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CO 2 emission induced by international trade brings a plenty of pressure on global warming. Hence, it is important to understand multi-regional CO 2 flows that result from global trade and flow variation of different paths. After transforming capital flows into CO 2 carbon flows, we built an ecological network model of the global trade system's carbon metabolism. Through ecological network analysis, we identified the direct and indirect effects of temporal CO 2 flows in the network. We found that the total integral flow through the network experienced a remarkable increase during the study period. In addition, total import and export flows of four countries, including US, China, Germany and Russia, turned out to be rather big. Direct flow share was usually beyond 50% between two geographical adjacent countries, while that share was below 50% when two countries are far away. This research reveals the importance role of indirect flows and can therefore provide an empirical basis for adjusting and optimizing global trade network. [ABSTRACT FROM AUTHOR]

International trade has shifted part of the responsibility for carbon mitigation from consumers to producers, therefore quantifying mitigation targets and allocating responsibilities have become the focus of research. This study quantified carbon transfers between mainland China and its trade partners from a consumption perspective, and identified the transfer paths from initial production to final production and then consumption. We projected China's allowed carbon increment before peak carbon, and recommend policy measures based on different national technological levels. Given China's 1.25 Gt net exports of carbon, the country's share of the allowed carbon increment before peak carbon would increase from 30% to 51% in 2015 before 2030. The net carbon transfer paths from China driven by consumption by its trading partners accounted for 87% of the total number of paths, with paths to the United States and Hong Kong for exports of both primary and final products being the most prominent. On the other hand, the net carbon import transfer paths driven by China's consumption were dominated by imports of primary products from South Korea and Russia. In comparison with the production country, a country that drives net carbon transfers and has a higher technological level should strengthen its industrial and consumption structures and reduce emission through technical assistance to countries with a lower technological level; the latter should improve production efficiency to reduce imported demand and mitigate the emission. Our study provides a methodological framework and theoretical guidance for a more scientific and equitable allocation of carbon mitigation responsibilities. [Display omitted] • Global consumption drove 1.25 Gt of net carbon transfer from China in 2015. • China's allowed carbon increment share before peak would increase from 30 to 51%. • China's net export carbon transfer paths were exporting primary and final products. • China's net import carbon transfer paths were importing primary products. [ABSTRACT FROM AUTHOR]

• The hierarchical structure could give information to a low-carbon city. • Energy-related carbon emission of economic activities dominated the system. • Integrated flows indicated the importance of primary consumers and producers. • Beijing's spatial gradients transformed from single-center to multi-center. • Beijing's ecological hierarchy indicated a better organized metabolic structure. An integral analysis of urban carbon metabolism can support efforts to build a more sustainable city: the spatial gradients provide insights into how to guide future land use and cover change, while ecological network hierarchy provide insights into the self-mutualistic interactions of the city's carbon metabolic structure. In this study, we combined a spatially explicit network with carbon budget of energy consumption and land use and cover change in Beijing, China. From 1990 to 2010, energy related carbon emissions accounted for roughly 90% of the city's total. The network's integrated flux decreased at an average rate of 7.5%. The output flux primarily decreased when moving outward from the center through the periphery of southeastern plains and towards the northwestern mountains. In contrast, the input flux increased moving from the periphery to both the center and mountains. The ecological hierarchy was irregular based on both the driving and pull weights for the components of the model, with excessively small producer and decomposer layers and excessively large consumer layers. The changing structure of Beijing's carbon metabolism over time indicated a tendency to a better organized city. Understanding the evolution of these hierarchies during urban development provides a more solid empirical basis for improving use of the urban space and reducing carbon emission. [ABSTRACT FROM AUTHOR]

An integrated analysis of urban carbon metabolism from both input and output perspectives can present new insights to support carbon mitigation. In this study, we combined a previously developed spatially explicit network model with an analysis of carbon sequestration and emission by different land use or cover types, and illustrate its use by examining carbon flows in Beijing, China, from 1990 to 2015. The goals were to characterize the temporal changes of the integrated (total direct + indirect) flow structure by applying ecological network analysis and to identify the structure of the urban metabolism by analyzing temporal and spatial changes of the integrated flows. The results showed that the similarity between input and output trophic structures and their spatial pattern indicate increasingly carbon-balanced urbanization by Beijing. The balanced input and output flows for the transportation and industrial land and cultivated land played key roles in forming a central area of aggregated carbon flows between the city's peripheral plains, which also resulted in similar trophic structures for inputs and outputs. Understanding the evolution of the integrated flows during urban development provides a more solid empirical basis for regulating land-use change, improving land consolidation, and reducing carbon flows. Image 1 [ABSTRACT FROM AUTHOR]