Desertification Assessment Using MEDALUS Method and GIS Techniques in North America Arid Environments

Desertification is a massive issue that affects many countries that have dry climates. The impacts of this phenomenon threaten the sustainability of natural resources, as well as agricultural, water, and food resources. Several factors that affect directly or indirectly desertification and making it worse are population growth, climate change, deforestation, overgrazing, natural disaster, and urbanization and other types of land development. This thesis research evaluated the desertification index in three counties in California State and three counties in New Mexico State by using the MEDALUS model (Mediterranean Desertification and Land Use) within a geographic information system (GIS). The model includes four indices that can affect desertification: soil quality, climate quality, vegetation quality, and management quality. For each quality index, several parameters were identified. For instance, soil quality index has five parameters that are slope, depth, organic matter, texture, and drainage. Each of these parameters is quantified according to MEDALUS method by giving them a sensitivity coefficient. Then the quality index obtained by combination of parameters. The final results, assessed with the proposed Land Desertification Sensitivity Index by using the MEDALUS method (based on 14 sub-indicators), showed that approximately 82% of the total study areas are critically sensitive to desertification, mainly due to aridity index, precipitation, fire risk, and land use in California counties, while in New Mexico the critical factors were organic matters, aridity index, precipitation, and land use. From the results it is clear that the MEDALUS method was appropriate to apply to study areas. In addition, this study suggests that the maps of ESAs can represent a valuable tool to promote and orientate effective policies of desertification mitigation and prevention