Tuesday, March 20, 2018

Following the Trail of a Giant: Alfred W. Crosby

The downside is that spring has been taking its time coming to South-Central, PA. It's snowing heavily again tonight. I've made the best of the sunnier days, however, to get down into the many ravines and valleys along the Susquehanna to search for signs and sounds to prove that, in fact, it is on the way.  The upside is that I've had more time to see into the woods and read the lay of land - one of my favorite things about winter.  During these weeks of exploring the deep places, the field of environmental history has lost a founder, Dr. Alfred W. Crosby (b. 1931), who greatly influenced how I look and think about land through the lens of biology and culture.

A "catwalk" trail follows a narrow ridge.

Crosby's work inspired and launched the whole new field of environmental history that includes ecology and biology as important frameworks for research and  interpretation.  His books The Columbian Exchange: Biological and Cultural Consequences of 1492 (1972) and Ecological Imperialism: The Biological Expansion of Europe, 900 - 1900 (1986) changed how I see the landscape around me. His work ignited my passion for environmental history.  By the time I graduated from high school in 1978 (and thanks to a progressive teacher in biology and evolution), I'd read and written a critical essay about Crosby's ideas of invasion biology  in The Columbian Exchange. What we see today, I summarized, is not pristine North American "nature" but the result of biological processes introduced by multiple waves of human invaders.

A wagon ford (foregound) can usually be found just before a creek's steep descent.

The myriad trails and pathways I take to access the deep ravines of the River Hills  can be made out clearly in the leafless landscape. Catwalks, the rocky, narrow ridgetop paths made by Susquehannock and earlier native peoples allow for winter views into these valleys and out across the river. Catwalks follow the spines of rocky ridges and the edges of cliffs formed by the great uplifted bedrock, sharp and boulder-filled. They aren't very safe for anyone on horseback, but their persistence as trails today show that we are still using them. Local  hunters still use catwalk trails for harvesting deer that move through the valley bottoms. I've done so myself.  Original human hunters, Indigenous people arriving after the retreat of glaciers, were the first wave of human invaders. Their mark on our landscape includes what we no longer see: wood bison, mastodon, ground sloth, giant beaver, and other megafauna that were ill adapted to human hunting pressure.

A trench ravine closes in quickly and any hope of a road is lost.

Well into a second wave of human invasion during the age of European discovery, Crosby argued that long before European settlements were established, introduced diseases had already moved rapidly ahead of them, wiping out up to 90% of native people. Diseases hit particularly hard those who lived in dense camp clusters and towns, which tended to be along rivers. Smallpox and the flu were particularly vicious, he asserts, reaching epidemic proportions long before settlers arrived. There was much evidence in our region of a plague-type epidemic: rapidly abandoned villages, empty camps, deserted horticultural sites.

A massive hemlock towers out of a deep ravine.

Crosby was very interested in how diseases traveled among both vulnerable human and non-human populations. The way was made clear for the tens of thousands of Europeans who followed the explorers because disease had preceded them. Benjamin Franklin boasted that by 1760 there were a million more "native" Britons in America courtesy of the 80,000 or so immigrants who began the process of colonization a century before. Crosby reshaped the idea of colonization in both its human and biotic history as the concept of ecological imperialism. 

Wilson Run Gorge

"These lands had to have a temperate climate, the migrants wanted to go where they could be more comfortably European in life style than at home, not less. To attract Europeans in great numbers, a country had to produce or show clear potentiality for producing commodities in demand back home in Europe - beef, wheat, wool, hides, coffee - and its resident population had to be too small to supply that demand. And so it was that so many Europeans poured into cornucopian North America, into Australasia, and into southern Brazil... bleaching out whatever Amerindian and African traces might have existed." (1) 

Otter Creek Gorge.

Crosby divided waves of Eurasian and European migrants according to how, when, and why they arrived. Eurasians crossed land bridges and introduced new hunting technologies. Europeans sailed to the New World and counted those who came for new economic opportunity or religious freedom. By 1750 up to 80% of new arrivals from Europe were indentured servants, military/naval conscripts, prisoners, and enslaved peoples from Western Africa. Economic opportunity led to exportations of products and resources back to Europe.

A trail so steep that switchbacks are marked with a triple blaze.

