Effective monitoring and evaluation of grain for green project in the upper and middle reaches of the Yangtze river

Abstract

A comprehensive analysis of normalized difference vegetation index (NDVI), land-use type, and digital elevation model (DEM) data by using the geographic information system (GIS) showed that the index had increased over time in 84 prefectures that were part of the Grain for Green Project. SPOT Vegetation (Satellite Pour l’Observation de la Terre Vegetation, or satellite observation of the earth’s vegetation) data and the NDVI showed that compared to 2000, in 2015 2.05% of the arable land in the study area was no longer cultivated and that 25% of the farmland with slopes steeper than 35° and 2.68% of the moderately sloped farmland (2-35°) had been turned into forests. The arable land had been converted mainly to woodland and grassland. The interpretation of thematic mapper (TM) images showed that forest cover had increased significantly (by nearly 22%); that vegetation cover was less than 10% over 95.27% of the area; and that the area with high vegetation cover had increased significantly. Superposition analysis of TM images and DEM data showed that the intensity of soil erosion had generally decreased, with the areas under mild and pole-strength soil erosion decreasing by more than 10%. However, the Grain for Green Project has failed to check severe soil erosion so far. At present, although 60% of the study area is covered by forests, the extent of change in the degree of vegetation cover varied over time, and the spatial distribution was uneven, being higher in the east than in the west. It is therefore important to continue to strengthen governance through such projects.