Simulating China's carbon dynamics using improved LUCC data: from source to sink
Z. YU , P. CIAIS, S. PIAO, R. A. HOUGHTON, C. LU, H. TIAN, E. AGATHOKLEOUS, G. R. KATTEL, S. SITCH, D. GOLL, X. YUE, A. WALKER, P. FRIEDLINGSTEIN, A. K. JAIN, S. LIU, G. ZHOU
Key Laboratory of Ecosystem Carbon Source and Sink, China Meteorological Administration (ECSS-CMA), School of Applied Meteorology, Nanjing University of Information Science and Technology, Nanjing, 210044, China

Carbon budget accounting relies heavily on Food and Agriculture Organization (FAO) land-use data reported by governments. Here we develop a new land-use and cover-change database for China, finding that differing historical survey methods biased China’s reported data causing large errors in FAO databases. Land ecosystem model simulations driven with the new data reveal a strong carbon sink of 8.9±0.8 Pg carbon from 1980 to 2019 in China, which was not captured in FAO-data-based estimations due to biased land-use and cover-change signals. The land-use and cover-change in China, characterized by a rapid forest expansion from 1980 to 2019, contributed to nearly 44% of the national terrestrial carbon sink. In contrast, climate changes (22.3%), increasing nitrogen deposition (12.9%), and rising carbon dioxide (8.1%) are less important contributors. This indicates that previous studies have greatly underestimated the impact of land-use and cover-change on the terrestrial carbon balance of China. This study underlines the importance of reliable land-use and cover-change databases in global carbon budget accounting.