Global population growth and limited availability of agricultural land pose challenges to the simultaneous pursuit of higher grain yields and agricultural sustainability. As reducing inequality is a key component of the sustainable development goals, reducing greenhouse gas (GHG) emissions in crop production while ensuring emission equity is crucial for sustainable agriculture in China.

Associate Prof. XU Xiangbo and Prof. ZHANG Linxiu at the Institute of Geographic Sciences and Natural Resources Research (IGSNRR) of the Chinese Academy of Sciences (CAS) and their collaborators found the year of 2015 was a turning point for GHG emissions intensity (GEI) levels, which dropped 16% in 2020, while inequality—measured as average GHG emissions per unit planted area—increased 13%. Reducing GEI levels and guarding against widening inequality require optimizing production factor inputs.

This study was published in Nature Food on 4 November 2024.

The researchers used the data obtained from the fixed observation rural survey (FORS) (1986‒2020) of the Ministry of Agriculture and Rural Affairs of the People’s Republic of China and the Chinese rural development survey (CRDS) led by the authors. Eventually, a sample of over 430,000 rural households from 1993 to 2020 was obtained. 

They found that the emissions from rice planting (particularly CH₄), field management (mainly N₂O), and fertilizer production were the three major contributors to total GHG emissions from crop production. From a crop-specific contribution perspective, the GEI was the highest for maize, rice, and wheat. But after 2015, the GEI of all crops showed a downward trend. The decomposition results based on GHG emissions per unit cultivated land area showed a similar trend.

Climatic conditions, geographical locations, and cropping systems vary greatly among different agricultural regions in China. The GEI of most agricultural regions peaked in 2015, except for a few agricultural regions which peaked between 2015 and 2018. The highest emissions were observed in the agricultural regions of southern China, 6.58 times greater than those in the Qinghai‒Tibet Plateau, the region with the lowest emissions.

They explored the dynamic relationship of driver forces. Overall, the time-varying effects of the TFP, farmland input, and all other inputs contributed to the decline in the GEI in China from 1993 to 2020. Given that agricultural GHG emissions caused by all other inputs before 2015 increased, the increases in the TFP and farmland input can be considered the primary driving forces behind that reduction.

The findings about the contribution of driving forces to the inequality in the GEI revealed that farmland input and all other inputs were the primary contributors and their influences have remained relatively consistent over the past three decades. Interestingly, the contribution of the TFP decreased over time and the contribution of agricultural labour input to the inequality in the GEI increased. Reducing the inequality in the GEI is the premise for reducing the GEI. Therefore, equitable GHG emissions reduction in crop production should be a key focus of scientists and policy-makers.

Reference:

Xu, X., Zhao, Q., Guo, J., et al. Inequality in agricultural greenhouse gas emissions intensity has risen in rural China from 1993 to 2020. Nature Food, 5, 916‒928 (2024).