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The remainder of the paper is structured as follows. We begin by describing the general aspects of the study area, focusing on the importance of the traditional cultural olive-growing landscape and its current situation. In the next section, we outline the cartographic sources and methodology used for data analysis. We then present the results and discuss implications for decision drawing our conclusions in the last part of the paper.

16.2Case Study: The Traditional Cultural Landscape of Olive Groves in Trevi (Italy)

16.2.1 Historical Overview of the Study Area

The olive-growing area in the municipality of Trevi is located between 250–300 and 550–600 m above the sea level. In this area, olive trees grow near the lower thermal limit. Olive groves that cover the foothills are not suitable for intercropping due to their planting density, and as a result, a unique and homogenous landscape can be seen all along the Umbrian valley (Bevilacqua 2012).

In this area, as well as in the entire Umbria Region, appearance of the olive tree was not spontaneous, and its introduction by inhabitants goes back to the Etruscan era. Historical evidence of olive tree cultivation in the Trevi area is offered by the discovery of a Roman sandstone mill. In the Middle Ages, olive tree cultivation in the area suffered a setback, and olive trees were grown within the city walls—or close to them—in small plots protected by stone walls, the so-called Chiuse (Bevilacqua 2012). Simultaneously, the number of pastures increased, and animal fats replaced olive oil.

Around the fifteenth century, planting of olive trees was resumed by local people to the detriment of the woods on mountain slopes. The olive-growing area significantly increased between the late eighteenth century and the nineteenth century, following the laws issued by the Papal State, which had jurisdiction over these territories. New plantings were subsidized, and local people were even allowed to uproot the wooded area on the condition that land with high slopes would be properly terraced. This engineering work, resulting from secular efforts, still characterizes the whole area. When the slope is moderate, plots are flanked by grassy embankments (ciglioni). At higher altitudes and steep slopes, semi-circular walls (the so-called lunette) and terraces protected by dry-stone walls have frequently been built (Bevilacqua 2012). These architectural landscape elements are sometimes mixed with rocky outcrops that have often been incorporated into the structure of the dry-stone walls.

This area has clear landscape value: olive trees dwell here as if they were on the top of a tower, and from a distance, they seem to climb into the woods, creating a pleasant colour contrast. Against the backdrop of the centenary olive trees, some watchtowers and many farmhouses with dovecotes still stand out, and beautiful

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little rural Romanesque churches and old painted and frescoed wayside shrines (typical of local tradition) can be found in the area.

In the eighteenth and nineteenth centuries, olive trees were multiplied by excising ovules from the mother plant stump. The scarcity of stumps prevented local people from making a qualitative selection based on olive production and on adaptability to the specific climate and soil of the area. Instead, such a selection occurred over the years thanks to the combined action of adverse climatic events and farming, resulting in the current high level of biodiversity of these olive groves. In the municipality of Trevi, modern olive growing based on regular planting distances is a recent phenomenon (olive trees are only 40–50 years old), and it has marginally affected some plots at lower altitudes. A diachronic analysis of land use from 1955 to 2012 shows that the olive-growing area decreased from 1266 ha in 1955 to 961 ha in 2012, meaning an overall decrease of 24%.

The reduction of the olive-growing area affected the entire territory devoted to olive cultivation; the phenomenon was particularly serious in the valley floor because of urbanization and in inaccessible mountain areas that were abandoned and colonized by forest cenoses (Fig. 16.1c). It is important to note that in some areas of the municipality of Trevi, especially in the Northeast, new olive groves have been planted.

Evaluation of the landscape’s integrity level1 confirms the reduction of the olive-growing area in the western part of the plain and the mountain margins to the East. It also clearly highlights that the olive grove belt of Trevi, which distinguishes the landscape of the eastern slope of the Umbrian Valley, shows high invariability in agricultural uses. This traditional landscape integrity is an asset to the area, and its conservation plays a crucial role not only from an agricultural, ecological, and cultural perspective but also in terms of promoting the local and regional value of olive oil production.

16.2.2Critical Issues in the Traditional Cultural Olive-Growing Landscape

There is reduction of the olive-growing areas, especially in marginal olive groves that are increasingly at risk of abandonment. In our study area, an olive grove can be classified as marginal based on different parameters: plant density (presence of less than 204 plants in the olive grove is considered marginal); land development (presence of terraces and lunette); slope (when the slope is higher than 25%, the

1Landscape integrity level was assessed using a particular methodology (in Italian Valutazione Storico-Ambientale, VASA), that is, through evaluation of the dynamics and integrity of the traditional agricultural landscape. VASA evaluations are required by Italian law to register the area in the National Registry of Rural Landscapes of Historical Interest, of farming practices, and of traditional knowledge (Art. 4 and Annexes 2 and 3 of Ministerial Decree no. 17070 of 19/11/ 2012).

