The region has been extensively inhabited for over two thousand years and is home to around 17 million people today. Click to enlarge.

After all, complex societies emerged on (geographically) and alongside (temporally) these landscapes. Moreover, by being located at the intersections of vast watersheds and even vaster oceans, the communities that arose around deltas and estuaries became critical hubs for the exchange of goods, knowledge, and culture. Deltaic and estuarine wetlands may indeed be historically marginal places, but not in the sense of the word that conveys the insignificant or the peripheral. Rather, deltas are margins of encounter. They mark borderlands not only between diverse cultures, but also between earth and water, saline and fresh, nature and society. They are borderlands in which all of these things get muddled in highly productive exchanges (and I’m no longer speaking just ecologically).

Yes, today human-occupied deltas may be facing massive ecological challenges, from rising sea levels and subsiding landscapes, to aquatic dead zones. They have been marked, perhaps indelibly, by human institutions that have sought to stabilize and control what are fundamentally dynamic environments.

But these places also suggest long, deep histories of accommodation and negotiation, of give and take across fluid, porous boundaries between land and water, human and environment.

Further Reading

Biggs, David. Quagmire: Nation-Building and Nature in the Mekong Delta. Seattle: University of Washington Press, 2010.

Büdel, J. “Deltas: A Basis of Culture and Civilization.” In Scientific Problems of the Humid Tropical Zone Deltas and their Implications. Paris: UNESCO, 1966, 295-300.

Day, John, Joel Gunn, William Folan, Alejandro Yáñez-Aranciba, and Benjamin Horton. “Emergence of Complex Societies after Sea Level Stabilized.” Eos, Transactions, American Geophysical Union 88, 15 (2007): 169-170.

Kennett, Douglas J., and James P. Kennett. “Early State Formation in Southern Mesopotamia: Sea Levels, Shorelines, and Climate Change.” Journal of Coastal and Island Archeology 1, 1 (2006): 67-99.

Stanley, Daniel J., and Andrew G. Warne. “Holocene Sea-Level Change and Early Human Utilization of Deltas.” Geological Society of America Today 7, 12 (1997): 1-7.

Vileisis, Ann. Discovering the Unknown Landscape: A History of America’s Wetlands. Washington, DC: Island Press, 1997.

Vörösmarty, Charles J., James Syvitski, John Day, Alex de Sherbinn, Liviu Giosan, and Chris Paola. “Battling to Save the World’s Deltas.” Bulletin of the Atomic Scientists 65, 2 (2009): 31-43.

Woodroffe, Colin D., Robert J. Nicholls, Yoshiki Saito, Zhongyuan Chen, and Steven L. Goodbred. “Landscape Variability and the Response of Asian Megadeltas to Environmental Change.” In Global Change and Integrated Coastal Management: The Asia-Pacific Region. Edited by Nick Harvey. Dordrecht: Springer, 2006, 277-314.

Blue Holes

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A few posts ago, I wrote about what happens when a river in high water jumps its banks to find a new channel or even form an entirely new delta. But often a flooding river overcomes its levees without changing course. Whether deposited by the river or built up by humans in search of flood protection, levees can fail, unleashing a torrent of water over the landscape in an event traditionally known along the lower Mississippi River as a “crevasse.”1

The Bell Crevasse, 1858

A crevasse on John M. Bell's plantation on April 11, 1858. Image from a supplement to "The Picayune," May 16, 1858.

Evidence suggests that some bends in the Mississippi River were even the site of frequent historic crevasses. In uptown New Orleans, for example, a narrow ridge of high ground extends away from the river in a way that’s inconsistent with the area’s natural levees.2 Known as the Carrollton Spur, the ridge likely formed with repeated crevasses near the Carrolton bend. Each burst of sediment-laden floodwaters through the riverbank built up the land one layer at a time.

The Carrolton Spur

Approximate location of the Carrolton Spur in New Orleans, marked by red dotted line. Note the way the spur extends perpendicularly away from the natural levee. Darker shades denote higher ground in this map, except in the case of the river itself. Map by author. Click to enlarge.

This kind of repeated crevassing, however, hasn’t really happened ever since humans have erected and maintained higher, more impermeable levees on the river. Which isn’t to say anthropogenic levees don’t fail, quite the contrary. The infamous breaches along the Industrial, 17th-Street, and London-Avenue canals during and after Hurricane Katrina are among some of the more destructive in recent memory (although, admittedly, those weren’t river levees). Rather, crevasses since European settlement have usually been met with unflagging efforts to repair the breach and prevent further outbursts in the future.

