The development of China's Yangtze River Economic Belt: how to make it in a green way?

Hydrology and water quality drive multiple biological indicators in a dam-modified large river

Freshwater biodiversity is increasingly threatened by dams and many other anthropogenic stressors, yet our understanding of the complex responses of different biotas and their multiple facets remains limited. Here, we present a multi-faceted and integrated-indices approach to assess the differential responses of freshwater biodiversity to multiple stressors in the Yangtze River, the third longest and most dam-densely river in the world. By combining individual biodiversity indices of phytoplankton, zooplankton, periphyton, macroinvertebrates, and fish with a novel integrated aquatic biodiversity index (IABI), we disentangled the effects of hydrology, water quality, land use, and natural factors on both α and β diversity facets in taxonomic, functional, and phylogenetic dimensions. Our results revealed that phytoplankton and fish species and functional richness increased longitudinally, while fish taxonomic and phylogenetic β diversity increased but phytoplankton and macroinvertebrate β diversity remained unchanged. Hydrology and water quality emerged as the key drivers of all individual biodiversity indices, followed by land use and natural factors, with fish and phytoplankton showed the strongest responses. Importantly, we found that natural, land use, and hydrological factors indirectly affected biodiversity by altering water quality, which in turn directly influenced taxonomic and phylogenetic IABIs. Our findings highlight the complex interplay of multiple stressors in shaping freshwater biodiversity and underscore the importance of considering both individual and integrated indices for effective conservation and management. We propose that our multi-faceted and integrated-indices approach can be applied to other large, dam-modified river basins globally.

Differential microbiome features in lake-river systems of Taihu basin in response to water flow disturbance

Introduction

In riverine ecosystems, dynamic interplay between hydrological conditions, such as flow rate, water level, and rainfall, significantly shape the structure and function of bacterial and microeukaryotic communities, with consequences for biogeochemical cycles and ecological stability. Lake Taihu, one of China's largest freshwater lakes, frequently experiences cyanobacterial blooms primarily driven by nutrient over-enrichment and hydrological changes, posing severe threats to water quality, aquatic life, and surrounding human populations. This study explored how varying water flow disturbances influence microbial diversity and community assembly within the interconnected river-lake systems of the East and South of Lake Taihu (ET&ST). The Taipu River in the ET region accounts for nearly one-third of Lake Taihu's outflow, while the ST region includes the Changdougang and Xiaomeigang rivers, which act as inflow rivers. These two rivers not only channel water into Lake Taihu but can also cause the backflow of lake water into the rivers, creating distinct river-lake systems subjected to different intensities of water flow disturbances.

Methods

Utilizing high-throughput sequencing, we selected 22 sampling sites in the ET and ST interconnected river-lake systems and conducted seasonally assessments of bacterial and microeukaryotic community dynamics. We then compared differences in microbial diversity, community assembly, and co-occurrence networks between the two regions under varying hydrological regimes.

Results and discussion

This study demonstrated that water flow intensity and temperature disturbances significantly influenced diversity, community structure, community assembly, ecological niches, and coexistence networks of bacterial and eukaryotic microbes. In the ET region, where water flow disturbances were stronger, microbial richness significantly increased, and phylogenetic relationships were closer, yet variations in community structure were greater than in the ST region, which experienced milder water flow disturbances. Additionally, migration and dispersal rates of microbes in the ET region, along with the impact of dispersal limitations, were significantly higher than in the ST region. High flow disturbances notably reduced microbial niche width and overlap, decreasing the complexity and stability of microbial coexistence networks. Moreover, path analysis indicated that microeukaryotic communities exhibited a stronger response to water flow disturbances than bacterial communities. Our findings underscore the critical need to consider the effects of hydrological disturbance on microbial diversity, community assembly, and coexistence networks when developing strategies to manage and protect river-lake ecosystems, particularly in efforts to control cyanobacterial blooms in Lake Taihu.

A 10-m scale chemical industrial parks map along the Yangtze River in 2021 based on machine learning

Strengthening industrial pollution control in the Yangtze River is a fundamental national policy of China. There is a lack of detailed distribution of chemical industrial parks (CIPs). This Study utilized random forest (RF) and active learning to generate the distribution map of CIPs along the Yangtze River at 10-m resolution. Based on Sentinel-2 imagery, spectral and texture features are extracted. Combined with the Points of Interest (POI), a multidimensional feature space is constructed. By employing partitioned training, classification of CIPs map is achieved on Google Earth Engine (GEE). Technical validation along the entire Yangtze River demonstrates a model accuracy of 80%. Compared to traditional manual survey methods, this approach saves significant time and economic costs while also being timelier. As the first publicly available CIPs map within a 5-km range along the Yangtze River, this research will provide a scientific basis for the fine governance of chemical industries in the region. Additionally, it offers a model guide for the accurate identification of the chemical industry.

Ecosystem health evaluation based on land use change-case study of the riparian zone of the Yangtze River in Jiangsu Province, China

Evaluating the ecosystem health of riparian zones is helpful for decision-makers to formulate appropriate management measures. However, there are few methods for such evaluation which account for both the human requirements and ecological aspects of riparian zones. To address this, we created a Pressure-State(Vigor-Organization-Resilience)-Response framework for evaluating the ecosystem health of the riparian zone of the Yangtze River in Jiangsu Province, a region experiencing intense land use changes. Evaluation indicators, including land use change and ecosystem services, were selected. The comprehensive index method was used to calculate the evaluation indicators of ecosystem health, namely pressure, state, and response, and the comprehensive evaluation indicator itself. Using the cold and hot spot analysis, we also analyzed the spatial heterogeneity of ecosystem health in the riparian zone, constructed an ecological management pattern, and proposed corresponding management and protection measures. The results show that (1) from 2010 to 2020, construction land in the study area increased by more than 20%, and all studied land types underwent some degree of conversion to construction land, with cultivated land and water bodies being the main focus of conversion. (2) In 2020, the average ecosystem health in the riparian zone was normal, with a spatial distribution characterized by "high dispersion and low clustering"; and (3) according to the results of the ecosystem health evaluation and cold and hot spot analysis, key areas for stronger ecological protection were identified and, based on this, a number of management recommendations were proposed.

Recognition, possible source, and risk assessment of organic pollutants in surface water from the Yongding River Basin by non-target and target screening

Organic pollutants in aquatic environment could have important implications on pollution stress on aquatic organisms and even on the risk of human exposure. Thus, revealing their occurrence in aquatic environment is essential for water quality monitoring and ecological risk purposes. In this study, a comprehensive two-dimensional gas chromatography connected with time-of-flight mass spectrometry (GC × GC-TOF-MS) was applied, to enable non-target and target analysis of pollutants in the Yongding River Basin. Based on the isotopic patterns, accurate masses and standard substances, certain environmental contaminants were tentatively identified which including polycyclic aromatic hydrocarbon (PAHs), organochlorine pesticides (OCPs), phenols, amines, etc. The compounds with the highest concentration were naphthalene (109.0 ng/L), 2,3-benzofuran (51.5 ng/L) and 1,4-dichlorobenzene (35.9 ng/L) in Guishui River. Wastewater treatment plants (WWTPs) discharges were a main source of pollutants in Yongding River Basin, as the types of compounds screened in the downstream river were relatively similar to those from WWTPs. According to the target analysis, a number of pollutants were selected due to the acute toxicity and cumulative discharge from WWTPs and downstream rivers. Three PAHs (naphthalene, Benzo(b)fluoranthene and pyrene) homologues showed moderate risk to fish and H. Azteca in Yongding River Basin, while the rest of the measured chemicals showed low ecological impact across the entire study area based on the risk assessment. The results are helpful for understanding the necessity of high-throughput screening analysis for assessing water quality of rivers and the discharge emissions of pollutants from WWTPs to the river environment.

