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Università degli Studi della Tuscia (2008)

A new GIS-based spatial modeling approach for desertification risk assessment in the Mediterranean Area. An Italian case study : Sardinia Island

Santini, Monia

Titre : A new GIS-based spatial modeling approach for desertification risk assessment in the Mediterranean Area. An Italian case study : Sardinia Island

Sviluppo di una nuova metodologia orientata al GIS per la valutazione del rischio di desertificazione nell’area Mediterranea. Un caso studio in Italia : Sardegna

Auteur : Santini, Monia

Université de soutenance : Università degli Studi della Tuscia

Grade : Tesi di dottorato di ricerca. 20. Ciclo 2008

Résumé
Desertification risk assessment has become a prior goal for environmental protection, recently even in the Mediterranean area. Assuming this phenomenon as interaction among predisposing (i.e. geographic location), triggering (i.e. extreme climatic events) and quickening (i.e. human activities) factors, a new model-based methodology was developed, combining synergically a wide range of desertification indicators developed by previous projects in Mediterranean area and included within the DPSIR (Driving force, Pressure, State, Impact, Response) scheme. The presented approach was applied for desertification risk evaluation in Sardinia (Italy). A large multi-thematic dataset has been acquired, processed and re-arranged in a GIS environment in order to supply the input to five models regarding several degradation processes typical in the study area : soil erosion, soil degradation, vegetation degradation, coastal aquifer salinization and overgrazing. The quantities resulted by modelling were normalized as indices varying from 0 (no degradation) to 1 (irreversible degradation) and they supplied a map of risk for each degradation process. These procedures were applied for two different periods according to the largest availability of data : the early nineties and the present. A total of ten single degradation indices were then integrated into a final one, combining in this way different factors of desertification, their magnitude, their changes, their development rate and giving them different weights according to the significance of each process and to the quality and detail of its input data. The final Integrated Desertification Index (IDI) has the same range of values and has been classified into 5 levels of increasing severity. The desertification risk map obtained using this methodology well reflects conditions observed on the ground. Further spatial statistic analyses allowed a comprehensive knowledge of features in most critical areas. This methodology allowed to highlight the spatial and temporal variability of desertification phenomenon, besides to estimate the land vulnerability in respects to each single degradation process. Starting from environmental vulnerability estima tion and jointly with socio-economic aspects regarding probable land use scenarios, we will identify areas at different risk for the future, again in a GIS-oriented approach, supplying an useful instrument for prevention, adaptation and mitigation countermeasures.

Mots Clés  : Desertification ;Land degradation ;Geographyc Information Systems ;Spatial modelling ;Hotspots analysis ;AGR/05

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