Levee workers in Plaquemines Parish, 1935

Ben Shahn, "Levee workers in Plaquemines Parish," October, 1935. Image courtesy of Library of Congress, Farm Security Administration and Office of War Information Photograph Collection.

Since crevasses often resulted in loss of life, property, or livelihood and since repairing levees took enormous amounts of labor, they are quite well-represented in the historical record. Looking at historic newspapers, plantation diaries, and official federal, state, and parish (Louisiana’s version of the county) records, one can develop a fairly comprehensive picture of major flood years since European settlement and their associated crevasses.

List of crevasses during the floods of 1890

One example of levee breaches in the historical record: a list of crevasses that occurred in Louisiana during the floods of 1890. Between mid-March and late-April over 20 occurred on the Mississippi River alone. Image taken from a map supplement to the "Times-Democrat," September 1, 1890. Click to enlarge.

Don Davis, a geographer at Louisiana State University, compiled much of this data for an essay in Craig Colten’s edited volume, Transforming New Orleans and Its Environs. One of the crevasses Davis unearthed for this project was, fittingly, the Davis Crevasse of 1884 (no relation). Named for the Davis railroad station near which it occurred, the breach was described by one observer at the time as:

“…by far the most destructive single crevasse known in the history of Louisiana. Its waters extend in a sea of more than a hundred miles along the west bank of the Mississippi river [sic].”3

While that claim about the crevasse’s historical destructiveness is a little dubious (until Hurricane Katrina, Sauvé’s Crevasse of 1849 was generally regarded as the most destructive to affect New Orleans), the breach did in fact open a 700-foot wide tear in the levee.

Now, what’s really cool about some of these events is the fact that we don’t just have to rely on historical documents to find evidence of their occurrence. If you take a drive today from downtown New Orleans west out past the airport and get on highway 310, you’ll cross the Mississippi. Make a quick left exit and follow the river back toward New Orleans for about three miles (you’ll pass a massive Monsanto facility when you’re about halfway). Take a right on Levee Road and another quick right at the fork and, after about half a mile, the road will dead end at Davis Pond.

A trip to Davis Pond

A trip to Davis Pond from New Orleans. Map courtesy of Google Maps, 2012. Click to enlarge.

But Davis Pond is no ordinary puddle. It’s actually a “blue hole,” or a water body that forms in a pit scoured out by the surging floodwaters of a massive crevasse. If you were brave enough to take a swim (don’t forget Monsanto’s agro-chem facility up the road) you’d be paddling around in what’s effectively a historical document. This is one of the things I love about environmental history and historical geography: the landscape becomes as much a part of your research method as the archive.

Davis Pond

Davis Pond, a "blue hole" produced by the Davis Crevasse of 1884. Image courtesy of Google Earth, 2012. Click to enlarge.

Not every crevasse produces a blue hole, of course, but here and there you’ll find them along the Mississippi. Craig Colten pointed out another one to me just downriver from New Orleans in the town of Poydras. Tapering from the present-day, Army Corps of Engineers levee down to a point near the town’s main intersection, it even more dramatically suggests a crevasse than Davis Pond. Today it’s mainly a residential amenity: about a dozen homes outfitted with small docks line its shores.

Poydras Pond

The "blue hole" left by the Poydras Crevasse of 1922. At its peak, the breach was 1,500 feet wide and scoured a pit 90 feet deep. Click to enlarge.

But on April 27th, 1922, a raging flood ripped a 1,500-foot wide hole in the levee, sending a 100-foot high wall of water across the landscape and scouring a 90-foot deep pit from the outskirts of town. Not long after, observers upriver at New Orleans saw that, freed from its confines, the flooding river began to rapidly retreat. Falling two feet in three days, the river spared the city, thanks largely to the destruction it unleashed at Poydras.

When the river once again threatened New Orleans in the disastrous floods of 1927, engineers remembered Poydras and, with the blessing of the city’s political and business leadership, dynamited the levees just a little further downriver at Caernarvon, in St. Bernard  Parish. That demolition sacrificed a largely Isleño (Canary Islander) settlement, a population that for some time had been relegated to the social and economic margins of the region.

Caernarvon Crevasse, April 27, 1927

On April 29, 1927, the US Army Corps of Engineers used 40 tons of dynamite to create a crevasse at Caernarvon, 13 miles downriver of downtown New Orleans. The breach was intended to save New Orleans from flooding at the expense of St. Bernard Parish. Image courtesy of NOAA's National Weather Service Collection, ID: wea00739. Click to enlarge.

