The Rich Diversity of the Edge

The edge between a forest and a field, with its mixture of habitats, can also host a rich diversity of species. Some are drawn to and thrive on the edge—generalists such as raccoons and coyotes—while other species cannot survive in or even enter the edge.

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I want to begin by thanking Common-place and the organizers of “The American Revolution Reborn.” I thank them for giving me not just this opportunity to share my work with you—to run with the big dogs—but also for giving me their validation that environmental history can help us understand the American Revolution. My paper for the conference looked at the science behind making saltpeter and forms part of a larger book project that brings together environmental history and the War of Independence. The project has been progressing at a glacially slow pace, but the conference has already sparked lots of ideas that will get things moving along. I’d like to mention a few of them here, and I’d like to dwell on one of them in particular.

The first session of the conference focused on global perspectives, and one member of the audience asked about connecting the Revolution to places other than the Americas and the Atlantic. Environmental history can help here. My paper examines how Americans made saltpeter for gunpowder, which naturally leads to the question, how did the British get their saltpeter? Well, almost all of it came from northeastern India, so what effects did wartime demand have on that environment? Deforestation for sure, and many others that I am starting to investigate. Similarly, what happened to the forests of northern Europe and western Russia, which supplied fir trees through the port of Riga? The Royal Navy used these huge trees as masts for ships of the line.

The second session of the conference brought to our attention the disaffected. One paper suggested that a person’s position was shaped, in part, by pre-existing conflicts. It also noted how some of the disaffected could tack back and forth from one side to the other, or how they could keep their heads down and stay out of trouble. Environmental history offers additional ways to think about these issues. For example, particular natural features of the land may have been the basis for some of those pre-existing conflicts. Control over a valuable resource may have given a person the power to approach first one side, and then the other. Alternatively, a livelihood involving work such as off-shore fishing or whaling may have enabled some to escape the conflict altogether.

The interactions between Loyalists, the disaffected, and rebels also prompted me to think about an environmental analogy on which I want to focus for the rest of this brief essay. Landscape ecologists study, among other things, the edges between two types of habitats. Think of a clearing in a forest, or a field next to a forest. At the edges of these habitats, you will find a transition zone where sunlight, wind speed, temperature, moisture, and other variables differ from what you find in the heart of either the forest or the field.

Now, what if we thought of communities of Loyalists, the disaffected, and rebels as separate habitats? One paper talked about how rebel communities put pressure on their inhabitants—to take this oath or join that militia. What happens if a Loyalist community, no matter what the size, appears and creates an edge? Can we come up with analogies to the natural variations in sunlight, wind speed, and moisture? Perhaps we see new variables at work, such as economic opportunities, cultural appeals, and social ties. Does this then change the rebel community’s pressure?

The edge between a forest and a field, with its mixture of habitats, can also host a rich diversity of species. Some are drawn to and thrive on the edge—generalists such as raccoons and coyotes—while other species cannot survive in or even enter the edge. Can the same be said for certain Loyalists, disaffected, and rebels? What would a generalist disaffected person look like, someone who can tack back and forth from one side to the other? What kind of rebel would not be able to come into contact with Loyalists? Furthermore, surprising relationships can develop in the edge. In north-central Florida, certain forest-dwelling birds will not go into the edge unless they see the tufted titmouse there; that bird’s presence may signal that the area is safe. The reliance of one species on another might get us to think in different ways about what another paper told us about Newport, Rhode Island. Did the “intimate connections” identified there facilitate the movement and survival of others in that edge environment?

I bring up edges because they make a particularly apt analogy for “The American Revolution Reborn.” Think of the meeting place of the conference, Franklin Hall at the American Philosophical Society, as an edge zone. The academic “forests” of Penn and Drexel were located just to the west of us; the public history “meadow” of Independence National Historical Park sat right next door; and we were drawn to this edge zone, joined by school teachers, retirees, lawyers, independent scholars, librarians, tour guides, consultants, docents, and many others. We all had specific knowledge of particular places and times, and by sharing that knowledge we made that edge zone especially rich during the days of the conference. Might Common-place be another such forum, another edge zone, where diverse students of the Revolution enrich one another’s experience and thinking?

There is one more feature of edges that may be appropriate here. Once an edge develops, certain conditions lead to the creation of more edge. Once some fallen trees create a clearing in a forest, other trees are now exposed to higher wind speeds, which can produce more blow-downs and more edge. This could be useful for thinking about how people interacted during the Revolution, but for now I want to keep the focus on us. Now that “The American Revolution Reborn” and Common-place have created this edge zone, I think the conditions are ripe for us to go out and create more edge in our home habitats. May this vibrant diversity of participants and ideas spread and flourish.

Further reading:

J.R. McNeill, Mosquito Empires: Ecology and War in the Greater Caribbean, 1620-1914 (Cambridge, U.K., 2010), an exemplary work of environmental history, contains one chapter that examines malaria in the southern campaigns of the War of Independence. Accessible general works on edge habitats include Jodi A. Hilty, William Z. Lidicker Jr., and Adina M. Merenlender, Corridor Ecology: The Science and Practice of Linking Landscapes for Biodiversity Conservation (Washington, D.C., 2006) and Mark A. Bush, Ecology of a Changing Planet (Upper Saddle River, N.J., 1997). Two articles that go into greater detail are Leslie R. Ries, Robert J. Fletcher Jr., James Battin, and Thomas D. Sisk, “Ecological Responses to Habitat Edges: Mechanisms, Models, and Variability Explained,” Annual Review of Ecology, Evolution, and Systematics, 35 (2004): 491-522, and Kathryn E. Sieving, Thomas A. Contreras and Kimberly L. Maute, “Heterospecific Facilitation of Forest-Boundary Crossing by Mobbing Understory Birds in North-Central Florida,” Auk, 121:3 (July 2004): 738-751.


This article originally appeared in issue 14.3 (Spring, 2014).

David C. Hsiung is the Charles and Shirley Knox Professor of History at Juniata College in Huntingdon, Pennsylvania.

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