Tension of Agricultural Land and Water Use in China's Trade: Tele-Connections, Hidden Drivers and Potential Solutions

Tele-connection of embodied carbon emissions from industries in China's trade: A complex network analysis

Regions can meet their development demands through trade, with the attendant environmental costs being shifted to other regions, and carbon emissions emitted from different industries could be transferred over long distances through the increasingly diversified trade network. However, it remains unclear how regional trade leads to the tele-connection and transfer of embodied carbon emissions form industries, and what is the structure and characteristics of the transfer. Thus, multiregional input‒output models and complex network analysis are employed to reveal the tele-connection of carbon emissions from industries in China. The results show that embodied carbon emissions from trade increased by 869.47 million tons during in five years, with North China being the largest outflow area, while the coastal regions being the inflow areas. Moreover, the secondary industry is the highest source of embodied carbon emissions, accounting for 96.68 % of the volume, and the transfer of carbon emissions mainly occurs in North and East China. In carbon emissions networks, North China holds a controlling position, as analysed by degree and strength. The first 23.3%-30% of nodes carry about 62.6%-72.4% of the entire carbon emissions flow, and the network conforms to scale-free features. Centrality further reveals that northern and coastal areas occupy core positions, with interregional carbon flows dominating the critical pathways in the network. The number of clusters evolved from three to four communities during 2012-2017 in the network, demonstrating that the carbon flow network is developing towards multipolarity and modularity. This study underscores the urgency of mitigating carbon emissions in industrial trade by identifying key nodes and cluster structures in emission networks.

Dynamic simulation of the water-land-food nexus for the sustainable agricultural development in the North China Plain

Inter-regional trade of agricultural products based on the flow of agricultural virtual resources is of great importance for sustainable agricultural development. We focused on grain crops (rice, wheat and maize) in the North China Plain (NCP), and used the Penman-Monteith equation to simulate crop water requirements. We further analyzed the flow of virtual land and virtual water associated with the grain trade using an environmentally expanded multi-regional input-output model. The coupling coordination of land, water, and food was evaluated to assess the rationality of regional agricultural production resource allocation. Between 2007 and 2017, agricultural virtual land and virtual water embodied in the grain trade between the NCP and other areas increased by 48.10 % and 34.41 %, respectively, indicating that the NCP is gradually consolidating its position as the main production area and distribution center of crops in China. Agricultural virtual resources in the NCP were mainly transported to the southeast coastal region, with an overall trend of resource movement from north to south. The total supply of agricultural land and water resources markedly increased in the NCP, whereas the transfer of virtual resources across regions showed a decreasing trend. Because of the irrational structure of crop cultivation and unevenness of regional resource allocation, the coupling coordination of the water-land-food nexus in the NCP is much lower than the national average. This study provides important information on the trade flows and coupling relationships of virtual water and land resources of three major food crops, which will help to alleviate resource pressure in agricultural production and promote sustainable agricultural development in the NCP.

Tele-connecting local consumption to cultivated land use and hidden drivers in China

China faces significant pressure on cultivated land resources due to the accelerated pace of urbanization in recent years. The study of embodied cultivated land offers a new perspective on alleviating pressure on cultivated land between different regions. However, the temporal dynamics characteristic and the intersectoral linkages of embodied cultivated land have rarely been systematically described. Therefore, we applied an environmental extended multi-regional input-output approach to analyze the spatial patterns and flow relationships of virtual cultivated land (VCL) between regional, provincial and sectoral scale in China from 2007 to 2017, considering both temporal and spatial dimensions. Then, we explored the hidden drivers of VCL change using structural decomposition analysis (SDA). Our results showed that trade embodied cultivated land increase by 8.5 % from 2007 to 2017. The flow trend is primarily flowed out from the less developed northwest China but with abundant cultivated land to the more developed regions of the southeast coast. Especially, in 2015, the net outflow of VCL from the northwest region reached 15.82 Mha, which was the maximum value during the study period. In addition, agricultural and construction sector were the major land consumption sector. VCL consumed by the agricultural sector declined 12.51 %, while the VCL consumed by construction sector had a significant growth in 2007-2017. Furthermore, the results of SDA revealed that cultivated land use intensity and per capita final demand were the main factors causing changes in embodied cultivated land. The results can help clarify the responsible parties for land consumption and provide a guarantee for alleviating the pressure on regional cultivated land resources.