A factorial-based dynamic distributive model for virtual-water management in multi-urban agglomerations - A case study of Yangtze River Economic Belt

The economic development, population growth and rapid urbanization in the Yangtze River Economic Belt (YREB) have resulted in an imbalance between socio-economic development and available water resources of adjacent urban agglomerations. Exploring the virtual water flow (VWF) of adjacent urban agglomerations in YREB is crucial for the collaborative management of water resources. In this study, a factorial-based dynamic distributive model (FDDM) is first developed to analyze the variations in virtual water transfers and inter/inner-sectoral relationships within multi-urban agglomerations, and expound the spatiotemporal diffusion effects of multiple water policy alternatives (and their combinations) for virtual water. The FDDM is applied in YREB's urban agglomerations covering Yangtze River Delta (YRDA), Middle Reach of Yangtze River (MRA) and Chengyu Urban Agglomeration (CYA). The FDDM is capable of i) quantifying the dynamic evolution of direct/indirect virtual water volume and virtual water transfer direction/path between and within urban agglomerations; ii) demonstrating the spatiotemporal changes of the control/dependent relationship within sectors in sub-urban agglomerations, as well as the evolution of utility relationship within the system; iii) evaluating the interactions of different water policies (and their combinations) within each sub-urban agglomeration/key sectors on the direct and indirect virtual water consumption of the system. Our major findings are: (i) YRDA always has the largest direct and indirect water consumption as well as the water consumption intensities from 2007 to 2017; (ii) The three national urban agglomerations have evolved in the direction of benign development; (iii) the interactions between YRDA and MRA, YRDA_FLF (sector of farming, forest, livestock, and fishery in YRDA) and MRA_FTO (sector of food and tobacco processing in MRA) on VWF are obvious. These results will provide a new insight for balancing urban agglomeration development and water resource utilization in YREB.

Evaluating the impact of power station regulation on the suitability of drifting spawning fish habitat based on the fuzzy evaluation method

Ecological regulation is an important means of reservoir adaptive management, but its effective evaluation faces two major difficulties: the response mechanism of fish spawning behavior is not completely clear, and how to establish a feedback regulation relationship of hydrological processes to improve the river environment is unknown. Based on a long-term series of early fish resources, hydrology, water temperature, and meteorology data, this research clarifies the fish spawning habitat requirements in the power station regulation environment, determines a habitat suitability evaluation index system and evaluation criteria, reveals the temporal and spatial variation characteristics of fish habitat suitability under power station regulation based on the fuzzy logic method, provides feedback to the existing regulation scheme, and proposes suggestions for sustainable adaptive management of the reservoir. The temporal and spatial variation characteristics of the spawning river sections habitat suitability are the comprehensive differences among multiple objectives and factors. The habitat suitability of each river section decreases after impoundment, especially in May, which is related to the delayed of water temperature changes under reservoir regulation. The reduced suitability of the Yibin(YB) river section is most affected by the impoundment regulation of the Xiluodu Reservoir (XLDR) and Xiangjiaba Reservoir (XJBR), while the Luzhou(LZ) river section is affected by the inflow of the Minjiang River (MJ) tributary, which reduces the suitability difference before and after impoundment. The Jiangjin(JJ) river section is less affected by the regulation of the XJBR and is greatly affected by tributaries and rainfall. How to adjust the regulation strategies under the new boundaries and new situations in the future, which are affected by the cumulative impact of the sustainable development of upstream cascades, is the focus of reservoir adaptive management. This research can provide technical support for the management of cascade reservoirs under future scenarios.

Comprehensive evaluation of water ecological environment in watersheds: a case study of the Yangtze River Economic Belt, China

The Yangtze River Economic Belt, an inland economic zone with global influence, has shown a trend of prosperous economic development in recent years. Economic development, water pollution, resource depletion, and other environmental problems continue to emerge. The steady state of the water ecological environment is an important aspect of ecological security. To investigate the regional water ecological security state, this study constructs a comprehensive evaluation indicator system within the framework of "driving force-carrying source-state-management" (DCSM). The entropy weight method was used to determine the weight of each indicator, and the weighted rank sum ratio model was introduced to classify the water ecological environment of the Yangtze River Economic Belt from 2010 to 2019. Finally, an adversarial interpretative structure model is used to refine the ranking of each region. The results show that the bearing state and driving force subsystems are closely related to the water ecological environment. The top three indicators are wastewater discharge of industrial added value of 10,000 yuan, water consumption per 10,000 yuan of industrial gross product, and water consumption per 10,000 yuan of tertiary gross domestic product. In addition, there are clear differences in the water ecological environment of the Yangtze River Economic Belt. The classification results show that Zhejiang and Jiangsu are rated as "excellent''; Yunnan, Guizhou, Anhui, and Jiangxi are in the "good" level; and Sichuan, Hunan, Chongqing, and Hubei are in the "medium" level. Shanghai is "poor." As a whole, the downstream is superior, the upstream is second, and the midstream is poor in an asymmetric "U"-shaped distribution. During the study period, the overall state of water ecology in the Yangtze River Economic Belt was at a medium level and has not yet reached a safe and steady state. The performance of areas with traditional industrialization as the main development path was poor. Therefore, it is necessary to pay attention to the overall water ecological security in the basin in the future, strengthen the regulatory role of the government's water ecological management, promote reform of traditional industries and resource-based regions, and achieve the sustainable development of the water ecological environment.

Variations and its driven factors of anthropogenic nitrogen loads in the Yangtze River Economic Belt during 2000-2019

Since the millennium, China has economically taken off with rapid urbanization, and anthropogenic nitrogen emission intensity has undergone remarkable changes. To better understand the impact of urbanization on anthropogenic nitrogen, this study calculated the spatio-temporal heterogeneity of anthropogenic nitrogen in the Yangtze River Economic Belt (YREB) since 2000, based on the estimation, using obstacle analysis to quantify the driving of industry and agriculture on N growth and using the gray model to analyze the impact of urbanization on N changes. Additionally, using the environmental pressure model to predict the future N load. The results indicated N load in the YREB increased rapidly from 21.4 Tg in 2001 to a peak of 24.5 Tg in 2012 and then decreased to 22.2 Tg in 2019. Although N flux gradually increased from the west to the east of the YREB, the growth rate had an opposite trend with a negative growth in the eastern region. Hotspots are mainly concentrated in urban agglomerations, which contributed to ~ 60% N load of the YREB, and the YREB contributed to ~ 90% N load of the Yangtze River Basin. Obstacle degree scores indicated wastewater was a major industrial driver of N growth before 2010, and then became waste gas; increased mechanization and fertilizer control effectively reduced nitrogen emissions during agricultural development. The gray analysis of urbanization indicated urban population, industry, and services had the strongest correlation with N load changes. Scenario simulations suggest N loads of the YREB remain at a high level by 2030; however, there are still opportunities to effectively control N growth through high technological innovation and reducing the proportion of industry under an enormous population. This research contributes to a better understanding of the impact of urbanization on anthropogenic nitrogen and helps developing countries to precisely control nitrogen hotspots and sources.

Development of multidimensional water poverty in the Yangtze River Economic Belt, China

As a basic natural and strategic resource, water is of great significance to the sustainable development of economies and societies. Owing to population growth, industrialization, the acceleration of urbanization, and global warming, water poverty is gradually increasing in some parts of the world. Effectively assessing water poverty from different dimensions is still a serious challenge for global water resources planning. This paper establishes a framework of multidimensional water poverty (MWP) from six dimensions: water management, water technology, water assets, water welfare, water resources, and water environment. The measurement model of MWP is built based on the Back Propagation Neural Network (BPNN), and the Spatial Correlation Analysis tool is used to visualize the spatial effects of MWP. The Yangtze River Economic Belt (YREB) was used as a case study and the main factors affecting the MWP of the YREB were determined by the Geodetector. When analyzing the results the following observations were made: (1) In terms of time distribution, the level of MWP in the YREB has gradually increased, and the poverty gap between the upper reaches, as well as the middle and lower reaches, shows an increasing trend. (2) With respect to spatial distribution, there is a continuously increasing agglomeration effect that shows a gradient-increasing distribution pattern of "West-Central-East." (3) The MWP in the YREB is mainly affected by these indicators in the three dimensions consisting of water resources, water technology, and water management. Specifically, R&D expenditure as a percentage of GDP, the proportion of water-saving irrigation area in the cultivable land area, the urban daily wastewater treatment capacity, the land surface water resources per capita, and the groundwater resources per capita play an important role in the MWP. Based on the above findings, targeted policy recommendations are proposed to alleviate the MWP in the YREB.

