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Highlights • A new evaluation framework of urban ecosystem health (UEH) is proposed. • UEH is evaluated from dimensions of structure, function, process and development. • The fuzzy matter-element model is established to evaluate the UEH states. • The health states of typical Chinese cities along the 'B & R' are assessed. • Suggestions are proposed to improve health states of different types of cities. Abstract As key social nodes and development engines, the status of various cities is important for the construction of "the Silk Road Economic Belt" and "21st Century Maritime Silk Road" (hereafter called the "B&R"). To comprehensively evaluate the status of cities along the B&R, the concept of urban ecosystem health was applied in this paper, and an innovative assessment framework of "structure-function-process-development" was proposed based on the understanding of the concept of urban ecosystem health. Then, four-layer assessment indicators were established to reflect the health status of urban ecosystems. Subsequently, a fuzzy matter-element model was constructed to measure the urban ecosystem health status, grade the health levels, and identify the limiting factors. A case study was conducted on 14 typical Chinese cities along the B&R. The temporal dynamics indicated that the health states of most of these cities gradually improved during the study period. With respect to spatial differences, city types could be ranked from high to low health in the order of coastal innovative and open cities, inland open cities, and open-window cities. Based on further analysis of limiting factors, suggestions to improve the ecosystem health levels of cities along the "B&R" were proposed for the different types of cities. [ABSTRACT FROM AUTHOR]

Abstract As many manufacturing cities are currently experiencing serious environmental deterioration and energy crises, it is essential that they implement sustainable transitions by using cleaner production (CP) as a hopeful tool. We summarized the CP instruments applied in manufacturing cities and investigated their effect in urban sustainable transitions in this paper, by selecting Dongguan-a typical manufacturing hub in China-as a case. 264 related documents of policies, regulations, files, and notices promulgated by the Dongguan government during 2002–2017 were analyzed via content analysis to reveal the priority of major utilized tools for policy makers. We also summarized and analyzed the lifespan, dynamic trajectory, performance, function, and quantitative outcome of integrated CP instruments for sustainable transitions. It was found that CP instruments effectively decrease pollution generation, save energy, reduce resource consumption, and adjust and optimize industrial structure. It was also revealed that CP instruments embedded in sustainable transitions strategies was more effective and efficient at urban scale than that at larger scale. This paper provides a general reference for integrating CP instruments to push forward sustainable transitions in manufacturing cities, especially those cities without local legislative power in developing countries. Highlights • Content analysis were applied to analyze various cleaner production (CP) policies. • CP instruments effectively assists sustainable transition at urban scale. • Combining pollution prevention with energy conservation is effective strategies. • CP level and energy efficiency are useful indices for industrial structure optimization. • Continuity impacts the performance and outcome of CP policies. [ABSTRACT FROM AUTHOR]

Abstract A stable and reliable urban energy supply is essential for supporting sustainable regional and even national development. Further, a general definition and method is necessary to comprehensively evaluate urban energy supply security for different energy resources, identify key problems, and conduct regulations. Therefore, ecological network analysis (ENA) is introduced as a general systematic analysis tool to simulate and assess urban energy supply security, based on the idea that various components related to energy supply exist and interact in a common network. The proposed ENA model was used to evaluate and compare the security of coal, crude oil, and natural gas supplies for Beijing during 1997–2012. The evaluation included overall sustainability assessment, system property analysis, and structure analysis of energy supply systems. The results showed that the coal supply had the highest level of supply security, followed by the crude oil supply and then the natural gas supply. In addition, the crude oil supply system showed the most competitiveness in terms of the energy supply systems' properties. Scenario analysis yielded suggestions for improving urban energy supply security by maintaining energy production, increasing energy consumption within a certain range, strengthening and diversifying supply sources, and increasing strategic energy reserves. The ENA-based general model provides a useful tool for systematic evaluation of urban energy security from the supply perspective to quantitatively support urban energy management. Highlights • Ecological network analysis is applied to evaluate urban energy supply security. • A general network model of urban energy supply systems is established. • The supply security of coal, crude oil, and natural gas in Beijing are evaluated. • Different energy supply systems are compared via structure and property analysis. • Suggestions based on scenario analysis are given to improve energy supply security. [ABSTRACT FROM AUTHOR]

Abstract With the increasing threat of global climate change nowadays, carbon emissions reductions in cities have aroused the concern of the world. Carbon emission is one of profiles that are closely connected to the urban metabolic system. Here, a global environmentally extended multi scale input-output model (EE-MSIO) was employed to track accurately the carbon emissions in the multi scale economic system from production and consumption perspectives. The four municipalities in China for Beijing, Tianjin, Shanghai and Chongqing were selected as the case. The findings reveal that final demands in the four Chinese municipalities not only trigger a large amount of carbon emissions within their own jurisdictional boundaries, but also impose emissions to other regions via domestic and international trade. The results evidenced that close to 50% in Chongqing and more than 70% of consumption-based carbon emissions in Beijing, Shanghai and Tianjin occurred outside the urban geographic boundary. Moreover, North China is the largest carbon producer for Beijing and Tianjin, Central China for Shanghai and Southwestern for Chongqing, while RoW and BRIIAT are the top two international carbon inflow sources for all four municipalities. [ABSTRACT FROM AUTHOR]

A stable energy supply is essential to support urban socioeconomic activities and to ensure urban sustainable development. A quantitative systematic method is necessary to evaluate and improve the security level or urban energy supply. Ecological network analysis (ENA) is thus applied as a useful general analysis tool to systematically simulate, evaluate, and compare energy supply security in different cities. Based on the established ENA model, we evaluated and compared the crude oil supply security for Beijing, Shanghai, and Tianjin from 1997 to 2012, via sustainability, stability, and structure analyses. The results indicate that the overall levels of crude oil supply security for the three cities showed similar features and increase trends during the study period, whereas the key influencing compartments were different. Correspondingly, related suggestions were proposed to improve urban crude oil supply security based on further scenario analysis, including diversifying supply sources, maintaining domestic supply, improving internal crude oil production, increasing consumption within a certain range, and strengthening strategic reserves, with different emphases for different cities. The ENA-based general method provides a new perspective on the systematic evaluation and regulation of urban energy supply security, which can support urban energy policymaking. [ABSTRACT FROM AUTHOR]

Energy has become a scarce global strategic resource, and energy supply security is receiving increasing attention. A common evaluation platform is necessary to systematically understand the supply security levels of different energy sources and help make the national energy strategy. Ecological network analysis (ENA) is thus regarded as a useful common tool to systematically simulate, evaluate, and compare the supply security for different energy sources, when considering the fact that modern energy systems have formed a complex global energy network through extensive energy trading. Based on the established ENA platform, we evaluated and compared China's crude oil and natural gas supply security from 2000 to 2012. To this end, we assessed the overall security level, investigated the relationship among different compartments within the network system, determined the system's structure, and analyzed the system's properties. It was found that the Chinese crude oil supply security level was higher than that of the natural gas supply and that the crude oil supply system was more mature in terms of multiple properties. Suggestions are proposed to improve the Chinese energy supply security based on further scenario analysis, including increasing domestic energy production, controlling energy consumption, diversifying foreign supply sources, and strengthening the strategic reserve. The ENA-based common platform can be used for the systematic evaluation and improvement of energy supply security and further support national energy policymaking for both developed and developing countries, both energy importers and exporters. [ABSTRACT FROM AUTHOR]

