Inputs for staple crop production in China drive burden shifting of water and carbon footprints transgressing part of provincial planetary boundaries

The food security risks in the Yangtze River Delta of China associated with water scarcity, grain production, and grain trade

Grain production consumes a large amount of water and is affected by the degree of water scarcity and participation in the grain trade in various regions. The grain trade has changed the food security risks in regions where grain exports and imports. Therefore, it is crucial to consider regional water scarcity to understand food security risks from the grain trade network. Here, we construct a new framework for measuring regional food security risks associated with water scarcity, grain production, and grain trade based on a cross-city grain trade network combined with virtual water flows to evaluate the regional food security risks in the Yangtze River Delta region (YRD) of China in 2017. The results show that under the current domestic grain trade pattern in China, the YRD and its four provincial-level administrative regions are in a net grain import state. The grain trade within the YRD is concentrated in exports from the two major grain-producing areas of Anhui and Jiangsu to Zhejiang and Shanghai, especially from northern Jiangsu to southeastern Zhejiang. The net import results of virtual blue water in most cities indicate that the YRD has shifted its water resource pressure to other grain exporting regions in China, with Shanghai and Zhejiang being the greatest beneficiaries. Extreme risk only exists in Shanghai, and severe and moderate risks are concentrated in Jiangsu. The current grain trade has reduced the overall food security risk in the YRD by 1.3 % but increased the risks in Shanghai and Zhejiang by 2.1 % and 0.8 % respectively. This study highlights the potential risks that excessive production of food in water-scarce areas in the grain trade system may bring to a stable food supply, providing useful information for a comprehensive understanding of the food and water security situation and for future trade-offs.

Physical and virtual water transfers in China and their implication for water planetary boundary

China is an extremely water-scarce country with an uneven distribution of regional water resources. We define two absolute sustainability indicators, using the multi-regional input‒output (MRIO) model to outline the contribution of China's physical and virtual water transfers in mitigating the problem of regional water boundary-exceeding. Although the overall use of freshwater resources is within the safe operation space, 55% of province's water resource development transgresses the local water planetary boundary. Physical and virtual water transfers effectively mitigate the stress of water supply to the water planetary boundary in China's water-scarce regions. Among them, the role of virtual water transfers occupies the main part. The cost of using physical water in water-receiving regions and the situation of virtual water flowing from water-scarce regions to developed water-rich regions cannot be ignored, and a small number of provinces are responsible for most of the virtual water net imports and exports. The obtained results are helpful for the redistribution of water planetary boundary transgressing responsibilities among provinces and the formulation of absolute sustainable water resources management policies.

Calculation and analysis of agricultural carbon emission efficiency considering water-energy-food pressure: Modeling and application

Agricultural carbon emission efficiency (ACEE) measurement, a tool for effectively achieving sustainable development goals, has garnered much attention. However, the impacts of resource pressures such as water, energy and food on ACEE have been overlooked, and the high dimensionality of the measurement model and insufficient sample data can easily distort the measurement results. Therefore, from a green development perspective, we established a new ACEE measurement framework considering the water-energy-food pressure index and a new integrated ACEE measurement model (CSMA-PPE-USSBM) that includes chaotic maps, the slime mould algorithm (SMA), projection pursuit evaluation (PPE) and the undesirable super slack-based measure (USSBM). The model was used to calculate ACEE in 13 prefecture-level municipalities in Heilongjiang Province, China, and analyze its spatiotemporal evolution and possible causes. The results showed that this model avoids the above problems. The reliability coefficient and stability coefficient reached 0.962 and 0.971, respectively; ACEE in Heilongjiang Province has much room for improvement, but there are obvious differences in carbon emission efficiency in different carbon emission type regions. The key driving forces of ACEE variation can generate significant scale effects. Provincial driving factors can affect ACEE variation in prefecture municipalities, where the influence range is limited or the influence of driving factors gradually emerges. The research results provide a theoretical reference for accurately measuring the regional ACEE and analyzing the driving mechanism of ACEE and green agricultural development.

Effect of greenhouse gas emissions on the life cycle of biomass energy production and conversion under different straw recycling modes

With the gradual growth of greenhouse gas (GHG) emissions during the agricultural cultivation cycle, GHG emissions specific to the production and conversion of biomass energy is becoming increasingly problematic. Current studies lack analysis of net GHG emissions generated during full life cycle of agricultural cultivation, straw use and bioenergy production. This study measures the global warming potential of biomass energy production and conversion processes under different agricultural cultivation cycle systems based on life cycle approach, accompanied by four straw treatment methods: fast pyrolysis, slow pyrolysis, flash pyrolysis and anaerobic fermentation. The demonstration of Heilongjiang Province showed that the net GHG emissions of rice and soybean over 52.39% and 101.57% higher than those of corn, respectively. The amount of standard coal saved by fast pyrolysis treatment, slow pyrolysis treatment and anaerobic fermentation treatment of straw was only 38.38%, 78.02% and 61.98% of that of flash pyrolysis treatment. The relationship between environmental pressure and economic growth was decoupled during 2011-2017 and coupled in 2017-2020. This study contributes to green production of biomass energy. The methodology in this paper can be used to account for and assess the carbon effect of the entire straw recycling chain in any region.