Though it remains unmarked, the blue hole in Poydras, LA is thus an odd kind of memorial. The intentional crevasse at Caernarvon that it inspired lives on in the social memory of New Orleans. Levee failures during Hurricane Betsy in 1965 inundated three neighborhoods in New Orleans and two in neighboring St. Bernard parish. Largely poor and African-American, residents of these neighborhoods were convinced that the Army Corps of Engineers had again dynamited levees in order to spare people “that mattered.” Those rumors persisted through 2005 when, once again, residents of the Lower Ninth Ward were certain that the city had sacrificed its poorest residents to preserve the fortunes of its wealthiest.

New Orleans flooding after Hurricane Katrina, 2005

New Orleans in flood. Photo taken sometime between August 31 and September 19, 2005. Image courtesy of NOAA. Click to enlarge.

There’s zero evidence that levees were intentionally dynamited during or after Hurricane Katrina. Yet the fact that these kinds of rumors emerged (and persisted) both in 1965 and 2005 speaks volumes about the ways class and race have historically been intertwined with environmental risk in the region. Indeed, the tragedy of Hurricane Katrina was so profoundly shaped by race and class that even without dynamited levees, the disaster exposed deep veins of inequality, neglect, and social discord.

If you know where (and how) to look, southern Louisiana’s landscape is full of unintentional monuments just like Poydras Pond. Whether etched, placed, or otherwise marked on the land, these monuments can serve as revealing guides to environmental histories and memories of social inequality.

Further Reading (and Viewing)

Barry, John. Rising Tide: The Great Mississippi Flood of 1927 and How It Changed America. New York: Simon and Schuster, 1997.

Campanella, Richard. Time and Place in New Orleans: Past Geographies in the Present Day. Gretna, LA: Pelican Publishing, 2002.

Colten, Craig. An Unnatural Metropolis: Wresting New Orleans from Nature. Baton Rouge: Louisiana State University Press, 2006.

Davis, Don. “Historical Perspective on Crevasses, Levees, and the Mississippi River.” In Transforming New Orleans and Its Environs. Edited by Craig Colten. Pittsburgh: University of Pittsburgh Press, 2000, 84-106.

Gomez, Gay. “Perspective, Power, and Priorities: New Orleans and the Mississippi River Flood of 1927.” In Transforming New Orleans and Its Environs. Edited by Craig Colten. Pittsburgh: University of Pittsburgh Press, 2000, 109-20.

When the Levees Broke: A Requiem in Four Acts. DVD. Directed by Spike Lee. Home Box Office, 2006.

Saucier, Roger T. Geomorphology and Quaternary Geologic History of the Lower Mississippi Valley. Vicksburg, MS: US Army Corps of Engineers Waterways Experiment Station, 1994.

Shallat, Todd. “In the Wake of Hurricane Betsy.” In Transforming New Orleans and Its Environs. Edited by Craig Colten. Pittsburgh: University of Pittsburgh Press, 2000, 121-37.

  1. The term, like “levee” (from “levée,” meaning “raised”) is testimony to the original French occupation of Louisiana. ↩
  2. While avulsions have left remnants of historic natural levees across New Orleans and away from the river—e.g., the Metairie and Gentilly Ridges—the high ground in Carrollton is not part of a historic natural levee either ↩
  3. “Territory submerged by the Davis Crevasse,” Daily States, May 22, 1884. ↩

A Watershed Border Crossing

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I recently came across a fascinating old post from landscape-architecture junky Geoff Manaugh over at BLDGBLOG (“building blog”). Manaugh summarizes an event that took place on June 4, 2011 as part of Political Equator 3, a border-crossing, mobile conference that was held simultaneously in San Diego and Tijuana.

The event in question was a participatory, performance-based art project that transformed a culvert into a “pop-up” border crossing. Mexican officials, stationed behind folding tables at the tunnel’s southern end, issued visas to conference-goers as they crossed from the United States into Mexico under the border fence.

Manaugh uses the language of porosity to describe the consequences this ephemeral, obscure port of entry has for the nation-state. He even calls for a history of similarly “peripheral” border crossings—as generated by “espionage, political asylum, wartime defection,… divided cities, and much more”—that blur the borders of sovereignty.

What interested me most, however, was the fact that this border crossing was also meant to highlight the social-ecological consequences of human borders. The culvert-turned-border-crossing allows water to drain unimpeded from Mexico into the United States. Tijuana and San Diego surround the mouth of the Tijuana River, which drains a watershed covering 1,750 square miles, most of which lies in Mexico.

Tijuana River Watershed

The Tijuana River Watershed covers 1,750 square miles, 3/4 of which lies in Mexico. The Tijuana River National Estuarine Research Reserve (TRNERR) is marked in red at the foot of the watershed. Map courtesy of TRNERR. Click to enlarge.

