Assessment of Land Degradation Using GLASOD and IMDPA Models (Case study: Yazd-Ardakan plain)

Land degradation is manifested by a significant decrease in biological productivity of land, as a result of natural events or improper human activities. The unfortunate consequences of this degradation are threats to food security, economic well-being and environmental problems caused by the reduction of the exploitation potential of water, soil and plants. The aim of present research is to compare and measure the state of land degradation based on two global GLASOD and Iranian IMDPA models. The great plain of Yazd-Ardakan located in central Iran was selected as the research area. The land unit map of area was prepared. The severity of land degradation was investigated based on the GLASOD and IMDPA models in each of the land units. Accuracy assessment and comparison of both models’ performance were done by calculating overall accuracy and kappa coefficient, as well as non-parametric tests of Spearman and Mann-Kendall, and the significance of the results were confirmed. The comparison of accuracy assessment results showed that the IMDPA production map matched the actual data on the ground by 82%, while this match in the map obtained by GLASOD model was 69%. According to the IMDPA and GLASOD models, desertification was progressing strongly in 33% and 12% of the region, respectively. The intensity of desertification in the moderate class was approaching the severe class, and if there is no proper management to control and prevent the desertification process in the region, in not-so-distant future, the area of land with severe desertification will increase. In general, the lack of soil surface cover is the main factor in increasing the intensity of desertification in the Yazd-Ardakan plain. This issue is result of combination of natural factors and destructive human factors in the region, which has significant effects on increasing the desertification process and soil degradation.