Alan Wiig Geography 810

14 May 2007

A review of large-scale anthropogeomorphologic studies: From deep-time to the post-anthropocene era

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ABSTRACT As earth moving and manipulation technologies have evolved, humans have gone

from hunting and gathering, to using iron ploughs, to industrial agriculture, and from walking footpaths to commuting on continental freeway systems. Humankind’s impact on global-scale geomorphology has grown with the exponential population gains. The rates of anthropic erosion that are a by-product of modern, global living now greatly exceed rates of natural soil formation. Anthropogeomorphology has over the last century attempted to quantify the extent of human-induced earth change. More recent scholarship has attempted to predict future change. Since humans are now the primary agent of geomorphology, the global scale and short timeframe of change will be as damaging to humanity’s long-term survival as global climate change. Keywords: humans, geomorphic agents, agriculture, construction, future landscape change, post-anthropocene era INTRODUCTION

Anthropogeomorphology, “the study of the role of humans as a geomorphological

agent,” goes back at least to the mid-nineteenth century and George Perkins Marsh’s Man

and Nature; or, physical geography as modified by human action (definition from Goudie

2000, 23). The sub-field is a dynamic, multi-disciplinary aspect of geomorphology intent

on quantifying humankind’s impact on the ground we live on—an oft-neglected yet

completely essential part of all our lives. In the hundred-fifty years between Marsh’s

study and the present day the ability of humans to affect geomorphology has only

increased with more, and more efficient, technologies. Recent articles have continued to

look with concern at how, with the increasing human population, almost no part of the

earth’s surface has been unaffected by anthropogeomorphology. Studies have also

looked into the deep past to set natural geomorphic baselines as a way to gauge the

impact humans will have on the earth’s surface into the future. Whereas much of the

general geomorphological literature deals with particular areas and their unique

situations, anthropogeomorphology looks at the large-scale effects of humans changing

the surface of the Earth.

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HISTORIC HUMAN-CAUSED EROSION

Although the extent of anthropogenic geomorphology has grown enormously

since the Industrial Revolution, it is a process that has occurred since the Paleolithic

period 1,000,000 years ago. The first anthropogeomorphic activity was the making of

seasonal shelters from rock through the moving of boulders for the walls, and

“foundations and floors from small rubble” (Hooke 2000, 843). Constructing rock

shelters was most likely the only major anthropogeomorphic activity until “ten thousand

years ago, in the late Paleolithic, [when] humans quarried flint” (Hooke 2002). This need

for flint for stone tools initiated the first instances of mining (Hooke 2000, 843).

The initial permanent human settlements have been traced back to around 14,000

BC. Agricultural cultivation started between 6,000 and 8,000 BC and led to the first

centralized, urban spaces (both Morris 1994, 3). The development of villages then cities,

meshed with the rise of agrarian societies, together initiated the use of more building

materials for the permanent dwellings and the need for irrigation projects to water the

crops. The construction of canals and dikes followed, and became the first large-scale

earth-moving activities (Hooke 2000, 843). In roughly the same time period the wheel

was invented, which “facilitated transport of geologic materials, both ore and stone, as

well as other trade goods. Because loads in carts cannot be moved efficiently over rough

terrain, roads were invented to make maximal use of the increased hauling capacity

provided by the wheel (Hooke 2000, 843).

Copper mining and then bronze smelting, combining copper with tin, initiated

new mining techniques. It was not until the Iron Age, 2,500 years ago, that iron became

cheaper and thus available to a larger population. This initiated a positive feedback loop

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where, as one activity required the other, iron plough blades as well as iron hand tools

allowed agriculture, mining, and stone masonry to advance upon the earth, creating the

need for more iron ore to be mined, and so on. The more iron cast, a greater

manipulation of the natural landscape was made possible (Hooke 2000; 2002). With

more processes, more materials, more efficient technologies, and most importantly, a

growing global population, anthropogeomorphology has continued unabated, growing

exponentially with the passing years (Haff 2003).

The primary cause of global-scale erosion became anthropogenic “sometime

during the latter part of the first millennium A. D.” Human-caused erosion is not just a

symptom of industrial society—it predates that by a millennium (Wilkinson 2005, 161).

Through an examination of “prehistoric denudation rates imposed on land surfaces solely

by natural processes,” Bruce Wilkinson determined that:

“Mean denudation over the past half-billion years of Earth history has lowered continental surfaces by a few tens of meters per million years. In comparison, construction and agricultural activities currently result in the transport of enough sediment and rock to lower all ice-free continental surfaces by a few hundred meters per million years. Humans are now an order of magnitude more important at moving sediment than the sum of all other natural processes operating on the surface of the planet” (2005, 161).

