Master Class: Ecology of Stone

Text and Images by Daniel Peterson

We all have different paths that lead us to dry stone and to using dry stone in the landscape. Many of us are drawn to the aesthetics of dry stoneworks. Some of us are drawn by the historic value and significances, and some are drawn by the timeless nature and longevity of dry stone. We are also drawn to dry stone because of the environmental benefits of dry stone. One of the main focuses of my business, HabAdapt, is taking into consideration the environmental implications of what we do in the landscape through designing, and interacting and working with nature. Initially, HabAdapt focused primarily on ecological restoration of urban environments, encouraging regional ecosystems of an area. Eventually this led to more human-inclusive design concepts of permaculture and land use diversity. I was drawn to using more dry stone in our projects due to the environmental implications of using readily available regional stone material, and the long-term sustainability of the structures that can be created with dry stone. We all have read about dry stone construction methods and the engineering behind the features, and we have experienced the workshops about how to build a structure that is long-lasting. Often we overlook the impacts on the environment around us, or the ecology of what we do when we design and build dry stone structures.

Above: A geranium growing on a stone wall at the Dawyck Botanic Garden in Peebles, UK

In the broadest sense, ecology is the science of the relationships between organisms (including humans) and their environments. Ecology includes life processes, materials in the environment (including stone), energy transfer, organism cooperation, competition, predation, succession, abundance, biomass, and distribution as well as observing patterns and interactions of these aspects. Ecology is defined as the study of ecosystems; an ecosystem is all of the organisms and the physical environment in which they interact.

When I am planning a dry stone project I often take into consideration not only the aesthetics of the structure itself and how it will be used in the space, but how it will interact and influence the space in which it will reside. The type of stone used influences the pH of the soils around the wall. For instance I would not typically consider planting plants in the Ericaceae family (heath or blueberry type plants) near a limestone wall since they perform best in acidic soil conditions. I would

consider plants in the Apiaceae family (carrots, parsley, etc.) near a limestone wall since they prefer alkaline soil conditions. Orientation of dry stone features or walls will influence energy movement in an area, too, by creating windbreaks or wind diverters, and for that matter water diverters. The albedo responses of different types of stone influence temperatures as well as light reflection, which may encourage or hinder plant growth. The thermal tendencies of different stone can determine whether you would want to sit on a ledge wall after it has been exposed to the sun all afternoon. I often use dry stone in our projects to create microclimates to encourage some plant choices that are more sensitive either to the extreme Midwestern temperatures or that alter the moisture of an area.

Research concerning the ecology of dry stone walls is currently mostly limited to case studies and anecdotal observations. That being said, an increasing amount of information supports the notion that dry stone structures may increase or support the

Above: The west (left) and east (right) side of a dry stone wall may indicate heat retention of the stone or thermal conductivity.
This image was taken early in the morning after an overnight snow event. The west side of the wall retained more heat than the east side
of the wall from the previous day’s sun resulting in less snow adhesion on the western side of the wall.

biodiversity of an area. The less uniform the stone used in the dry stone feature, the more biodiversity is encouraged in the dry stone feature. Dry stone walls that are more heterogeneous than concrete or natural rocky walls support more fauna in the form of amphibians and mollusk species, especially if vegetation and lichens are present (Manenti 2014). I have observed numerous insects warming on the walls, particularly on dry stone walls with a low albedo, or low light reflective potential. The darker stone retains more heat on cooler days during the beginning or end of the growing season. The walls in our yard support several Eastern American toads (Anaxyrus americanus). I have also encountered Eastern Tiger salamanders (Ambystoma tigrinum) hunting along the base of dry stone walls, primarily if the walls are within a few hundred yards of water sources.

Above: Anaxyrus americanus (Eastern American Toad) emerges from its hiding place in a wall to hunt for the afternoon and Mbystoma Tigrinum (right), commonly known as the Tiger Salamander, on its way to being relocated after it was found working along a dry stone wall.

Ecology in essence is passive, whereas environmentalism is typically active and uses ecology along with other sciences to improve or enhance the ecosystem for both human and nonhuman needs. A UNESCO statement on the relationship between dry stone walling and human cultural heritage bridges the gap between ecology and environmentalism well: “Such structures testify to the methods and practices from prehistory to today to organize their living and working space by optimizing local natural and human resources. They play a vital role in preventing landslides, floods, and avalanches, and in combating erosion and desertification of the land, enhancing biodiversity and creating microclimatic conditions for agriculture” (UNESCO [no date]). Even though the UNESCO statement is for specific countries, the dry stone craft has global importance and is given credibility with the statement.