Spatial-Temporal Evolution and Improvement Measures of Embodied Carbon Emissions in Interprovincial Trade for Coal Energy Supply Bases: Case Study of Anhui, China

On account of the long-term dependence on energy trade and the phenomenon of embodied carbon emissions in interprovincial trade (ECEs-IPT), energy supply bases (ESBs) in the economic integration regions (EIRs) are under unprecedented dual pressure of achieving carbon emissions (CEs) reduction targets and ensuring security and stability of the energy supply. This problem has attracted more and more attention and research by experts and scholars. This paper took Anhui, the coal ESB of the Yangtze River Economic Belt (YREB), as an example and took the key stage of rapid development of regional economic integration (REI) and accelerated the realization of CEs reduction targets in YREB from 2007 to 2017 as the study period. From the perspectives of regions and industry sectors, we calculated the transfer amount of ECEs-IPT in Anhui among the YREB, analyzed the spatial-temporal evolution pattern of ECEs-IPT, and revealed the industrial characteristics of ECEs-IPT. Then, we classified the industry sectors and proposed the direction of industrial improvement measures. The results showed that, during the decade, the amount of provinces undertaking the net ECEs-IPT outflow from Anhui increased significantly and spatially expanded from only Jiangxi Province to almost all of the YREB. In addition, 39.77% of the net ECEs-IPT outflow of Anhui was concentrated in petroleum processing, coking, and nuclear fuel processing (RefPetraol), metal smelting and rolling processing (MetalSmelt), and electricity and heat production and supply (ElectpowerProd) that trade with Shanghai, Jiangsu, Zhejiang, and Jiangxi. The analytical model and results will provide a useful reference for the global similar coal ESBs, especially the coal ESBs within the EIRs, to formulate improvement measures for regions or even the world to ensure stability of the energy supply and achieve regional CEs reduction targets.

Spatial-temporal evolution and driving factors of grey water footprint efficiency in the Yangtze River Economic Belt

At present, the deterioration of the water ecosystem has constituted a bottleneck for the further development of the Yangtze River Economic Belt (YREB). As a crucial indicator for evaluating the degree of water pollution, grey water footprint (GWF) is of great significance for rationally evaluating the water environment of the YREB. In this study, we calculated the GWF efficiency of the YREB based on the panel data of 9 provinces and 2 cities from 2005 to 2019. On this basis, spatiotemporal methods and Logarithmic Mean Divisia Index (LMDI) model were adopted to analyze the spatial-temporal evolution characteristics and driving factors of GWF efficiency in the YREB. This study drew the following conclusions: (1) the GWF efficiency in the YREB was on an uptrend, with the average annual growth rates of the upstream, midstream and downstream being 17.35 %, 18.31 % and 17.8 % respectively from 2005 to 2019. (2) The GWF efficiency in the YREB showed a weak trend of polarization and the gap between different regions continued to widen. Besides, it was characterized by stability and owned a positive spatial correlation in both geographic distance and economic distance. (3) The improvement of the technology level, water use efficiency, wastewater treatment capacity, economic development level and the reduction in the industrial pollution intensity contributed positively to boosting the GWF efficiency. Meanwhile, the effect of environmental regulation made a significant negative contribution to GWF efficiency. Therefore, in the process of building the YREB, while emphasizing the coordinated development of the economy, all regions should also carry out joint pollution control.

Climate, hydrology, and human disturbance drive long-term (1988-2018) macrophyte patterns in water diversion lakes

Macrophytes are affected by many natural and human stressors globally but their long-term responses to these multiple stressors are not often quantified. We employed remote sensing and statistical tools to analyze datasets from both short-term (2017-2018) field investigations to explore seasonal patterns, and long-term (1988-2018) Landsat remote-sensing images to detect annual patterns of macrophyte distributions and study their responses to changes in climate, hydrology, and anthropogenic activities in a chain of water diversion lakes in eastern China. We found: 1) biomass and species richness of macrophytes peaked in summer with dominant species of submerged macrophytes Ceratophyllum demersum, Potamogeton pectinatus, and Potamogeton maackianus and floating macrophytes Trapa bispinosa, and non-native species Cabomba caroliniana spread in midstream Luoma Lake and Nansi Lake in summer, while Potamogeton crispus was dominant in all the lakes in spring; 2) water physicochemical parameters (chloride and water depth), lake characteristics (area and water storage), climate factors (air temperature and precipitation), and anthropogenic activities (commercial fishery and urban development) were significantly correlated to the seasonal distribution of macrophytes; 3) long-term data showed a significantly negative correlation between coverage of floating macrophytes and precipitation where the wettest year of 2003 had the lowest coverage of floating macrophytes; and 4) climate (air temperature) and hydrology (water level) were positively correlated with total macrophyte coverage, but human disturbance indexed by the gross domestic product was negatively driving long-term coverage of macrophytes. Our study has important implications for understanding the long-term succession of macrophytes under both natural and human stressors, and for future environmental management and ecological restoration of freshwater lakes.

Evaluation of Common Prosperity Level and Regional Difference Analysis along the Yangtze River Economic Belt

Common prosperity is the essential requirement of socialism as well as the common aspiration of social people. This article constructed an evaluation index system of 25 indicators for common prosperity, covering four dimensions of material wealth, harmonious social life, rich spiritual life, and livable ecological environment. The TOPSIS method was used to comprehensively rank nine provinces and two municipalities in the Yangtze River Economic Belt. The results show that the level of common prosperity along the Yangtze River Economic Belt increased significantly from 2010 to 2019, and the level of common prosperity in the lower reaches of the Yangtze River Economic Belt is much higher than that in the middle and upper reaches. According to the differences in common prosperity levels among regions, provinces and cities are divided into three categories: high, unbalanced, and low. Combined with the characteristics of each type of region, policy suggestions were put forward from the perspectives of strengthening the regional industrial cooperation mechanism, deepening the construction of regional livelihood infrastructure and basic public services, and improving the ability of regional environmental coordination.

Land use, hydrology, and climate influence water quality of China's largest river

Influences of multiple environmental factors on water quality patterns is less studied in large rivers. Landscape analysis, multiple statistical methods, and the water quality index (WQI) were used to detect water quality patterns and influencing factors in China's largest river, the Yangtze River. Compared with the dry season, the wet season had significantly higher total phosphorus (TP), chemical oxygen demand (COD), total suspended solids (TSS), and turbidity (TUR). The WQI indicated "Moderate" and "Good" water quality in the wet and dry seasons, respectively. Compared with other sites, the upper reach sites that immediately downstream of the Three Gorges Dam had lower TP, TN, TSS and TUR in both seasons, and had lower and higher water temperature in the wet and dry seasons, respectively. Water quality patterns were mainly driven by heterogeneity in land use (i.e., wetland, cropland, and urban land), hydrology (i.e., water flow, water level), and climate (i.e., rainfall, air temperature). Water quality in the wet season was primarily driven by land use while the joint effect of land use and hydrology primarily drove in the dry season. Decision-makers and regulators of large river basin management may need to develop programs that consider influences from both human and natural drivers for water quality conservation.

Ecological risk assessment and environment carrying capacity of soil pesticide residues in vegetable ecosystem in the Three Gorges Reservoir Area

Soil contamination by pesticide residues has become an increasing concern of ecological protection. However, the soil environmental carrying capacity (SECC) of pesticide residues in agricultural ecosystems was limited studied. Based on the concept of ecological risk assessment, a modified system on the environment carrying capacity was proposed for estimate SECC of pesticide residues in agricultural soils. Subsequently, the assessment on ecological risk and SECC of soil pesticide residues in vegetable ecosystem were performed in the Three Gorges Reservoir Area (TGRA). In 201 topsoil samples, 62.1% of the pesticide compounds were detected over limit of quantitation, and exhibit a high proportion of multiple pesticide contamination. Pyrethroid insecticides and herbicide glyphosate showed most frequent occurrence and high levels. The SECC of the TGRA varies with the limit standard, annual cumulative amount and risk quotient of each pesticide contaminant in soils. Except that fenpropathrin has exceeded SECC, chlorfenapyr, β-cyfluthrin and glyphosate posed the greatest threat to SECC in the next 50 years. Additionally, ecological risks by pesticide residues in vegetable ecosystem can be affected by various planting activities. These results will contribute to guide the rational application of pesticides and control soil environmental risks, thereby achieving the agricultural green development in the TGRA.

Impacts of land finance on green land use efficiency in the Yangtze River Economic Belt: a spatial econometrics analysis

This paper uses the Global Malmquist-Luenberger Index (GMLI) based on directional distance function (DDF) super efficiency model to measure the urban green land use efficiency (UGLUE) of 108 cities in the Yangtze River Economic Belt (YREB) from 2007 to 2018, and it utilizes the spatial economic model to analyze the impact of land finance on the UGLUE and its mechanism of action. The results show that, firstly, the UGLUE in the YREB shows a steady development trend, the overall efficiency level is high, and there are spatial agglomeration characteristics. Secondly, the impact of land finance on the UGLUE presents "inverted U-shaped." With the continuous expansion of the scale of land finance, the impact of land finance on the UGLUE in the city has changed from positive to negative. Thirdly, land finance has a spatial spillover effect. Land finance will inhibit the improvement of UGLUE in surrounding areas through the "peer effect." With the continuous expansion of land finance scale, land finance will promote the improvement of UGLUE in surrounding cities through the "warning effect."