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area can be scarcely accessed by mechanical vehicles); and altitude (above 500 m, the soil and climatic conditions are considered unfavourable). In the municipality of Trevi, the dividing line between marginal and non-marginal olive groves can be set at 400 m above the sea level. This limit is roughly located on the old road of the so-called Strada delle Selvette to the North and the so-called Strada dei Condotti (or dell’Acquedotto medievale) to the South. This imaginary line also allows one to identify and divide older and newer olive groves according to their cultivation methods.

Older olive groves partly date back to Roman times and were later expanded by the Benedictines; their irregular planting distance follows the mountainous and upland terrain. On the valley-facing side, plots are delimited mainly by grassy embankments. Newer olive groves were planted instead, thanks to the benefits offered under the Papal State, in mostly purposely deforested areas with quite steep slopes and stony soil. The planting distance is quite regular, and stepped terraces vary according to the steepness of the slope. Towards the valley, plots are often protected by grassy embankments or dry-stone walls that sometimes turn into semi-circular walls (lunette). To date, their preservation status varies.

Moreover, some old peri-urban olive groves are located in the surroundings of Trevi, sometimes in areas with steep slopes (e.g. Costa di Santa Caterina). The planting distance follows the ground patterns, while plots are highly terraced, and steps are often very narrow. As seen above, towards the valley, olive groves are protected by variously preserved dry-stone walls and grassy embankments.

This particular landscape of terraced olive groves expresses, more than anything else, the diversity of traditional Umbrian landscapes shaped by the history of local communities.

For the municipality of Trevi, it represents a fundamental source of income from olive oil production, synergy with the historical and cultural heritage, local food and wine traditions, slow tourism, and so on. At the same time, the area shows several problems related to the management of terraced olive groves and the fragility of this form of agriculture. In the light of that concrete proposals and actions for the recovery and conservation of terraced olive-growing landscapes are needed. Such proposals also require identifying and prioritizing intervention areas, as well as establishing a consortium of stakeholders able to make the appropriate interventions.

16.2.3Structural and Technical Data of Olive Groves in the Municipality of Trevi

Out of the 961 ha of olive groves mapped in 2012, only 683 were surveyed during the last Agricultural Census in 2010 (Table 16.1), which means a further loss of olive-growing hectares. Moreover, according to data from the Agricultural Census, in 2010, 412 out of the total 529 agricultural enterprises based in the municipality

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Table 16.1 Structural data of agriculture in the municipality of Trevi
	1982	1990	2000	2010
Farms (number)	707	691	700	529
Farms (ha)	5628	5262	5219	5170
Farms with olive groves (number)	365	380	445	412
Farms with olive groves (hectares reserved for olive	605	601	615	683
groves)
Average farm size (ha)	7.96	7.62	7.46	9.77
Average olive grove size (ha)	1.66	1.58	1.38	1.66
Source ISTAT, Agricultural Census 2010

Table 16.2 Agricultural land use: Olive groves in Trevi (whole municipality)

Farm activities	2013 (ha)
Olive grove	675.81
Wood	209.02
Pasture	69.20
Cereal	42.79
Tare and uncultivated area	25.22
Alfalfa	21.32
Vineyard	11.23
Legumes	7.30
Truffle	6.34
Oilseeds	1.88
Farmhouse and annex	1.21
Annual forage	1.18
Orchard	1.15
Horticultural crop	1.00
Vegetable garden	0.09
Short rotation forestry	0.07
Total	1074.81

Source Our elaboration on SIAN database, 2013

(78%) were olive producers and olive-growing cooperatives. Moreover, 360 (87%) out of the total 412 olive-growing holdings surveyed in 2010 Agricultural Census are listed in the National Agricultural Information System database in 2013 (in Italian, Sistema Informativo Agricolo Nazionale, SIAN). This database includes all the farms that have applied for payments under the Common Agricultural Policy (CAP).

However, the olive-growing area in 2013 (675 ha, SIAN database) corresponds to 99% of the 2010 Agricultural Census area (683 ha). The 675 ha of olive groves are part of a wider agricultural production context and account for 63% of the total