Several years ago I had the opportunity to teach and evaluate other teachers’ farms in Haiti with the organization Mindful Generations, a 501(c)3 focusing in training farmers to teach other farmers in environmentally conscious and regenerative land use practices. We were touring farms in the Hinche region when we arrived at Lucnes’s farm. Lucnes had improved the growing conditions to the extent that he was producing crops during the dry season in Haiti. Late November through early March is considered the dry season in Haiti. I was touring the farms in Hinche near the end of the dry season as the wet season was starting. What I found most intriguing about his farm was that he had used the stone from his fields to create a series of dry stone check dams to control the water movement across his farm and increase ground water infiltration. He had used

Above: Luncnes explaining his process of determining where to place the check dams on his valley farm in Hinche,Haiti.

Top: The image may be oversimplified, but it exemplifies how some of the Haitian landscape looks during the dry season.

stone to achieve every key point in the UNESCO statement. The check dams were slowing the water down as it moved across his farm reducing soil erosion and increasing organic deposition. The pooling water encouraged local wildlife to return to the area to control some of the pest insects (e.g., amphibian tadpoles eating mosquito larvae). The increase in water storage resulted in extending the growing season into the dry season, when he was able to still bring fresh crops into market for sale. Initially, other local farmers thought he was buying produce from outside the region and reselling it, but after some insistence by Lucnes, the other farmers traveled to his farm to see that he was growing produce during the dry season.
His actions resulted in numerous farmers modifying how they were approaching the land and their land stewardship. When asked how he came up with his plan of using the stone, he said in Haitian Creole, “I wasn’t doing much since nothing was growing because it was dry, so I thought, what do I have to lose by implementing some of the strategies I learned in the class. I had all of this stone just lying around, so since it is a resource and I have it, I may as well use it.” For those of you who are not familiar with Haiti, the landscape varies in vegetation cover depending on the region, with estimations of anywhere from 20 to 40% tree canopy cover, depending on what study is referenced (not the dire 2% tree canopy coverage that has been cited for decades).

Left: A view of one of Lucnes’s check dam constructions.

Below: Dan Peterson discussing with local farmers Lucnes’s use of stone resources to control water during a trip to Hinche, Haiti. Photo: Catherine Rose

The landscape is, however, fragmented in vegetation coverage similar to most populated places. The fragmentation may exacerbate erosion issues, river embankment collapse, and flash flooding in certain regions.
Ecological restoration is a process that assists in the recovery of an ecosystem that has been degraded, damaged, or destroyed (Galatowitsch 2012). The dry stone features we build may aid in improving and supporting the habitat and biodiversity around us; hence they are part of the ecological restoration process when properly implemented.

About Daniel Peterson — Daniel is a Minneapolis based landscape designer who focuses on ecologically sound, full service landscape design and installation. A majority of his projects involve restorative practices incorporating native plant communities, permaculture practices, water management, and dry stone construction. Daniel holds a Level III, advanced Dry stone certification and dry stone teaching certification. He is also currently serving as president on the Board of Directors for The Stone Trust.

Above: Another view of Lucnes’s check dam construction. He had constructed two check dams when I had visited his farm, and he was in the process of gathering more stone to replace the wood wattle dams with earth and stone.

References

Galatowitsch, S. (2012). Ecological Restoration., Sunderland, MA:
Sinauer Associates.

Gjeta, E., Titus, J., and Titus, P. (2021). “Plant Species Occupy Different Habitats on the Fortress Walls in Elbasan, Albania.” Hacquetia 20(1):81–90.

Hollingsworth, L., and Collier, M. (2020). “Ground Flora of Field Boundary Dry Stone Walls in the Burren, Ireland.” British and Irish Botany 2(4):352–76.

Manenti, R. (2014). “Dry Stone Walls Favour Biodiversity: A Case-Study from the Appennines.” Biodiversity and Conservation 23, 1879–93.

UNESCO (no date). “Art of Dry Stone Walling, Knowledge and Techniques.” https://ich.unesco.org/en/RL/art-of-dry-stone-walling-knowledge-and-techniques-01393 (retrieved August 2021).

Watson, A. (1989). ” Removal of Dry-Stone Walls on Some North-East Scottish Farms.” Landscape Research 14(2):18–21.