Since the launch of China’s reform and opening up policy, the process of urbanization in China has accelerated significantly. With the development of cities, inter-city interactions have become increasingly close, forming urban agglomerations that tend to be integrated. Urban agglomerations are regional spaces with network relationships and hierarchies, and have always been the main units for China to promote urbanization and regional coordinated development. In this paper, we comprehensively consider the network and hierarchical characteristics of an urban agglomeration, while using urban flow to describe the interactions of the inter-city networks and the hierarchical generalized linear model (HGLM) to reveal the hierarchical driving mechanism of the urban agglomeration. By coupling the HGLM with a cellular automata (CA) model, we introduced the HGLM-CA model for the simulation of the spatial expansion of an urban agglomeration, and compared the simulation results with those of the logistic-CA model and the biogeography-based optimization CA (BBO-CA) model. According to the results, we further analyzed the advantages and disadvantages of the proposed HGLM-CA model. We selected the middle reaches of the Yangtze River in China as the research area to conduct this empirical research, and simulated the spatial expansion of the urban agglomeration in 2017 on the basis of urban land-use data from 2007 and 2012. The results indicate that the spatial expansion of the urban agglomeration can be attributed to various driving factors. As a driving factor at the urban level, urban flow promotes the evolution of land use in the urban agglomeration, and also plays an important role in regulating cell-level factors, making the cell-level factors of different cities show different driving effects. The HGLM-CA model is able to obtain a higher simulation accuracy than the logistic-CA model, which indicates that the simulation results for urban agglomeration expansion considering urban flow and hierarchical characteristics are more accurate. When compared with the intelligent algorithm model, i.e., BBO-CA, the HGLM-CA model obtains a lower simulation accuracy, but it can analyze the interaction of the various driving factors from a hierarchical perspective. It also has a strong explanatory effect for the spatial expansion mechanism of urban agglomerations.
Residential segregation is a dual process of socio-spatial differentiation in residents and spatio-temporal heterogeneity in dwelling. However, most of the existing studies are established from the single perspective of urban residents based on demographic data, which is difficult to reveal the dynamics and complex spatial reconstruction within and between cities. With the characteristics of both stability and timeliness, the rapidly changing housing market is one of the processes and results of socio-spatial reconfiguration, and it is undoubtedly a better lens to observe residential segregation. This paper adopts methods such as multi-group segregation index, multi-scalar segregation profiles, and decomposition of segregation index, with Nanjing and Hangzhou as case cities, and establishes multi-scalar segregation profiles and comparative models based on three geographical scales of census tract, block and grid, and different residential types. A quantitative study was conducted on the degree and pattern of multi-scalar residential segregation in Nanjing and Hangzhou from 2009 to 2018. The paper found that the spatial segregation index is an improvement of the non-spatial segregation index. There are differences between Nanjing and Hangzhou in the evolution process of residential segregation. Nanjing has a higher degree of spatial differentiation as a whole, among which spatial components have a more significant impact.
Administrative divisions are the important foundation of national governance and social development, and the adjustment of administrative divisions is a critical way to promote regional coordinated development. Under the background of globalization and regionalization, timely adjustment of administrative divisions is a major step to reconstruct the regional development pattern. In the perspective of regional coordinated development, this paper constructs an Administrative Rank Potential Energy (ARPE) model to explore the mechanisms of administrative division adjustment (ADA) under coordinated regional development based on the theory of regional interaction, spatial field energy model and power exponential function. The results show that: (1) The development potential and influence of an administrative region are closely related to the administrative jurisdiction, administrative resources, and the potential of regional coordinated development. (2) The growth rate of ARPE in the study area from 2010 to 2015 was 20.7% compared to the period 2005 to 2010, and the potential for coordinated development increased to 3.05% from 0.21% before the “cancelling” the prefecture-level city of Chaohu. (3) The measurement results of the usefulness of ADA can not only distinguish the complex impacts brought about by social development, but also accord with real social and economic development conditions. The ARPE focuses on the both regional integrated development and individual development, thereby serving as a reference for explaining and evaluating adjustments to administrative divisions at the macro- and micro-scales.