Driving forces and variation in water footprint before and after the COVID-19 lockdown in Fujian Province of China

The COVID-19 outbreak has injured the global industrial supply chain, especially China as the world's largest manufacturing base. Since 2020, China has implemented a rigorous lockdown policy, which has sternly damaged sectoral trade in export-oriented coastal areas. Fujian Province, which mainly processes imported materials, has a more profound influence. Although the COVID-19 lockdown has had some detrimental consequences on the world economy, it also had some favorable benefits on the global ecology. Previous studies have shown that the lockdown has altered the physical water quantity and quality, but the lack of total, virtual, and physical water research that combines water quantity and water quality simultaneously to pinpoint the subject and responsibility of water resources consumption and pollution. This research quantified the physical, virtual, and total water consumption and water pollution among 30 sectors in Fujian Province based on the theory of water footprint and the Economic Input-Output Life Cycle Assessment model. SDA model was then used to investigate the socioeconomic elements that underpin variations in the water footprint. The results show that after the lockdown, the physical water quantity and the physical grey WF in Fujian Province decreased by 2.6 Gm³ (-6.7%) and 0.4 Gm³ (-1.3%) respectively. The virtual water quantity decreased by 2.3 Gm³ (-4.5%), whereas the virtual grey WF rose by 1.5 Gm³ (4.3%). The total water quantity dropped by 3.3 Gm³ (-4.9%), while the grey WF increased by 1.2 Gm³ (2.5%), i.e. the COVID-19 lockdown decreases physical water quantity and improves local water quality. More than 50% of the water comes from virtual water trade outside the province (virtual water is highly dependent on external), and around 60% of the grey WF comes from physical sewage in the province. The COVID-19 lockdown reduced water outsourcing across the province (paid nonlocally decrease) but increased pollution outsourcing (paid nonlocally increase). And gross capital formation's contribution to the growth in water footprint will continue to rise. As a result, this study suggested that Fujian should take advantage of sectoral trade network to enhance the transaction of green water-intensive intermediate products, reduce the physical water consumption of blue water-intensive sectors, and reduce the external dependence on water consumption. Achieving the shared responsibility of upstream and downstream water consumption and reducing the external dependence on water in water-rich regions is crucial to solving the world's water problems. This research provides empirical evidence for the long-term effects of COVID-19 lockdown on the physical and virtual water environment.

Exploring the drivers of quantity- and quality-related water scarcity due to trade for each province in China

Previous studies have explored virtual water flows due to interprovincial trade within China as well as related impacts on both regional quantity- and quality-related water scarcity aspects. However, the driving forces behind changes in these impacts remain unknown, especially the quality-related water scarcity. Exploring these driving forces can provide targeted measures to mitigate the negative impact of trade on these two types of water scarcity issues. In this study, blue and grey water footprints have been calculated under the consideration of interregional trade between provinces within China and those attributed to international exports from 2007 to 2015. This calculation was based on multi-regional input output model (MRIO). Moreover, the drivers of changes in blue and grey water footprints due to trade have been explored through structural decomposition analysis. The results showed that blue and grey water footprint increased and then slightly decreased from 2007 to 2015 in China. At the same time, interregional trade made an increasing contribution to the blue and grey water footprint, and the proportion increased from 28.8% to 35.0% and from 22.4% to 28.6%, respectively, from 2007 to 2015. The roles of importers and exporters regarding the blue and grey water footprint driven by interprovincial trade within China have changed little, and the quantity- and quality-related water scarcity issues of the main exporters have been intensified by interprovincial trade. A reduction in the water footprint intensity yielded the largest contribution to curb the increase in blue and grey water footprint driven by interprovincial trade. Our study showed that an improvement in efficiency of water use from both quantity and quality perspectives is the key to accomplish sustainable water use in China, especially considering the impact of trade on regional quantity- and quality-related water scarcity issues.

