Patterns and driving forces of cropland changes in the Three Gorges Area, China

Human activities, especially the launch of massive projects such as the Three Gorge Project (TGP) for the constructing the world’s largest dam, the Chinese Western Region Development Project, and the Ecological Protection Projects designed to protect the natural vegetation, greatly changed the landscape pattern in the Three Gorges reservoir area (TGRA) in recent decades. In this study, remote sensing was employed to monitor pattern dynamic of the cropland, cropland quality, and cropland cultivation intensity in TGRA during the implementation period of TGP, and then the driving forces of cropland change were discussed. The results showed that the cropland area decreased by 4%, with an average annual reduction of 3,977 hectares. Of the decrease, the high-yield cropland accounted for 61%; this led to a decline in the quality of the entire cropland. Along with the decrease in cultivation intensity, the multiple cropping indexes reduced by 7% from 2003 to 2009. Urban expansion topped the list of driving forces contributing to the decline, which contributed 45% of the decline. Submergence caused by rise of water level is another sponsor to cropland reduction. Contribution of submergence to the cropland decrease was up to 16%. Besides, the ecological rehabilitation project and development of orchard industry also contributed to the decline. In 2007, the cropland with slope gradient larger than 25°, which should be returned to forests or pastures according to the land policy, still accounted for 20%.