This paper studied the fertilizer rate (FR), fertilizer use efficiency (FUE) and fertilizer overuse rate (FOR) of rice, corn and wheat in China from 1998 to 2018 and briefly analysed the reasons why farmers were willing to apply more fertilizers. (1) The FR of grain in China reached 373.7 kg/ha in 2018, an increase of 26.8% compared to that in 1998. In 2018, the FR for corn was the highest, at 411.2 kg/ha, compared to the values of 338.3 kg/ha for rice and 371.7 kg/ha for wheat. (2) In recent years, the FUE of grain in China has obviously improved, with values of 32.9% in 1998, 36.7% in 2008, and 39.3% in 2018. In 2018, the FUE for rice was the highest (41.2%), followed by that for corn (39.9%), and the FUE for wheat was the lowest (36.0%). (3) By 2018, fertilizer was overused in all zones of rice, corn and wheat. In 2018, the average FOR for wheat reached 69.0%, which was 35.9% higher than that for corn and 42.8% higher than that for rice. (4) The lower price of chemical fertilizers was the main reason leading to overapplication. (5) Establishing market mechanisms and adjusting regional planting structures can be effective in reducing the application of chemical fertilizers.
To realize efficient and sustainable poverty alleviation, this study firstly investigated the identification of multidimensional poverty and relative poverty, and then explored relevant poverty alleviation pathways. Poverty levels in 31 provinces including the autonomous regions and municipalities of China were identified at the county level using the average nighttime light index (ANLI), county multidimensional development index (CMDI), and a method combining multidimensional poverty index and relative poverty standards. Poverty alleviation pathways for poverty-stricken counties were explored from the aspects of industry, education, tourism and agriculture. The results revealed that nearly 60% of counties in China were primarily under relative poverty, most of which were corresponded to light relative poverty. In terms of ANLI and CMDI, 63% and 79% of the national poverty-stricken counties, as of 2018, could be identified, suggesting that CMDI had a higher performance for identifying poverty at the county level. In terms of poverty alleviation pathways, 414, 172, 442, and 298 poverty-stricken counties were receptive to industry poverty alleviation, education poverty alleviation, tourism poverty alleviation, and agriculture poverty alleviation, and 61% of counties had more poverty-causing factors, implying that multidimensional poverty alleviation is suitable in most of the counties.
Protected areas have a double mandate of both “protection” and “use.” Nature- based tourism is considered an effective tool in terms of environmental conservation. Understanding the causes and consequences of a spatiotemporal succession of tourism construction is an important channel to explore the changes of tourism-environment interaction in the protected area. To analyze the spatio-temporal variations in tourism construction lands, we adopted Mt. Bogda as an example. We systematically quantified the interaction between these changes and environmental variables and explored the evolution process of tourism-environment interaction of the mountainous protected area in the northwest arid region. Our results revealed the following: (1) In the Bogda protected area, the proportion of tourism construction lands first appeared to be increasing, then decreasing dramatically, and finally growing slowly. The spatial expansion of tourism construction lands followed the “core-periphery” pattern, respectively showing shapely infilling, reasonable agglomeration, barycenter shift, and outlying growth from 1990 to 2018 as the stages of concentrating on the core. (2) The higher land-use intensity of tourism construction drove the changes of landscape fragmentation, diversity, stability, primitive, and nature degree in the protected area. The coupling coordination between tourism and the environment in the Bogda area decreased at first, and then slowly increased. Meanwhile, tourism did not cause irreversible damage to the natural environment, and the coupling coordination degree between tourism and the environment was still in the state of balanced development. It expressed the states of original balanced, development exceeds environment and barely balanced, and superiorly balanced. The historical evolution of tourism-environment interaction in Bogda reflects the pattern of periodic changes in China’s protected areas to a certain extent.
