An analysis of the impact on land use and ecological vulnerability of the policy of returning farmland to forest in Yan'an, China.

During the past decades, land use change has taken place around the Loess Plateau at unprecedented rates. Due to the impact of existing land use policy, great changes have taken place in the land use types in this ecologically vulnerable area. Taking eight counties in Yan'an, Shaanxi province, China, as the study area, this study analyzed the long-term (from 1997 to 2011) changes in land use and ecological vulnerability. Based on thematic mapper (TM) images of Yan'an in 1997, 2004, and 2011, the dynamic changes in land use are analyzed with the application software for remote sensing (RS) and geographic information system (GIS) since the implementation of the policy of returning farmland to forest. Combined with the land use data, the local socio-economic data, and natural resources condition, ecological vulnerability is evaluated using the spatial principal component analysis (SPCA) model in Yan'an region. Using the natural breaks classification (NBC), the evaluation results are divided into five categories: potential, slight, light, medium, and heavy. The results show that although the regional land use types changed markedly, the ecological vulnerability in the study shows greater than average optimism, and the ecological vulnerability index of the southern four counties is lower than that of the northern four counties. In 1997-2011, the eco-environmental quality gradually improved in most areas. However, it gradually deteriorated in some regions.