"Green" economic development in China: quantile regression evidence from the Yangtze River Economic Belt

As China's economy began transitioning from one focused on high-speed growth to one focusing on high-quality development, sustainable green development has become the main goal pursued by the government. This study empirically measures the marginal impact of per capita GDP, technological innovation level, industrial structure, openness, fiscal decentralization, and urbanization level on per capita wastewater discharge in 11 provinces (cities) along the Yangtze River Economic Belt (YREB) from 2008 to 2018 using a quantile model. The key findings were as follows: (1) factors such as the per capita GDP, industrial structure, foreign direct investment, and urbanization in the YREB significantly increased water resource pollution; (2) the quantile model regression results showed that the relationship between economic growth and ecological pollution followed the so-called environmental Kuznets inverted U-curve. Wastewater discharge per capita was low in areas with low per capita GDP, meaning that the ecological environment in these areas was more fragile and that the environmental pollution costs due to economic growth were therefore relatively much higher in these areas; (3) fiscal decentralization significantly reduced water resource pollution in relatively developed areas although the effects in the relatively developing areas were not significant; and (4) the effects of technological innovation on reducing water resource pollution in the YREB were positive but not very significant. The results also confirmed that traditional patterns of economic growth increased water pollution in the YREB. For this reason, the government needs to urgently improve policies-for example, upgrading economic structures, preventing over-urbanization, speeding up technological innovation, introducing environmentally friendly foreign investment, and providing more rewards to best practitioners of environmental governance-that is conducive to the achievement of green ecological development.

Water Environment Quality Evaluation and Pollutant Source Analysis in Tuojiang River Basin, China

A water environment quality evaluation and pollution source analysis can quantitatively examine the relationship among water pollution, resources, and the economy, and investigate the main factors affecting water quality. This paper took COD, NH3-N, and TP of the Tuojiang River as the research objects. The water environment quality evaluation and pollution source analysis of the Tuojiang River Basin were conducted based on the grey water footprint, decoupling theoretical model, and correlation analysis method. The results showed that grey water footprint decreased, and the water environment quality improved. Among the pollution sources of the grey water footprint, TP accounted for the highest proportion. Moreover, the economic development level and the water environment were generally in a state of high-quality coordination. Farmland and stock breeding pollution accounted for the largest proportion of agricultural pollution and were thus the main source of the grey water footprint. The results of Pearson’s correlation analysis indicated that the source of the pollutants were the imported pollution from the tributaries and agricultural pollution (especially stock breeding and farmland irrigation). These results showed that the quality of the water environment was improving, and the main factors affecting the water environment were stock breeding and farmland pollution in agriculture. This study presents a decision-making basis for strengthening the ecological barrier in the Yangtze River.

Spatial and temporal patterns of heavy metals and potential human impacts in Central Yangtze lakes, China

Lakes in the central Yangtze River basin have experienced increasing levels of human disturbance during the past several decades, yet large-scale environmental patterns in these lakes and their driving factors remain unclear. Herein we examined spatial and temporal patterns of copper (Cu), zinc (Zn), lead (Pb), arsenic (As), and seven other heavy metals from 16 lakes experiencing a gradient of human disturbance. These lakes were divided among six groups: suburban reservoirs (SR), suburban high-aquaculture lakes (SH), suburban low-aquaculture lakes (SL), suburban no-aquaculture lakes (SN), urban aquaculture lakes (UA) and urban no-aquaculture lakes (UN). Spatially, water-column concentrations of Cd, Ni, Co, Mn, Fe, and Al, and sediment concentrations of Ni were significantly lower in SR compared to other lake groups. Except for Al, heavy metal concentrations did not differ between SN and SL lakes in the water-column or sediments. SH lakes exhibited significantly greater concentrations of Cu, Co, Cr, Mn, and Al in the water-column and Zn in sediments compared to SN lakes. UA lakes contained significantly lower concentrations of Zn, Cd, and Al in sediment compared to UN lakes, though no significant differences were detected within water-column samples. Temporally, with all lake groups combined, summer water-column concentrations of Cd, Pb, Co, Mn, and Al were lower compared to spring and autumn. Additionally, summer sediment concentrations of Zn, As, Co, Fe also were lower compared to autumn. Further results indicated that low-density fish stockings without external feed inputs appeared to have little impact on heavy metals in both suburban and urban lakes. However, high-density fish stockings with external feed inputs were associated with increased heavy-metal concentrations across all lakes. Overall, urbanization has great potential to increase sediment heavy-metal ecological risks. These findings are crucial for developing heavy-metal pollution control and management strategies for freshwater lakes.

The Carbon Neutral Potential of Forests in the Yangtze River Economic Belt of China

Prediction of forest carbon sink in the future is important for understanding mechanisms concerning the increase in carbon sinks and emission reduction, and for realizing the climate goals of the Paris Agreement and global carbon neutrality. Based on stand volume data of permanent monitoring plots of the successive national forest inventories from 2004 to 2018, and combined with multiple variables, such as climatic factors, soil properties, stand attributes, and topographic features, the random forest algorithm was used to predict the stand volume growth-loss and then calculated the forest biomass and its carbon sink potential between 2015 to 2060 in the Yangtze River Economic Belt of China. From 2015 to 2060, the predicted forest biomass carbon storage and density increased from 3053.27 to 6721.61 Tg C and from 33.75 to 66.12 Mg C hm−2, respectively. The predicted forest biomass carbon sink decreased from 90.58 to 73.98 Tg C yr−1, and the average forest biomass carbon storage and sink were ranked in descending order: Yunnan, Sichuan, Jiangxi, Hunan, Guizhou, Hubei, Zhejiang, Chongqing, Anhui, Jiangsu, and Shanghai. The forest biomass carbon storage in the Yangtze River Economic Belt will increase by 3.67 Pg C from 2015 to 2060. The proportion of forest C sinks on the regional scale to C emissions on the national scale will increase from 2.9% in 2021–2030 to 4.3% in 2041–2050. These results indicate higher forest carbon sequestration efficiency in the Yangtze River Economic Belt in the future. Our results also suggest that improved forest management in the upper and middle reaches of the Yangtze River will help to enhance forest carbon sink in the future.

Land-Greening Hotspot Changes in the Yangtze River Economic Belt during the Last Four Decades and Their Connections to Human Activities

The spatial patterns of the normalized difference vegetation index (NDVI) changes in the Yangtze River Economic Belt (YREB) and their potential causes during the last four decades remain unclear. To clarify this issue, this study firstly depicts the spatial patterns of the NDVI changes using global inventory modelling and mapping studies (GIMMS) NDVI data and Moderate Resolution Imaging Spectroradiometer (MODIS) NDVI data. Secondly, the Mann–Kendall test, regression residual analysis and cluster analysis are used to diagnose the potential causes of the NDVI changes. The results show that the regional mean NDVI exhibited an uptrend from 1982 to 2019, which consists of two prominent uptrend periods, i.e., 1982–2003 and 2003–2019. There has been a shift of greening hotspots. The first prominent greening trend from 1982 to 2003 mainly occurred in the eastern agricultural area, while the second prominent greening uptrend from 2003 to 2019 mainly occurred at the junction of Chongqing, Guizhou and Yunnan. The greening trend and shift of greening hotspots were slightly caused by climate change, but mainly caused by human activities. The first greening trend was closely related to the agricultural progress, and the second greening trend was associated with the rapid economic development and implementation of ecology restoration policies.

Club Convergence and Spatial Effect on Green Development of the Yangtze River Economic Belt in China with Markov Chains Approach

The Yangtze River Economic Belt (YREB) is one of four major national development strategies in China, accomplishing the balance between protection and development of YREB has long-term and comprehensive significance to the implementation of China’s green development concept. This paper aims to have a more comprehensive understanding of the green development level of 126 cities in YREB from 2008 to 2017 by constructing an innovative evaluation system of “capacity level-coordination level-comprehensive level”. And on this basis, further analysis is carried out to check whether there is spatial effect in green development by means of the Markov chain. The main conclusions are as follows: (1) Urban green development comprehensive level in YREB is characterized by convergence, and the convergence phenomenon is more prominent in high-level cities; (2) In general, the distribution of high-value cities is decreasing from east to west; (3) The transition of club convergence is significantly influenced by neighbor background. Overall, the YREB is undergoing a transformation to step into the greener development path, still needs to take a series of synergistic guidance strategies to solve the problem of unbalanced regional development.