China is in a critical period of transforming from the oil and gas era to the renewable energy era. To better understand the process of energy interaction between China and the rest of the world, this study aimed to investigate the basic theoretical cognition of global energy interaction and analyze the pattern and changes of energy interaction between China and the rest of the world with the method of complex networks, multi-region input-output analysis, and other technical methods. The main findings are as follows: (1) Chinas coal-based energy production structure and the huge demand for oil and gas indicate that ensuring overseas oil and gas supply is the most direct logic of energy interaction between China and the rest of the world, and the interaction scopes are mainly concentrated in oil- and gas-rich countries and regions. (2) With the development of renewable energy, the logic of energy interaction of China with the rest of the world has changed from countries and regions rich in oil and gas to countries with global renewable energy development and installation needs for its comparative advantages for manufacturing, which forms a renewable energy trade map that covers all major countries and regions in the world. (3) The overseas energy investment target of China has expanded from a limited number of host countries to Europe, Southeast Asia, and other countries and regions. The investment business is not only limited to the oil and gas field, but also expanded to solar energy, wind energy, hydro-power, and other renewable electricity generation projects. (4) As a global manufacturing and trading power, part of the energy consumed by China is embodied in the global production network and trade network for redistribution. The scope of energy interactions between China and the world will further expand to countries with general commodity trade relations with China, forming the global “energy hub” function. This study can provide a theoretical perspective and decision-making for a deeper understanding of the energy interactions between China and the world, maintaining national energy security, and participating in global energy economic governance.
With the implementation of the Grain for Green Project, vegetation cover has experienced great changes throughout the Loess Plateau (LP). These changes substantially influence the intensity of evapotranspiration (ET), thereby regulating the local microclimate. In this study, we estimated ET based on the Penman-Monteith (PM) method and Priestley-Taylor Jet Propulsion Laboratory (PT-JPL) model and quantitatively estimated the mass of water vapor and heat absorption on the LP. We analyzed the regulatory effect of vegetation restoration on local microclimate from 2000 to 2015 and found the following: (1) Both the leaf area index (LAI) value and actual ET increased significantly across the region during the study period, and there was a significant positive correlation between them in spatial patterns and temporal trends. (2) Vegetation regulated the local microclimate through ET, which increased the absolute humidity by 2.76-3.29 g m?3, increased the relative humidity by 15.43%-19.31% and reduced the temperature by 5.38-6.43°C per day from June to September. (3) The cooling and humidifying effects of vegetation were also affected by the temperature on the LP. (4) Correlation analysis showed that LAI was significantly correlated with temperature at the monthly scale, and the response of vegetation growth to temperature had no time-lag effect. This paper presents new insights into quantitatively assessing the regulatory effect of vegetation on the local microclimate through ET and helps to objectively evaluate the ecological effects of the Grain for Green Project on the LP.
With so many sports becoming increasingly popular, sports have come to play an important role in promoting the process of globalization and formatting the world city network (WCN). Previous studies have constructed the WCN based on the distribution of international sport federations (ISFs) and the sites of international sport events (ISEs), but there is still a lack of systematic research on the intercity connections caused by ISEs. Taking three most recent Olympic Games as cases, this paper explores intercity connections and WCN based on ISEs. The results show that (1) the Olympic WCN has city nodes around the world except in Antarctica, and the number and activity values of the cities in host countries may increase intensively during the Olympic Games. (2) A hierarchical city system with four tiers (global central cities, specialized central cities, national central cities and specialized cities) is formed by the intercity connections caused by the Olympic Games. (3) The WCN based on the Olympic Games, is made up of many subnetworks, while many differences occur due to the diverse decisions made by the Organizing Committee for the Olympic Games (OCOG), host cities or even host countries in the events associated with sponsorship activity and publicity activity. This study not only broadens the relevant fields of sports culture-oriented WCN research but also explores the instability of the WCN, which makes it an effective reference for WCN research based on ISEs.
