Change of surface cover greenness in China between 2000 and 2010

Surface greenness reflects the situation of vegetation cover. Vegetation index calculated from the Red and Near Infrared bands of remote sensing images, whose values indicate the level of photosynthetic activity, is monotonically related to surface greenness when vegetation canopy does not fully cover the background soil. Especially for desert regions, vegetation index is positively correlated with vegetation coverage. Therefore, vegetation index can be used to study the change in greenness of desert areas. This study collected MODIS Normalized Difference Vegetation Index (NDVI) data from 2000 to 2010 and analyzed their change over China in this period. The results showed that an increasing trend of NDVI occurred over 66.84% (OLS fitting) or 64.27% (LAD fitting) of China, indicating that China's greenness is increasing overall. Meanwhile, desertification of China decreased. Areas showing large increase in greenness are found in Shaanxi, Shanxi, Ningxia, Henan, Shandong, Qinghai, and Gansu while regions with large decrease in greenness are found in Northeast Inner Mongolia, South Tibet, Jiangsu, and Shanghai. Changes of Qinghai, Gansu, Xinjiang and South Tibet could probably be driven by climate factors. Decrease of greenness in Northeast Inner Mongolia was related to agricultural reclamation. Decrease of greenness in Jiangsu and Shanghai was related to rapid urbanization. Climate factors did not exhibit obvious correspondence to the large increase in greenness in Shaanxi, Shanxi, Ningxia and Gansu, indicating that the changes might have been caused by human factors. The reduction of desert areas in China could probably have been caused by human management and protection at the national scale.