The abandoned fieldstone walls of New England are as iconic to the region as lobster pots, urban greens, sap buckets and fall leaves. They seem to be everywhere: a latticework of dry, lichen-covered stone ridges separating a patchwork of otherwise moist soils.
In other states, stone walls can be found here and there, but only in New England are they virtually ubiquitous. This is due to a regionally unique combination of hard crystalline rock, glacial soils and farms with a patchwork of small plots.
Nearly all were built by European settlers and their draft animals, who brought glacial stones from agricultural fields and pastures to fence lines and boundaries and then threw or piled them like lines. Although the oldest walls date from 1607, most were built in the agricultural century between the American Revolution and the cultural shift to cities and industry after the Civil War.
The mass of stone that farmers moved in that century boggles the mind: an estimated 250,000 miles of barricades, most of them stacked to thigh height and the same width. That’s long enough to circle our planet ten times around the equator, or to reach the moon at its closest approach to Earth.
Natural scientists have been working to quantify this phenomenon, which is larger in volume than the Great Wall of China, Hadrian’s Wall in Britain and the Egyptian pyramids at Giza combined. This work began in 1870 and led to the U.S. government’s Census of Fences in 1872. Today, scientists use 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 landforms characteristic of the region, created in the run-up to the Anthropocene era – a time when human intervention dominates all others. I have written about the history of stone walls and how to interpret them in the field, and developed the Stone Wall Initiative to draw public attention to their importance in New England. Now I am working with students and colleagues to develop a formal interdisciplinary science of stone walls that will help researchers understand and preserve them.
Caves and trails
My brother-in-law enjoys his backyard wall in Lee, New Hampshire, mainly for its aesthetic, historical, and literary atmosphere. The wildlife that live near it depend on it as a unique habitat.
For lichens and moss, the dry stones of the wall are surfaces where plants cannot compete. For plants, such walls are edges that separate areas of soil into zones that are sunny or shady, windward or leeward, uphill or downhill, wetter or drier. Stone walls provide small mammals with porous volumes in which they can live their secretive lives. Predators use the walls as hunting hatches and travel corridors.
For fun, my brother-in-law installed a motion-activated infrared video camera on the wall in his backyard to see who was using the wall and how. On June 21, 2023, the summer solstice, he filmed a bobcat (Lynx Rufus) hide behind it and then use it as a raised path.
The more we as researchers learn about the abandoned stone walls of New England, the more we realize that they transcend and erase the narrow approaches of our scientific disciplines. These archaeological artifacts are so ubiquitous that they have become a geological landform that in turn creates a new 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, the stone walls of New England have never been technically defined, classified, or given a common terminology in a peer-reviewed journal. It seems they have fallen through the disciplinary cracks.
My first step to change this situation was to write a mini-monograph in 2023 for the journal Historical Archeology on the “Taxonomy and Nomenclature for the Stone Domain in New England.” The goal is to merge the study of these stone walls into an interdisciplinary science by following the precedents of other disciplines – particularly the 18th-century Linnaean taxonomy that biologists still use today. This is how the approach works:
Define and classify
To scientifically understand the stone walls of greater New England, you must start with a technical definition based on field criteria rather than tradition or inference. There are many types of historic stone features: rubbish piles, cairns, litter, lines, ovens, gravestones, cobblestones, patios and more. The goal is to isolate walls as a collection of objects within this larger domain.
For example, a definition might require that every wall be made of stone; composed of particles, rather than one huge plate; continuous; elongated; and sufficiently high. Without such explicit criteria, one person’s wall is another’s oblong pile, and one person’s trash heap is another’s holy place.
It is nice if descriptions and classifications can be loose and flexible, such as with music genres, fashion styles and disciplines within the academic world. These are typologies, bins, boxes. But to understand the world scientifically, researchers must convert descriptions into precise definitions and use them in binary, rule-based classifications. These are taxonomies.
Every scientific area needs 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 refer to the size, shape, composition, source and arrangement of stones; the vertical and horizontal structures of levels, courses and terminations; and their topographical settings in the landscape.
The classification of stone walls begins with the stone domain – the entire constellation of historical stone objects. From there we carve a distinct class of stone walls separated from other rock formations, such as concentrations and lines, as well as notable individual stones, such as Plymouth Rock. Then, using diagnostic criteria, we divide classroom walls into five families – freestanding, flanking, supporting, enclosing and blocking – and further divide them into types, subtypes and variants within a new taxonomy.
What stone walls can tell us
At this stage, my students, colleagues and I are just beginning to combine the science of stone walls with village-scale LiDAR techniques. Exciting spatial patterns emerge.
Different types of walls occur in predictable arrangements. For example, we often find well-built double walls near cellar holes, with simpler single walls at greater distances and waste piles beyond. Such patterns provide an independent source of primary documentary evidence that researchers can use to interpret past cultural behavior, above and beyond the written historical documents and the much smaller artifacts from excavations.
Such spatial patterns can also be used for ecological interpretations. For example, a bobcat is more likely to hunt along a normal single wall than other subtypes because it has the required stability and height to support the cat and enough empty space for prey to live in.
These structures – these raised drylands – are in some ways analogous to the region’s wetlands, which are also landforms that farmers created or significantly altered as they settled the land in the 18th and 19th centuries. However, since the 1990s, wetlands have earned robust science, a solid legal framework, and excellent management protocols.
In my opinion, the time has come to do the same for the stone walls of New England. These dryland structures are so ubiquitous, enormous and unique compared to other habitats that it is high time for wildlife scientists to give them the respect they deserve.
This article is republished from The Conversation, an independent nonprofit organization providing facts and trusted 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 about New England’s historic stone walls. He is an advocate for their conservation and management, and a frequent speaker on the subject to land trusts, historical societies, environmental nonprofits, public libraries, and “friends of…” organizations.