Agriculture takes a large proportion of greenhouse gas (GHG) emissions, playing an essential role in achieving global climate goals. However, targeted mitigation opportunities for agricultural GHG are still unclear due to the lack of standalone analyses at sub-national and food-specific scales. Here, we accounted for agricultural GHG emissions in 2000–2020 in mainland China and found that the largest emission sources by region, product group, process, and gas were Hunan province, rice cultivation, enteric fermentation, and CH 4 , respectively. Agricultural emissions peaked in 2015 and temporarily declined by 8% by 2020 and possibly decline by 30–36% by 2060, primarily owing to the reduction potential from meat production in eastern and northern China. The emissions produced and land needed per unit of food product reduced mostly, while emissions per unit of land use increased in many regions and food groups. We conclude that the opportunities and challenges for GHG mitigation lie in a few top emitters in central China where intensities were unexpectedly much larger than the levels of the national average and marginal agriculture in the northeast. [ABSTRACT FROM AUTHOR]

In the era of climate change, life cycle analysis (LCA) has been acknowledged as a useful method for examining carbon footprints of products or services., Once captured and stored by trees and other plants, biogenic CO 2 would re-enter the atmosphere sooner or later after the use phase of the product. And many LCA studies did not calculate the temporary carbon storage in biogenic carbon. Thus, this paper proposed a hybrid LCA approach to provide a structured methodology for evaluating carbon footprint of copying paper in consideration of temporary carbon storage. The developed method was then applied to a paper mill of China. It is indicated that the hybrid LCA method could provide a comprehensive methodology for accounting carbon footprints as well as assessing effects of delaying GHG emissions. The results shows that the carbon footprint of 1000 kg copying paper was 647.89 kg CO 2 under scenario 1 and -5094 kg CO 2 under scenario 2. Concurrently, the effect of delaying the emission of the temporarily stored carbon in copying paper was 7.67%, 15.52%, or 23.58% for a certain period of time (i.e., 10, 25, or 30 years). [ABSTRACT FROM AUTHOR]

Nowadays, the air pollution of China is more and more serious, especially in Jing-Jin-Ji region. The improper energy consumption structure and the pollutants emission of coal industry chain are the main cause of the air pollution. In this study, based on the Energy Balance Tables of Beijing, Tianjin and Hebei in 2012, we used the model of inter-regional transportation, proposed a Regional Coal Industry Chain Balance Table, clarified the material/energy flows, and accounted the energy utilization efficiency in Jing-Jin-Ji region. It can help to realize the optimal balance of pollutant emissions control and energy supply, which is scientifically innovative. [ABSTRACT FROM AUTHOR]

Collectively, the EU is among the world’s largest greenhouse gas (GHG) emitters, though remarkable decreases in GHG emissions have been observed in recent years. In this work the GHG emissions for the 28 EU member states between 1991 and 2012 are accounted for and compared according to the inventory method of the Intergovernmental Panel on Climate Change (IPCC). The structure of GHG emissions at a national level, their distribution between countries, and trends across the period are then analyzed. National emission sources and sinks are decomposed for each country to elucidate the contribution of each sector (energy, industrial processes, solvents and other product use, agriculture, land use/land-use change and forestry, and waste) to the national totals. Germany was the largest emitter, with net emissions totaling 939 Tg CO 2 equivalent in 2012, 60% more than the UK and 89% more than France, the second and third biggest emitters, respectively. The energy sector and agriculture were found to be the largest sources of emissions in most countries. Four quadrants were established to compare countries’ performance in emission intensity, carbon removal rate, and net reduction rate of GHG emissions. Slovenia, Portugal, Sweden, and Finland were located in Quadrant II as they displayed relatively low emission intensities and high carbon removal rates. Conversely, Hungary, Greece, Cyprus, the Czech Republic, and Poland were located in Quadrant IV because of their relatively high emission intensities and low carbon removal rates. Some suggestions for integrating the annual results and the trends both within and among countries into national and regional emissions reduction strategies are also included. The unified accounting framework and analysis of the structure of GHG emissions may also be useful for other countries and regions. [ABSTRACT FROM AUTHOR]

As a relatively clean energy, natural gas will be increasingly in demand to meet short-term low-carbon targets. The gap between the demand and supply of natural gas will be increasingly scrutinized, which highlights the significance of natural gas supply security. Considering the extensive connections among various aspects related to natural gas supply and the complex interactions behind these connections, ecological network analysis was applied to simulate the natural gas supply system in China and systematically measure its overall security level. Network Information Analysis, Structural Analysis, and Utility Analysis were conducted. It is found that the Chinese natural gas supply security increased during 2000–2011. In terms of the influence of different compartments on the whole natural gas supply system, in order from the largest to smallest influence they are: supply sources, consumption sector, refining, and reserve sectors. And the relationships among compartments became stronger in the later stage than that in the earlier stage of the study period. Suggestions on improving China’s natural gas supply security were proposed based on the results and further scenario analysis. The network model developed herein is a new perspective for natural gas supply security assessment, which can be used as guidance for policy making. [ABSTRACT FROM AUTHOR]

Rising pressure of population growth and economic development, limited energy supplies, and improved concerns over environmental effects have forced decision makers to contemplate comprehensive optimization of urban energy systems planning. A multi-objective optimization model at urban sector scale is proposed in this study to achieve sustainable development of energy, economic, and environmental systems, by integrating objectives of minimal energy consumption, energy cost, and environmental impact. To comprehensively measure the environmental objective, the life cycle assessment method is used to calculate the environmental impact caused by various pollutants in the chain of energy production, transportation, and consumption. Based on the 1995–2010 data, the optimization model is applied to Beijing, China to obtain a reasonable solution of energy mix in 2015 and 2020, where the four energy resources (i.e., coal, oil, natural gas, and electricity which account for over 96% of the total energy consumption) are distributed to the six key sectors (agriculture, industry, construction, transportation, commerce, and household). The results estimate a decline in the proportion of coal to the total energy consumption and an increase for others. The decrease in energy consumption is only observed in the industry sector. It also found that the effect of energy savings and emissions reduction when considering the environmental impact is better than that neglecting the environmental impact. It concludes that the multi-objective optimization model integrating environmental impact is useful for reasonable allocation of energy resources across the urban sectors, which could help balance economic, energy and environmental goals and provide more detailed and practical support for urban energy system management. [ABSTRACT FROM AUTHOR]

Approximately half of the global population resides in cities and accounts for over 80% of global carbon emissions. To improve efficiency in carbon emission reduction, and enhance adaptability of cities to climate change, it is essential to undertake accounting of urban carbon cycle. This plays a prominent role in global carbon cycle. An integrated accounting framework for urban carbon cycle was established herein to support uniform accounting and place-specific comparisons, covering natural and artificial carbon cycles, vertical and horizontal carbon flows, carbon storage and fluxes, and carbon inputs and outputs. Guangyuan, a mountainous city in China that was seriously stricken by Wenchuan earthquake in 2008, was chosen as the case to demonstrate the framework and investigate the effects of post-earthquake reconstruction on carbon cycle. The results show: 1) the proposed framework could effectively assess dynamics of carbon cycle under external disturbances, 2) there were abundant vegetation and correspondingly a large natural carbon tank and vertical carbon input, and low industrialization degree and correspondingly small horizontal and vertical carbon outputs in Guangyuan, 3) the post-earthquake reconstruction led to a series of impacts on carbon cycle, from both aspects of amount and structure, and 4) such impacts of post-earthquake construction on artificial carbon cycle were distinct with a tendency toward low-carbon development in Guangyuan. The results were helpful for investigating the effects of natural disturbance and human interference on urban carbon cycle, which in turn could improve the adaptation to climate change. [ABSTRACT FROM AUTHOR]