More important than the erosion alone, this erosion associated with agriculture and

construction “exceed soil formation by an order of magnitude” (2005, 161). Not only do

human actions account for the majority of erosionary activities, it also greatly outpaces

soil formation. To determine these rates Wilkinson set a baseline through estimating the

“uplift and erosion [of sedimentary rock which] results in a progressive decrease in

epoch-long interval rock volume with increasing age.” He goes on, stating that “data on

surviving amounts of sedimentary rock therefore allow for estimation of epoch-long rates

of sediment accumulation, which in turn relate to rates of physical and chemical

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denudation over Earth’s subaerially exposed surface for at least the past half-billion

years” (2005, 161). As the base level of all human actions, the amount of earth-change

construction and agriculture accomplish in creating sustenance and shelter are so grand

they are difficult to conceive of. We as humans both individual and as a species impact

the Earth enormously: “soil and rock movement currently amounts to ~21t per person

per year (6 from construction, 15 related to farming)” (Hooke 2000). Also, over-

irrigation, which leads to soil salination, and fertilization of cropland are both instances

of chemical weathering (Brown 1970, 79). Even if the erosion is balanced across

continents, the overdeveloped north accounts for much more than the global south.

Wood and other construction products are made elsewhere, and agricultural commodities

and products travel to global markets. The links are complicated and only the earth-

change is universal.

Construction sites cause significant erosion—in Japan alone urban land use

development accounted for 1.3 x 10 (to the 9th) cubic meters a year in 1970 (see

Appendix 1 for a graphic representation of human-caused erosion) (Kadomura 1980,

138).1 The need for construction materials from offsite and out of the area, of a sort that

modern modes of transportation make possible, is also impacting geomorphic processes

greatly: “Demand in the UK [for aggregates for concrete] has gone from 20 million tones

per annum in 1900, to 50 m tones in 1948, to 276 m tones in 1973. It is an increase per

capita from 0.6 tones per year to 5 tones per year” (Goudie 2000, 269).

1 Kadomura goes on, writing that “the rate of lowering caused by both construction and agricultural activities [in Japan] may reach 4,000 cubic meters per kilometer square a year, eight times the background level of mean erosion rate in mountainous areas, or 80 to 400 times that in hilly lands.”

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At the rate it is occurring today, “the amount of [eroded] material would fill the

Grand Canyon of Arizona in ~50 years,” again a scale much larger than that of the

landscape, which is the largest the human eye can take in. This matters

geomorphologically because “over the interval of anthropogenic erosion, delivery of

sediment to rivers quickly exceeds rates of transport that are possible in fluvial systems

that have more or less attained geomorphic equilibrium over a significantly longer

prehistory with an appreciably lower sediment flux” (Wilkinson 2005, 163-164). What

humans do at every level is to disrupt geomorphic equilibrium; this is anthropoge’s end-

result.

MODERN ANTHROPOGE STUDIES

Eric H. Brown sets out a classification methodology in his article Man shapes the

earth. He writes that “man, the geomorphological process, creates new landforms in two

ways: as the direct instrument of change, and through his diversionary influences upon

other geomorphological processes.” Examples would be digging a ditch, or embanking a

river to prevent or hinder its meandering. Over the last 150 +/- years the scale of these

processes has increased in area to encompass the globe, and the scope of the processes

has increased as well (76). Brown goes on to further discuss more direct anthropoge,

listing the creation and maintenance of transportation networks, including air and sea,

since ports for both take up large amounts of land, all of which needs to be relatively flat

and stable and not actively eroding. Extractive industries create incidental but direct

effects, as do sunken roads that can channel rainwater (77).

The indirect influence of man on the form of the ground occurs especially through

the sealing of the surface of the Earth—the ground becomes fossilized under roads and

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buildings. Ten percent of the total land area in urbanized countries, as of 1970, is

“preserved” this way. Undoubtedly this number has only grown since then. Man’s

influence on the land through mechanical and chemical weathering of the soil should not

to be disregarded, as it “alters the temperature regime and permeability within the first

meter below the Earth’s surface, where most geomorphological activity is concentrated”

(Brown 1970, 78-79). These indirect actions account for the most geomorphic change; in

addition to road building, it is represented in part by slope erosion following ploughing or

grazing and the acceleration of coastal processes by embankment, jetty, and groyne

building (see Appendix 2).

In The human impact on the natural environment, Andrew Goudie shifts the term

“indirect” in a useful way. He classifies indirect anthropogenic landforms as ones that

tend to involve the acceleration of natural processes, like hydraulic mining, and are the

“most crucial aspect of anthropogeomorphology” (2000, 263). Much of Goudie’s

discussion of anthropoge is done to update one of the classic studies in the field, R. L.