Water footprint and virtual water flows from the Global South: Foundations for sustainable agriculture in periods of drought

Freshwater availability has decreased alarmingly worldwide, with agriculture playing a vital role in this trend. The assessment of the agricultural water footprint (WF_agricultural) and virtual water flows (VWF) is fundamental not only in local water resources management and protection, but also in our understanding of the synergies between local water consumption and global markets. Thus, the WF_agricultural - broken down into its components (blue, green, and gray) - of the leading 21 crops (grouped in fruit, legumes, cereals, and vegetables), grown in four basins with the most significant agricultural activity in central Chile was determined, estimated in two consecutive years 2017-2018. In addition, due to their great importance in exports, VWFs were assessed, establishing connections according to their origins and destinations. The results show that the green and gray water footprints increased significantly in the south-central basins, while blue water consumption increased in the basins of the central zone, reflecting an evident WF_agricultural transition in accord with latitude and climate conditions. Furthermore, VWF showed an annual increase of 44 %, in about 116 destinations, with Asia, Europe, and North America being the preferred destinations, with annual variations of VWF_{blue- gray} associated with increases in exports of apples, cherries, grapes, blueberries, and walnuts, market preferences and growing areas. The present study is an initial step toward sustainable agriculture in a commodity exporting country, one that is relevant in the exploitation of virtual water yet faces severe water deficit problems, distribution, and local water policies. Therefore, contributing to encouraging the efficiency and value of water in the process of a new institutional framework.

Imbalance in the city-level crop water footprint aggravated regional inequality in China

Crop production is the main consumer of water resources. The heterogeneous water resource endowments and imbalanced crop water use exacerbate regional resource consumption inequality. In this study, we quantified the crop water footprint (CWF) of 356 cities in China from 2000 to 2020, measured the inequality between the city CWF and water resources, and identified different strategies to alleviate regional CWF inequality. We found that the average CWF from 2000 to 2020 varied widely across cities, ranging from 0.03 × 10⁸ m³ to 806.78 × 10⁸ m³, and the inequality between city CWF and local water resource endowment was increasing. China had a strong dependence on green water in crop production, and its proportion increased from 52.48 % to 67.17 %. The Gini coefficient of the green water footprint increased from 0.545 to 0.621, and the degree of inequality increased significantly. In addition, the blue water and gray water continuously showed great inequality, especially the blue water, the Gini coefficient of which was 0.724 in 2020. The results show significant disparities in CWF among cities, which have highly exacerbated regional inequality in China. Improving the utilization rate of green water is an important measure to balance the allocation between serving the natural ecosystem and meeting the basic human needs. This study revealed for the first time the inequality of city-level CWF and highlights the severe situation of inequality among regions in China. Balancing the inequality between CWF and water resource endowment at city-level is conducive to fundamentally solving the problem of unreasonable water resource allocation.

Water-climate change extended nexus contribution to social welfare and environment-related sustainable development goals in China

Climate change exacerbates uncertainties in water resource management, water supply, and treatment that are energy intensive and then exert great pressure on climate change mitigation; hence, interrelated and contradictory characteristics within the water-climate change (WC) nexus system are needed to be studied. The nexus thinking and coordination of WC would impact many realistic practices and assist in sustainable socioeconomic development since traditional single-target policies have sometimes been out of function. Hence, the ability to direct water production and use as well as climate change mitigation has become a hotspot recently. Furthermore, we find that there has been no complete research on reviewing the impacts of the WC nexus in different areas on the Sustainable Development Goals (SDGs). Hence, this paper builds a core nexus of WC and then analyzes those effects on social and environmental aspects in many areas, including sewage treatment, energy transition, waste treatment, land management, and ocean management. This paper discusses how WC interlinkages are utilized to realize SDGs in those areas. Moreover, uncertainties derived from exogenous hydrology, climate change, and anthropogenic endogenous systems for realistic problems appeal to gradually increasing concern. Finally, implications offer valuable guidelines for integrated management of water and carbon emissions, as well as sustainable socioeconomic development in the future.