China's energy dependence on energy supply chain have been increasing rapidly in recent years. The long-term energy supply plays an important role to guarantee the energy security. Therefore, our emphasis placed on energy supply chain predictive analysis and security evaluation in China. In this study, a linked MARKAL-CGE-EIA model system is proposed to simulate the macro-level energy technology, macro-level economy and environmental impacts of China. The CGE module is used to produce a multi-sector simulation of economic growth and industrial structure change. A MARKAL module is used to analyze particular technologies within the energy system, given estimates of associated energy demand and the relative prices of fuel and other inputs. A third module of Environmental Impact is applied to make an analysis of pollutant emissions. The energy indicators are used to perform an assessment of the dynamic behavior and security trends of a national energy system's trajectory from 2000 to 2050. The results of our study will enable energy policy planners to understand these inter-linkages by addressing energy early-warming indicators and scenarios to the aggregate industrial sectors, the energy technology details, and environmental impacts. [ABSTRACT FROM AUTHOR]

Abstract: Methods and indicators are needed to assess the urban ecosystem health status, amongst which energy and material metabolism should be integrated to enhance understanding of ecological patterns and processes of urban ecosystems. Therefore, emergy synthesis combining energetics with systems ecology is applied to assess systematically the health status of urban ecosystems. Combining ecosystem health levels with spatial geographical information of different land use subsystems, the spatial distribution of urban ecosystem health is obtained, which is helpful for urban ecological regulation and spatial optimization. Taking the situation of Guangzhou, China in 2005 as a case study, the relative health states based on emergy indicators and set pair analysis is evaluated. Results show that the health levels of the cultivated land, as well as areas with middle and low density buildings are relatively positive, while that of high density building and traffic areas are relatively weak. Through analysis of different land use subsystems, required factors of a healthy ecosystem are summarized, including moderate economic productivity but without much exploitation and disturbance, reasonable structure of energy and resources usage, medium resilience under pressure, moderate ecosystem service provisioning, and small environmental impact on surroundings. The spatial distribution of urban ecosystem health states is also obtained, such that the northern part of Guangzhou is defined as the conservation area, the middle and southern parts are defined as the maintenance area, while the south central and south western parts are defined as the key regulation area where a suitable scheme should be implemented to control the population density and resolve the concomitant problems. Moreover, the impact power of different indicators on the final health status is classified into five levels when combining the indicator weights with the main assessment factors of urban ecosystem health, which is useful for defining the regulation priority amongst a few indicators. [Copyright &y& Elsevier]

Abstract: In this paper, a dynamic low-carbon model was developed to show a quantitative and consistent future snapshot. This study presents three scenarios for Chongqing''s energy consumption and related CO2 emissions up to 2020, which includes basic development scenario, macro-policy control development scenario and low carbon development scenario. It explains the crucial technologies for Chongqing city as it leaves a business-as-usual trajectory and embarks on a low carbon pathway. A major finding from the scenario analysis is that low carbon and energy-saving policies can dramatically improve Chongqing''s position. Under the low carbon scenario, several suggestions for policy making are proposed. This dynamic low-carbon model would benefit from the allocation of decision-making powers in the areas of regulation, policy-making and planning for low carbon development. [Copyright &y& Elsevier]

Abstract: The development of urban ecosystems is usually restricted by a few key limiting factors, including both the natural resource condition and the socioeconomic performance. To link the natural, economic and social subsystems together and uniformly measure the multiple ecological flows within and amongst these subsystems, emergy analysis was applied in this paper to describe the status quo of urban ecosystems in terms of energy and materials metabolism. Three typical cities, namely Guangzhou, Shenzhen and Zhuhai all in the Pearl River Delta urban cluster in China, are chosen as the cases, regarding the urban cluster as an important developmental pattern and trend of urban ecosystems. Using the data in 2005, an emergy-based analysis was conducted for the three cities from aspects of emergy structure, emergy intensity, emergy welfare, environmental pressure and ecologic economic interface. Based on the comparative results, the limiting factors of these urban ecosystems were further analyzed. This paper presents a meaningful comparison among different urban ecosystems in the same region, and provides a useful framework for urban ecological management based on limiting factors analysis of urban ecosystems. [Copyright &y& Elsevier]

Abstract: City interaction, though of great importance in the context of market-oriented economy, has rarely been studied quantitatively compared to structure and function inside the city due to the tribulation when acquiring and disposing the relational data between cities. Herein, we quantified city-to-city relations in ecological and economic contexts with the application of emergy analysis, which proved to be a promising approach to evaluating various city flows on a common basis. Emergy diagram of urban system was constructed, and the related relational data were chosen from the ecological and economic aspects respectively to form two integrated indicator systems incorporating the transfer of labor, material and currency, etc. Based on the ecological and economic emergy of urban system, the city-to-city sustainability index was established to identify the sustainable conditions of the two cities, and hopefully, it could reveal potential complementarity or competition between these cities over time. With the introduction of emergy analysis, this study provided a new way to quantify city interaction; it might also shed light on how an enhancement and amelioration of inter-city cooperation could substantially contribute to the sustainable development on a regional scale. [Copyright &y& Elsevier]

Abstract: The importance of addressing cumulative environmental impact of large development projects on rivers has been increasingly highlighted. Consideration to potential impact pathways may be difficult, however, without appropriate analytical methods. By introducing ecological network model, this paper focuses on the quantification of the cause-effect relationships inherent the cumulative effects of dam construction from a holistic perspective. With Lancang river of Longitudinal Range-Gorge Region (LRGR) as an example, the risk-based interaction instead of the conventional energy or material flow of ecological network model has been created to conceptualize the cumulative effects network model. Based on this model, the network structural and functional analysis were adjusted for the assessment of potential eco-environmental impact within the ecosystem, thus demonstrating how the risk-based ecological network analysis can be used to characterize the holistic cumulative effects of dams on the temporal and spatial scale. [Copyright &y& Elsevier]

Abstract: Dam construction has become one of the most controversial and wide-debated issues these days, mainly due to the unanticipated ecological risk it brings to river basin. Though the environmental impact caused by dam project has been reported in considerable literatures, most of them were concerned with the condition of aquatic ecosystem (e.g., hydrology, water quality, sediment, and aquatic fauna) with the potential risk of terrestrial ecosystem remaining unsettled. This study estimated the ecological risk on terrestrial ecosystem after dam construction by focusing on the heavy metal pollution and distribution of plant community in Lancang River of LRGR. The heavy metals were determined, and the plants were investigated in the reservoir and downstream of three dams built on the river. The results showed that notable changes had taken place in both objects, which indicated the existence of ecological risk on river ecosystem. This study might serve as the first step of computing dam-induced risk in wholeecosystem scale. [Copyright &y& Elsevier]