Large regional differences and uneven regional development are fundamental challenges for China. Balanced regional development is an important issue in research on development geography. This study reviews the course of balanced regional development in China and summarizes its characteristics in each period. The results show that inter-regional development in China has undergone successive periods of balanced and unbalanced development. Each period has enhanced social development and contributed to a more balanced regional development. This paper discusses the scientific connotation of balanced regional development, and invokes sustainable development theory to argue that we should pay attention to the differences in resource endowments among regions, and solves the imbalance among the economy, humans, and nature to promote the spatial balance of regional development and green development for better coordination between economy and ecology. The balanced promotion of the well-being of people in each region is the ultimate goal of balanced regional development. We then use concepts from development geography to examine China’s path of balanced regional development from the three perspectives of society, the economy, and ecology. Suggestions are also provided for the balanced development of China’s regions and the improvement of public well-being.
The Yangtze River Watershed in China is a climate change hotspot featuring strong spatial and temporal variability; hence, it poses a certain threat to social development. Identifying the characteristics of and regions vulnerable to climate change is significantly important for formulating adaptive countermeasures. However, with regard to the Yangtze River Watershed, there is currently a lack of research on these aspects from the perspective of natural and anthropogenic factors. To address this issue, in this study, based on the temperature and precipitation records from 717 meteorological stations, the RClimDex and random forest models were used to assess the spatiotemporal characteristics of climate change and identify mainly the natural and anthropogenic factors influencing climate change hotspots in the Yangtze River Watershed for the period 1958-2017. The results indicated a significant increasing trend in temperature, a trend of wet and dry polarization in the annual precipitation, and that the number of temperature indices with significant variations was 2.8 times greater than that of precipitation indices. Significant differences were also noted in the responses of the climate change characteristics of the sub-basins to anthropogenic and natural factors; the delta plain of the Yangtze River estuary exhibited the most significant climate changes, where 88.89% of the extreme climate indices varied considerably. Furthermore, the characteristics that were similar among the identified hotpots, including human activities (higher Gross Domestic Product and construction land proportions) and natural factors (high altitudes and large proportions of grassland and water bodies), were positively correlated with the rapid climate warming.
Glaciers are a reliable freshwater resource in arid regions of West China and the vulnerability of its changes is closely related to regional ecosystem services and economic sustainable development. Here, we took the Qilian Mountains as an example and analyzed the spatiotemporal characteristics of glacier changes from 1998 to 2018, based on remote sensing images and the Second Chinese Glacier Inventory. We estimated the basic organizational framework and evaluation index system of glacier change vulnerability from exposure, sensitivity and adaptability, which covered the factors of physical geography, population status and socio-economic level. We analyzed the spatial and temporal evolutions of glacier change vulnerability by using the vulnerability evaluation model. Our results suggested that: (1) Glacier area and volume decreased by 71.12±98.98 km2 and 5.59±4.41 km3, respectively, over the recent two decades, which mainly occurred at the altitude below 4800 m, with an area shrinking rate of 2.5%. In addition, glaciers in the northern aspect (northwest, north and northeast) had the largest area reduction. Different counties exhibited remarkable discrepancies in glacier area reduction, Tianjuan and Minle presented the maximum and minimum decrease, respectively. (2) Glacier change vulnerability level showed a decreasing trend in space from the central to the northwestern and southeastern regions with remarkable differences. Vulnerability level had increased significantly over time and was mainly concentrated in moderate, high and extreme levels with typical characteristics of phases and regional complexity. Our study can not only help to understand and master the impacts of recent glacier changes on natural and social aspects but also be conducive to evaluate the influences of glacier retreat on socio-economic developments in the future, thus providing references for formulating relevant countermeasures to achieve regional sustainable development.