The Tijuana Estuary

Now, lying at the mouth of the Tijuana River, completely within the boundaries of San Diego county (and therefore wholly within the United States) is the Tijuana River Estuary. Designated a National Estuarine Research Reserve under the US Department of Commerce and a “Wetland of International Importance” under the United Nations Ramsar Convention on Wetlands, the reserve contains a national wildlife refuge and is an important rest stop for birds migrating along the Pacific Flyway.

The estuary is a coastal wetland where freshwater from the Tijuana River watershed mixes with the Pacific ocean to produce a fundamentally dynamic salt-marsh ecosystem. Thanks to wave action, tides, and seasonal changes in the river’s flow, the permeable boundaries between fresh, brackish, and salt water constantly shift across the landscape. The river mouth itself, meanwhile, also shifts north and south along the coast as storms, rough seas, and changes in streamflow alter the topography of the estuary.

Because the estuary sits at the foot of a watershed, whatever happens upstream, whether in Mexico or the United states, has a dramatic impact on its ecology, regardless of border fences. The culvert traversed by the Political Equator 3 conference ensures drainage within the watershed, but it also illustrates the ways social, economic, and environmental challenges and inequalities upstream transcend political boundaries. Squatter settlements totaling over 85,000 people in Los Laureles canyon on the outskirts of Tijuana—settlements that are themselves emblematic of failures in Mexican social policy—produce erosion and pollution problems that are felt acutely in the estuary (indeed, some of those problems no doubt flow through this very culvert).

Colonia San Bernardo in Los Laureles Canyon

Colonia San Bernardo, a squatter settlement located at the southwestern end of Los Laureles Canyon. Home to over 85,000 migrants from all over Central America, Los Laureles Canyon settlements like this are emblematic of failing economic and social policies surrounding immigration and global trade. Los Laureles is also the site of extensive poverty-driven erosion and pollution, problems that acutely affect the Tijuana River Estuary downstream and across the US border. Image courtesy of Jon Hill, November 8, 2008. Click to enlarge.

No matter how impermeable the border is made in terms of immigrating bodies, the fate of the estuary will always be intimately connected with the fate of marginalized people and communities across the fence. The culvert not only reveals the ways watersheds collapse distance and undermine artificially imposed boundaries, it also highlights some of the ironies and contradictions of those boundaries. What, for instance, would rigidly narrow immigration and border policies look like if they were re-conceived in terms of social and ecological watersheds? What could such a porous set of policies achieve beyond simply preserving ethnic purity jobs and economic resources for American citizens?

You can read more about the Political Equator 3 border crossing (and see some photos from the event) at BLDGBLOG and At the Edges.

And, just in case you want to get a better sense of the place in which this border crossing appeared, I’m almost 100% certain—after close examination of the photos posted at BLDGBLOG and a little topographical research in Google Earth—this is the culvert traversed by Political Equator 3:


View Culvert in a larger map

The Physical Environment 3: Building on Its Own High Ground

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This is the third in a series of three introductory posts I’m dedicating to the physical environment of deltaic landscapes. The first post looked at land-building and the timing of delta formation across the globe. The second discussed the quirks of topography in river deltas. Today, I’ll conclude the series by revealing what happens when, as is the case on a deltaic plain, a river occupies the landscape’s high ground.

Holding the high ground?

Bird's Foot Delta of the Mississippi River

As the river lays down new land, it also lengthens. Image courtesy of NASA, 2007. Click to enlarge.

The Mississippi River’s deltaic plain begins near Baton Rouge, Louisiana. From here down to the Gulf of Mexico, the region’s high ground is always found closest to the river in the form of its natural levees. That the river is constantly surrounded by, and indeed building upon, its own high ground has some pretty remarkable consequences. As the Mississippi lays down new land, it also lengthens. And as it lengthens, the slope of the river flattens, its waters slow, and sediment starts accumulating in the riverbed. Over time, the river ends up being quite a bit higher in elevation than the surrounding territory, natural levees aside.

Since water always takes the path of least resistance, the only things keeping the river in its channel under these conditions are its natural levees. Given a large enough flood, the river could easily overcome its banks to find a much steeper, much more direct path to lower ground. This kind of event—called an “avulsion”—takes place in deltas with some frequency, both at large and small scales.

Small scale: meander cutoffs, meander scars, and oxbow lakes

NASA - Rio Negro Meander Scars - 2010

Meander scars and oxbow lakes in the floodplain of the Rio Negro, Argentina. Image courtesy of NASA, 2010.

