by New England’s abandoned stone walls are as emblematic of the region as lobster traps, urban greens, sap buckets, and fall foliage. They seem to be everywhere: a latticework of dry, lichen-covered stone ridges separating a mosaic of otherwise wet soils.
Stone walls can be found here and there in other states, but only in New England are they nearly ubiquitous. This is due to a unique combination in the region of hard, crystalline bedrock, glacial soils and mosaic farms of small plots of land.
Almost all were built by European settlers and their draft animals, who hauled glacial stones from agricultural fields and pastures to fences and boundaries, then threw them or piled them into lines. Although the oldest walls date to 1607, most were built in the agrarian century between the American Revolution and the cultural shift toward cities and industry after the Civil War.
The mass of stone that farmers moved in that century is staggering: there are an estimated 400,000 kilometers (240,000 miles) of barricades, most stacked thigh-high and of similar width. That’s enough time to circle our planet 10 times at the equator or to reach the Moon at its closest approach to Earth.
Natural scientists have been working to quantify this phenomenon, which has a volume larger than the Great Wall of China, Hadrian’s Wall in Britain, and the Egyptian pyramids of Giza combined. This work began in 1870 and generated the U.S. government’s 1872 Fence Census. Today, scientists are using a technique called LiDAR, or light detection and ranging, to measure and map stone walls in New England. .
As a geologist, I am interested in walls as distinctive landforms of the region, created during the period leading up to the Anthropocene, an era in which human action dominates all others. I wrote about the history of stone walls and how to interpret them in the field, and developed the Stone Wall Initiative to bring public attention to their importance in New England. I am now working with students and colleagues to develop a formal interdisciplinary science of stone walls that will help researchers understand and preserve them.
dens and paths
My brother-in-law enjoys his backyard wall in Lee, New Hampshire, primarily for its aesthetic, historical, and literary atmosphere. The wild animals that live in your neighborhood depend on it for their unique habitat.
For lichens and moss, dry wall stones are surfaces where plants cannot compete. For plants, these walls are borders that separate patches of soil into sunny or shady areas, windward or leeward, uphill or downhill, wetter or drier. Stone walls offer small mammals porous volumes in which to live their furtive lives. Predators use walls as hunting blinds and travel corridors.
Just for fun, my brother-in-law installed a motion-activated infrared video camera on his backyard wall to see who was using the wall and how. On June 21, 2023, summer solstice, he filmed a lynx (rufus lynx) hiding behind it and then using it as a causeway.
The more we researchers learn about New England’s abandoned stone walls, the more we realize that they transcend and efface the narrow treatments of our academic disciplines. These archaeological artifacts are so ubiquitous that they have become a geological relief that in turn creates a novel ecological habitat. These walls are also literary icons, historical sites, and spiritual oracles, as Robert Frost recognized when he wrote “Mending Wall,” on an old farm in Derry, New Hampshire.
But despite their importance, New England stone walls have never been technically defined, classified, and provided with common terminology in a peer-reviewed journal. Apparently, they fell into disciplinary fissures.
My initial step in changing this situation was to write a mini-monograph in 2003 for the journal Historical Archeology on the “Taxonomy and Nomenclature of Stone Domain in New England.” Their goal is to merge the study of these stone walls into an interdisciplinary science following precedents from other disciplines, particularly Linnaeus’ 18th-century taxonomy that biologists still use today. Here’s how that approach works:
Defining and classifying
Scientifically understanding the stone walls of Greater New England requires beginning with a technical definition that relies on field criteria rather than tradition or inference. There are many types of historic stone features: spoil heaps, cairns, scatters, lines, kilns, headstones, paving stones, patios and more. The goal is to isolate the walls as a set of objects within this larger domain.
For example, a definition may require that each wall be composed of stone; composed of particles, rather than a huge slab; continuous; elongate; and high enough. Without such explicit criteria, one person’s wall is another person’s long pile, and one person’s trash pile is another person’s sacred place.
It’s nice when descriptions and classifications can be vague and flexible, as is the case with musical genres, fashion styles, and academic disciplines. They are typologies, containers, lockers. But to make scientific sense of the world, researchers need to turn descriptions into precise definitions and use them in binary, rule-based classifications. These are taxonomies.
Each field of science requires its own language. Chemists group elements with similar properties, such as halogens and noble gases. Biologists divide life forms into domains, kingdoms, phyla, and smaller groups with shared characteristics.
Terms in stone wall science imply the size, shape, composition, source and arrangement of stones; the vertical and horizontal structures of steps, rows and terminations; and its topographic adjustments to the landscape.
The classification of stone walls begins with the mastery of the stone: the entire constellation of historical stone objects. From there, we carve a distinct class of stone walls that is separate from other sets of rocks, such as concentrations and lines, as well as notable individual stones, such as Plymouth Rock. Then, using diagnostic criteria, we divided class walls into five families (freestanding, flanking, supporting, enveloping, and blocking) and broke them down into types, subtypes, and variants within a new taxonomy.
What can stone walls tell us?
At this stage, my students, colleagues, and I are just beginning to combine stone wall science with village-scale LiDAR techniques. Tantalizing spatial patterns are emerging.
Different types of walls are presented in predictable arrangements. For example, we commonly find well-constructed double walls near basement voids, with simpler single walls at a greater distance and piles of debris beyond them. Such patterns provide an independent source of primary documentary evidence that researchers can use to interpret past cultural behaviors, beyond the written documents of history and the much smaller artifacts of excavation-based archaeology.
These spatial patterns can also be used for ecological interpretations. For example, a bobcat is more likely to hunt along a single normal wall than other subtypes because it has the stability and height to support the cat and enough empty space for its prey to live.
These structures – these elevated drylands – are in some ways analogous to the region’s wetlands, which are also landforms that farmers created or significantly modified when they settled the land in the 18th and 19th centuries. However, since the 1990s, wetlands have gained solid science, a strong legal framework, and excellent management protocols.
In my opinion, the time has come to do the same with the stone walls of New England. These dryland structures are so ubiquitous, massive, and unique relative to other habitats that it is high time natural scientists gave them the respect they deserve.
This article is republished from The Conversation, an independent, nonprofit news organization bringing you data and analysis to help you understand our complex world.
It was written by: Robert M. Thorson, University of Connecticut.
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Robert M. Thorson created and coordinates the Stone Wall Initiative, an online resource on New England’s historic stone walls. He is an advocate for its conservation and management, and a frequent public speaker on this topic for land trusts, historical societies, environmental nonprofits, public libraries, and “friends of…” organizations.
