Valpolicella: save the terraced vineyards to counteract the effects of climate change

The value of the viticultural landscape and its diverse surfaces has been acknowledged for several years. The landscapes of terraced vineyards supported by dry stone walls are especially impressive, and they represent “a harmonious relationship between man and nature”, to use the motivation that UNESCO has included, “the rural practice of the art of dry stone walls” in the list of intangible elements declared a World Heritage Site. Dry stone walls are even more than this. Their function in defending against hydrogeological instability is much broader than what is actually known, as it also functions to counter meteorological excesses induced by climate change. Furthermore, when we add the fact that they are all over Italy - the 2016 CNR Consiglio nazionale delle ricerche (Italian National research council) census quantified them at 140.000 km, but it seems to actually be half a million - as in many other Countries, it is clear that maintaining them is definitely essential. In Valpolicella, people have been aware of their functions for a long time, because intensive viticulture developed here only 50 years ago. But, for hundreds of years the agronomic and hydraulic systems made its 222 kilometers of hills “adorned” by “marogne” cultivatable. Marogne is the name for dry stone walls in the Verona area. The dry stone walls were which were built also using an effective, and very beautiful technique, such as the herringbone, in which the stones are placed vertically and in opposite parallel planes.
The role of dry stone walls in addressing climate change on terraced vineyards and innovative solutions to manage water resources and stabilize the territory were the main theme and focus at the conference organized by the Consorzio Tutela Vini Valpolicella, recently held in Sant’Ambrogio di Valpolicella. “Wine-growing areas such as Valpolicella, which represent a delicate balance between environment and production”, emphasized Christian Marchesini, president of the Consortium, “climate change is a challenge that can no longer be postponed. Our goal is to raise awareness and inform technicians, producers and institutions that is crucial to adopt preventive strategies and advanced technical solutions to manage these problems. This conference was organized and proposed to be a platform of discussion regarding safeguarding the landscape and the production heritage of inestimable value, to protect future generations”.
The art of building dry stone walls - that is, not using “cementing” materials between stone and stone - has been almost completely lost, and not only in Valpolicella, as there are very few “marognini” now, which is also due to the high costs of restoration and reconstruction. “The knowledge of this art has been almost lost, but it must be recovered to limit the collapse that an increase in the landslides going forward would produce on our hills”, Michele Moserle, historian of dry stone walls and professor of Landscape Architecture, who also holds courses to impart this ancient art, said with concern. “A stimulus and a task for ITLA, the International Terraced Landscapes Alliance, also supported by UNESCO, to collect funds, which the PNRR Piano nazionale di ripresa e resilienza (National Recovery and Resilience Plan) has also allocated for restoration”, he added.
Terraced landscapes are a thousand-year-old stratagem to have sufficiently deep soil for agriculture on slopes that would otherwise not be possible. They are also a fortification to slow the flow of water downstream and the loss of fertile soil that it takes with it. They drain water by letting it filter between the stones where plant and animal communities that contribute to biodiversity form and thrive. Therefore, dry construction is essential; that is, no binding materials between stone and stone. Otherwise, in extreme stormy weather - which does occur in Valpolicella - the terraces flood, creating asphyxiation problems for the vines, and hydrogeological instability. On the contrary, in drought situations, they constitute water reserves useful for limiting water stress by retaining rainwater on a horizontal plane. In times when atmospheric phenomena are excessive, such as heavy and concentrated rainfall and long- term temperature increases, the terraces and dry stone walls that support them become much more important. This age-old challenge has found solutions based on highly sophisticated monitoring technologies to understand and simulate the effects of extreme weather phenomena and to guide interventions that make the vineyards of the hills resilient. Paolo Tarolli, full professor of Agricultural Hydraulics at the University of Padua, explained, “ Climate change is causing many problems to traditional cultivation models and even beautiful landscapes, such as terraces, especially in terms of water management. It is raining more often and the rainfall is much more concentrated, so we need to understand the preferential routes of water flow in order to manage it. Over the past few years, my research group has focused its attention on the use of remote sensors, drones, and aircraft mounted lasers, to be able to return a three-dimensional, very high-resolution model of terraced landscapes, which is functional for simulating the effects of precipitation events to verify water flows and, therefore, implement a series of interventions, such as effective ditches and drainage or micro-reservoirs”. These small reservoirs - the specific objective of Tarolli's research group - scattered in the sloping vineyards, act as "reservoirs" to collect excess water, and at the same time as a water reserve, though limited, to be used in case of water shortages as well as an oasis for wild fauna. In other words, they simultaneously face the two climatic excesses using a truly brilliant solution. However, the solution requires upstream studies at the district level to be implemented in a sensible and organized way.