At smaller scales, avulsions work to cut through meanders (creating a “cutoff”) and form new river channels alongside older ones to produce distinctive patterns of meander scars and oxbow lakes.

In 1944, a U.S. Army Corps of Engineers consultant named Harold Fisk used a spectacular aesthetic sensibility to map these patterns as produced by the lower Mississippi over the last 10,000 years. You can download high-quality PDFs of Fisk’s maps from the Army Corps of Engineers here.

Harold Fisk - plate 22-09 - 1944

Plate 22-09 from Harold Fisk's "Geological Investigation of the Alluvial Valley of the Lower Mississippi River," 1944. Click to enlarge.

Large scale: “delta switching”

Meanwhile, large-scale avulsions in the Mississippi River have resulted in much more dramatic landscape transformations. In these events, the river spills over to build an entirely new lobe of land out into the Gulf of Mexico. Also called “delta switching,” this process has occurred about seven times over the last 7000-8000 years.

Delta Switching

The seven deltaic lobes of the Mississippi River. The Balize delta is the current "bird's foot" delta. Image public domain from Wikimedia Commons. Click to enlarge.

In fact, we’re overdue for another. If it weren’t for a serious piece of infrastructure called Old River Control near Simmesport, La, the Mississippi would likely be flowing down to the Gulf through the mouth of Atchafalaya River, over 100 miles west of the current Balize (or “bird’s foot”) delta of the river. Given that the Mississippi River is one of the world’s busiest commercial waterways, imagine the havoc that would cause not only the city of New Orleans, but also the entire United States.1

References

Fisk, Harold. Geological Investigation of the Alluvial Valley of the Lower Mississippi River. Vicksburg, MS: US Army Corps of Engineers, Mississippi River Commission, 1944.

Gupta, Avijit (ed.). Large Rivers: Geomorphology and Management. Hoboken, NJ: Wiley, 2008.

McPhee, John. The Control of Nature. NY: Farrar, Straus, and Giroux, 1989.

Roberts, Harry. “Delta Switching: Early Responses to the Atchafalaya River Diversion.” Journal of Coastal Research 14, 3 (1998): 882-899.

  1. John McPhee told this story with unparalleled skill in a 1987 issue of The New Yorker. You can also read it in his collection, The Control of Nature. ↩

Mountains and Rivers

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I’m delaying the third post on deltaic physical environments (the other two are here and here) to briefly write about a map I recently came across at Big Map Blog (which you absolutely should follow, by the way).

Colton - Mountains and Rivers - 1856

George W. Colton, "Mountains and Rivers," 1856. Image courtesy of the David Rumsey Map Collection. Click for high-resolution, zoomable image.

Produced by George Colton in 1856, the map depicts, left to right, several dozen major world rivers decreasing in length and several hundred mountains increasing in size.

Be sure to click the image above for a super high-resolution, deep-zoom version.

Although the map completely abstracts individual rivers from their particular uplands, I still love the way its arrangement of features implies the massive redistribution of sediment that takes place in large watersheds.

Of course, not all the rivers shown here end in deltas. Sometimes tides, waves, sediment loads, and the physical features of both the river and the body of water into which it drains all combine to prevent land from accreting at a river mouth, forming an estuary instead.

But even though such kinds of conditions might not allow for land-building, rest assured that each river depicted on this map is diligently transporting bits and pieces of its uplands down to its mouth. The Alabama/Mobile/Tombigbee, for example, ends in an estuary rather than a delta, but it still discharges 4.5 million tons of sediment into Mobile Bay each year. And it’s one of the smaller rivers show here (in the right third of the image).

Additionally, Colton’s map documents not only the diversity of deltaic landforms around the world, but also suggests just how many deltas have in fact been historically important sites of human occupation. Moving from left to right on the map, the Mississippi, Yangtze, Ganges and Brahmaputra (“Burrampooter” according to Colton), Niger, Tigris and Euphrates, Indus, and Rhine river deltas—to name just a handful—have all supported major population centers, some of which are thousands of years old.

And finally, I’d say that the map is just great for exploring. Zoom right in and you’ll find glaciers, active volcanos, major architectural and natural landmarks, and even some traces of Alexander von Humboldt’s Latin American expedition.

There are a lot more wonderful, super high-resolution thematic maps like this one available through both Big Map Blog and David Rumsey’s Map Collection. Be sure to check both sites out for similar treasures, regardless of your field/subject of interest.

 

The Physical Environment 2: High Ground, Low Ground

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This is the second in a series of three introductory posts focused on some of the basics of deltaic physical environments. Last time, I looked at what defines a river delta as well as the timing of coastal delta formation globally around 7000-8000 years ago.