Quantitative assessment of agricultural horizontal ecological compensation in China, from the perspective of virtual land and virtual water

A stable and complete agricultural horizontal ecological compensation (AHEC) is an essential means of reconciling agricultural ecosystem protection and regional development and is also the key to the sustainable use of agricultural water and land resources. Unlike previous methods of studying agricultural ecological compensation (AEC), this study analysed the direction and amount of net transfer of agricultural land and water use along with inter-provincial trade. In conjunction with the value of ecosystem services embedded in agricultural land and water resources, this study calculated AHEC standards and estimated payments/reimbursements from each province. We found that agricultural land and water resources continued to flow from the underdeveloped inland provinces to the developed coastal provinces in 2017. In addition, the value of agricultural ecosystem in the central and coastal areas can be further enhanced by reducing the negative value of their cropland. Even though the ecological compensation standards for virtual agricultural water use (AWU) was much lower than the ecological compensation standards for virtual agricultural land use (ALU), the integrated AHEC in 31 provinces was more reasonable than considering only virtual ALU and virtual AWU. These findings are of great theoretical and application significance for the government to establish a systematic and feasible framework for inter-provincial AHEC and serve as a reference for other countries to conduct related research.

Water-saving co-benefits of CO2 reduction in China's electricity sector

Electricity sector is the largest CO₂ emitter and water user in China's industrial sectors. The low-carbon transition of China's electricity sector reduces its cooling water consumption. Here we firstly quantify CO₂ emission and virtual water embodied in electricity trade with Quasi-Input-Output model. Then, we analyze the impacts of energy substitution, efficiency improvement, and electricity trade on water-saving co-benefits of CO₂ reduction with the differences between the baseline scenario and counterfactual scenario. Results show that the low-carbon transition contributes to water-saving in China's electricity sector. Virtual water and embodied CO₂ have relatively decoupled from electricity trade since 2012. Water-saving (+10.4% yr^-1) outweighed CO₂ reduction (+8.4% yr^-1) through energy substitution and efficiency improvement in the 'new normal' stage. Our work emphasizes the need to integrate water-saving co-benefits of CO₂ reduction into electricity system planning and highlights the challenges to facilitate coordinated development of the electricity-water nexus in China.

Water footprint of nations amplified by scarcity in the Belt and Road Initiative

The growing water scarcity due to international trade poses a serious threat to global sustainability. Given the intensified international trade throughout the Belt and Road Initiative (BRI), this paper tracks the virtual water trade and water footprint of BRI countries in 2005-2015. By conducting a multi-model assessment, we observe a substantial increase in BRI's water footprint after taking water scarcity into account. Globally the BRI acts as a net exporter of virtual water, while the export volume experiences a decreasing trend. Noticeable transitions in nations' role (net exporters vs. net importers) are found between the BRI and global scales, but also between with and without considering water scarcity. Overall economic and population growth is major drivers of scarcity-weighted water footprint for BRI nations, as opposed to the promotion of water-use efficiency and production structure that can reduce water scarcity. Improving international trade and strengthening cooperation on water resources management deserve priority in alleviating the water scarcity of BRI.

Limited water scarcity mitigation by expanded interbasin physical and virtual water diversions with uneven economic value added in China

Interbasin water diversion projects and virtual water transfers embedded in exchanged goods and services are two effective solutions to water deficits. However, the associated real responses in water quantity and quality scarcities and the economic efficiencies remain unclear. Here, we tracked the blue water scarcities, water pollution levels, and economic value added through interbasin physical and virtual water diversions across nine river basins by sector in China from 2007 to 2015. The total national blue and grey water footprints were 365 Gm³yr^-1 and 592 Gm³ yr^-1, in which the Yangtze River basin accounts the most for 32 % and 37 %, respectively, by 2015. The physical water diversions increased by 52 % to 16.9 Gm³yr^-1. The blue virtual water transfers increased by 24 % to 176 Gm³yr^-1, whereas the grey virtual water transfers decreased by 10 % to 266 Gm³yr^-1. Agriculture related interbasin virtual water flows showed opposite directions to those driven by the industry sector. Although with uneven value added while growing, limited effects mitigated water quantity and quality stresses, especially in the drier Yellow, Northwest, and Hai River basins where the capital is located. Half of the basins had low and declining synergy scores, suggesting an urgent need to achieve synergies between resources, the environment, and the economy across basins.

