The cork oak (Quercus suber) grows naturally only in the western part of the Mediterranean. It finds an ideal environment for growth in Portugal, Spain, France, Tunisia, Algeria, Morocco, and on the Italian Tyrrhenian coast, in particular in Sardinia, which can be considered the geographic center of its diffusion.
In Sardinia, the cork oak lives in places up to 900-950 meters above sea level, although the optimal conditions for its location are between 500 and 800 meters, where the climate is more temperate and the rainfall is higher. Cork oaks form forests in which they are either the dominant species or in consortium with holm oaks, oaks, and other types of wood.
The cork and oak forests on the island cover an area of about 90,000 hectares, representing over half of the forest trees on the island. It is, therefore, a very important component, mostly found in Goceano, in Gallura, on the Buddusò plateau, in the territories of Abbasanta, Sorgono, Orune and Bitti, in Sarrabus, and in Iglesias. Over 85% of the cork oaks are privately owned. Its excessive fragmentation makes it difficult to implement a joint management plan to improve the conditions of the existing trees.
Forest fires are such a serious problem in Sardinia that they have significantly affected the conditions of cork oaks. In the long run, repeated fires over time result in die-offs, fungal attacks, and agamic reproduction, which can weaken or deplete the stumps. Other problems can be connected to overgrazing (inhibition of natural regeneration), plowing activities (damage to root systems), and infestations of defoliating insects and other pathogens.
On the Giara, the cork oak represents the prevalent type of forest, which occupies 46 percent of the surface of the plateau with semi-natural forest formations, as conditioned by secular human activities and adapted to both climactic conditions, in particular the wind, and soil conditions, which are generally shallow. In this sense, these trees play a crucial role in soil conservation and combating desertification and, they contribute to the sustainable development of the towns within the SCI.
Like all woodlands, the cork oak forests, along with many other species, create suitable habitats for many species of fauna and can be considered places of fundamental importance for the conservation of Mediterranean biodiversity.
Cork is a product that is periodically retractable from these plants, which has a significant economic importance in the Mediterranean context as well as in the rest of the world. It is a scar tissue that is present in all Quercus suber which produces a very thick layer that covers all the woody parts of the plant. This precious material is produced by cork cambium, commonly called "mother of cork", which has the ability to regenerate tissue indefinitely when the bark is removed.
The extraction of the cork is a regulated operation under Regional Law n. 4 (1994) and can be performed once every decade.
The first extraction can be performed when the plant has reached a diameter of at least 60 centimeters and a height of 130 centimeters. These operations must be carried out by experienced staff in order to avoid damage to the plants or incorrect extractions. The first extraction produces the "male cork" or "sugherone", whose value is not high and is normally used in construction for the manufacture of insulating and soundproofing panels.
Subsequent cuts can be performed at different heights, but they must always follow the procedures established by the law. The result is the “friendly cork” (or "female cork"), which is valuable for the manufacture of stoppers.
The ecological implications of a regulated production are obvious: since it is a renewable material, the use of cork in this way implies the preservation and care of the individual plants as well as, in many cases, an increase in the total number of cork oak trees. Moreover, it must be said that the transformation of the cork leaves no waste: the small quantities of material that remain are used as fuel to create the thermal energy necessary for the operation of the same production cycle.
For centuries, the cork has been the raw material for the construction of many objects used daily, both in the home and in the fields, such as containers for making cheese; large trays to serve meat at large communal lunches; and plugs to close barrels, jugs, and demijohns.
The tradition of the region, from this point of view, is similar to the one practiced throughout the rest of the island. In the Giara, however, the cork is grown and harvested more carefully than elsewhere, with more consistency, and, to this day, it is still extracted from the cork oak trees of the Giara in order to be brought to the regions that have always been involved in its processing (most notably the region of Gallura)
This relationship can also be seen in the composition of the forests of the plateau, since over time the number of holm oaks has been reduced in favor of cork oaks. These forests, frequented by the famous Giara horses to take refuge from the summer heat, are, in fact, the result of incessant human activity. Like every other environmental element in this region, the forests show the signs of a special balance between nature and culture. This is a fragile balance that has been broken repeatedly by several events in recent centuries. Here, as in many other parts of Sardinia, the old oak trees were cut down between 1880 and 1920 and then again during the Second World War. Since then, their regrowth has been slowed down by the lack of consistency of the soil and the excessive grazing of domestic animals. Thus, the cork oaks of the Giara are rather thin today, with a low average trunk diameter.
The conservation of this important environmental and economic resource is, therefore, due to the regulated use of cork and the special attention that the local communities give to this habitat.
However, there have been management and silvicultural problems, such as excessive and frequent cleanups of the undergrowth to encourage overgrazing, which is deleterious to the woodland habitat.
In this respect, the recognition by the European Community of the Site of Community Importance “Giara di Gesturi” and the cooperation of all the towns actively contribute to the growing reconciliation between traditional productive activities - breeding and the extraction of raw cork - and the need to preserve the natural heritage of the Marmilla. The health of the forest, the production of cork, the breeding of livestock, and the preservation of the typical landscape, flora, and wildlife of the Giara represent some of the many goals that are integrated in a unique and complex project aimed to promote and preserve the natural and cultural heritage of this land.