Natural levee and backswamp

A key thing to remember about deltaic landscapes is that the rivers running through them are creating, rather than eroding, land. I know I probably sound like a broken record on that front, but it’s also easy to overlook some of its implications. When we think of a typical riparian landscape, I think we often imagine a river valley, in which the highest ground is furthest from the river.

Thomas Cole - The Oxbow - 1836

A river valley. Note the high ground is furthest from the river. Image: Thomas Cole's "The View from Mount Holyoke, Northampton, Massachusetts, after a Thunderstorm," 1836 (more commonly known as "The Oxbow"). Click to enlarge.

Because of the way rivers deposit sediments in deltas, however, the highest ground is actually closest to the river. During seasonal flooding in these landscapes, sediment-laden water rises above the riverbank. As it spreads over the floodplain, that water suddenly slows, allowing particles of suspended sediment to settle and build on the landscape.

Trudeau - Plan of the City of New Orleans - 1798

Carlos Trudeau's map of New Orleans in 1798. Note that settlement hugs the Mississippi and that lands furthest from the river are marked as "cypress swamp." Click to enlarge.

Since the heaviest (and therefore largest) particles settle first, the high ground in river deltas always forms closest to the river. This embankment is called the natural levee. The further one gets from the main channel of the river, the smaller the particles of sediment that accumulate. The relatively narrow strip of high ground that constitutes the natural levee, then, begins to slope back down until it becomes a low wetland known in Louisiana as “backswamp.”

So, while deltas are typically very flat places, what little elevation there is usually hugs the river. That topography is particularly visible in the patterns of historical settlement in the Mississippi River delta.

Abbot - Approaches to New Orleans Map - 1863

Henry L. Abbot's Civil War map of "Approaches to New Orleans," 1863. Note that 65 years after Carlos Trudeau's map, settlement still hugs the high ground adjacent to the river. Click to enlarge.

 

 

 

While levees, drainage projects, and other extensive alterations to the landscape have allowed people to build homes and expand urban areas into what was once swampy low ground, places like New Orleans first emerged on the natural levee immediately along the river.

But where does all this sediment come from?

River deltas aren’t building new land and high ground from sediment plucked out of thin air. This material all comes from somewhere. And the way to figure out that “somewhere” is to look at a map of a river’s watershed. In the case of the Mississippi, you’ll notice that its waters are supplied by streams and rivers from as far west as the Rockies and as far east as the Appalachians.

Shannon1 - Mississippi River Watershed - Wikimedia Commons

Mississippi River sediments originate as far west as the Rockies and as far east as the Appalachians. Image courtesy of user "Shannon1," Wikimedia Commons. Click to enlarge.

If we think about the distinction between river valleys and river deltas as being one of eroding versus accreting landscapes, we can start to imagine that large river systems are massive sediment redistribution programs. Rain and snowmelt falling higher up in the watershed carry weathered rocks and soils from across the continent down to the mouth of the Mississippi. There, deposited as sediment, these fragments of distant landscapes build the delta. In a way, then, Deltas are the means by which ancient mountains get transformed into new shorelines.

But humans have also radically interfered with that sediment redistribution process in deltas all over the world and the Mississippi River delta is no exception. These days, most sediments are either trapped behind dams throughout the watershed or prevented from spreading over the landscape by the levees lining the river. Land-building in the Mississippi’s deltaic plain has, except in a few locations, practically ceased.

Suspended Sediments 1700 vs 1990 - USGS Circular 1133 - 1995

Sediments reaching the Mississippi River delta have declined significantly since 1700 due to dams and levees. Diagram from Meade (ed.), "Contaminants in the Mississippi River, 1987-92," 1995, pg. 18. Click to enlarge.

References

Campanella, Richard. Bienville’s Dilemma: A Historical Geography of New Orleans. Lafayette, LA: University of Louisiana at Lafayette, 2008. Also be sure to check out Campanella’s website at http://richcampanella.com/.

Gupta, Avijit (ed.). Large Rivers: Geomorphology and Management. Hoboken, NJ: Wiley, 2008.

Meade, Robert (ed.). Contaminants in the Mississippi River, 1987-92. Reston, VA: US Geological Survey, Circular 1133, 1995.

#Envhist and the Ivory Tower

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ASEH 2012

Last week, the American Society for Environmental History (ASEH) held its annual meeting here in Madison. I originally intended to continue with my series of posts on the physical landscapes of river deltas, but after a fantastic program of paper sessions, workshops and roundtables, a mind-blowing plenary talk by Jenny Price, and much, much more, I feel like I can‘t not put together some thoughts on the event.