Exploring the green development path of the Yangtze River Economic Belt using the entropy weight method and fuzzy-set qualitative comparative analysis

Green development is an effective way to achieve economic growth and social development in a harmonious, sustainable, and efficient manner. Although the Yangtze River Economic Belt (YREB) plays an important strategic role in China, our understanding of its spatiotemporal characteristics, as well as the multiple factors affecting its green development level (GDL), remains limited. This study used the entropy weight method (EWM) to analyze the temporal evolution and spatial differentiation characteristics of the GDL in the YREB from 2011 to 2019. Further, fuzzy-set qualitative comparative analysis (fsQCA) was used to analyze the influence path of GDL. The results showed that the GDL of the YREB increased from 2015 to 2019, but the overall level was still not high, with high GDL mainly concentrated in the lower reaches. The GDL model changed from being environmentally driven and government supported in 2011 to being environmentally and economically driven since 2014. The core conditions for high GDL changed from economic development level (EDL) to scientific technological innovation level (STIL) and environmental regulation (ER). The path for improving GDL is as follows: In regions with high EDL, effective ER, moderate openness level (OL), and high STIL are the basis, supplemented by a reasonable urbanization scale (US). In areas with low EDL, reasonable industrial structure (IS) and STIL are the core conditions for development; further, EDL should be improved and effective ER and OL implemented. Alternatively, without considering changes to EDL, improvement can be achieved through reasonable OL and US or effective ER. This study provides a new method for exploring the path of GDL and a reference for governments to effectively adjust green development policies.

Basin-Scale Pollution Loads Analyzed Based on Coupled Empirical Models and Numerical Models

Pollutant source apportionment is of great significance for water environmental protection. However, it is still challenging to accurately quantify pollutant loads at basin-scale. Refined analytical methods combined the pollution discharge coefficient method (PDCM), field observation, and numerical model (Soil & Water Assessment Tool, SWAT) to make quantitative source appointment in the Tuojiang River, a key tributary of the upper Yangtze River. The chemical oxygen demand (COD), total nitrogen (TN), total phosphorus (TP), and ammonia nitrogen (N-NH4+) were analyzed. Results showed that the urban sewage treatment plant point source has the largest contribution to COD, TN, and N-NH4+, while TP is mostly from the agricultural sources throughout the year. The total inflowing loads of pollution sources are significantly affected by rainfall. The overall pollution characteristics showed that pollutant loads present in different seasons are as follows: wet season > normal season > dry season. The month with the highest levels of pollutants is July in the wet season. Among the nine cities, the city that contributes the most COD, TN and N-NH4+, is Neijiang, accounting for about 25%, and the city that contributes the most TP is Deyang, accounting for 23%. Among the sub-basins, the Fuxi River subbasin and Qiuxihe River subbasin contribute the most pollutant loads. The technical framework adopted in this paper can be used to accurately identify the types, administrative regions and sub-basins of the main pollution sources in the watershed, which is conducive to management and governance of the environment.

Environmental implications from the priority pollutants screening in impoundment reservoir along the eastern route of China's South-to-North Water Diversion Project

Screening priority pollutants from vast anthropogenic contaminants discharged into aquatic environment is urgent for protecting water quality definitely. The multi-criteria scoring method involved in the occurrence (O), persistence (P), bioaccumulation (B), ecological risk (Eco-T), and human health risk (Hum-T), was established for pollutants prioritization in waters and applied in Dongping Lake, the final impoundment reservoir along the eastern route of China's South-to-North Water Diversion Project (SNWDP). A total of 170 chemicals including heavy metals (HMs), volatile organic chemicals (VOCs), polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), phthalate esters (PAEs), and antibiotics (ANTs) were investigated as the candidates. Accordingly, 42 chemicals including 8 PAEs, 7 OCPs, 7 PCBs, 5 PAHs, 13 HMs, and 2 VOCs were made up the list of priority pollutants for Dongping Lake, suggesting the necessity of routine monitoring high priority groups and revising the existing list. Multiple risk assessment indicated higher ecological and human health risks induced by HMs than by organic pollutants. Spatial distribution of risks stressed the retention of toxic organic chemicals by the lake body and the accumulation of HMs along the transfer route, respectively, thus triggering ecosystem responses and potential effects on the water-receiving areas as expected.

Effects of Urbanization on Landscape Patterns in the Middle Reaches of the Yangtze River Region

The middle reaches of the Yangtze River region (MRYRR) are China’s first trans-regional urban agglomeration, located in the center of the Yangtze River Economic Belt. The MRYRR is an important ecological reserve, and its land cover changes are affected by both socio-economic development and geographical environment. In this paper, Landsat ETM/TM/OLI remote sensing images were used to monitor land use and landscape patterns from 1990 to 2015. Through supervised classification, land use transfer matrix, landscape pattern metrics and correlation analysis, the spatial-temporal patterns of land use change and its relationship with socio-economic in the study area were revealed. The results showed that: (1) the main land use types in the study area were cropland (CL) and forestland (FL), accounting for more than three-quarters of the study area. During the study period, built-up land (BL) increased, CL decreased, FL increased first and then decreased; (2) the BL expanded mainly by occupying CL and FL, and regional landscape pattern was gradually fragmented, with complex patch shape and increasing diversity and heterogeneity. Among them, the BL is gradually gathered, and the FL and CL are gradually fragmented; (3) in the past 25 years, the urbanization process in this region has been obvious, and the Gross Domestic Product (GDP) has increased by 36 times. The socioeconomic variables were positively correlated with BL, orchard (OL) and Shannon diversity index (SHID), and negatively correlated with CL, Wasteland (WL), mean patch size (MPS) and contagion size (CONTAG). The results showed that the urbanization development has a great impact on the region, and the ecological protection task is still challenging. It is necessary to protect high-quality cropland and draw a red line for ecological protection. We should strengthen the construction of ecological corridors and ecological nodes to adapt to regional sustainable development.

Assessing potential ecosystem service dynamics driven by urbanization in the Yangtze River Economic Belt, China

Ecosystem services (ESs) link natural and social processes and play an important role in sustaining ecological security, human well-being, and sustainable development. However, uncertainties in future socioeconomic land use drivers may result in very different land use dynamics and consequences for land-based ESs. In this study, land use transitions in the Yangtze River Economic Belt (YREB) were simulated in the short term (2018-2030), medium term (2030-2040), and long term (2040-2050) using the future land use simulation (FLUS) model based on the local shared socioeconomic pathways (SSPs). According to the projected land use types, six ESs were quantified and assessed regarding how they would evolve under particular land use changes. The results of land use simulations showed that the main features were urban sprawl and a decrease in cropland. In particular, intensive urban sprawl occurred around existing urban areas, and a large amount of cultivated land was converted into urban land. In the YREB, urban land will increase from 88,441 km² in 2018 to 156,173-192,900 km² in 2050, while the cropland area will decrease from 607,131 km² in 2018 to 500,183-596,313 km² in 2050. As a consequence of urban expansion, all ESs exhibited decreasing trends, except for several services under SSP1. Food production (FP), carbon storage (CS), water conservation (WC), soil retention (SR), air purification (AP), and habitat quality (HQ) will decline by 8.98-21.4%, 1.95-6.781%, 2.97-6.5%, 0.9-1.7%, 1.20-5.15%, and 6.11-12.86%, respectively. The ES integrative assessment indicated distinct provincial differences. Developed eastern provinces have higher populations and urbanization; however, these traits result in greater ES losses. We suggest that future land management should control the blind expansion of urban land and enhance the protection of cropland and natural habitats to reduce ES losses.

