Desertification Risks: Sensitivity And Limits Of The Medalus Method In Semi-arid Areas (center Of Tunisia)

Environmental indicators are essential tools for tracking environmental risks especially land use degradation. Supporting the environmental evaluation and research items needs usually a heavy and costly field work. For these reasons, some methods and indicators of risks have gained in importance in many countries and in international reports. As part of their commitment to transparency to real information, public authority increasingly uses a reduced number of indicators or select existent methods to report on major environmental issues. These economic and time justifications cannot nor ignore or hide the disadvantages of these methods apart from their validation areas especially in arid countries. The study concerned the application of an European method for the evaluation of the risks of desertification namely “the Mediterranean Desertification and Land Use or MEDALUS method”, which had deserve more researches to adapt it to the arid conditions. Indeed, testing this method to the desertification risks evaluation of the agricultural land-use in Tunisia has showed its limits. The review of parameters used and the re-calibration of the risks levels to the agricultural units have improved the results of this method in arid conditions. This improvement was limited about 10% (land degradation risks has reduced from 90.5% to 81% of surface studied) when adapted soil quality index to local conditions and re-calibration of risks levels were applied. But these results do not prevent that validation of the method would improve analyzes and understanding of this phenomenon in local conditions.