Abstract: Dam construction results in variations of hydrology, river morphology and habitat and the biota associated with the reservoir change significantly compared to the assemblage before dam construction in order to match these changed environmental conditions. Some attempts so far have been made to ascertain the changed properties of aquatilia due to dam construction. Most of them, however, were focused on perturbances to single factors, such as rearing habitats, reproduction and migration routes, etc. Few have been done on the performance of aquatilia from the whole-ecosystem perspective. Herein, we evaluate the structural properties of aquatic animals and their complex ecological relationships within the ecosystem before and after dam construction based on ecological network analysis. This study provides a feasible way for integral ecosystem evaluation with the application of ecological network analysis to river ecosystem subjected to human disturbance. [Copyright &y& Elsevier]

Abstract: An evaluation framework of emergy-based urban ecosystem health indicators was established to measure and describe the urban ecosystem health status in terms of energy and materials metabolism, when combing with the classical urban ecosystem health factors. Set pair analysis was also employed to guarantee and promote the objectivity of the ecosystem health criteria. Set pair analysis defines the approximate degree of a real index set relative to an optimal index set, and this is evaluated to describe the relative health levels of urban ecosystems based on the emergy indicators. Six cities in the Yangtze River Delta urban cluster in China were selected as case studies using 2005 data, and the relative urban ecosystem health levels were evaluated using the emergy indicators and set pair analysis. The evaluation showed that the urban ecosystem health states of Shanghai and Hangzhou are relatively good, while the health states of Wuxi and Suzhou are relatively poor. The health states for the cities based on concrete factors were also analyzed to identify regulatory directions for the improvement of the health status of those cities with relatively poor ecosystem health. This paper presents a meaningful comparison between different urban ecosystems at different indicator levels, and provides a useful framework for urban ecological management with respect to urban ecosystem health status. [ABSTRACT FROM AUTHOR]

Abstract: Considering its characteristics in terms of structure, function, performance and evolution, the urban ecosystem can be regarded as a vital organism. Based on the concept of urban vital organism, the framework of urban vitality index covering producing power, living status, ecological ascendancy and vital force, is constructed to represent the urban ecosystem development status from the economic subsystem, social subsystem, natural subsystem and ecological regulatory subsystem, respectively. Meanwhile, set pair analysis, an assessment method which can link different objects and describe their relationships, was combined with the urban vitality index to evaluate the relative urban ecosystem development levels. Choosing the situation of Beijing city from 1986 to 2005 as the case, the change of urban ecosystem development levels during the period were analyzed, by using the relative assessment model based on urban vitality index. Based on the results of the urban vitality index and its each factor, the change of urban ecosystem development on the scales of the whole ecosystem and each studied subsystems can be revealed, which implies the focus of urban ecological planning and management in the future. [ABSTRACT FROM AUTHOR]

Abstract: In order to implementing theoretical urban ecosystem health assessment into practical urban management more effectively, it is necessary to find out the relationship between the urban ecosystem health status based on the internal metabolism characteristics and the external performance of the urban ecosystem. Eleven indicators are selected to describe the performance of the urban ecosystem from aspects of resources condition, social civilization, economic development and environmental load. The correlation analysis between the emergy-based urban ecosystem health status in view of energy and material flows and the ecosystem status based on the eleven indicators is conducted to reveal the relationship between the internal biophysical foundation and the external performance of the urban ecosystem. It is indicated that the resources basis and the economic development level correlate with the emergy-based urban ecosystem health status, which implies the measurement of effectively and reasonably utilizing and exploiting resources, adjusting the economic development pattern and industrial structure should be paid much attention to improve the urban ecosystem health level and optimize the urban ecosystem management. [ABSTRACT FROM AUTHOR]

Abstract: Due to the important role of cities for regional, national, and international economic development and the concurrent degradation of the urban environmental quality under rapid urbanization, a systematic diagnosis of urban ecosystem health for sustainable ecological management is urgently needed. This paper reviews the related research on urban ecosystem health assessment, beginning from the inception of urban ecosystem health concerns propelled by the development needs of urban ecosystems and the advances in ecosystem health research. Concepts, standards, indicators, models, and case studies are introduced and discussed. Urban ecosystem health considers the integration of ecological, economic, social and human health factors, and as such it is a value-driven concept which is strongly influenced by human perceptions. There is not an absolute urban ecosystem standard because of the uncertainty caused by the changing human needs, targets, and expectation of urban ecosystem over time; thus, suitable approaches are still needed to establish health standards of urban ecosystems. Several conceptual models and suitable indicator frameworks have been proposed to organize the multiple factors to represent comprehensively the health characteristics of an urban ecosystem, while certain mathematical methods have been applied to deal with the indicator information to get a clear assessment of the urban ecosystem health status. Instead of perceiving the urban ecosystem assessment as an instantaneous measurement of the health state, it is suggested to conceptualize the urban ecosystem health as a process, which impels us to focus more studies on the dynamic trends of health status and projecting possible development scenarios. [Copyright &y& Elsevier]

Nitrogen (N) is an essential element for food production. Under the influences of correlated variables of food demand and socio-economic development, a hybrid approach was proposed to identify reactive nitrogen (Nr) loss from livestock-based food and biofuel production systems. The approach included the following components: (1) crop simulation model, DeNitrification-DeComposition, taking into account several field situations and climate change scenarios, and (2) correlation analysis of five types of livestock-based food demand and economic benefits based on copula functions and Markov Chain Monte Carlo simulation. The approach was applied to the Guangdong–Hong Kong–Macao Greater Bay Area (GBA) in China. Production of fodder crops (maize, wheat and soybeans) was examined under two climate change scenarios, Representative Concentration Pathways 4.5 and 8.5. Influence of international trade of soybeans, wheat, and maize on nitrogen fertilization was examined under two additional scenarios. Results showed that compost production from livestock manure and food loss in the production of 1000 kg of livestock-based food would reduce demand for 10.45 kg of urea in crop production, accounting for 9.2%–14.66% of total nitrogen fertilizer demand. Among all livestock-based food, fertilizer demand between 2020 and 2030 is projected to be the highest in fodder crop production to support pork production. Total Nr loss of livestock-based food production in GBA was estimated to be 1.10 to 1.58 Mt under scenario 1, and 1.09 to 1.57 Mt under scenario 2. • Focused on reactive nitrogen loss from livestock and biofuel production system. • A hybrid fodder production and food demand/economic development approach was used. • Used copula–MCMC simulation analysis of joint probabilities of correlated variables. • Reactive nitrogen loss per tonne of pork production would be larger than other livestock-based food in 2020 and 2030. [ABSTRACT FROM AUTHOR]

Noncooperative policies for transboundary pollution abatement are inefficient and ineffective, but cooperative policies for pollution abatement are seldom successful in regions that have different development goals and conflicting interests. In this paper, by extracting the key components that lead to the success of pollution reduction policies between Hong Kong (HK) and Guangdong, we aim to construct a general framework for cooperative environmental management. The incentive for and the dynamic trajectory, core measures, and outcomes of cooperative pollution abatement policies to address transboundary air pollution were studied using incrementalism analysis. The context that drives the abnormal increment of cooperative policies between HK and Guangdong was analyzed to determine the factors that affect the full cooperation process. The political union between HK and China is the main driving force for fostering cooperative policies in these two regions that have highly asymmetric economic development levels and pollution emission intensities. The factors for successfully designing cooperative pollution reduction policies are revealed from trust building, political support, efficient governance, precise policies, a rational cost-sharing mechanism, and detailed management and implementation plans. Innovative multi-level and cross-department governance, and an unequal but rational cost-sharing scheme sustain long-term cooperation. A general framework is derived from these empirical key components and constructed as a systematic approach to provide a guide for designing cooperation in transboundary pollution reduction for the sustainable management of cross-border natural resources in different regions with conflicts of interest. • An empirical framework of cooperative air pollution abatement model is constructed. • Factors contributing to foster cooperative polices is analyzed via incrementalism model. • Political support produces adequate institutional arrangements and precise policies. • A matching cost-sharing mechanism can catalyze and stabilize the cooperation model. • Multi-level and cross-department policies sustain long-term cooperation. [ABSTRACT FROM AUTHOR]