Water-carbon nexus relationship and interaction mechanism analysis within Beijing-Tianjin-Hebei urban agglomeration

As the total water resources consumption control and carbon mitigation continuous improvement, the weak water-carbon incorporate management is increasingly exposed. In this study, a water-carbon nexus assessment framework is proposed to analyze the nexus relationship between water consumption and carbon emission, and distinguishes the coupled water-carbon transmission intensity and the transfer paths under regional and industrial scales. According to the practical input-output table, water consumption, and carbon emission information, the framework is applied to Beijing-Tianjin-Hebei urban agglomeration (BTHUA), a population, resource, and trade intensive area of China. Inter-regional/intra-regional water consumption and carbon emission transfer fluxes between sectors, the pairwise ecological relationship, and the water-carbon nexus were analyzed. Results indicated that the water-carbon transfer indexes from Hebei to Beijing and Tianjin were 161.85 kg/m³ and 113.88 kg/m³ in the study period, along with the most water consumption and carbon emission, and the worst water-carbon nexus. From the industrial perspective, electricity and gas supplying industry provided 7.8% and 29.1% of the total carbon transfer in Tianjin and Hebei, as the most key node sectors on the water-carbon nexus in the BTHUA. The research provides valuably supporting the adjustment of the existing urban agglomeration water-carbon nexus management schemes.

Carbon emissions from land use in Jiangsu, China, and analysis of the regional interactions

Land carbon emissions are primarily determined by land use type, and these emissions could be transferred during interprovincial trade activities. This study took Jiangsu in China as a case, assigned all the energy-related carbon emissions to land, and analyzed the transferred land use carbon emissions through the application of a tele-coupling framework. Finally, the physical spatial distribution of transferred land use carbon emissions within Jiangsu at high resolution was simulated. China and Jiangsu emitted 2.27 × 10⁹ t and 1.43 × 10⁸ t of carbon in 2012, respectively, with industrial and mining land being the biggest emission source, generating more than 70% of their total emissions. Overall, Jiangsu's net carbon emissions transferred to other provinces was 2.41 × 10⁶ t in urban land and 9.03 × 10⁵ t in industrial and mining land, and these carbon emissions were mainly transferred to Hebei, Shandong, and Inner Mongolia. Land utilization intensity and economic development influenced the carbon emission transfer to some extent. Other provinces also transferred a large amount of carbon emissions to Jiangsu, of which 2.57 × 10⁶ t was in urban land and 3.18 × 10⁷ t was in industrial and mining land. Our simulation showed that the emissions in both land use types exhibited a south-north difference within Jiangsu; more specifically, urban land carbon emissions were mainly concentrated in core urban areas, especially in Suzhou, Wuxi, and Nanjing, whereas industrial and mining land carbon emissions were mostly distributed in the periphery of core urban areas and along the Yangtze River. To balance economic development and environment protection, the government must limit the expansion of construction land (especially industrial and mining land), and developed regions should implement various types of ecological compensation measures to help less developed regions reduce carbon embodied in trade activities.

The impact of agricultural trade approaches on global economic modeling

Researchers explore future economic and climate scenarios using global economic and integrated assessment models to understand long-term interactions between human development and global environmental changes. However, differences in trade modeling approaches are an important source of uncertainty in these types of assessments, particularly for regional projections. In this study, we modified the Global Change Analysis Model (GCAM) to include a novel logit-based Armington trade structure, to examine two approaches to modeling trade: (1) an approach that represents segmented regional markets (SRM), and (2) an approach that represents integrated world markets (IWM). Our results demonstrate that assuming IWM, i.e., homogeneous product modeling and neglecting economic geography, could lead to lower cropland use (i.e., by 115 million hectares globally) and terrestrial carbon fluxes (i.e., by 25%) by the end of the century under the default GCAM scenario, compared with the logit-based Armington SRM structure. The results are highly heterogeneous across regions, with more pronounced regional trade responses driven by global market integration. Our study highlights the critical role that assumptions about future trade paradigms play in global economic and integrated assessment modeling. The results imply that closer harmonization of trade modeling approaches and trade parameter values could increase the convergence of regional results among models in model intercomparison studies.

