Managing Domestic Trade for Sustainable Food Systems in China: Implications for GHG Fluxes and Nitrogen Emissions

Grain production plays a critical role in ensuring national food security in China but is also a significant source of greenhouse gas (GHG) emissions, nitrogen (N) pollution, and water resource depletion. The shift in grain production centers from southern to northern China over the past four decades, driven by inter-provincial grain trade, has substantially altered the spatial distribution of carbon and nitrogen cycling processes, with important implications for agricultural ecosystems and climate mitigation strategies.

Using over 40 years of data, we show that inter-provincial grain trade in China (wheat, maize, and rice) increased more than fivefold between 1980 and 2020, from 22 to 128 million tonnes. This shift resulted in a 213% increase in N pollution and a 253% rise in GHG emissions associated with agricultural trade, alongside a 606% increase in blue water use and worsening water scarcity in northern regions. Our findings highlight that trade-driven shifts in regional production patterns, influenced by factors such as increased mechanization, population density, and urbanization, have intensified environmental challenges, particularly by increasing ammonia (NH3) and nitrogen oxide (NOx) emissions, which contribute to both GHG fluxes and air quality degradation.

To mitigate these impacts and balance food security with environmental sustainability, we propose a targeted policy intervention-a national subsidy mechanism-to compensate northern provinces for their disproportionate environmental burdens. An annual transfer of approximately US$30 million from southern to northern provinces could incentivize sustainable practices, reduce reactive nitrogen emissions, and enhance overall environmental quality while supporting agricultural productivity. Our study provides evidence-based recommendations for policymakers to develop integrated approaches that consider both GHG mitigation and nitrogen management in managed agricultural ecosystems.