How Effective Is the Green Development Policy of China's Yangtze River Economic Belt? A Quantitative Evaluation Based on the PMC-Index Model

Although many countries around the world, especially China, highlight the strategy of green development, there has been little research evaluating the effectiveness of green development policies in local area. This study explores 16 policy texts with the theme of green development in the Yangtze River Economic Belt in China. Using the Policy Modeling Consistency Index (PMC-Index) model, the paper establishes a multi-input-output policy table and scientifically and systematically evaluates these policies. The results show that the average PMC index of the 16 policy texts is 6.83, indicating a high overall quality of policy texts. The index identifies two states of policy effectiveness as being good and excellent; 50% of the total texts fall into these categories and do not fall into the category of having a low level of policy effectiveness. Five indicators, including policy timeliness, social benefits, policy audience scope, and incentives and constraints, significantly impact the PMC-Index of the policy. Six representative policy samples were selected and analyzed. The advantages and disadvantages of the policy can be more fully understood by the degree of depression of the PMC's three-dimensional curved surface (PMC-Surface) model. Finally, the paper provides theoretical recommendations for the optimization of the green development policies.

Pharmaceuticals in two watersheds in Eastern China and their ecological risks

Pharmaceuticals are of increasing environmental concern due to their potential threat to aquatic ecosystems. Intensive human activities are a major factor influencing the level of pharmaceutical pollution in aquatic ecosystems. In this study, we investigated the occurrence, ecological risks of 31 pharmaceuticals and the possible influence of human activities on pharmaceutical distribution in two watersheds in the Yangtze River Delta, Eastern China. The target compounds were grouped into six categories: three non-steroidal anti-inflammatory drugs, ten antibiotics, six cardiovascular drugs, five hormones, six psychotropic drugs, and one antiparasitic. All target pharmaceuticals were detected in the surface water samples, with dexamethasone (100% of samples), tetracycline (100% of samples), and cefradine (100% of samples) being the dominant compounds (maximum concentrations of 686, 128, and 2280 ng/L, respectively). The total pharmaceutical concentrations were significantly higher in the urban watershed (711-2790 ng/L, mean = 1150 ng/L) than in the peri-urban watershed (467-1525 ng/L, mean = 863 ng/L) (p < 0.05). Distinct variation in the total pharmaceutical concentration also occurred between the dry season (507-2790 ng/L, mean = 1100 ng/L) and the wet season (467-1525 ng/L, mean = 943 ng/L). Ecological risk assessment showed that in the two watersheds, benzylpenicillin potassium, tetracycline hydrochloride, chlormadinone, ampicillin, cefotaxime acid, atorvastatin, sertraline hydrochloride, and oxazepam posed a medium potential risk (0.1 < risk quotient < 1), while norethisterone posed a high potential risk (risk quotient > 1). Redundancy analysis revealed that the concentrations of pharmaceuticals in various categories were positively correlated with land-use type (urban and agricultural land-use percentages), population density, and distance from town in both watersheds. Urban and agricultural activities were likely the main factors influencing the concentrations and composition of pharmaceuticals in these aquatic environments. Positive correlations were also found between total pharmaceutical concentrations and population density in both watersheds, suggesting a significant contribution of human disturbance to pharmaceutical pollution. The results provide useful information for pharmaceutical pollution control, ecological risk assessment, and sustainable water management at the watershed scale.

Impact of Regional Green Development Strategy on Environmental Total Factor Productivity: Evidence from the Yangtze River Economic Belt, China

Chinese government policy officially identify the Yangtze River Economic Belt (YREB) as one of regional green development strategies firstly in 2014. This strategy can be regarded as quasi-natural experiment, this paper aims to test its impact on regional environmental total factor productivity (TFP). First, slack-based measure model is used to calculate the environmental TFP from 2005 to 2017 at provincial level. Second, based on Chinese official statistics, differences-in-differences (DID) method is applied to construct an evaluation model of policy effect, combining with the kernel matching in propensity score matching (PSM) method. The results show that environmental TFP of YREB has significant spatial differences, with characteristic of high-east and low-west, its average level is 11.69 percentage points higher than the national average. YREB strategy promotes regional economic growth, but it does no effect on the regional environmental TFP yet. Modelling suggests that YREB strategy may play a role in the short term. From the significance of the control variables, infrastructure construction level is positively correlated with environmental TFP, while per capita GDP, financial development and energy consumption intensity have negative effect on environmental TFP. Based on this, policymakers should focus on green development, promoting industrial transformation, and enhancing environmental protection.

A holistic assessment of water quality condition and spatiotemporal patterns in impounded lakes along the eastern route of China's South-to-North water diversion project

Water quality is one of the key determinants for assessing effectiveness and success of water diversions, but rarely studied at a spatial scale that crosses large river basins. Multiple statistical methods and the water quality index (WQI) were used to assess overall condition and detect spatiotemporal patterns of water quality in a series of impounded lakes along the Eastern Route of China's South-to-North Water Diversion Project. Principal components analysis and analysis of variances identified three groups with distinct water quality characteristics: upstream Gaoyou Lake and Hongze Lake showing relatively higher nutrients, turbidity, and total suspended solids; downstream Dongping lake and Donghu Lake showing higher conductivity, total hardness, and chloride; and Luoma Lake and Nansi Lake intermediate between the two former groups. The WQI indicated overall "Good" water quality with an improving trend from upstream to downstream lakes. The upstream Gaoyou Lake had over 55% of the monitoring sites with "Moderate" water quality in all the seasons. Management should focus on preventing high nitrogen, phosphorus, turbidity, and total suspended solids in upstream lakes, high chloride in downstream lakes, high nitrogen during water diversion seasons, and high phosphorus during non-water diversion seasons. These findings greatly improved our understanding of the spatiotemporal water quality patterns of the impounded lakes, and can be used to develop water quality management strategies. This study exemplifies a methodology for investigating and securing water quality for inter-basin water transfer projects.

Modeling the Contribution of Crops to Nitrogen Pollution in the Yangtze River

Agriculture contributes considerably to nitrogen (N) inputs to the world's rivers. In this study, we aim to improve our understanding of the contribution of different crops to N inputs to rivers. To this end, we developed a new model system by linking the MARINA 2.0 (Model to Assess River Input of Nutrient to seAs) and WOFOST (WOrld FOod STudy) models. We applied this linked model system to the Yangtze as an illustrative example. The N inputs to crops in the Yangtze River basin showed large spatial variability. Our results indicate that approximately 6,000 Gg of N entered all rivers of the Yangtze basin from crop production as dissolved inorganic N (DIN) in 2012. Half of this amount is from the production of single rice, wheat, and vegetables, where synthetic fertilizers were largely applied. In general, animal manure contributes 12% to total DIN inputs to rivers. Three-quarters of manure-related DIN in rivers are from vegetable, fruit, and potato production. The contributions of crops to river pollution differ among sub-basins. For example, potato is an important source of DIN in rivers of some upstream sub-basins. Our results may help to prioritize the dominant crop sources for management to mitigate N pollution in the future.

Population and Economic Projections in the Yangtze River Basin Based on Shared Socioeconomic Pathways

The shared socioeconomic pathways (SSPs) were designed to project future socioeconomic developments as they might unfold in the absence of explicit additional policies and measures to limit climate forcing or to enhance adaptive capacity. Based on the sixth national population census and the third economic census data of China in 2010, this paper projects the population and economic conditions of the Yangtze River basin from 2010 to 2100 under the SSPs. The results showed that: (1) the population growth rate in most areas of the Yangtze River basin will decrease from 2021 to 2100. The population of the eastern Sichuan Province will decrease obviously, while it will increase obviously in Shanghai during this period. The population of the Yangtze River basin will decline from 2010 to 2100 under the SSPs except for SSP3; (2) The GDP (Gross Domestic Product) in most regions will increase by more than CNY 30 billion (Chinese Yuan) compared with 2010 and the total GDP will continue to rise after 2020; (3) The population of the three major urban agglomerations will decrease from 2020 to 2100. However, the GDP of the three major urban agglomerations will increase year by year, among which the YRDUA (Yangtze River Delta Urban Agglomeration) has obvious economic advantages. The GDP growth rate will maintain above 6% in 2020 under different SSPs, and then the growth rate will slow down or stall, even with negative growth in SSP1 and SSP4; (4) The GDP Per of the Yangtze River basin shows growth under different SSPs and it will maintain a growth rate of 6–9% until 2020. While the average annual growth rate of the SSP5 will be about 2.56% at the end of the 21st century, and it will remain at about 1% under other scenarios. This paper provides a scientific basis for the study of future population and socioeconomic changes and climate predictions for quantifying disaster risks.