Urban resilience is an emerging research topic of urban studies, and its essence is described by the ability of cities to resist, recover, and adapt to uncertain disturbances. This paper constructs a “Size-Density-Morphology” urban ecological resilience evaluation system, uses a coupling coordination degree model to measure the degree of coupling coordination between urbanization and ecological resilience in the Pearl River Delta from 2000 to 2015, and conducts an in-depth discussion on its spatiotemporal characteristics. The results show the following. (1) From 2000 to 2015, the urbanization level of cities in the study area generally increased while the level of ecological resilience declined. The coupling coordination degree between the two systems decreased from basic coordination to basic imbalance. (2) In terms of spatial distribution, the coupling coordination degree between urbanization and ecological resilience of cities presented a circular pattern that centered on the cities at the estuary of the Pearl River and increased toward the periphery. (3) Ecological resilience sub-systems played variable roles in the coupling coordination between urbanization and ecological resilience. Specifically, size resilience mainly played a reverse blocking role; the influence of morphology resilience was generally positive and continued to increase over time; the effect of density resilience was positive and continued to decline and further became negative after falling below zero. The main pathways for achieving coordinated and sustainable development of future urbanization and ecological resilience in the Pearl River Delta include: leading the coordinated development of regions with new urbanization, improving ecological resilience by strictly observing the three areas and three lines, adapting to ecological carrying capacity, and rationally arranging urban green spaces.
In 2020, the decisive victory of building a moderately well-off society in all aspects means that absolute poverty in rural China has been completely eliminated. Consolidating and expanding the achievements of poverty alleviation and establishing a long-term mechanism to solve relative poverty have become key issues in high-quality development of underdeveloped areas. In this study, human-earth system is employed to analyze the element composition, structural organization and functional state of underdeveloped areas. The results show that poverty in underdeveloped areas stems from the lack of the coupling and coordinating mechanism among human, economic, resource and environmental elements, which is not conducive to transforming the ecological advantages into the advantages of regional development. In the antipoverty stage, underdeveloped areas innovate the human-earth coupling and coordinating mechanism through a series of targeted measures, promote the organic combination of poverty alleviation, ecological conservation and sustainable development, and boost the transformation of regional development and the increase of farmers’ incomes. Focusing on the 14th Five-year Plan (2021-2025) and the long-term goal of 2035, governments in underdeveloped areas should make full use of the policy support to explore scientific methods of modern governance and sustainable development. In particular, it is necessary to practice the concept that “clear waters and lush mountains are invaluable assets” and take the road of the ecologicalization of industry and the industrialization of ecology by establishing a policy system of “green land”, “green people”, “green industry” and “green right”, thus building an endogenous growth mechanism of sustainable poverty alleviation and green development in China’s underdeveloped areas.
The westerly winds and East Asian summer monsoon play a leading role in climate change of southwestern North America and eastern Asia since the Last Glacial Maximum (LGM), respectively. Their convergence in arid and semi-arid regions of the Asian continent (AAC) makes the regional climate change more complicated on the millennial-scale. There are still limitations in applying paleoclimate records and climate simulations of characteristic periods to investigate climate change patterns since the LGM in this region. In this study, we adopt two indexes indicating effective moisture and rely on a continuous simulation, a time slice simulation, and numerous paleoclimate records to comprehensively investigate the climate change modes and their driving mechanisms since the LGM in AAC. Results demonstrate a millennial-scale climate differentiation phenomenon and three climate change modes possibly occurring in AAC since the LGM. The western AAC largely controlled by the westerly winds is featured as wet climates during the LGM but relatively dry climates during the mid-Holocene (MH), coinciding with the climate change mode in southwestern North America. Conversely, dry conditions during the LGM and relatively wet conditions during the MH are reflected in eastern AAC governed by the East Asian summer monsoon, which leans to the climate change mode in eastern Asia. If climate change in central AAC is forced by the interaction of two circulations, it expresses wet conditions in both the LGM and MH, tending to a combination of the southwestern North American and eastern Asian modes. Precipitation and evaporation exert different intensities in influencing three climate modes of different periods. Furthermore, we identify the significant driving effects of greenhouse gases and ice sheets on westerly-dominated zones of AAC, while orbit-driven insolation on monsoon-dominated zones of AAC.
