Cropland displacement contributed 60% of the increase in carbon emissions of grain transport in China over 1990-2015.

Rapid urbanization and population growth have increased the need for grain transportation in China, as more grain is being consumed and croplands have been moved away from cities. Increased grain transportation has, in turn, led to higher energy consumption and carbon emissions. Here we undertook a model-based approach to estimate the carbon emissions associated with grain transportation in the country between 1990 and 2015. We found that emissions more than tripled, from 5.68 million tons of CO2 emission equivalent in 1990 to 17.69 million tons in 2015. Grain production displacement contributed more than 60% of the increase in carbon emissions associated with grain transport over the study period, whereas changes in grain consumption and population growth contributed 31.7% and 16.6%, respectively. Infrastructure development, such as newly built highways and railways in western China, helped offset 0.54 million tons of CO2 emission equivalent from grain transport. These findings shed light on the life cycle environmental impact within food supply chains.

Spatial optimization of urban land and cropland based on land production capacity to balance cropland protection and ecological conservation.

Cropland protection strategies have provided a strong contribution to limit cropland transformation worldwide. However, it negatively affects ecological land (e.g., forest, grassland, and wetland). Identifying a win-win approach for cropland protection and ecological conservation is important. Land use optimization plays a vital role in solving conflicts among land uses. Thus, in this research, taking China (mainland) as the study area, we optimized the spatial distribution of urban land and cropland to balance the requirement of cropland protection strategies and their negative effects on ecological land according to the spatial heterogeneity of land agricultural production capacity by using the LAND System Cellular Automata model for Potential Effects (LANDSCAPE). Specifically, we developed three optimization scenarios from compensational, occupancy, and occupancy and compensational sectors. We also developed one non-optimization scenario to remain comparable. Results show that compared with the non-optimization scenario, the reduced loss of ecological land in compensational, occupancy, and occupancy and compensational optimization scenario is 7180, 247, and 7277 km2, respectively. Our research indicates that we should prioritize the quality of compensated cropland when developing cropland protection strategies and planning, considering the low efficiency of the occupancy optimization and the cost of policymaking and implementing.

Impacts of cropland expansion on carbon storage: A case study in Hubei, China.

When cropland expansion encroaches on ecological land (e.g., forest, grassland, wetland), it seriously affects carbon storage which plays an important role in global climate change. Taking Hubei as the study area, this study explored the effects of cropland expansion on carbon storage in both 2000-2010 and 2010-2030 in different scenarios by using the Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) model and the LAND System Cellular Automata model for Potential Effects (LANDSCAPE). The results showed that cropland expansion led to a massive loss of carbon storage (1.76 Tg C) during 2000-2010, which is expected to continue during 2010-2030 in different scenarios. The loss is predicted to be 3.70 Tg C in the Business-As-Usual scenario and be 0.88 Tg C in the Requisition-Compensation Balance of Cropland Policy scenario. Noticeably, the loss of carbon storage due to cropland expansion was 1.12 times more than that due to urban expansion during 2000-2010. For the period of 2010-2030, the loss of carbon storage caused by cropland expansion is predicted to be 3.89 times more than that caused by urban expansion in the Business-As-Usual scenario, while the losses caused by cropland expansion and urban expansion are predicted to be almost equal in the Requisition-Compensation Balance of Cropland Policy scenario. The main cause of carbon storage loss due to cropland expansion is that it leads to the considerable loss of forest and wetland. This study highlights the importance of considering the loss of carbon storage caused by cropland expansion when conducting cropland protection policies and land use planning.