Impacts of China's Three Gorges Dam Project on net primary productivity in the reservoir area

China's Three Gorges Dam Project (TGP) is the world's largest hydroelectric power project, and as a consequence the reservoir area is at risk of ecological degradation. This study uses net primary productivity (NPP) as an important indicator of the reservoir ecosystem's productivity to estimate the impacts of the TGP in the local resettlement region of the Three Gorges Reservoir Area (TGRA) over the 2000–2010 period. The modeling method is based upon the Carnegie Ames Stanford Approach (CASA) terrestrial carbon model and uses Moderate Resolution Imaging Spectroradiometer (MODIS) remote sensing data for modeling simulation. The results demonstrate that total NPP in the resettlement region decreased by 8.0% (632.8 Gg) from 2000 to 2010. The impact of the TGP on NPP is mainly mediated by land-use change brought about by the large-scale inundation of land and subsequent massive resettlement of both rural and urban residents. Nearby resettlement, land inundation, and relocation of old urban centers and affiliated urban dwellers are responsible for 54.3%, 28.0%, and 5.8% respectively of total NPP reduction in the resettlement region over the study period. The major national ecological projects implemented in the TGRA since 1998 have played a key role in offsetting the negative impacts of the TGP on NPP in the region. ► Spatial and temporal change of NPP was estimated with the CASA model and MODIS remote sensing data. ► The impact of the TGP on NPP is mainly mediated by land-use change brought by the large-scale inundation and resettlement. ► Near resettlement, inundation and urban relocation are responsible for 54.3%, 28.0% and 5.8% of NPP impact, respectively. ► The major national ecological projects have played a key role in offsetting the negative impacts of the TGP on NPP.