Life and identity of East & South -West Magnesia
Crovetti ascribes the stability of the agricultural ecosystem to the marked complexity in the intraspecific and interspecific relationships between the insects associated with the olive resulting primarily from the lengthy growing period. Considering the biotic forms, the flora in the olive grove ecosystem presents an exceptional resemblance to the flora of Mediterranean type ecosystems.
Consequently, the artificial system of an olive grove, as opposed to what stands in other agroecosystems, is very similar to the natural mediterranean ecosystems, even in its functional, efficient condition. This claim is proved by a number of researches. The cultivated olive tree is the grafted form of a wild olive tree, which is a basic element of evergreen (maquis) vegetation, one of the principal types of mediterranean ecosystems. Many olive groves have substantially resulted from the vaccination of the wild olive tree that already existed there. According to phytogeographers one of the main flora communities with one of the widest expansions in the Mediterranean space is the Oleo-Ceratonion, which, as its name suggests, is characterized by the presence of the olive tree.
The existence of a significant number of diverse plants of the Mediterranean flora in cultivated olive groves ensures the conditions for the creation of a multitude of habitats for animals. The olive has a wealth of arthropod fauna, comprising one hundred or so phytophagous species in addition to others described as being useful or indifferent .
Indeed, 15 insect classes have been identified, which include from 94 to 125 families. The large number of insects and the rich flora ensure food to an important number of birds: 31 species have been located in olive groves . It is inhabited both by winter birds and nesting ones. Fruit-eating birds have been noted over the winter season. The existence of the olive is, consequently, of the highest importance for many types of fauna that survive during the winter such as black birds (Turdusmerula) and starlings (Sturnus vulgaris), and migration birds en route.
The ecological effects of olive growing are also international, since they are related to the migration of birds from North Europe. Further, a relatively large number of mammals has also been located there, more than 12 species. It should be stressed, however, that olive trees are evergreen trees and produce fruit with high energy content, which are available during the winter period. The maintenance of the traditional olive grove is benign for the environment, since these show low soil erosion rates and a high bio-diversity.
As a result of the change of use to pasturage land, it has been determined that there is a significant decrease of plant coverage and a limited number of woody plant species in abandoned olive groves. Thus, a cultivated olive grove presented plant coverage of 81.2% by 11 woody types. After twenty or thirty years since the change of use of the land, the percentage of plant coverage was decreased to 33.2% and 29.6% respectively, while the number of woody species was limited to only five.
The conservation of the olive grove system, in productive condition, contributes to the sustainability of the natural resources through their preservation by the maintenance of the soil, the reduction of rainfall’s losses, and their exploitation. Olive trees are drought resistant and because of their extensive rooting system are some of the few crops that can survive on only 200–300 mm of annual rainfall (Fresco, 1996).Throughout the centuries, the traditional olive plantations are the kind of cultivation that maintained the productive possibility in the barren and dry Mediterranean soils, with very high erosion levels. In these terraced areas, the erosion is decreasing with the protection of the minimal soil, and the reduction of the outflow and nutrient losses, since they elongate the remaining time of rainfalls on the surface of the soil. Consequently, the terraces favor the percolation of the water in the underground waters and its appearance in lower altitude regions, in the form of spring water.
The trend for quality products is satisfied in this certain cultivation, since the chemical substances used for the production of olive oil are the lowest possible among not only its competitive products but among all other agricultural products of the Mediterranean. From this point, even in the case of conventional cultivation of the olive, it is compatible with sustainable agriculture, and it neither consumes the natural resources, nor depreciates them. A productive olive grove is still closer to the natural eco-systems, because the interventions taking place during cultivation are very limited.