Assessing Intensity of Desertification and Land Rehabilitation Using the Change Vector Analysis Method (Case study: Dehshir Plain, Yazd province, Iran)

Desertification is one of the main ecological and environmental problems in Iran. It is remarkably urgent to monitor and assess this phenomenon and its impact on ecosystem components such as vegetation covers to prevent and combat desertification. This study aimed to evaluate the Change Vector Analysis (CVA) method’s efficiency in assessing and monitoring desertification in Dehshir Plain, Yazd province, central Iran. For this purpose, the imagery of Landsat 5 from 1994 to 1998 (T1) and Landsat 8 from 2014 to 2018 (T2) were selected in June and July period on the Google Earth Engine platform. Then, the Bare Soil Index (BSI) and Normalized Difference Vegetation Index (NDVI) were calculated for the two periods. The direction and the strength of changes in NDVI and BSI were determined based on the CVA method. The results showed that 27.27% and 38.65% of the region surfaces were in degraded and rehabilitated states, respectively. The severity of degradation was higher in the central and northern parts of the study area. Adversely, rehabilitation has increased in the south, west, and east parts of the region. The results of CVA and field reality showed that this method could well reveal changes in ecosystem components over time, which is due to the comparison of two different periods using land cover indicators such as plants and soil. Our finding suggested that the CVA was an appropriate method for monitoring and assessing the desertification phenomenon and determining the area under degradation or rehabilitation in arid regions.