Challenges to saving China's freshwater biodiversity: Fishery exploitation and landscape pressures

China has over 1320 freshwater fish species, 877 of which are endemic. In recent decades, over-exploitation and landscape pressures have threatened them and led to a severe aquatic biodiversity crisis. In response, large-scale fishing bans have been promulgated to protect freshwater biodiversity in major Chinese rivers since the early 1980s. Here, we present the historical background and current challenges to the fishing bans. Implementing large-scale fishing bans may help improve China's current freshwater biological resources and biodiversity to some extent. But implementing fishing bans alone is not sufficient to solve the crisis because of shortcomings of the current bans and expanding human pressures in most river basins. Thus, we recommend regulating other anthropogenic pressures, expanding duration and extent of current fishing regulations, establishing a comprehensive monitoring program, and initiating basin-scale ecological rehabilitation. These programs are also needed in other developing countries facing similar biodiversity crises and human pressures.

Eutrophication and heavy metal pollution patterns in the water suppling lakes of China's south-to-north water diversion project

This study used non-supervised machine learning self-organizing maps (SOM) in conjunction with traditional multivariate statistical techniques (e.g., hierarchical cluster analysis, principle component analysis, Pearson's correlation analysis) to investigate spatio-temporal patterns of eutrophication and heavy metal pollution in the water supplying lakes (i.e., the Gao-Bao-Shaobo Lake, GBSL) of the eastern route of China's South-to-North Water Diversion Project (SNWDP-ER). A total of 28 water quality parameters were seasonally monitored at 33 sampling sites in the GBSL during 2016 to 2017 (i.e., 132 water samples were collected in four seasons). The results indicated that: 1) spatially, the western and south-western GBSL was relatively more eutrophic and polluted with heavy metals; and 2) temporally, the lakes suffered from high risks of heavy metal contamination in spring, but eutrophication in summer while water quality in winter was the best among the four seasons. Two main potential sources of pollution and transport routes were identified and discussed based on the pollution patterns. These findings contributed considerably to providing in-depth understanding of water pollution patterns, as well as potential pollution sources in the water-supplying region. Such understanding is crucial for developing pollution control and management strategies for this mega inter-basin water transfer project.

Global trends in water and sediment fluxes of the world's large rivers

Water and sediment transport from rivers to oceans is of primary importance in global geochemical cycle. Against the background of global change, this study examines the changes in water and sediment fluxes and their drivers for 4307 large rivers worldwide (basin area ≥1000 km²) based on the longest available records. Here we find that 24% of the world's large rivers experienced significant changes in water flux and 40% in sediment flux, most notably declining trends in water and sediment fluxes in Asia's large rivers and an increasing trend in suspended sediment concentrations in the Amazon River. In particular, nine binary patterns of changes in water-sediment fluxes are interpreted in terms of climate change and human impacts. The change of precipitation is found significantly correlated to the change of water flux in 71% of the world's large rivers, while dam operation and irrigation rather control the change of sediment flux in intensively managed catchments. Globally, the annual water flux from rivers to sea of the recent years remained stable compared with the long-time average annual value, while the sediment flux has decreased by 20.8%.

Impacts of Precipitation and Temperature on Changes in the Terrestrial Ecosystem Pattern in the Yangtze River Economic Belt, China

The terrestrial ecosystem plays an important role in maintaining an ecological balance, protecting the ecological environment, and promoting the sustainable development of human beings. The impacts of precipitation, temperature, and other natural factors on terrestrial ecosystem pattern change (TEPC) are the basis for promoting the healthy development of the terrestrial ecosystem. This paper took the Yangtze River Economic Belt (YREB) as the study area, analyzed the temporal and spatial characteristics of TEPC from 1995 to 2015, and used spatial transfer matrix and terrestrial ecosystem pattern dynamic degree models to analyze the area transformation between different terrestrial ecosystem types. A bivariate spatial autocorrelation model and a panel data regression model were used to study the impacts of precipitation and temperature on TEPC. The results show that: (1) The basic pattern of the terrestrial ecosystem developed in a relatively stable manner from 1995 to 2005 in the YREB, and transformations between the farmland ecosystem, forest ecosystem, and grassland ecosystem were more frequent. The temporal and spatial evolution of precipitation and temperature in the YREB showed significant regional differences. (2) There was a significant negative bivariate global spatial autocorrelation effect of precipitation and temperature on the area change of the forest ecosystem, and a positive effect on the area change of the settlement ecosystem. The local spatial correlation between precipitation or temperature and the terrestrial ecosystem showed significant scattered distribution characteristics. (3) The impacts of precipitation and temperature on TEPC showed significant regional characteristics on the provincial scale. The impact utility in the tail region is basically negative, while both positive and negative effects exist in the central and head regions of the YREB. Moreover, the impact showed significant spatial heterogeneity on the city scale. (4) The Chinese government has promulgated policies and measures for strategic planning, ecological environment protection, and economic support, which could effectively promote ecological and sustainable development of the YREB and promote the coordinated development of the ecology, economy, and society in China.

The Impact of High-Tech Industry Agglomeration on Green Economy Efficiency—Evidence from the Yangtze River Economic Belt

Development is the eternal theme of the times. However, the transformation of the development mode is imminent, and we should abandon the extensive economic development mode and turn to the efficient development of an intensive mode. The high-tech industry will be the decisive force in future industrial development. The agglomeration of the industry will help form economies of scale, thereby improving the effective allocation of resources and promoting productivity. The increase in green economy efficiency is a key factor in achieving green development and an important indicator of achieving the coordinated development of economic development and environmental protection. Therefore, in this study, we try to improve the efficiency of the green economy through industrial agglomeration to achieve green development. In order to solve this problem, we took the Yangtze River Economic Belt as the research object, used Super Slacks-based Measure (SBM) data envelopment analysis (DEA) and general algebraic modeling system (GAMS) to study the green economy efficiency, and then used the system generalized moment method (SGMM) to study the impact of high-tech industry agglomeration on green economy efficiency. According to the empirical test, we found that (1) the green economy efficiency of the Yangtze River Economic Belt shows a volatile upward trend, (2) the green economy efficiency of the Yangtze River Economic Belt differs with time and by region, (3) the agglomeration of the high-tech industry has a lagging effect on the improvement of green economy efficiency, and (4) the regression coefficients of economic development and foreign direct investment are positive and those of environmental regulation and urbanization are negative. Finally, in this paper, we provide corresponding policy recommendations to promote the agglomeration of high-tech industries, thereby improving the efficiency of the green economy.

Does China's Yangtze River Economic Belt policy impact on local ecosystem services?

The ecological protection of the Yangtze River Economic Belt (YREB) is one part of China's national strategy, and to identify the spatiotemporal variation of ecosystem service values (ESV) and examine the YREB policies performances can provide effective knowledge and supports for making ecological protection policies. In this paper, the ESV of YREB's 11 units were measured based on equivalent factor value method. Panal data and regression discontinuity model were used to discuss the impact of the ecological protection policies issued 2012 and 2014 on the ESVs. The results showed that: (1) From 2009 to 2016, the total ESVs of the YREB increased from 617.49 billion USD to 844.84 billion USD, showing a pattern of slow increase (2009-2012), substantial growth (2012-2014) and stability of high level (2014-2016). Forestland and water body were the key types of land to ecological protection. For the average of all measured years, the two lands accounted for 43.24% of total ecological land and provided 82.36% of total ESVs;(2) Generally, all the units were closely related to the ecological protection policy and were positively affected. In the first period (2009-2012), the ESVs of 11 units had three statuses: declined, kept steady and moderately increased. After strong policy implementation, all units rose sharply (2012-2014) and maintained a steady increase at a high level (2014-2016); (3) Ecological protection policies have a significant positive effect on the ESVs. The policy in 2012 suppressed the downward trend of ESVs increase and the policy in 2014 had a positive impact to increase ESVs. This study proved that possible to achieve a win-win situation of urban development and ecological environmental protection by implementing ecological protection policies.