Although estimates of total CO 2 emissions from global estuaries are gradually decreasing, current numbers are based on limited data and the impacts of anthropogenic and seasonal disturbances have not been studied extensively. Our study estimates annual and seasonal CO 2 fluxes in China's Yellow River Estuary (YRE) which incorporated spatiotemporal variations and the effects of water and sediment regulation (WSR). Aquatic metabolism was estimated using Odum's open water dissolved oxygen methods and used to represent the production and assimilation of CO 2. Net ecosystem production (NEP) was used to represent the CO 2 flux from biological activities and estimate the major CO 2 emitters in the YRE. According to our measurements, the annual CO 2 release was 6.14 ± 33.63 mol C m−2 yr−1 from 2009 to 2013 and the annual CO 2 efflux from the 1521.3 km2 of estuarine surface area was 0.11 ± 0.61 Tg C yr−1 in the YRE. High CO 2 emissions in autumn were balanced by high CO 2 sequestration in summer, leading to a lower than expected annual net CO 2 efflux. The system is an atmospheric CO 2 source in spring and winter, near neutral in early summer, a large sink in late summer after WSR, and finally a large atmospheric CO 2 source in autumn. Discharge events and seasonality jointly affect estuarine CO 2 flux. High CO 2 sequestration in summer is due mainly to a combination of high water temperature, chlorophyll a levels, dissolved inorganic carbon, and solar radiation and low turbidity, discharge, and chemical oxygen demand (COD) after WSR. WSR supports the high gross primary productivity rate which exceeds the increase in ecosystem respiration. Although the YRE, as a whole, is a source of atmospheric CO 2 , the amount of CO 2 released is lower than the average estuarine value of mid-latitude regions. Our findings therefore suggest that global CO 2 release from estuarine systems is overestimated if spatiotemporal variations and the effects of anthropogenic disturbance are excluded. The NEP method is effective for estimating the CO 2 flux, especially in estuaries where CO 2 variation is mainly due to biological processes. Image 1 • Net ecosystem production was used to represent CO 2 flux from biological processes. • Annual net CO 2 efflux was lower than expected in the Yellow River Estuary. • Annual CO 2 emission from biological processes is 6.14 ± 33.63 mol C m−2 yr−1. • High CO 2 emissions in autumn were balanced by high CO 2 absorption in summer. • Water and sediment regulation affect CO 2 flux slightly less than seasonal factors. [ABSTRACT FROM AUTHOR]

During the rapid urbanization process, the unequal distribution of green spaces (GS) has become a prominent topic in academic discussions due to its implications for social justice. Nonetheless, the equity of GS availability among different types of residential neighborhoods remains unclear, posing a challenge to achieving environmental justice in urban greening practices. This study, taking Shenzhen as a case study, examines the equity of GS availability between urban villages (UV) and residential quarters (RQ), two common residential neighborhood types in Chinese cities. We initially categorized both inner-GS and outer-GS based on their location inside or outside the boundary of residential neighborhoods and assessed GS availability at various accessible distances. Subsequently, the Theil index was applied to evaluate the inequity of GS availability, encompassing both the inequities within and between UV and RQ. Our findings reveal that UV exhibited higher GS inequity than RQ across all accessible distances. Furthermore, within UV, GS inequity decreased as the accessible distance increased, while the opposite trend was observed for RQ. Notably, although significant inequities existed in inner-GS availability between UV and RQ, outer-GS played a crucial role in mitigating this imbalance. These results provide valuable insights into GS equity across different residential neighborhood types and offer recommendations for enhancing/balancing the equity of GS availability in Shenzhen. • The inequity of GS availability between UV and RQ in Shenzhen was estimated. • UV exhibited higher GS inequity than RQ across all accessible distances. • The inner-GS inequity between UV and RQ contributed 31.4% to the total inequity. • The imbalance of inner-GS between UV and RQ was mitigated by Outer-GS. • Outer-GS mitigated the inner-GS inequity of UV but aggravated that of RQ. [ABSTRACT FROM AUTHOR]

Clarifying the current status and variation trends of ecosystem services (ESs) supply and demand (ESSD) matching is helpful in providing comprehensive information for ecological management decisions. Most existing studies focus on the static matching between ESSD, ignoring changes in ESSD matching and whether such changes are sustainable for people's demand or not. This study firstly attempts to develop a zoning method based on static and dynamic matching of ESSD. Taking the county/district as the primary research unit, we quantified the supply and demand of six typical ESs in the Greater Bay Area (GBA) from 2000 to 2020, which included grain production (GP), vegetable production (VP), fruit production (FP), water yield (WY), carbon sequestration (CS) and water purification (WP). Further, we identified ESSD's static and dynamic matching characteristics, and formulated four matching types (ESs surplus-sustainable type (S–S), ESs surplus-unsustainable type (S-US), ESs deficit-sustainable type (D-S), and ESs deficit-unsustainable type (D-US)) as ecological management zones. The results showed that ESSD in the GBA are extremely mismatched, with an overall surplus in surrounding ecological barrier areas and a serious deficit in central core areas. For GP, VP, FP and CS, the mismatch is gradually intensified, while for WP and WY, the mismatch is gradually alleviated. The S–S type was largely reflected in GP, VP, FP and WP, the S-US type was concentrated in WY, and they all mainly distributed in the surrounding areas. Meanwhile, the D-S type was mostly reflected in CS and WP, and the D-US type was mainly occurred in the central areas. This study proposed a zoning approach based on static and dynamic matching of ESSD, which can provide more reasonable guidance for regional ecological management. [ABSTRACT FROM AUTHOR]

The optimal agricultural structure and population size within typical watersheds needs to be identified based on the water ecological carrying capacity (WECC). However, real-world systems of water ecological management are complicated as multiple uncertainties exist in the system parameters, which need some effective optimization methods to deal with. This research presents an inexact simulation-based fuzzy credibility-constrained mixed-integer programming (ISFCCMIP) model. Through integrating interval linear programming, fuzzy credibility-constrained programming, mixed-integer programming, global nutrient export from watersheds, and the Kirchner–Dillon model within a general framework, the developed ISFCCMIP model can effectively deal with the multiple uncertainties in the simulation and optimization processes of water ecological management systems. The developed ISFCCMIP model is applied to a real-world case study in the Xinfengjiang Reservoir Watershed. Results show that the total population that can be carried by the watershed WECC would decrease from [204885, 412367] to [121235, 271280], when the credibility level increases from 0.55 to 0.95. On the contrary, the total agricultural benefit would increase from [3.72, 5.06] × 108 to [3.75, 5.10] × 108 $. The total population in the base year far exceeds the watershed WECC. Although the total agricultural benefit in the base year is between the upper and lower bounds of the optimized results, the agricultural structure is not reasonable and needs to be adjusted. Concurrently, multiple results on the optimal agricultural structure and population size are obtained under different credibility levels and in different carrying capacity scenarios. Such results can provide a series of decision alternatives for watershed policy makers to consider the tradeoff between socio-economic development and water ecological protection. The results also assist the sustainable development of the Xinfengjiang Reservoir Watershed. The proposed model is effective for the optimal management of agricultural structure and population size within a reservoir watershed based on the WECC under multiple uncertainties. It also provides a reference for other areas with similar concerns. • An inexact simulation-based fuzzy mixed-integer programming model was developed. • The model is used for watershed management based on water ecological carrying capacity. • Water quantity and quality conditions and their joint effect can be considered. • The model can address uncertainties in both simulation and optimization processes. [ABSTRACT FROM AUTHOR]