Sustainable conjunctive water management model for alleviating water shortage

Water shortage poses a great challenge to the health of population and environment and impedes socio-economic development. Therefore, a comprehensive model is necessary to promote the adaptation of the whole socio-economic system to limited water resources. To achieve it, a sustainable conjunctive water management model (SCWM) was developed. In SCWM, direct (physical) and indirect (virtual or embodied) water consumptions of multiple water resources in future scenarios are projected, and the sustainable performances of various water-saving scenarios are quantified from the perspectives of water resources, economy, and ecosystem under water capping policy. A case study of Shaanxi, a typical water shortage province in central-eastern China, is conducted aimed at conquering the irrational use of surface- and ground-water subjected to the constraint of future total water use quota. Key findings contain optimal possibility of adapting water shortage via saving water through increasing industrial water efficiency to 11.12 m³/10,000 CNY and reducing 40% of agricultural final demand (Summation of direct and indirect water savings of the two scenarios are 41.57 × 10⁸ m³ and 20.27 × 10⁸ m³, respectively.) and nonsynergistic effects of simultaneous decreasing final demand of multiple sectors on water consumption intensity (WCI) of total (all kinds of water) water, surface- and ground-water. To devise effective policies for conjunctive management of surface- and ground-water, positive utility, economic structure and water productivity should be heeded, and proposals emphasize trade-offs between surface water saving and groundwater conservation, water metabolic and socio-economic systems sustainability and negative interaction of multiple sectors on economy and WCI should be framed. The innovation of this study is the development of SCWM, which can provide sustainable solution for future multiple-source water saving management measures thoroughly concerning direct and indirect water and sectorial interactions. The model not only brings insights to Shaanxi's water management but also can be used for other similar arid area.

Exploring solutions to alleviate the regional water stress from virtual water flows in China

China has long faced an uneven distribution of physical water resources, which has been further exacerbated by the virtual water transfers embodied in the interregional trade. To alleviate such unfavorable influences of interregional virtual water flows on regional water scarcity, this paper first combined a multi-regional input-output model and a structural decomposition analysis to identify the major driving forces behind the changes in interregional virtual water flows from 2002 to 2012, and then conducted a scenario analysis to explore solutions for sustainable water resource management in China. Results indicated that the virtual water outflows from water-deficient developing regions (Northwest and Northeast) to water-abundant developed regions, such as East Coast and South Coast, have been increasingly intensified from 2002 to 2012. During the period, the final demand predominated the increase of virtual water transfers, while the improvement of water use efficiency dominated the decline in virtual water flows from 2002 to 2012. Results from the designed scenarios indicated that the negative impacts of interregional virtual water flows on the water stress can be effectively relieved, indicating the high priority of regional water use efficiency improvement, especially in water-starved regions.

Mobility of arsenic in the growth media of rice plants (Oryza sativa subsp. japonica. 'Koshihikari') with exposure to copper oxide nanoparticles in a life-cycle greenhouse study

The increasing arsenic (As) concentration in agriculture media poses increasing risks to both environment and human health. Arsenic mobility determines its bioavailability and entry into the food chain. Nanoparticle application may help to control As mobility in crop cultivation media, and thus decreasing As bioavailability for plants. This research studied the adsorption kinetics of As(V) on copper oxide nanoparticles (nCuO) and nCuO dissolution in a hydroponic solution, and the effects of nCuO on As mobility in a greenhouse system exposed to As(V) addition of 10 mg/kg and nCuO at 0.1-100 mg/L for a life-cycle growth of rice. Arsenic adsorption was dependent on both the total mass and the concentration of nCuO as well as the initial concentration of As(V), while nCuO dissolution was mainly dependent on nCuO concentration regardless of As(V). Arsenic in the simulated paddy was quickly mobilized from soil to aqueous phase during week 1, and further interacted with components in water phase, sediment-water interfacial transition and rice plants. Copper (Cu) and As speciation in the soil were observed by X-Ray Absorption Near Edge Spectrometry. Dissolved Cu was complexed with organic ligands. As(V) was adsorbed to kaolinite, or reduced to As(III) and adsorbed to ferrihydrite. Percent As removal from water phase in the growth container was determined by both nCuO application and As(V) initial concentration. Based on our previous finding that As accumulation in rice grains was significantly decreased by nCuO at 50 mg/L and the results of this study on As adsorption capacity of nCuO and As removal from water due to nCuO application, nCuO at 50 mg/L was proposed to be an appropriate application in rice paddy to immobilize As. Further research is needed in actual agriculture to verify the appropriate nCuO application and get an integrated beneficial effect for rice plants and humans.

