The existence and importance of terracing in Italy is attested ever since the Neolithic Age and is well documented from the Middle Ages onward. Contour terraces and regular terraces remained in use until the second postwar period, because sharecropper contracts guaranteed their constant maintenance. Terraces were thus a regular feature of many hill and mountain landscapes in Italy, as well as in many southern European countries.
Among the ecosystem services that terraced landscapes can provide, the reduction of hydrogeological risk is probably one of the most important. The role of terracing in the hydrologic behavior of slopes has become a topic of interest, especially in Mediterranean areas [9
], as they constitute a system that strongly modifies runoff processes on steep slopes [15
], erosion [13
], and infiltration [10
]. The study of terracing has gained special importance over the last years with the growth of awareness of their economic, environmental, and cultural-historical importance, as well as of the hydrological functions of terraced landscapes in farm areas, including erosion control, slope stabilization, lengthening of concentration times, and reduction of surface runoff [4
]. These kind of traditional agricultural landscapes are today not only included in the UNESCO Cultural landscapes but represents the main focus of the Globally Important Agricultural Heritage Systems program of the FAO.
The first consequence of terrace abandonment is the occurrence of degradation processes such as erosion and mass movements, due to an initial increase in hydrological connectivity and the degradation of risers [3
]. Furthermore, recent studies highlighted how colonization of slopes by woods goes together with the deterioration of terraces, both as cause and effect [21
]. This consequently leads to an increase of erosion and landslide risks. On the other hand, the growth of more complex vegetation canopies gives an increasing stability to slopes over time, due to root reinforcement and erosion control [22
In central Italy, abandoned terraces are becoming a serious hazard because of their uphill proximity to human settlements. For this reason, several studies have already been carried out in the Tuscany and Liguria regions [14
]. Investigations by Agnoletti et al. [31
], highlighted certain aspects of the relationship between terracing and hydrogeological risk. As regards the hydrogeological aspect, terrace abandonment resulted in a process of erosion and shallow instability. Other studies in the Apuan Alps area [18
] highlighted the relationship between the abandonment of terraces and landscape dynamics and the decrease of biodiversity, with the consequences of the hydrogeological disasters that occurred in the Cardoso basin in 1996.
The aim of this paper is to analyze the role of agricultural terraces in terms of landslide prevention and soil protection, comparing results from a survey of the landslides carried out immediately after the 25 October 2011 rainstorm in Cinque Terre, with other scientific studies carried out in other terraced areas of the world.
History of Cinque Terre and Its Viticulture
According to available historical sources, in pre-Roman times the Cinque Terre area was peopled partly by Liguri, Apuani and partly by Tigulli. There are divergent testimonies about the first building of terraces. For example, the bronze tablet known as the Polcevera Table (117 BC) reports that the ancient Liguri were already growing grapes and building contour terraces in pre-Roman times. Pliny the Elder celebrates the vinum lunense and mentions its presence in the Maritime Alps of a wild grape known as raetica. What is certain is that the historical terraced landscape of Cinque Terre is the result of major transformations undertaken by human beings over 1000 years of history, through the harsh, continuous, and assiduous toil of generations who over centuries replaced the shrublands and woods covering the slopes with vineyards growing on terraces [32
After the early Middle Ages, which witnessed a barbarization of farming practices, the first timid signs of a recovery begin to be noticeable around the year 1000. Lands that had been abandoned for a long time, or devastated by the violence of Saracen incursions, were farmed again, leaving ample room for grapevines. Historical documents indicate that Cinque Terre also witnessed a new bloom around the year 1000. This is when the famous five towns were founded, and the first agricultural landscaping works undertaken. It is also around this time that terracing became widespread, thanks to the control of the land exercised by Benedictine monasteries and parishes. “The local people were charged with farm work in exchange for protection. Deforestation, valley-bottom hydraulic works, the opening up of some mountain paths, and the spread of terracing and olive-growing contributed to redefine the organization and image of the landscape, notwithstanding interruptions and slowdowns due to Saracen invasions until the eleventh century” [33
]. Three main forms of terraces were built—contour terraces, lunettes, and terraces in the strict sense. The first type was used in the interior of Liguria, where slopes are not excessively steep (along ridges or valley bottoms). Vegetables were usually grown on the terraces and they were retained by short grassy scarps. The second type, especially popular in the Middle Ages, was used to prevent the land in which individual trees are rooted from being washed away. These terraces had crescent-shaped dry-stone walls and were built on steep slopes. Terraces in the strict sense, instead, consist of a succession of dry-stone walls that retain the cultivable plots, which are more or less wide, depending on the inclination of the slope. Usually the stones of the terrace walls are laid without a binder to allow excess water to drain away. Thus, the harsh toil that made the land cultivable gave rise to a “stepped land” [34
The first descriptions of Cinque Terre date from the early fourteenth century. Jacopo Bracelli, chancellor and historiographer of the Genoese Republic was the first to provide a fairly accurate description of this area of Liguria, in his Descriptio orae Ligusticae (1448). “Then along the coast stand five lands almost at equal distances from one another, which are Monterosso, Vulnezia, now vulgarly known as Vernazza, Cornelia, Manarola and Rio Maggiore, famous not only in Italy but also among the French and the English for the excellence of their wine”. These five towns were spontaneously associated under a single name, both because of the quality of their wine and because they all grew grapes in the same way, on terraces that left a strong mark on their landscape and sharply distinguished it from the rest of the extreme versant of Liguria. Thanks to the foundation of these municipalities and the cessation of the incursions of Saracen pirates, both the settlements and the crops began to expand along the coast and inland. The terraces became a collective resource to be defended, as attested by prescriptions in municipal statutes, such as the one of Celle in 1414, forbidding the taking of stones from terrace walls or the tilling of the soil too close to the walls at risk of damaging them.
The year 1874 witnessed the publication of the Guida delle Alpi Apuane, edited by Cesare Zolfanelli and Vincenzo Santini, which offers an accurate and detailed description of Cinque Terre. “From Portovenere, following the coastline railway towards Genoa, one encounters the cove of Cinque Terre (…) and there are some extremely patient farmers who, so as not lose the advantage of their experience, plant vineyards on slopes of bare rock. Having built a low wall, they bring soil from other places; but sometimes misfortune hits them, and the industrious grower sees the whole thing washed down to sea by the water.”
In 1920, local viticulture had been seriously impacted by Phylloxera, which in very few years caused the death of all varieties of grapes grown in the area. After the Phylloxera epidemic, viticulture had a hard time recovering, partly due to the lack of labor. As early as the late nineteenth century, as agricultural income decreased, the first migratory flows began, first towards cities, then towards foreign countries, especially the Americas.
From the 1970s onward (Figure 1
), Cinque Terre witnessed a more than 70% decline of its agriculture and fishing. The towns of Vernazza and Riomaggiore were those that experienced the worst decline of viticulture; for example, the loss of over 52 ha was reported in Riomaggiore between 1982 and 1990, and 24 ha in Vernazza [35
]. This decrease of vineyard surface can be regarded as a constant trend over the last thirty years. The depopulation of the countryside has determined a constant reduction of the maintenance required by the terraces. Terraced viticulture in the Cinque Terre area is an economic, historical, and cultural heritage, a landscape modeled by human beings with the sweat of their brow to guarantee their livelihood. But if the population declines, this heritage is placed in jeopardy.