• We explored the short-term effects of turbidity levels on aquatic metabolism. • Increasing turbidity has a rapid negative effect on aquatic metabolism. • Photosynthetic oxygen and gross primary production are thereby limited. • Gross primary production declined more than ecosystem respiration. • Suspended-sediment-induced turbidity may severely impair aquatic metabolism. The ecological response to suspended-sediment-induced turbidity is an important consideration for large engineering projects and ecological conservation in estuarine wetlands. However, few studies have quantified the effects of increasing suspended sediment on ecosystem functioning. To explore the effects of short-term turbidity variations on the aquatic metabolism of a wetland ecosystem, we conducted a controlled experiment based on the turbidity characteristics in the Yellow River estuarine wetland. Four turbidity disturbance levels (10, 50, 150, and 250 Nephelometric Turbidity Units (NTUs)) were applied to artificially cultivated wetlands and the subsequent variations and potential causes thereof were analyzed. The results showed that increases in turbidity significantly reduced the gross primary production (GPP) and ecosystem respiration (ER) rates within a single day. The GPP declined more than the ER, leading to lower net ecosystem production and a more heterotrophic water column. Increased turbidity limited photosynthetic oxygen production and thus limited the GPP rate. Even a slight increase in turbidity (for example, from 10 to 50 NTU) had rapid negative effects on the GPP and ER rates, while lower solar radiation and temperature decreased the GPP and ER much further. The results of this study imply that increased exposure to suspended-sediment-induced turbidity may severely impair aquatic metabolism in wetland ecosystems with submerged plants. [ABSTRACT FROM AUTHOR]

• The method of compiling the multi-regional input output is optimized. • Carbon emissions of urban agglomerations (UAs) are studied from multiple perspectives. • Carbon flows within the UA driven by final demand and primary inputs are identified. • Carbon emissions of the UA are predicted when considering uncertainty. Urban agglomerations (UAs) play a momentous role in carbon reduction. The prerequisites for achieving carbon reduction goals in UAs are accounting and predicting their carbon emissions. When considering carbon reduction goals in China, it is crucial to pay attention to the joint influence of carbon emissions and economic benefits. Hence, in this study, an improved multi-regional input–output (MRIO) approach was established to quantify and predict carbon emissions for the UA, incorporating a biproportional scaling method (RAS) and Latin hypercube sampling (LHS). Specifically, a) the carbon emissions of UAs were quantified using the MRIO model from the perspectives of production, consumption and income; b) the carbon flows between cities in UAs were identified based on final demand and primary inputs, and c) the features of UAs' carbon emissions in the future were predicted using RAS and LHS. To verify the effectiveness of the approach, a case study of a typical UA region in China [i.e., the Pearl River Delta (PRD)] was proposed. The results showed that the contribution of sectors to carbon emissions could be identified from multiple perspectives, and carbon flows can help regions coordinate emissions reductions. The majority of future carbon emissions would be generated from the areas of population and economic agglomeration (i.e., Guangzhou and Shenzhen), although the growth trend of carbon emissions of those would keep lower. The policy of carbon reduction should be urgently carried out in locations with high carbon emissions growth rates (e.g., Zhaoqing and Zhuhai). To improve the ability for carbon reduction in the PRD, cooperation in multiple cities to promote energy efficiency is advocated. The government should also increase technical support for carbon reduction and consider the balanced development of the economy, population, and resources in the PRD. [ABSTRACT FROM AUTHOR]

To improve the capabilities of conventional methodologies in supporting greenhouse gas (GHG) emission mitigation from food production under uncertain conditions, an integrated approach was developed through incorporating copula-based violation risk analysis into a general life cycle analysis (LCA) framework. This approach strengthened the applicability of LCA in terms of uncertainty and risk reflections for food systems in the background of urbanization under multiple GHG emission targets. In detail, such an approach can (a) reflect uncertainties of food production and consumption processes, (b) tackle joint probability of two correlated variables (i.e., GHG emissions and economic benefits) through the employment of Archimedean copula (i.e., Gumbel, Frank, and Clayton copula) and Gaussian copula, and (c) assess violation risk of GHG emissions in food production considering the trend of future urbanization. A case study was proposed to illustrate application of the approach in Dalian City, China. Considering uncertainties of dietary patterns in 2020, two scenarios (scenarios of baseline and increase) were proposed according to dietary structures of urban and rural residents. In detail, the scenario of baseline represented the recent dietary pattern of Dalian in 2015. Scenario of increase indicated 50% rise in beef, mutton, and milk compared with the dietary pattern under the scenario of baseline. The results showed that based on the current agenda upon GHG emission intensity in China, violation risks under the scenario of baseline would be more prominent than the violation risks under the scenario of increase. [ABSTRACT FROM AUTHOR]

• A systematic framework was proposed to assess urban flood resilience (UFR). • Each resilience phase (e.g., resistance, adaptation, & recovery) were considered. • The system framework incorporated hybrid flood model and system performance curve. Urban flooding can seriously threaten urban ecological security and human life, and therefore urban flood resilience (UFR) is important for urban safety and stability. To comprehensively evaluate urban system performance during the entire process of rainfall, runoff, flooding, and drainage, we developed a systematic framework for UFR assessment covering runoff simulation, flood estimation, and resilience assessment, which broadly corresponded to the phases of resistance, adaptation, and recovery. The UFR in the phases of resistance, adaptation, and recovery was simulated and assessed using a system performance curve (SPC) and technically combining with the hybrid flood model while mainly considering the total simulation time and inundated urban proportion in SPC. Because the extent of urban flooding can be influenced by climate change and the rate of urbanization, we chose the corresponding representative factors of precipitation and infiltration rate and considered 21 simulation scenarios (seven rainfall return periods and three infiltration rates) for which UFR was quantified according to urban system performance. The effectiveness of this framework was demonstrated in application to a typical highly urbanized area (i.e., Dongguan, China). The following results were derived: (1) The inundated area under the pessimistic scenario (i.e., S19) would be nearly four times greater than that under the optimistic scenario (i.e., S3); (2) The values of UFR in Dongguan were 0.9494–0.9863, locating at the high and very high level; (3) The lowest UFR value was 0.6552 in the Shuixiang New City district; and (4) The rainfall return period was the main factor influencing UFR under relatively short rainfall return periods (i.e., S1–S9), while infiltration rate was the principal influencing factor under relatively long rainfall return periods (i.e., S10–S21). The proposed systematic framework could be applied in other cities and large-scale regions like urban agglomerations and provinces. [ABSTRACT FROM AUTHOR]