Telecoupling cropland soil erosion with distant drivers within China

Soil erosion on cropland is a result of the interaction between nature and human activities. The socioeconomic influencing factors of soil erosion have been less studied than the biophysical processes and previous studies have mainly focused on the impacts of local socioeconomic factors on soil erosion in the same region. However, since agricultural activities are densely connected to other socio-economic activities, the need for agricultural products from distant regions could potentially drive local soil erosion accompanying agricultural production. To the best of our knowledge, these telecoupling effects have not been studied. Here, we combined the Revised Universal Soil Loss Equation (RUSLE) and multiregional input-output analysis (MRIO) models to quantify the contribution of China's cross-provincial economic demand to local soil erosion at the provincial, sectoral, and supply chain levels. Our results show that a large amount of soil erosion in the southwest, northeast, and central regions is linked to the economic needs across provinces. Agriculture and food processing are the most important distant driving sectors. The driving effect of household consumption on soil erosion mainly occurs on shorter supply chains, while exports and capital formation drive soil erosion through longer chains. Our results indicate that local soil erosion management must consider the impact of distant agricultural product needs and coordinate food production and supply on a national scale to protect the ecological function of the land.

Understanding the industrial NOx and SO2 pollutant emissions in China from sector linkage perspective

Since the most stringent-ever clean air policy was implemented in 2013 in China, main industrial air pollutant emissions have notably decreased. However, there are few studies on air pollutant emissions of industrial sectors driven by supply chain before and after implementing this policy. This paper attempts to provide a new perspective from industrial linkage to understand the emission of air pollutants. Based on Input-Output model framework, we revealed the linkages of SO₂ and NO_x emissions between sectors from 2012 to 2017 and the driving forces behind emission changes. Moreover, we simulated the possible impact of the key sector linkages on air pollutant emissions. Results show that the most noteworthy change during this period is that the metal melting sector has replaced the power sector, as the largest pollutant output emission sector associated with other sectors, especially the transport equipment sector. The main reason of this phenomena is that the emission intensity reduction rate of metal smelting sector (e.g., only 17% for NO_x) is far less than other sectors. In the future, the development of the equipment manufacturing may put pressure on the metal smelting sector to reduce emissions. For example, when the transport equipment sector increases total output by 20% ~ 40%, the metal smelting sector will be driven to emit 0.04Mt ~0.08Mt of NO_x. This paper provides a basis to quantitatively analyze the industrial sector linkages and identify the key sectors from 2012-2017, and helps decision makers better understand the impact of sector linkage on pollutant emissions.

Quantifying economic-social-environmental trade-offs and synergies of water-supply constraints: An application to the capital region of China

