Spatio-temporal distribution and trends monitoring of land desertification based on time-series remote sensing data in northern China

Land desertification is a significant research area among current global ecological and environmental issues. Desertification not only affects the ecological environment, but is also closely related to human society. With the development of new technology, outstanding progress has been made in the development of desertification monitoring and evaluation indicators. The objective of this study was to assess the trends and distribution of land desertification in northern China using time-series GIMMS NDVI 3 g and MODIS-NDVI remote sensing data from 1991 to 2019. The Dimidiate Pixel Model was chosen to calculate the Vegetation Coverage Index (VCI). The Sen's slope estimator and the Mann–Kendall statistical test were used to analyze the spatial trends of the VCI. The residual trend method was applied to assess human and climate factor induced land degradation. Data from the study area showed that the total area of desertification in northern China decreased year by year from 1991 to 2019, but the area of very severe desertification demonstrated an increasing trend. At the same time, areas of severe, moderate, and mild desertification showed a decreasing trend. From the overall analysis, a trend of overall decrease and local aggravation of land desertification was revealed. The residual analysis showed that desertification control measures and favorable climatic conditions have played key roles in the process of desertification reversion; while climate fluctuations, reclamation and livestock have led to the development of further desertification.