The decline of the cork oak growing in Sicily is accompanied by the loss of the functions proper to agroforestry systems

Abstract

The cork oak is one of the most important tree species in the Mediterranean basin, where it covers more than 2 million hectares. Among evergreen oaks, Quercus suber stands out for the variety of cultural systems in which it has been successfully employed, including typical agroforestry systems. Accordingly, a wide range of ecosystem services may be associated to cork oak, including the preservation of biodiversity, carbon sequestration and forage production. In the Mediterranean, the cork oak represents a key species for many natural and seminatural landscapes and habitats, as well as playing a prominent role for the economic and social development of local communities. However, there is increasing concern about the long-term conservation of Quercus suber forests and agroforestry systems throughout the distribution range. In fact, a range contraction of Quercus suber natural distribution is expected in the next decades, especially in the southern edge and at lower altitudes of species’ natural distribution range. Many factors have been invoked to explain the on-going process, among which overgrazing, soil pathogens and land-use changes are prominent. The aim of our work was to assess the variation in time of the area covered by the cork oak in Sicily. Different bibliographic sources were consulted, of course including the available National and Regional forest inventories. Although some discrepancies in inventory and historical data were found, an increasing trend of the area covered by the cork oak in Sicily would seem to have occurred. Notwithstanding this, a parallel worsening of the conservation status of most of these stands has been at the same time observed at a regional level. The frequent wildfires and the progressive abandonment of the cork oak cultivation have been suspected to play a major role in the current situation. It must be kept in mind that in many areas the cork oak has been favoured by man against other tree species, so the cork oak stands are in effect secondary forest stands, which rely on continuous human management. Hence, the clear decline observed is increasingly compromising the ability of the cork oak to provide ecosystem services for the community, although the area has increased. Particularly, the degradation processes may cause the loss of the ecosystem functions proper to the cork oak agroforestry systems as they are very simplified. Thus, the value linked to the production of cork is lost, along with the pasture value, and last but not least the landscape value. In this perspective, the management of cork oak forests in Sicily should be promoted, for instance through the adoption of specific sustainability indicators and fostering quality productions. Active interventions and sound restoration practices are urgently needed if we are to preserve the valuable social, ecological and landscape value of Quercus suber stands occurring in Sicily.