The Chinese breadbasket is not where it used to be. Reshaped land systems have extended distances between food production and consumption, thus increasing carbon emissions associated with grain transport.
Although foods are produced locally, trade enables food access remotely, turning food transport emissions — driven by the interactions between location-based land systems and object-oriented food systems — into an additional challenge to production emissions. Although grains emit less than meat during production and usually do not require fresh-keeping treatments after harvest, grains’ tonnage and food-miles are relatively higher than other food products, making them the second largest contributor of food-miles emissions after fruits and vegetables. Moreover, due to the varied transport tasks, grains’ domestic food-miles emissions overtake those of international food-miles by 1.4 times, raising a red flag about emissions driven by domestic grain trade and transport in large, populous countries such as China, India and the United States. China, specifically, is enhancing domestic grain production to ensure food self-sufficiency. Despite having had 19 consecutive years of bumper harvests in grain production, with grain output exceeding 650 billion kg for 8 years in a row, the country has experienced a substantial shift in grain production spatial patterns. Therefore, it is critical to know how reshaped land systems for grain production affect food-miles and thus the carbon emissions associated with transport.
Now writing in Nature Food, Zuo and colleagues unveil the nature and magnitude of the changing carbon emissions associated with land systems and grain transport in China between 1990 and 2015. The authors first measured the extended distances between grain production and consumption by reconciling the spatial patterns of the changing distribution of population and cropland. They then analysed the spatial flows of grain transport by harnessing the doubly constrained spatial interaction model with the support of integrated transport network data, including road, railway and waterway. Finally, the authors estimated the carbon emissions associated with grain transport based on modelled spatial flows and the carbon emission conversion factors of different transport modes.
Zuo and colleagues found that the mean centre of cropland moved approximately 62 km north, while the mean centre of population moved approximately 18 km south. This resulted in an extended distance between the mean centres of cropland and population from approximately 260 km to approximately 321 km during 2.5 decades. When considering the transformed grain consumption pattern due to the changing dietary structure, the distances between production and consumption were further extended from approximately 179 km to approximately 329 km during this period. These changes reflect the Chinese breadbasket’s shift northward due to multiple environmental–socioeconomic factors, such as urbanization, climate change and land-use change, which is accordant with existing studies and has reversed the traditional food system to the new ‘grain transportation from North China to the South’ pattern.
By breaking down inter-provincial flows of grain across the three analysed transport modes, Zuo and colleagues further found that railway has been the most critical transport mode for supplying grain to Southwest China, and that grain from the Northeast dominated the market share of grain transported by railway. At the same time, inter-regional grain transport by road increased markedly. The total grain transport-induced carbon emissions in China have tripled from 5.68 million tons in 1990 to 17.69 million tons in 2015; grain production displacement accounted for more than 60% of these emissions, and the change of grain consumption structure and population growth contributed 31.7% and 16.6% of emissions, respectively. Interestingly, the development of transport infrastructures, such as newly built highways and railways in western China, helped offset 0.54 million tons of carbon emissions associated with grain transport.
Given that climate change and urbanization have been reshaping land system patterns and posing environmental consequences on food systems, the study by Zuo and colleagues provides a timely reminder of the need to build more concordant land systems towards China’s vision on food security and the 2060 carbon neutrality goal. In line with the current study, others have found spatially imbalanced land systems that increase environmental unsustainability as well, for example, expanded irrigated cropland in water-scarce regions, and unused multiple cropping potential in agroclimatic resource-abundant areas. Urgent actions are therefore required for reallocating land systems — particularly agricultural production — while considering multiple factors such as population, diet, climate, land use and transport infrastructure. The key is to mitigate the spatial mismatch among resource endowment, agricultural production and food consumption, and to understand the trade-offs involved. Synergistic strategies also include protection and optimized use of cropland, improvement of food logistics, development of local food systems and avoiding food waste.
https://www.nature.com/articles/s43016-023-00715-y