What was the environmental cost of ecological imperialism? The loss of native people are the saddest and cruelest chapters of Crosby's work,  but he speaks also about the exchange and demise of native animals for European oxen, horses, hogs, and poultry - even the honeybee. I've done some research on a once-common species of American bumble bee succumbing to introduced pathogens from domestically raised, packaged, and accidentally released European bumble species for a growing greenhouse industry in Canada and the Northeast. The exchange/demise is still occurring and disease is still the main factor.

What is missing?

Crosby brings attention to European naturalized weeds and grasses we can count among our biological inventories. "The eastern third of the United States and Canada, where half the population still lives, though it has been over three and a half centuries since the founding of Jamestown and Quebec, is the Neo-European seedbed of North America." (2)  On a spring day, even in the remote bottoms of these deep gorges, I can find in abundance black mustard, plantain, thistles, nettles, nightshade, dandelion, groundsel, dock, knot-grass, and mullein. Add to these, up on the cultivated plateaus of farmland and forest, all the forage crops including white clover. European flora (weeds) according to Crosby, "moved with amazing speed, sometimes bounding ahead of the settled frontier." (3)

An early-mature woodland at the edge of a ravine - this was once open pasture.

Crosby recast the human migration history of the Mid-Atlantic and Northeast as a great biological invasion and his ideas were unsettling for some established historians when Ecological Imperialism was first published. His work continues to have its critics especially among those who revere European dominion narratives and who hold history against certain ideological qualifiers. There can be no denying, however, that the spread of infectious diseases was the monumental consequence of European migration to North America. By some biological invasion histories, we are still under-estimating the numbers of native people whose deaths were attributed to smallpox. Crosby can be considered a giant among historians for his work on pathogens and contagions, but there is so much more.

Bug and Amos lead me up an old wagon road, to a steep switchback, and on to a catwalk trail.

Among his other works - some of which blew my head off when I first read them - are his books America's Forgotten Pandemic: The Influenza of 1918 (1976). This work informed my own research into the ecologies of industrial warfare, landscape of war, and WWI.  Crosby's book inspired the excellent centennial documentary Influenza 1918 shown on American Experience, PBS. Throwing Fire: Projectile Technology Through History (2002) inspired some new venues of research into the effects of biological and explosive weaponry on farmlands in my dissertation work.

Steep gradients in the river hills valleys ensured a healthy crop of mills and small factories in the 1800s.

Crosby's work inspired my fascination for the technologies of European societies that enabled exploration and exploitation across such a large global landmass. My interest in milling technologies, hydro and wind power, navigation, surveying, and time-keeping are the direct result of reading his book The Measure of Reality: Quantification of Western Society, 1250 - 1600 (1997). I remember sitting in an old gristmill-turned-nature center where I once volunteered, so totally engrossed in this book that I didn't notice the had sun set and someone had locked me in. I had to call someone with keys to come let me out. After that I got my own set of keys. Of course, this led me down a huge rabbit hole to explore the technologies, sciences, and maths of other cultures and their chain of impact on Mid-Atlantic natural history. It was a busy year of reading that had me thinking hard about going for my doctorate in agricultural history and landscape studies. Hence, my early PhD work with native bumble bees, agricultural technologies, and European imports...

Bug and Amos listen politely to a quote by Alfred Crosby.

Thinking about the influence Alfred Crosby has had on me as an environmental historian and backwoods wanderer, I looked down at my tired pups who have accompanied me on all six weeks' worth of ravine hikes. "We will content ourselves with one last archaeological trench," quoting Crosby from The Measure of Reality.  "Trench" seemed to a much safer term to use around coonhounds as compared to rabbit hole. Each ravine, every gorge, holds evidence of past cultures' impact on the land and the fact that I can see and interpret that evidence, rooted intellectual and physically in the environmental and biological consequences of colonization, we'll continue to follow the trail of the giant.  Rest in history, Dr. Crosby.

An "archeological trench." 


Crosby, A. Ecological Imperialism: The Biological Expansion of Europe, 900-1900. Cambridge University Press, 1986.

 (1) "The lands had to have temperate climates...." pg. 298.
 (2) "The eastern third of the United States..." pg. 149.
 (3)  "The weeds could move ..." pg. 162

American Experience "Influenza 1918" is available to stream and includes interviews with Alfred Crosby. http://www.pbs.org/wgbh/americanexperience/films/influenza/

Smithsonian interview with Crosby on the Columbian Exchange.

Obituary, Alfred W. Crosby,