It was the first time I’d properly attended this particular academic conference and I was really struck by the energy and creativity of this community of thinkers and writers. One session titled “In Pursuit of the Natural: Nature and Bodies in American Environmental History” gathered scholars exploring some really rich intersections between human biology, laboratory animals, gender and environmental politics, disability, and ideas of labor and nature. I’m thinking of two papers here in particular.

Jessica Martucci gave a talk about the history of La Leche League (a breastfeeding activist organization started by young Chicago mothers in the 1950s) and fears around toxic breast milk that emerged in the latter 20th century.

Jennifer Seltz presented a fascinating piece on African clawed frogs and early pregnancy testing (many of these animals, after being harvested in South Africa in the 1940s and 50s, were shipped to doctors’ offices in North America and Europe where they were kept as living pregnancy tests. A female patient’s urine would be injected into a female frog. If the animal ovulated within a day, that signaled the woman was pregnant).

These two papers were, I think, emblematic of what I loved about the conference, and I’m not exactly talking about their content (though that was certainly very, very cool). Martucci and Seltz brought together scholarship from a wide range of disciplines in thought-provoking, and revelatory ways, all while telling really engaging stories. What’s more, it’s not hard to see how those stories can really matter for people outside the academy.

Digital Environmental History

That possibility of mattering beyond the academy brings me to what was by far the most inspiring event of the meeting. Yesterday, about seven or eight presenters (mostly historians, though certainly not all) packed a conference hall for a roundtable on “digital environmental history.” Work in the “digital humanities”—at least as I understand it—can range from simply blogging, to quantitative analyses of historic texts (e.g., a keyword analysis of Shakespeare’s collected works), to historic data visualization, to massively complex and interdisciplinary multimedia projects.

A lot of exciting stuff has been happening around the digital humanities lately and, especially since I’m no expert, I won’t try to summarize that field of scholarship here (for background, I recommend checking out Dan Cohen’s blog, Bill Cronon’s columns as president of the American Historical Association, and Digital Humanities Now). What I will say is that, in addition to being a set of tools and approaches, the digital humanities also have some pretty far-ranging implications for the academy and knowledge production. And those implications will seem familiar for anyone who has thought about the social and political transformations the web as a whole has engendered over the last two decades: new forms of public discourse and participation, massive challenges to copyright, the de-centering of expertise, new opportunities for communication and collaboration, etc., etc. etc.

Accordingly, the presentations at the roundtable were remarkable for the breadth of exciting, novel, and above all (at least for me) publicly oriented work they represented. Two examples are particularly illustrative:

Jessica van Horssen told us about how she had transformed her dissertation about the town of Asbestos in Quebec into a digital graphic novel as well as a series of EHTV episodes. Van Horssen’s work has created space not only for collaborations with researchers across disciplines (such as epidemiologists), but also for dialogue with members of Asbestos’s community.

Finn Ryan, meanwhile, showed us a fantastic short film from Climate Wisconsin, a multimedia project he directs and produces oriented toward community participation and education around climate issues in the state.

I’m not going to hold forth on the ways new media are creating upheaval in the academy. Far better thinkers and writers than I have been discussing the digital revolution with eloquence and insight for a while now. But I will say that van Horssen and Ryan’s work shows concretely just how much potential there is for the digital humanities to reach beyond the often-maligned ramparts of the Ivory Tower. It’s through these kinds of projects that I’m starting to see how digital technologies, paired with the work of creative, community-oriented and critically minded scholars, can facilitate important exchanges between the academy and broader publics.

And these media don’t only hold great promise in terms of producing work that better serves and is more accessible to the people whose tax dollars pay for scholarly research. They also create a space for envisioning new forms of scholarly production (like a graphic novel or short film) and new opportunities for interdisciplinary and community-based collaboration.

If you’ll permit me a metaphorical stretch to keep with the themes of this blog, I’ll suggest that digital environmental history holds the potential for making some long-standing boundaries around environmental scholarship—form, expertise, participation, audience, and so on—a great deal more porous.