The removal of antibiotics from the environment have become a critical issue due to their toxicity and persistence. Among various approaches, microalgae-based technology has emerged as a promising, cost-effective, and eco-friendly option. Unfortunately, a systematic and quantitative analysis of the antibiotic removal efficiency by microalgae is still lacking. Therefore, this study conducted a meta-analysis including 27 peer-reviewed publications to address this gap. The study analyzed the overall antibiotic removal efficiency and influencing factors (antibiotic type, microalgae genus, temperature, hydraulic retention time (HRT), and light intensity), and identified appropriate microalgae for specific antibiotic removal, using the effect size of response ratio. Results showed that microalgae had a significant positive effect on the removal of antibiotics, and antibiotic type, microalgae genus, HRT, and light intensity significantly impacted the overall antibiotic removal efficiency. Haematococcus exhibited better removal efficacy than the commonly used Chlorella and Scenedesmus. For specific antibiotic removal, Chlamydomonas and Chlorella were recommended for macrolide antibiotic, Chlorella for beta-lactam antibiotic, and Haematococcus for sulfa antibiotic. This study offers valuable insights for future research and can help locate the most appropriate microalgae for removing specific antibiotics. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, a hybrid approach was established to identify future heterogeneity of urban ecosystem health (UEH) transferred by variations of land-use, socio-economic development, and ecological function in lower scales of cities (i.e., districts), incorporating uncertainty analysis into a multi-criteria decision assessment framework. In consideration of multiple driving factors of UEH scores, the contribution of the main indicators to UEH scores was identified by geographical detector model. To verify effectiveness of the approach, a case study was applied in Dongguan City of China. The results indicated that UEH scores of Dongguan didn't greatly change during 2010–2020. Conversely, the scores would increase from 2023 to 2030, influenced by socio-economic development and ecological function under the district scale. Concurrently, the heterogeneity of urban ecosystem health ranks (UEHRs) in 32 districts occurred during 2010–2020, further influencing UEH scores of Dongguan. Owing to inconsistent of land-use, ecological function, and socio-economic development of districts, the heterogeneity of UEHRs was intensified in 2025–2030. From 2010 to 2020, the spatial variations of UEH scores in Dongguan City depended on the synergy of land-use intensity and economic growth. The joint influence from economic development, energy consumption and land-use patterns would contribute greatly to the variations of UEH scores in Dongguan City from 2023 to 2030. Thus, heterogeneity of UEHRs under district scale as well as promotion for sustainable economic development should be paid attention to by decision-makers, to identify internal characteristics in urban ecosystems. [ABSTRACT FROM AUTHOR]

• The spatial distribution of prioritized afforestation types in each scenario was identified. • Favorable scenario can reduce trade-off between CS and WC and increase SC and SF equally. • The strategy of suitable afforestation type selection in Northern China was proposed. Afforestation is one of the most important measures to control soil erosion and desertification in Northern China. Meanwhile, considering that afforestation in Northern China needs to increase carbon sequestration (CS) and reduce water consumption (WC), it is essential to select prioritized afforestation types in suitable regions. In this work, we identified ecologically vulnerable zones based on soil water and wind erosion assessment, evaluated tree and shrub afforestation suitability, and thus recognized potential afforestation regions. Further, we set four scenarios for different goals, and identified the prioritized afforestation types in each scenario. The results showed that potential afforestation regions are mainly distributed in the Loess Plateau, Western Liao River, Ordos Plateau, and Tarim Basin. Scenario 1 (aiming to minimize WC) is dominated by shrub afforestation and grassland restoration. This scenario will reduce WC by 3.1%-6.4% compared to other scenarios, but it will also decrease CS by 9.4%-56.1% and soil conservation (SC) by 7.7%-13.0%. Scenario 2 (aiming to maximize CS) is dominated by tree and shrub afforestation. This scenario will fix 41.8%-56.1% more carbon, and consume 3.0%-6.4% more water than the other scenarios. Meanwhile, this scenario can maximize SC, but also may reduce sand fixation (SF). Scenario 3 (aiming to maximize CS in humid region and minimize WC in arid region) and Scenario 4 (aiming to enhance both SC and SF) are dominated by shrub afforestation, tree afforestation and grassland restoration. The two scenarios can balance CS and WC, and have advantages in improving both SC and SF. In addition, Scenario 4 performs better than Scenario 3. In the future, it is better to implement tree afforestation mainly in sub-humid area, and conduct shrub afforestation mainly in arid and semi-arid regions. This study can provide guidance for the planning and management of afforestation projects in Northern China and other water scarcity areas. [ABSTRACT FROM AUTHOR]

As an effective measure to promote socio-economic development, industrial transformation indirectly changes the characteristics of urban underlying surfaces, leading to the complexity of controlling nonpoint source (NPS) pollution in cities. However, the relationship between industrial transformation and urban NPS pollution, as well as the critical socioeconomic factors influencing the characteristics of urban NPS pollution during the period of industrial transformation, is still unclear, seriously affecting urban water environment management. In this research, indicator systems for the estimation of industrial transformation and urban NPS pollution were first established. Then, the characteristics of industrial transformation and urban NPS pollution were analyzed through an entropy weight method and a volume–concentration model. In addition, critical socioeconomic factors affecting urban NPS pollution during periods of industrial transformation were identified using Pearson correlation analysis and a grey correlation model. Using Dongguan City in South China as the study area, the results showed that the level of industrial transformation in this city shows an upward trend, and the towns with relatively high level of industrial transformation gradually gathered around Songshan Lake. The four urban NPS pollution index (i.e., chemical oxygen demand, suspended solids, total nitrogen, and total phosphorus) significantly increased during the slow transformation period (2000–2010), then slightly decreased during the rapid transformation period (2010–2020). The pollution loads exhibited significant spatiotemporal heterogeneity. A significantly negative correlation (p < 0.05) was observed between industrial transformation and urban NPS pollution levels during the transformation period. It was found that fertilizer, electricity, and water consumptions, as well as permanent population were the critical socioeconomic factors affecting urban NPS pollution. Control of the application amounts of fertilizers and improvement in the efficiencies of urban water and electricity use are the effective methods for preventing and controlling urban NPS pollution during the period of industrial transformation. In addition, industrial enterprises should increase their investment in research and development activities to accelerate industrial transformation and reduce the urban NPS pollution load. This research contributes to urban NPS pollution control in the area undergoing industrial transformation. • A comprehensive method was proposed for evaluating urban NPS pollution during the period of industrial transformation. • The relationship between industrial transformation and urban NPS pollution was analyzed for the first time. • A significant negative correlation was observed between the levels of industrial transformation and NPS pollution. • Critical socioeconomic factors affecting urban NPS pollution during the industrial transformation period were identified. [ABSTRACT FROM AUTHOR]