Sustainable water management is one of the sustainable development goals (SDGs) and is characterized by a high level of interdependencies with other SDGs from regional to global scales. Many water assessment studies are restricted to silo thinking, mostly focusing on water-related consequences, while lacking a quantification of trade-offs and synergies of economic, social, and environmental dimensions. To fill this knowledge gap, we propose a "nexus" approach that integrates a water supply constrained multi-regional input-output (mixed MRIO) model, scenario analysis, and multi-criteria decision analysis (MCDA) to quantify the trade-offs and synergies at the sectoral level for the capital region of China, i.e. the Beijing-Tianjin-Hebei urban agglomeration. A total of 120 industrial transition scenarios including nine major industries with high water-intensities and water consumption under current development pathways were developed to facilitate the trade-off and synergy analysis between economic loss, social goals (here, the number of jobs) and environmental protection (with grey water footprint representing water pollution) triggered by water conservation measures. Our simulation results show that an imposition of a tolerable water constraint (a necessary water consumption reduction for regional water stress level to move from severe to moderate) in the region would result in an average economic loss of 68.4 (± 16.0) billion Yuan (1 yuan ≈ 0.158 USD$ in 2012), or 1.3 % of regional GDP, a loss of 1.94 (± 0.18) million jobs (i.e. 3.5 % of the work force) and a reduction of 1.27 (± 0.40) billion m³ or about 2.2% of the regional grey water footprint. A tolerable water rationing in water-intensive sectors such as Agriculture, Food and tobacco processing, Electricity and heating power production and Chemicals would result in the lowest economic and job losses and the largest environmental benefits. Based on MCDA, we selected the 10 best scenarios with regard to their economic, social and environmental performances as references for guiding future water management and suggested industrial transition policies. This integrated approach could be a powerful policy support tool for 1) assessing trade-offs and synergies among multiple criteria and across multiple region-sectors under resource constraints; 2) quantifying the short-term supply-chain effects of different containment measures, and 3) facilitating more insightful evaluation of SDGs at the regional level so as to determine priorities for local governments and practitioners to achieve SDGs.

Dynamic simulation for comprehensive water resources policies to improve water-use efficiency in coastal city

Coastal cities play an important role in regional economic development and sustainable development strategies of water resources and their ecological environment. As a typical coastal city in Hebei Province, Qinhuangdao city is facing severe problems, such as water shortages and water environment deterioration, while social and economic development continues. Based on input-output analysis, we established a dynamic optimization model among Qinhuangdao city's socioeconomic development, water resources and water environment. The 2013-2030 simulation after introducing comprehensive water resources policies of regional development, examines the regional socioeconomic development, optimizes the water resources supply structure and improves the water environment under the optimal scenario, and evaluates policy feasibility through cost-benefit analysis (CBA). The simulation results suggest that under the optimal scenario, the water-use efficiency (WE) of Qinhuangdao is improved by 59.14% and the proportion of reclaimed water and desalinated seawater in the water supply structure is increased by 13.70%. In addition, it has achieved an average annual gross regional production (GRP) growth rate of 6.36% and an average annual chemical oxygen demand (COD) emission rate of 17.95%. Moreover, the net present value (NPV) of the projects under the optimal scenario is 1.534 billion Chinese yuan (CNY), which means that the policy is economically feasible. Our research is helpful to improve the WE, optimize the water supply structure and protect the hydrogeological environment in coastal cities with water shortages and can provide a reference for Qinhuangdao city and other similar coastal cities to realize the rational utilization of water resources and regional sustainable development.

Exploring consumption-based planetary boundary indicators: An absolute water footprinting assessment of Chinese provinces and cities

The water planetary boundary (PB) has attracted wide academic attention, but empirical water footprint research that accommodates local biophysical boundaries remains scarce. Here we develop two novel quantitative footprint indicators, the water exceedance footprint and the surplus water footprint. The first measures the amount of excessive water withdrawal (exceeded amount of water withdrawn against local water PBs) and the latter evaluates the potential of surplus water that can be sustainably utilised (amount of surplus water available within local water PBs). We quantify the extent to which demand for goods and services in Chinese provinces and cities are driving excessive withdrawal of local and global water resources. We investigate both territorial and consumption-based water withdrawal deficit and surplus against local water withdrawal PBs. We also trace how PB-exceeded water and surplus water are appropriated for producing certain commodities. In 2015, China's domestic water exceedance reaches 101 km³ while the total water exceedance footprint is 92 km³. We find that 47% of domestic excessive water withdrawal is associated with interprovincial trade. Exceeded water transfers were dominated by agricultural trade from the drier North to the wetter South. A revised virtual water trade network informed by exceedance and surplus water footprint metrics could help address sustainability concerns that arise from the trade of water-intensive commodities. Our findings highlight that policy targets need to accommodate PB exceedance of both direct and virtual water use.