An evaluation of land degradation and desertification in the Jeffara Plain, Libya.

The research develops the Mediterranean Desertification and Land Use methods and makes then more appropriate for studying land degradation in arid and semi-arid zones. In this research, three approaches were applied to land degradation assessment in the central southern part of the Jeffara Plain in Libya: remote sensing, Mediterranean Desertification and Land Use (MEDALUS) and Universal Soil Loss Equation (USLE).The Mediterranean Desertification and Land Use Method was used to determine the environmentally sensitive areas (ESAs) in the study area. In addition, this model has been developed by adding two parameters: groundwater management and wind speed. These were not directly applied in the original MEDALUS model and their incorporation makes the method more suitable to the arid and semi-arid zones.Landsat images were used for the years 1986, 1996 and 2002 and Spot images for the year 2009. The supervised classification (the enhanced maximum likelihood classification) algorithm was applied to generate land cover maps together with the matrix analysis. They were used to analyse and extract land information covering the changes in the study area; they detected and assessed the changes for the period from 1986 to 2009.In addition to processing the satellite MODIS images, the data were used to identify the relationship between the climate and the vegetation indices (NDVI) for the period from 2001 to 2009.The Universal Soil Loss Equation (USLE) was used with a Geographic Information System (GIS) to determine quantitatively the average annual soil loss in the study area. A GIS file was created for each factor of the USLE: precipitation, soil type, land cover, and slope, combined with the cell-grid modelling procedures in Arc GIS to predict the soil erosion risk.The results obtained from remote sensing demonstrated significant decrease in natural vegetation and significant degradation in most of the land in the study area. About 85% of the study area was 'moderate' or 'severe' in terms of degradation, as defined land cover maps and land degradation maps were produced for the study area. Findings from the Mediterranean Desertification and Land Use method showed that almost 75% of the total study area was sensitive to 'critical' desertification. A map for the environmentally sensitive areas vulnerable to desertification was produced for the study area.In contrast, the results obtained from USLE revealed 'slight' erosion rates in the rangelands and the agricultural lands which together account for 76% of the total land area. A soil erosion map was also produced for the study area.