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by Alberto Del Genio
Dry stone walls have likely been built by farmers since the origins of agriculture. In fact, to make it easier to cultivate the land, stones scattered on the ground were piled up at first at the edges of the fields chosen for cultivation.
It is likely that the idea then came naturally to use these stones to build walls in order to demarcate the territory, but also to prevent the intrusion of strangers or wild animals.
Later, when animal breeding began, they were built to prevent them from straying; then, as time went on, fences were built to separate the various animals, to segregate the sick ones or the parturients and newborns.
If the megalithic cyclopean walls, made with extreme skill with stones that only the cyclops were thought to have been able to raise, given the size of the blocks used, have been dated to 4500 A.D., it is likely that the dry-stone walls, certainly of simpler construction, were built much earlier, perhaps much closer to 7000 AD, the date of the beginning of cultivation of the fields, as per recent research.
But what is meant by a dry stone wall? It is a wall built with only stones well interlocked with each other so as to have good stability, without the use of mortar or binding substance, but at most a little dry soil. The construction technique is very simple: it uses commonly used hand tools such as shovels, hoes, picks, heavy hammers, mallets, and lead wire.
We begin construction by making a furrow in the chosen soil along the entire length of the wall to be built; the width of the furrow must be 50 cm for a planned wall 1 meter in height, for larger sizes it must be at least 60 cm.
Large stones are laid on the sides of the furrow, a little below the floor level; the middle part is filled with smaller stones.
We then begin to raise the wall, using stones that are shaped from time to time with a heavy hammer so that they can match each other as closely as possible. In the gaps that may result, small stones are possibly introduced in order to increase the stability that occurs essentially by gravity. For this purpose, the wall should have a slope of 10 percent for walls 1 meter high, while for larger sizes it can be up to 20 percent.
The highest part of the wall is covered with earth or better with flat stones for a width of about 30 cm. In Salento, the top of the wall is often completed with a row of large stones of similar shape and size, also in order to further increase stability.
The manner in which the stones are assembled varies from one farmer to another depending on the teachings received, personal technical ability, the material available, and the time to be spent. The aesthetic result can also vary greatly until sometimes achieving results of extraordinary beauty.
Over time then they were used in the sloping territories in order to create useful terraces to make the land cultivable. Once the wall has been built, it is filled in behind for its entire length with soil taken from elsewhere; at the upper level reached by the carried-over soil, leaving a slope of about 3 percent in order to allow rainwater to drain away, a further wall is built to create another terracing, continuing upward until the desired level is reached. The latter type has been used in Italy in various locations. Particularly famous are the terraces on the Sorrento peninsula that have allowed the cultivation of Amalfi lemons and the production of the Sorrento peninsula's D.O.P. olive oil.
Terracing has proven particularly useful because it stabilizes slopes by preventing soil runoff and landslides, and creating useful areas for agriculture. They have also been found to be crucial in maintaining biodiversity. They have even been referred to as "ecological corridors," allowing the passage of insects or small reptiles such as grass snakes and lizards that help the healthy environment. Between the stones then, and close to the walls, spontaneous vegetation grows, which by creating a special microclimate, helps the crops to overcome drought and heat in the summer months, thanks in part to the phenomenon of condensation of nighttime moisture on the stones themselves.
In 2018, Italy with the collaboration of France, Spain, Greece, Cyprus, Slovenia, Croatia and Switzerland gained UNESCO recognition in the intangible heritage representation for the art of dry stone walling.
Dry stone walls are yet another testament to the human ability to adapt to nature, improve it and protect it by using only materials taken on the spot, relying only on the experience gained over the years by their predecessors.
