Characterization of greenhouse gas emissions and water requirement of farmland in China's main grain-producing areas under future climate scenarios

CONTEXT: Addressing the key challenges that climate change posed by agricultural sustainability requires special attention to greenhouse gas emissions and agricultural water use. Differences among crops and regions significantly affect the water-carbon characteristics of grain production to climate change. However, the mechanisms underlying this impact and its assessment at high resolution over long timescales remain insufficiently understood. OBJECTIVES: This study aims to estimate the cumulative greenhouse gas emissions (cGHG) and water requirement of maize, rice, and wheat under different climate scenarios in China's major grain-producing areas from 2021 to 2100, and to quantify their temporal and spatial variation characteristics. METHODS: Based on the future climate data of six global climate models (GCMs) under the CMIP6, this study used the calibrated the Denitrification Decomposition (DNDC) model and the improved Penman-Monteith formula to quantify the GHG emission and water requirements during the growth period of maize, rice, and wheat under three societal development scenarios of SSP1-2.6, SSP2-4.5, and SSP5-8.5 from 2021 to 2100. RESULTS AND CONCLUSIONS: The result showed that the parameterized DNDC model performed well in the study area, with a yeild R2 of 0.98 and a root mean square error (RMSE) of 247.25 kg/ha. Under multiple emission scenarios, the cGHG of maize and wheat showed a significant downward trend over time, while the cGHG of rice increased. The emission hotspots were mainly concentrated in the Huang-Huai-Hai region and the middle and lower reaches of the Yangtze River. The water requirement (ETc) of the three crops increased significantly with time and showed a reverse pattern with the spatial distribution of cGHG. The high ETcvalues areas were concentrated in the central part of the study area and the western part of Inner Mongolia, and the water deficit was also the most serious. SIGNIFICANCE: This study clarifies long-term trends and spatial variations in water-carbon fluxes, providing essential data to inform climate adaptation strategies in agriculture, water conservation efforts, and emissions reduction initiatives.