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History and ecology of stone walls

  • This stone wall inspired poet Robert Frost’s “Mending Wall” with two steps he put in for his children to walk across at the Frost Farm in Derry. Jim Cole / AP file



Take Me Outside
Saturday, December 31, 2016

Winter is a wonderful time to get out and enjoy the natural world. When I do, I often encounter old stone walls in the woods. These relics of our region’s history tell many stories about past inhabitants and current residents of the landscape.

The majority of New England’s stone walls were built within a 30- year period from 1810-40. During this time, agriculture was a driving force and most residents were farmers. These intrepid farmers and their ancestors had spent earlier decades cutting down trees to build homes, barns and other structures and opening up land for planting crops and pasturing livestock. Early fences, used to contain cattle and sheep, were made of wood and stumps from the downed trees.

In the early 1800s, Merino sheep were brought into New England and things changed. The great sheep boom began. A worldwide market for Merino wool provided subsistence farmers with a flush of cash. More land was cleared and pastures were created, bordered by sturdy stone walls.

The stone structures were usually as high as a man’s thigh. Then, wooden fences were added on top to bring the barriers to the height necessary to keep sheep from escaping. Census records indicate that in 1840, New Hampshire was home to 600,000 sheep. Surrounding states were part of this movement as well, and it is estimated that over 250,000 miles of stone walls were built in New England and New York during this period of time. The mass of these meandering rock piles is said to be greater than that of the pyramids of Egypt.

It is remarkable to think that the product all of that work of hauling rocks and laying walls, was only used for a few decades. By 1850, New England farms were being abandoned. The great exodus to the west had begun. Farming in deep, rich, rock-free soil of the mid-western prairies was much easier. Thanks to the Erie Canal and expanding railroads the products from those farms could be easily shipped back east. New England’s open farm fields, up to 80 percent of the landscape, began to grow back to forests. Today when we see walls crisscrossing through the woods, it’s interesting to reflect on the fact that the land was not forested when the walls were built.

In addition to being an artifact of our agricultural past, New England stone walls provide a rich habitat for wildlife. They act as a barrier, collecting fallen leaves and debris which provide stock piles of food and shelter for many small woodland fauna. Most stone walls were built without mortar, using gravity and the shape of the stones to hold them together. As a result there are miniature caves and tunnels created in the spaces between the stones that provide ideal shelter for small creatures.

Even in winter when snow covers the ground, the walls are noticeable as they rise above the forest floor. It is worth taking a close look to see what tracks and signs are left as clues of the current residents or visitors. Look for little footprints of mice, chipmunks, squirrels or weasels coming in and out of the crevices. Larger mammals will use the walls as a trail system, leaving tracks along the top of the partition. You may even find signs left by foxes using the old farmer’s boundary wall to declare the boundaries of their territory by depositing scat.

In warmer months, countless invertebrates – insects, worms and spiders – make their homes in the gaps of stone walls. Reptiles such as common garter snakes and wood frogs may also use them for shelter and hibernate beneath them during the winter.

South facing walls, where the snow melts more quickly, absorb the sun, retain the heat of the sun and provide warmth to animals within or near the walls. Snow free stones also reveal a wide variety of lichen and moss that grows on these mineral surfaces.

The farmers who built the great walls of New England are long gone. But their legacy lives on as the remnants of their efforts continue to provide boundaries for territories, shelter for animals and miniature green pastures and add to the diversity of wildlife habitats.