Farm Boundaries as Agroecological Systems

South-central Pennsylvania, framed by the great folds of the Appalachians to the north and west, by the Mason Dixon Line to the south, and by the rise of hills that bound the lower Susquehanna River to the east, was claimed by settler-farmers of western European descent during the early and mid-eighteenth century. They utilized river and stream valleys to gain access to the fertile lowlands and rich uplands of the region, following in the steps of surveyors to mark farm boundaries with timber fences cut from the cloak of forest. The social and ecological imprint of these boundary structures has endured for hundreds of years.¹

Today this is a patchy domesticated landscape, a mosaic of farms and forest, fields and ravines, pastoral valleys and resistant ridges. This familiar ground has been partitioned many times, but has remained mostly rural. Dividing the fields and pastures are fencerows, wild hedges, and stone fences—some clearly managed and maintained, others overtaken by forest or removed to make way for progress. Overall, a sense of cultural stability and rootedness prevails, yet ecologically this landscape has been anything but stable. Boundary structures provide historical and ecological insight into how agricultural lands were managed and how they changed. In addition, they have become important conservation landforms, especially with regard to pollination systems that support bee-dependent agriculture.

An agroecologist uses conservation, history, ecology, and agriculture to see a working landscape holistically, as narrative. My interest in agricultural boundary structures is rooted in agrarian history, bees, and orchards, and the biogeophysical features related to the human manipulation of the landscape. Indeed, recent research on wild bee populations suggests that hedgerows, tree lines, and other boundary structures—heretofore largely overlooked as historical primary sources—can provide clues to the health and productivity of agricultural lands in the past. These clues provide important new opportunities for historians and other scholars to experience boundary structures as more than simply legal borders or edges of cultivation. But, to paraphrase environmental historian Donald Worster, we must first “get out of doors altogether” and walk them.²

Setting the Historical Fence

The earliest settler-farmers initially established boundaries with timber zig-zag or snake fencing or the upturned root masses of stumps hauled from the ground by draft animals. To prepare for cultivation, they collected surface stones and tossed them aside (usually toward boundary edges), stashed them under rail fences, or piled them into large stacks of fieldstone in the center of pastures and hayfields. Subsequent deforestation resulted in severe topsoil loss, exposing hundreds of large stone slabs and thousands of fist-sized rocks per field. The settler-farmers collected these each spring after snowmelt and frost heave. As fertile soils were lost, lower soil horizons were exposed, offering a generation’s worth of work to remove weathered shards and blocks of parent rock.³

Stone dumps grew into linear landscape features. Rock boundaries created suitable habitat for insects, mammals, reptiles, and amphibians that became associated with the farming way of life: black rat snakes, field rodents, toads, chipmunks, skunks, groundhogs, foxes, and wild bees. Catskills naturalist-farmer John Burroughs later wrote of field edges piled high with country rock, a squirrel’s hoarding heaven: pockets of ash seeds, acorns, chestnuts, and beechnuts stashed in crevices and hollows. If forgotten and in the right environment, these sprouted the following summer.⁴

As annual cultivation intensified, erosion by wind and rain removed additional surface soils. Stones, long buried by topsoils and upper horizons, erupted from the land as if by magic. As human hands lifted, carried, and stacked millions of rocks, field boundaries and fencerow dumps grew waist high and many times as wide. By the 1840s waste stone had become a commodity, easily mined from boundary piles for use in foundations, chimneys, well linings, springhouses, and root cellars. Constructing the beautiful Pennsylvania stone fence became the work of industrious farmers and laborers who built from the waste heaps miles of elegant drystack stone boundaries.⁵

Figure 1.

Evolving from human-constructed boundaries, fencerows matured as wild hedges, offering...