by The stone walls of an abandoned New England park are more or less as iconic as the region with lobster pots, homemade greens, sap buckets and fall foliage. They seem to be everywhere – a lattice of lichen-crusted dry stone ridges separating a patchwork of otherwise moist soils.
Stone walls can be found here and there in other states, but only in New England are they almost ubiquitous. That’s because of a unique regional mix of hard crystalline bedrock, glacial soils and farms with patches of small parcels of land.
Almost all were built by European settlers and their draft animals, who scuttled glacial boulders from agricultural fields and pastures into fence lines and boundaries, then threw or stacked them as lines. Although the oldest walls date to 1607, most were built in the agrarian age between the American Revolution and the cultural shift towards cities and industry after the Civil War.
The mass of stone moved by farmers in that century sets the mood – some 240,000 miles (400,000 kilometers) of barricades, most stacked thigh-high and equally wide. That’s long enough to cover our planet 10 times at the equator, or to reach the Moon at its closest approach to Earth.
Natural scientists are 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 the US government generated the 1872 Census of Hálta. Today, scientists are using a technique called LiDAR, or light detection and ranging, to measure and map stone walls across New England.
As a geologist, I am interested in walls as regionally specific landforms, created during the pre-Anthropocene period – a time when human agency dominates all others. I wrote about the history of stone walls and how to interpret them in the field, and I 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.
Forts and paths
My brother-in-law enjoys his backyard in Lee, New Hampshire, primarily for its aesthetic, historical, and literary surroundings. The wild things that live in its vicinity depend on it as a unique habitat.
For lichens and mosses, the dry stones of the wall are surfaces where plants cannot compete. For plants, such walls are edges that separate patches of land into sunny or shaded zones, uphill or downhill, wetter or drier. Stone walls provide pore spaces for small mammals to live their peaceful lives. Predators use the walls as hunting blinds and travel paths.
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, the summer solstice, he filmed a bobcat (Lynx rufus) hide behind it and then use it as an elevated path.
The more we researchers learn about the abandoned stone walls of New England, the more we realize that they defy and defy the narrow treatments of our scholarly disciplines. These archaeological artifacts are so ubiquitous that they have become a geological feature that 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, New England stone walls have never been technically defined, classified or given common terminology in a peer-reviewed journal. They fell, it seems, through disciplinary cracks.
My first step towards changing 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.” His goal is to merge the study of these stonewalls into an interdisciplinary science by following the precedents of other disciplines – in particular, the 18th century Linnaeus taxonomy which is still used by biologists today. Here’s how that approach works:
Defining and classifying
To understand the stone walls of New England more scientifically, one must begin with a technical definition based on field criteria rather than tradition or inference. There are many types of historic stone features – waste heaps, cairns, spreaders, lines, kilns, tombstones, cobblestones, patios and more. The goal is to isolate walls as a series of objects within this larger domain.
For example, a definition may require that all walls consist of stone; composed of particles, rather than one giant slab; continuous ; faded; and quite high. Without such obvious criteria, one person’s wall is another person’s long pile, and one person’s waste pile is another person’s sacred site.
It’s nice when descriptions and classifications can be loose and flexible, as in musical genres, fashion styles, and disciplines within academia. These are typologies, bins, pigeons. But to make scientific sense of the world, researchers must convert 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 the science of stone walls relate to the size, shape, composition, source and layout of the stones; the vertical and horizontal structures of the leagues, courses and territories; and their topographical positions on the landscape.
The classification of stone walls begins with the stone domain – the entire constellation of historical stone objects. From there, we carve out a distinct class of stone walls that are separated from other rock assemblages, such as concentrations and lines, as well as significant individual stones, such as Plymouth Rock. Then, using diagnostic criteria, we divide the walls of the class into five families – freestanding, lateral, supporting, enclosing and blocking – and break them down into types, subtypes and variants within a new taxonomy.
What can stone walls tell us
At this point, my students, colleagues and I are just applying the science of stone walls to village-scale LiDAR techniques. Exciting spatial patterns are emerging.
Different types of walls occur in predictable settings. For example, we tend to find well-constructed double walls near cellar holes, with simpler single walls further away and waste piles beyond them. Such patterns provide an independent source of primary documentary evidence that researchers can use to interpret past cultural behavior, in addition to the written documents of history and the much smaller excavation-based artifacts of archaeology.
Such spatial patterns can also be used for ecological interpretation. For example, a bobcat is more likely to hunt along a typical single wall than other subspecies because it has the necessary stability and height to support the cat and plenty of empty space to live in.
These structures – these raised dry lands – are similar in some ways to the region’s wetlands, which are also landforms created or significantly altered by farmers when they settled the land in the 18th and 19th centuries. Since the 1990s, however, wetlands have deserved sound 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, massive and unique compared to other habitats that it’s time natural scientists gave them the respect they deserve.
This article is republished from The Conversation, a non-profit, independent news organization that brings you reliable facts and analysis to help you make sense of 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 their conservation and management, and a frequent public speaker on this subject for land trusts, historical societies, environmental non-profits, public libraries, and “friends of…” organizations.