Sherlock’s Man as a geological agent: An account of his action on inanimate nature,

from 1922. Sherlock’s work is cited as the first significant account of anthropoge, and

his overall conclusion is that humans works like glaciers—unorganized and generally

destructive (Sherlock 1923; Cleland 1924).

The large-scale and unsustainable, indirect and direct modification of the earth’s

surface has been a by-product of industrial capitalism for the last two centuries. In a

sense, technology allows the same human populations to work like better, stronger, larger

glaciers. Similar to glaciers, humans have no coherency and arbitrary progression, can

work over the same areas many times, leaving materials from other environments behind,

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and often scraping away traces of the previous landscape, be it human or natural. Unlike

glaciers, humans are not bounded into the higher latitudes; they can work like glaciers in

the tropics and these actions will not be hindered by global climate change.

PREDICTIONS OF FUTURE CHANGE

In line with the growing concern over global climate change, recent studies and

especially conference presentations have predicted future anthropogenic change. Given

that “the human impact on landscapes is magnified by technology,” and that the same

technology is allowing for more humans to live longer with materially better lives, “the

human impact on landscape resources—water, vegetation, soil, minerals, and space—

expands at an exponential rate,” predicting future change is imperative (Haff 2003).

Modeling climate change requires making assumptions about human behavior, but only

has to account for one global system. Modeling geomorphology requires also factoring

in hydrologic and ecologic models. This creates greater uncertainties about the outcomes

than climate models have, when concurrently the timeframe to make decisions based on

the models, regarding how to reign in anthropic landscape change, is shrinking rapidly

(Haff 2003). If anthropoge is not slowed significantly, the geologic time scale will merge

with the human one, with extreme consequences to geomorphic equilibrium. The

problem is that “if we permit the removal of soil at a faster rate than is produced we are

destroying our very being” (Brown 1970, 84). Humans being the primary agent of

geomorphic change is less dire than the extremely short timeframe the change occurs in

today. A particular action could become irreversible before it was even noticed.

Unlike most geomorphological literature, anthropogeomorpology’s predictive

work is a distinct political turn, one that attempts to illuminate how humanity’s

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geomorphic actions, if they are to continue, will catastrophically change the face of the

earth, so much so that life as we know it will not be possible, which would make any and

all scholarship, geomorphic or not, moot. Peter Haff sums it up the situation well:

“Man will no longer be just a perturbation of Nature, to which Nature responds. Rather, Man-plus-Nature will become one system, which will have its own (dynamical) rules that need to be discovered. The transformation of the earth’s surface by intelligence can be expected to be long-term and irreversible, and will ultimately replace much of “natural” geomorphology.” (2000)

Similar to the position global climate change was in until the last few years, there seems

to be little political will to address the situation. The intelligence Haff writes of is

unconstrained and cooperating only in the sense that nearly everyone alive today is

contributing to the problem.

CONCLUSION: POST-ANTHROPOCENE GEOMORPHOLOGY

Some geographers are taking the predictive models further, to imagine what will

remain of humankind’s creations over geologic time. Kerry Cato raised the question “If

human alteration of the Earth were to immediately cease, what would remain in a million

years?” (2002). The natural processes would continue, with rivers eventually

overtopping or destroying dams. Concrete buildings will crack, allowing the steel

supports to oxidize, leading to the collapse like dominoes of entire city blocks. All steel

structures will disappear. What will survive will be “large open pit mines in places such

as Arizona, [which will be] lakes. The Egyptian pyramids, if not buried, will be minor

topographic features. Aluminum soft drink cans and pieces of glass will remain. Many

of these preserved in sanitary landfills” (Cato 2002).

Trevor Paglen’s scholarly imagination roams even further. He posits to “think of

the human landscape in terms of geology: buildings are temporary mineral deposits,

mountain-moving and mining are accelerated processes of erosion, and global warming is

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akin to climactic fluctuation, not dissimilar to an ice-age” (2007). Living organisms of

all types from simple to complex have impacted the landscape—life is not separate from

it. What makes humankind’s impact unique and geologically unstable is the global scale

and extremely constrained timeframe. Paglen writes, “whether anthropoge is momentary

or lasting geologically, it will never be entirely erased from the Earth. There will always

be remnants of the Anthropocene age in future layers of sediment.” He goes on, ending

the essay by looking to the future-time where humans become a source of carbon-based

energy as the dinosaurs and other past organisms are to today in the form of crude oil:

“Human activities will become like prehistoric forests and swamps now existing as layers

of coal deep in the earth, or prehistoric animals transmuted into pockets of underground

natural gas. In geologic time, life is a peculiar kind of rock, plants are living coal, and

flesh is a temporary state of gas” (Paglen 2007).