Flux of organic carbon burial and carbon emission from a large reservoir: implications for the cleanliness assessment of hydropower

Accurately quantifying the budget of carbon sources and sinks in hydropower reservoirs is important for evaluating the cleanliness of hydroelectricity. However, current research on carbon emissions from reservoirs has rarely taken into account the organic carbon (OC) buried in sediment. Only greenhouse gas emissions from the water-air interface at reservoirs have been examined, which would result in an overestimation of the greenhouse effect of reservoirs. In November 2017, this study investigated the distribution of sediment in the Hongfeng Reservoir (HFR) in southwest China, a typical large hydropower reservoir, by using an underwater seismology monitoring system. We estimated the flux of OC into sediment using the results of a sediment survey and a dataset compiled from references. Our results show that, the HFR retained 200,715 t of OC in the sediment since its impounding after dam construction to the sampling year of 2017, when the average burial flux was 3,521 t-C a^-1 (10⁶ g C a^-1) and the modern burial flux was 5,449 t-C a^-1. After excluding the exogenous OC, the modern valid carbon sink of the sediment was 4,632 t per year. Under the current state of the reservoir, taking the modern valid carbon sink value, the carbon emissions from the reservoir's surface, and the discharge water from the dam into consideration, the net carbon sink of the HFR is found to be 1,098.9 t-C a^-1. If the hydroelectricity generated by the reservoir is converted to a carbon sink, then the total net carbon sink becomes 12,972.9 t-C a^-1. This work argues that both reservoir sediment and hydroelectricity are important carbon sinks and both should be included in assessments of the greenhouse effects of reservoirs.

Quantifying the impacts of climate variability and human interventions on crop production and food security in the Yangtze River Basin, China, 1990-2015

Food security has become a global policy concern due to its important role in sustaining development and human well-being. Using spatial autocorrelation analysis of statistical data at the county-level, this study quantifies the change in spatial and temporal patterns of crop production in the Yangtze River Basin of China since 1990 and draws out policy implications for food security in the country. Four panel models were constructed to examine in what ways and to what extent four major factors (climate variation, sown area, fertilizer use intensity, and population size) influence the capacity for crop production. The results show that total crop production increased by 15.2% in 1990-2015, while there exists significant spatial heterogeneity in crop output across the upper, middle and lower sections of the Basin. The spatial agglomerations of crop production (hotspots) in the Basin have varied significantly over time, with the hotspots in the lower section having disappeared since 2000. Over a quarter of the total number of counties (649) in the region have experienced a high risk of food shortages, with 19.4-27.4% of counties having experienced severe or moderate shortages of per capita food availability since 1990. This percentage increased from 9.3% to 16.2% in the lower section, while it declined from 53.9% in 1990 to 41.9% in 2015 in the upper section and remained unchanged in the middle section. The variables of sown area, fertilizer use intensity, total precipitation in the growing seasons and time (Year) have significant positive effects on the growth of crop production, but mean temperature in the growing seasons of crops and total population have significant and negative relationships with crop outputs. Establishing a reliable food supply system, safeguarding high-quality cultivated land and increasing fertilizer use efficiency are suggested as imperative countermeasures to mitigate food security risks in the Yangtze River Basin.

Threshold Effect of High-Tech Industrial Scale on Green Development—Evidence from Yangtze River Economic Belt

Based on the panel data of 11 regions in the Yangtze River Economic Belt from 1998 to 2016, we tested and analyzed the effects of high-tech industrial expansion on green development. For these regions in the Yangtze River Economic Belt, we wanted to investigate the potential linear relationship between the scale of high-tech industry and green development or the possible threshold effect. We wanted to determine if this relationship is different in various regions of the Yangtze River Economic Belt. According to the empirical test, we found that: (1) for the entire Yangtze River Economic Belt region, the influence of high-tech industrial scale on green development doubled the threshold effect, and a marginal efficiency diminishing effect existed with the further increase in scale; (2) due to the differences among the regions, the threshold effect was different in different regions, with a double threshold effect in the lower reaches, a single threshold effect in the middle reaches, and no threshold effect in the upper reaches; and (3) regarding the high-tech industrial scale, the downstream areas were too large to weaken its promoting effect on green development. In the middle reaches, the positive impact on green development was still increasing, and the high-tech industrial scale should be further expanded. However, in the upstream areas, high-tech industrial scales did not reach the threshold value and the relationship between the high-tech industrial scale and green development was linear. Therefore, local high-tech industries should be cultivated and developed.

Spatial Pattern Evolution and Optimization of Urban System in the Yangtze River Economic Belt, China, Based on DMSP-OLS Night Light Data

It is of great significance to research the spatial pattern of the urban system of the Yangtze River economic belt to analyze the characteristics and laws of the spatial structure of the Yangtze River economic belt and to promote the optimal development of the urban system of the Yangtze River economic zone. In this paper, the time data of the Yangtze River economic zone are corrected using Landsat satellite data and the clustering analysis method. The threshold of the urban built area is obtained by comparing the auxiliary data with other auxiliary data. Based on this threshold, a total of eight typical landscape pattern indicators—including the total area of the landscape, the total patch number, and the aggregation index—are used, and then FRAG-STATS 4.2 software is used to analyze the spatial pattern of urban development in the Yangtze River economic zone from 1992 to 2013. The results show the following: (1) During the period from 1992 to 2013, the urbanization of the Yangtze River economic zone expanded rapidly; the area of urban built-up area increased by a factor of 9.68, the number of patches increased by a factor of 2.39, and the patch density increased greatly, indicating that the Yangtze River economic zone, with an increasing number of towns and urban areas, continues to expand. (2) The complexity of the landscape patch shape gradually increased, the small and medium-sized cities continued to grow, more small towns emerged, and the total length of the border and the average density had average annual growth rates of 21.56% and 21.58%; the degree of aggregation and the mutual influence are increasing. (3) The maximum plaque index and the aggregation index show an overall declining trend. However, there are some fluctuations and disorder in the process of evolution, such as the total area of the landscape, the total patch number and the total patch density, which reflects that the Yangtze River economic zone is in the process of urbanization and has irregular and disordered characteristics.

Ecosystem services trade-offs and determinants in China's Yangtze River Economic Belt from 2000 to 2015

Ecosystem services (ES) play an important role in sustaining ecological security, sustainable development and human well-being. This study investigates spatio-temporal changes in five key ES in the Yangtze River Economic Belt of China in 2000-2015-water conservation (WC), soil retention (SR), carbon sequestration (CS), biodiversity conservation (BC) and food supply (FS), by applying three ecological models (InVEST, RUSLE, CASA). Employing scenario simulations, the study quantifies distinct effects of significant factors on ES changes. Using spatial overlapping and Spearman's rank correlation respectively, the study distinguishes spatial patterns of synergies and trade-offs between five ES at the grid and city-scales. The results show that CS, FS, WC and SR presented an overall upward trend, increasing by 22.7%, 16.9%, 6.4% and 4.7%, respectively, while BC remained steady with a marginal degradation. Change in these five ES exhibited dramatic spatial heterogeneity. Across 131 cities, 98.5% of which increased in CS, 87.7% in WC, 68.5% in FS, and 53.1% in SR, while more than half experienced slight degradation in BC. There is high heterogeneity and a great diversity among spatial distributions of ES synergies and trade-offs, which is largely dependent on ES pairs and spatial patterns of land use. Land use/land cover change was the dominant force driving changes in SR, BC and CS, while meteorological factors exhibited a greater effect on WS change than land use/land cover change. The paper examines the synergies between WC-SR, CS-BC and BC-FS on the city level, while WC-BC exhibits significant trade-offs, and no significant relationships for other ES pairs. It is imperative that ES trade-offs at different scales are incorporated to strengthen ecological protection and management policies in project implementation, maintaining ES within vital regions in China. More sophisticated methods and more ES indicators need to be incorporated to enhance the robustness and completeness of assessment.

Evaluating indirect and direct effects of eco-restoration policy on soil conservation service in Yangtze River Basin

The conservation impacts of policies that promote large-scale ecological restoration of ecosystem services and socio-economic development are well documented around the world. However, the effect of socio-economic development resulting from such policies on ecosystem services is rarely analysed, although it is important to do so if these policies are to be sustainable. We analysed the socio-economic impacts of soil conservation services from 2000 to 2015 in the Yangtze River Basin under the Grain to Green Programme (GTGP). Also we assessed the driving forces behind the programme: conservation policies, urbanization, agricultural development, and population growth. Our results show that during 2000-2015, cultivated area decreased by 7.5%, urban area increased by 67.5%, forest area increased by 2.1%, and soil erosion was reduced by 19.5%. The programme not only contributed significantly to an improvement in soil conservation services but also enhanced them significantly through faster urbanization. Furthermore, vegetation cover and crop yields increased synergistically, mainly due to high-efficiency agriculture that reduced the negative effect of the GTGP on agricultural production. Overall determining the indirect and direct effects of the GTGP on soil conservation and agricultural production are important for furthering our understanding of the long-term effects of ecological restoration policies, and the present study offers practical insights for ecological restoration of other watersheds.