Greenhouse gas emissions and net carbon sequestration of the Beijing-Tianjin Sand Source Control Project in China

A methodology for carbon accounting and net mitigation estimation for national ecological restoration projects in China (CANM-EP) was developed, and this method simultaneously considered carbon sequestration, on-site greenhouse gas (GHG) emissions from ecosystem management, off-site GHG emissions and other changes in the ecosystem GHG budget. Based on this methodology, the annual variance and composition of carbon sequestration, GHG emissions and net carbon sequestration were analyzed for the first stage of the Beijing-Tianjin Sand Source Control Project (BTSSCP) (2001–2010) in the respective project provinces. The total carbon sequestration in the BTSSCP from 2001 to 2010 was 71.25–71.66 Tg C, and the additional GHG emissions from the BTSSCP were 7.28–7.50 Tg Ce, which counteracted 10.2–10.5% of the sequestered carbon. Among the different project measures in their corresponding ecosystems, the counteraction effect of grassland management in the grassland ecosystem was over 50%, which was much higher than that of afforestation and the conversion of cropland to forest. The net carbon sequestration in the BTSSCP was 63.75–64.38 Tg Ce, and the annual average was 6.38–6.44 Tg Ce·yr−1. The annual rate of net carbon mitigation for Beijing, Tianjin, Hebei, Shanxi and Inner Mongolia was 1.16–1.17, 1.29–1.30, 1.06–1.07, 0.85–0.86 and 0.63–0.65 t Ce·ha−1·yr−1, respectively. The GHG emissions offset a minor part of the carbon sequestration in the BTSSCP. Therefore, the BTSSCP makes a relatively significant contribution to GHG mitigation in China.