Assessing land degradation and land use in the Libyan Al-jabal Alakhdar region.

This research examines and identifies the causes of land degradation in a semi-arid area in eastern Libya subject to soil loss through water erosion. Temporal changes in landscape cover are detected between 1984 and 2008 using satellite imagery: a 26% decrease in dense vegetation and shrubs, a 100% increase in agricultural land and an increase of 5% in both irrigated crops and bare soil occurred. Soils and climate information was used to apply a theoretical model of desertification (MEDALUS) within GIS to the study area. Statistical verification of the model employed extensive data from a comprehensive assessment of the study area by a focus group of experts assembled for this research. Theoretical relationships to significantly improve the model were developed using new field data, including actual stocking rates, dry biomass and plant palatability, to describe grazing intensity. The environmental impact of these human activities in natural areas can now be applied. Spatial changes were explored using a further model with the universal soil loss equation (USLE), which was independently verified in both 1984 and 2008 to easily allow mapping of the changes extent and assessment in those 24 years. A new soil conservation practice factor is introduced for natural areas based on grazing intensity. The model results indicate that in 1984, the natural land had only a slight risk of land degradation due to the protection provided by the high density of cover and sustainable grazing intensities, unless the land slope is very steep.By 2008, an additional 26% of the study area suffered from different degradation levels, caused by land use change. Only 20% of the study area remains dense, natural vegetation under sustainable grazing intensity but a further 5% of land is grazed and converted to sparser vegetation cover. Agriculture and overgrazing are the main drivers of unnatural soil erosion, indicating that some farming practices are unsustainable. This work has comprehensively quantified the rate extent and causes of land degradation in the north-east of Libya. This knowledge can be used to organise more sustainable land management to avoid further land degradation and to mitigate that already observed.