• The influence mechanism of discharge variation on NEP was explored in the PRE. • Low GPP and high ER caused lowest NEP rate at Humen with largest discharge. • Restriction of discharge increase on NEP exceeded stimulation of seasonal factors. • High discharge intensified low NEP, hypoxia and acidification at three outlets. Clarifying the influence of hydrological variations on ecological function is a topic of considerable interest in watershed ecological flow assessment and water resource management. Net ecosystem productivity (NEP) is a useful composite indicator of ecosystem function, reflecting material cycling and energy flow. However, the effects of hydrological variations on NEP, especially the influence mechanism, remain unclear due to the complex environmental characteristics in estuaries. We analysed the spatial–temporal variability of the aquatic environment and NEP through in-situ monitoring and field sampling from December 2018 to January 2020 at three outlets (Humen, Jiaomen, and Hongqimen) with different hydrological conditions in the Pearl River Estuary (PRE), China, and explored the influence mechanism of hydrological variation on NEP. The 155 groups of effective metabolism values were estimated using Odum's open-water method. The daily ecosystem respiration (ER) was higher than the gross primary production (GPP); therefore, water bodies were dominated by net heterotrophy at the three outlets. The daily NEP (–4.34 ± 1.40 mg O 2 L–1d–1), O 2 concentration (5.2 ± 1.02 mg L–1), and pH (7.53±0.24) were lowest at Humen, which also had the largest discharge and tide volume, deepest water depth, and widest channel. Seasonally, the NEP in the summer (–3.30 ± 1.39 mg O 2 L–1d–1) and autumn (–3.19 ± 1.60 mg O 2 L–1d–1) was lower than those in the spring (–1.56 ± 1.92 mg O 2 L–1d–1) and winter (–2.17 ± 1.50 mg O 2 L–1d–1). The inhibitory effect of increased discharge on the metabolic rate exceeded the stimulation provided by seasonal factors, such as increased temperature and solar radiation. The scour and dilution effect caused by discharge increase reduced chlorophyll a concentration; meanwhile, the increase in turbidity resulted in a decrease in the photosynthetic rate and GPP. ER was stimulated by heterotrophic microorganisms and high total suspended solids, resulting in a decrease in O 2 and endogenous organics, thus causing the low NEP, hypoxia, and acidification phenomenon. Our results suggest that lengthening the discharge pulse period in summer and autumn will further decrease NEP and increase the area of hypoxia and acidification at the three outlets in the PRE. [Display omitted] [ABSTRACT FROM AUTHOR]

Understanding the complex ways in which urbanization influences energy-environmental efficiency (EEE) is essential for achieving energy savings and emission reductions. The multidimensional impacts of urbanization on EEE were evaluated using a hybrid approach that combined a super slack-based measure (SBM) model with a stochastic impacts by regression on population, affluence, and technology (STIRPAT) model. This approach was applied to evaluate the influences of multi-dimension urbanization on EEE, taking account of undesirable outputs from environmental pollution. The appropriateness of the approach was verified using panel data of 21 cities in Guangdong Province from 2005 to 2016. The results indicated there existed obvious regional differences in the indexes of urbanization and EEE in Guangdong Province during this period. Further analysis of the multidimensional impacts of urbanization revealed that two factors (i.e., proportion of the urban resident population and urban compactness) had significant positive impacts on EEE. Conversely, the impacts of the following three factors on EEE were significant negative: (1) per capita GDP, (2) contribution of the secondary industry, and (3) proportion of land used for urban construction. Some factors (e.g., population size and urban built-up area) did not have significant effects on EEE in Guangdong Province. These findings indicated that decision makers in Guangdong Province could consider the positive influences of the population urbanization and the negative influences of the land urbanization on EEE. • The impacts of multidimensional urbanization on energy–environmental efficiency (EEE) were studied. • Imbalances in EEE within Guangdong Province were reflected. • A hybrid approach of super-SBM and extended STIRPAT model was proposed. • There were positive and negative influences from population and land urbanization on EEE respectively. [ABSTRACT FROM AUTHOR]

With the accelerating pace of globalization, uncertainty and unknown risks within open and complex urban systems increase with the occurrence of problems such as the conflict between humans and natural land use, water scarcity, and the continuing loss of biodiversity. Thus, the improvement of urban resilience has emerged as an important issue in the context of global urbanization. However, a knowledge gap remains in its evaluation from the perspective of systematic resource/element metabolic processes. To understand the urban resilience response mechanism better and depict metabolic processes systematically, an urban resilience assessment framework of "robustness-adaptability-restorability-coordination" based on the cross-media carbon metabolism network model was established. Principles of material flow analysis and ecological network analysis were applied to examine the urban resilience of Guangzhou, China, from 2010 to 2020. Results showed the urban resilience level decreased from a carbon metabolism perspective during the study period. This was reflected in an overall decline in system robustness and restorability, relatively unchanged adaptability, and a non-beneficial coordination relationship. Recommendations such as regulating key sectors (e.g., agriculture and construction) were proposed to improve urban resilience. This research will bring a new insight into future urban resilience assessment and contribute the urban sustainable development. [ABSTRACT FROM AUTHOR]

• Investigate the urban cross-media carbon metabolism network structure systematically. • Identify the key nodes and paths of the urban cross-media carbon metabolism network. • MFA and ENA were employed to establish the network and evaluate its structure. • The construction and transportation sectors were identified as key nodes. • Collaborative regulation of key nodes/paths benefits the system improvement better. Optimizing the structure of the carbon metabolic network is essential for enhancing network performance. However, a knowledge gap remains in systematically evaluating the network structure and comprehensively identifying the key nodes and paths, particularly in a carbon metabolism system that involves the frequent transition of carbon element across the air, water, and soil mediums. Hence, taking Guangzhou, China, as a case study, we constructed a cross-media metabolism network model based on material flow analysis. Subsequently, the general structural characteristics and key nodes/paths of the network were investigated through the integration of trophic structure analysis, contribution analysis, and stability analysis in ecological network analysis. The results primarily suggest that the connections among nodes in the carbon metabolism network have become looser, and the metabolic system structure was in a medium state with some defects from 2010 to 2020. Sectors of construction and transportation, as well as carbon flows from the agriculture sector to the construction sector and the energy conversion sector to the transportation sector, were identified as the key nodes and paths influencing the structural characteristics. Subsequently, twenty-one optimization scenarios were developed, with the results suggesting the advantage of collaborative regulation of key nodes/paths (e.g., increasing the carbon flows both from the agriculture sector to the construction sector and from the energy conversion sector to the transportation sector by 50%). This work may provide useful guidance for the structure optimization of the carbon metabolism system. [ABSTRACT FROM AUTHOR]

[Display omitted] • Heterogeneous effects of UGS availability and spatial configuration on LST were explored. • UGS availability is negatively associated with both daytime and nighttime LST. • The Gini coefficient of UGS distribution has a positive effect on solely daytime LST. • The impacts of UGS availability on LST decrease with increased LST quantiles. • The impacts of UGS spatial configuration increase with increased LST quantiles. The impacts of the availability and spatial configuration of urban green spaces (UGS) on their cooling effects can vary with background climate conditions. However, large-scale studies that assess the potential heterogeneous relationships of UGS availability and spatial configuration with urban thermal environment are still lacking. In this study, we investigated the impacts of UGS availability and spatial configuration on urban land surface temperature (LST) taking 306 cities in China as a case study covering a multi-biome-scale. We first calculated the availability of surrounding UGS for urban built-up pixels in each city using a distance-weighted approach, and its spatial configuration was quantified through the Gini coefficient. Then, we employed various regression models to explore how the impacts of UGS availability and the Gini coefficient on LST varies across different LST quantiles and between day- and nighttime. The results revealed that UGS availability was negatively associated with both daytime and nighttime LST, while the Gini coefficient showed a positive impact solely on daytime LST, indicating that an adequate and equally distributed UGS contributes to lower environmental temperatures during the daytime. Furthermore, the impact of UGS availability on LST decreased during both day- and nighttime with increased background LST quantiles. Whereas the impact of the Gini coefficient increased only with daytime LST quantile levels, with its effect remaining almost insignificant during the night. Our findings provide new insights into the impacts of UGS on urban thermal environment, offering significant implications for urban green infrastructure planning aiming at lowering the urban heat island. [ABSTRACT FROM AUTHOR]