Humans have changed the earth’s geomorphology and will be part of the geologic

cycle for the next few million years, until the current continental plates fully subduct.

Technological engineering and ingenuity, and the sheer size of the population guarantee

this to be the case. Water held behind dams—not to mention silt—has already slowed the

spin of the earth slightly (Leslie 2005, 4). What effects are anthropoge having that are

still not known? As Eric Brown wrote, “If we permit the removal of soil at a faster rate

than it is produced we are destroying our very being” (1970, 84). The question

remains—will anthropogenic change completely overwhelm the natural geomorphic

processes, and will we care enough to change our actions before it is too late?

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Appendix 1.

Environments Rates of Erosion (m3/km2-yr)

Natural or Little Affected Areas

World Average and Non-

mountainous 50

Mountainous 500 Alpine and Arctic 1,000-2,000

Japan Mounainous, Average 500

Hills and Upland 10.-50 Moderate River 100-500 High Mountains 500-1,000

Central Highland 1,000-10,000 Large Scale Landslide 10,000-100,000

New Tephra-Covered Slopes 100,000 Affected or Remodeled

Areas

Agricultural Land Japan

Grass 5.-50 Common Crops 50-500 Orchard, without mulching 500-1,500 Pineapple, 1st year, N

Okinawa 1,000-50,000

Furrow and Bare Land 1,000-50,000 Construction

Construction Site, Tama New Town

15,000

Construction Site, N Okinawa

10,000-100,000

Construction Site, NE USA 5,000-50,000 Extremely Denuded Slopes,

Japan 10,000-100,000

Extremely Smoke-Damaged Slopes,

10,000

Japan and Canada Badland, NE USA and

Crimia 100,000

(Kadomura, 1980, 134)

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Appendix 2. “A jetty was built at West Bay [near Bridport, in Dorset, England] to facilitate entry to the harbour. Top: in 1860 it had had little effect on the coastline. Center: by 1900 sediment accumulation had taken place in the foreground but there was less sediment in front of the cliff behind the town. Bottom: by 1976 the process had gone even further and the cliff had to be protected by a sea-wall. Even this has since been severely damaged by winter storms.” (Goudie 2000, 316)

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Works Cited Brown, E. H. (1970). "Man shapes the Earth." The Geographical Journal 136(1): 74-85. Cato, K. D. (2002). "What will remain in a million years?" GSA 2002 Denver Annual Meeting abstract. Cleland, H. F. (1924). "Review: Man as a geological agent." Geographical Review 14(3): 499-500. Gilbert, G. K. (1917). Hydraulic-mining debris in the Sierra Nevada. U. S. G. Survey, U.S. Gov't Print. Off. Goudie, A. (2000). anthropogeomorphology. Dictionary of physical geography, 3rd ed. D. S. G. T. Andrew Goudie. Malden, MA, Blackwell Publishing. Goudie, A. (2000). The human impact on the natural environment. 5th ed. Cambridge, MA, The MIT Press. Haff, P. K. (2000). "Prediction and the anthropic landscape." Eos Trans. AGU, 81 (48) Fall Meet. Suppl., Abstract xxxxx-xx. Haff, P. K. (2003). "Modeling and predicting human impact on landscape." GSA 2003 Seattle Annual Meeting, abstracts. Haigh, M. J. (1978). Evolution of slopes on artificial landforms-Blaenavon, U.K. Chicago, University of Chicago. Hooke, R. L. (2000). "On the history of humans as geomorphic agents." Geology 28(9): 843-846. Hooke, R. L. (2002). Humans are geomorphic agents. Geological Society of America 2002 Denver Annual Meeting, Denver, CO. Kadomura, H. (1980). "Erosion by human actvities in Japan." GeoJournal 4(2): 133-144. Leslie, J. (2005). Deep water: The epic struggle over dams, displaced people, and the environment. New York, Farrar, Straus and Giroux. Morris, A. E. J. (1994). A history of urban form: Before the industrial revolutions, third edition. New York, Longman Scientific & Technical/ John Wiley & Sons, Inc.

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Murray, A. B. (2003). "The interplay between patterns of human coastal development and large-scale patterns of coastal erosion/accretion." Framing land use dynamics international conference, Utrecht. Paglen, T. (2007). "Remnants of California: Anthropogeomorphology." Retrieved 10 May 2007, from http://www.paglen.com/pages/projects/remnants/anthro_geo.htm. Sherlock, R. L. (1923). "The influence of man as an agent in geographical change." The Geographical Journal 61(4): 258-268. Wilkinson, B. (2005). "Humans as geologic agents: A deep-time perspective." Geology 33(3): 161-164.