Title: Assessing desertification and land degradation using trends of Normalized Difference Vegetation Index time series: case study in steppe zone in Mongolia

Desertification and land degradation are causing a serious environmental problem in Mongolia, with climate change and human activities being major contributors to the land degradation. This study was aimed to assess land degradation and desertification using the remotely sensed Normalized Difference Vegetation Index (NDVI) time series and the amount of precipitation. GIS and statistical analyses were used to estimate the trend of the annual average NDVI for June, July and August from 2006 to 2016. Moreover, analyses were conducted to identify the effects of precipitation variation and human activities on the trend of NDVI. The Mongolian real steppe subzone was selected as a study site since the area is vulnerable to desertification. The study results reveal an increasing trend in NDVI values in 86.54% of the total study area and a decreasing trend in NDVI values in 13.5% from 2006 to 2016. Overall, 13.5% of the total area, or a 2,923.4 sq. km area, has been affected by desertification. The human impact zone had a higher declining trend than the no impact zone. There was a positive moderate correlation between change in precipitation and the NDVI trend in the study area. The study indicates that the effects of precipitation variance on the changes in the trend of the NDVI resulted from more than human activities in the study area.