Of course, since I really am new to thinking about all of these issues, I can’t claim to offer much critical or revelatory insight. Nor can I come even close to summarizing the most exciting developments in the digital humanities. Instead, I’d suggest taking a glace at some of the following resources:

Essays

Maria Bustillos’s essay on Wikipedia for The Awl

Bill Cronon’s AHA column about Wikipedia

Wilko von Hardenberg’s piece on the #envhist hashtag

A Journal of American History roundtable on “The Promise of Digital History”

Tools and primers

The Environmental History app from NiCHE

Tooling Up for Digital Humanities at Stanford

William Turkel’s digital humanities workflow

More people (and things) to follow

Active History (also on Twitter: https://twitter.com/#!/ActiveHist)

Ant, Spider, Bee

Jon Christensen

Jim Clifford

The #envhist hashtag on Twitter

Fred Gibbs

Wilko von Hardenberg

Finn Arne Jørgensen

Sean Kheraj

The Rachel Carson Center Environment and Society Portal

The Physical Environment 1: River Deltas and Delta Time

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In my first post, I gestured at some of the reasons I do research in the greater Mississippi River delta. But what is a river delta anyway and what distinguishes this delta in particular? Over the next three posts I’ll answer those questions by covering some of the fundamentals of delta physical geography. This stuff will probably be a little basic for many physical scientists and perhaps a little far afield for most humanists. But to both camps: please stick with me. The “basics” always bear repeating, especially given how extraordinary deltaic landscapes actually are. And besides, the physical-landscape side of things matters deeply for the cultural and historical work I do throughout my project.

So, with that said…

What is a river delta anyway?1

Bird's Foot Delta of the Mississippi River

The "bird's foot" delta of the Mississippi River. Note the fingers of sediment extending new land into the Gulf of Mexico. Image courtesy of NASA, 2007. Click to enlarge.

Most simply, deltas are landforms that develop wherever a river enters a large body of water—whether ocean, lagoon, or even lake (yep, there are inland deltas)—and deposits sediment more rapidly than can be eroded. Over time, the accumulation of sediment—usually sand, silt, and clay—cause the shoreline to advance, effectively building new land.

Deltas get classified according to the various forces that dominate that land-building process. Which is to say, deltas are defined by whether waves, tides, or the sediment load of the river itself most highly influence the shape of the landform. The active part of the Mississippi delta is classified as fluvial (i.e., river) dominated because of its high sediment loads compared with wave and tide action. Fluvial dominated deltas tend to stretch long fingers or large, broad lobes of shoreline into whatever body of water they encounter.

The Nile River Delta

The term "delta" comes from the Greek capital letter "D," which was thought to resemble the triangular shape at the mouth of the Nile River. Base image courtesy of NASA, 2000. Click to enlarge.

Oh, and why “delta?” The Ancient Greeks believed that the triangular island of sediment at the mouth of the Nile looked much like their triangular letter “D,” or “delta.”2

Delta time

Deltas are fundamentally more dynamic than most other large landscape features. Not only do land-building and erosion take place in what is geologically just a blink of an eye, but the deltas that exist on the planet today are also just really young landforms. It’s fitting, then, that in mathematics and the sciences, “delta” stands for change.

Dboutte - Coastal Change Diagram of Southeastern Louisiana - Wikimedia Commons

The land-building that began at the mouth of the Mississippi River around 7000 years ago was also beginning at coastal deltas around the globe. Image courtesy of user "Dboutte," Wikimedia Commons. Click to enlarge.

Now, one of the most surprising things I’ve learned in trying to get some basic delta geomorphology under my belt is that all of the world’s coastal deltas are about the same age.

Basically, when the last ice age ended about 18,000 years ago, sea levels rose so rapidly that shorelines around the world were pushed several miles inland. Once sea levels began to stabilize about 7,000 years ago, river sediments were able to accumulate (or “accrete”) to form the deltaic landscapes seen around the globe today. So, just as the Mississippi River began building land out into the Gulf of Mexico, so too the Ganges, Yangtze, and Nile rivers (to name just a few) were forming new landscapes in the Bay of Bengal, the East China Sea, and the Mediterranean.

 

  1. This post draws on: Avijit Gupta, “Introduction,” in Large Rivers: Geomorphology and Management, edited by Avijit Gupta (Hoboken, NJ: Wiley, 2008), 1-5; Sampat Tandon and Rajiv Sinha, “Geology of Large River Systems,” in Large Rivers: Geomorphology and Management, edited by Avijit Gupta (Hoboken, NJ: Wiley, 2008), 7-28 ↩
  2. While Herodotus often gets credit for introducing the technical term in the 5th century, BCE, Francis Celoria argues he only used the word as a proper place-name (i.e., Delta, capital “D”) for the mouth of the Nile and that that name had already been in use for as much as several centuries. Only much later in around 200 CE, claims Celoria, did the word take on the general, technical significance it has today. Francis Celoria, “Delta as a Geographical Concept in Greek Literature,” Isis 57, no. 3 (1966): 385-88 ↩