Vegetation plays an important role in the dry deposition of particles with significant spatial variability, but the magnitude remains unclear at the global scale. With the aid of satellite products, this study estimated the vegetation-related dry deposition of fine particulate matter (PM2.5). Methodologically, dry deposition was first calculated using an empirical algorithm. Then, deposition on the leaf surface was estimated to evaluate the influence of vegetation. Our results showed that the mean deposition velocity (Vd) of global PM2.5 was 0.91×10?3 µg·m?2·s?1, with high velocities observed in sparsely vegetated regions because of the high friction velocity. Under the combined effect of the PM2.5 mass concentration and deposition velocity, the global mean dry deposition reached 0.47 g·m?2·yr?1. Global vegetation absorbed 0.26 g·m?2·yr?1 from PM2.5 pollution sources, contributing 54.98% of the total dry deposition. Spatially, vegetation-related dry deposition was high in the Amazon, Central Africa and East China due to dense vegetation coverage or serious pollution. Temporally, the increasing trends were mainly in Central Africa and India because of worsening air pollution. The results of this study helped to clarify the impact of vegetation on air pollution, which supported related land management and planning for air quality improvement.
The article considers the long-term (1941-2018) transformation of the Krasnodar valley reservoir, the largest in the North Caucasus. The main functions of the Krasnodar reservoir are irrigation of rice systems and flood protection of land in the Krasnodar reservoir region and the Republic of Adygea. According to topographic maps, Landsat satellite images (1974-2018) and field observations (2016-2018), four stages of transformation of the floodplain reservoir are identified. The selected stages are characterized by both natural causes (the transformation of the filling deltas into the extended deltas, etc.) and man-made causes (runoff diversions in the delta areas, etc.). The key factor of transformation is the formation of deltas of rivers flowing into the reservoir. Each of the selected stages, against the background of a gradual reduction in the area and volume of the reservoir, is characterized by the peculiarities of the formation of river deltas with the formation of genetically homogeneous sections of delta regions. During the period of operation of the reservoir, the delta of the main Kuban River moved up to 32.4 km and took away an area of 35.4 km2 of the reservoir. During the formation of the deltas of the Kuban and Belaya rivers, a bridge was formed on the Krasnodar reservoir. The evolution of the delta regions led to the division of the reservoir into two autonomous reservoirs. The total area of the delta regions was 85.9 km2 by 2018, i.e., 21% of the initial area of the reservoir. The transformation of the Krasnodar reservoir leads to a decrease in its regulated volume and gradual degradation.
Climate change is a global environmental crisis, but there have been few studies of the effects of climate change on cereal yields on the Tibetan Plateau. We used data from meteorological stations and statistical yearbooks to assess the impacts of climate change on cereal yields in Tibet. Three types of statistical models were selected: fixed-effects model, first-difference models, and linear detrending models. We analyzed the impacts of climate change (including the minimum temperature, precipitation, growing degree days and solar radiation) on cereal yields in Tibet from 1993 to 2017 at the county, prefecture-level city, and autonomous region scales. The results showed that the sensitivity of cereal yields in Tibet to temperature (minimum temperature and growing degree days) was greater than their sensitivity to precipitation and solar radiation. The joint impacts of climate variables were positive, but the sensitivity and significance varied in different regions. The impacts of minimum temperature, precipitation, and solar radiation were positive in all cities, apart from the negative impacts of growing degree days on cereal yields in Lhasa. The impacts of climate trends on cereal yields in Tibet were positive and the results were in the range of 1.5%-4.8%. Among the three types of model, the fixed-effects model was the most robust and the linear detrending model performed better than the first-difference model. The robustness of the first-difference model decreased after adding the interaction terms between different climate variables. Our findings will help in implementing more spatially targeted agricultural adaptations to cope with the impacts of climate change on the agro-ecosystem of the Tibetan Plateau.
Investigating topographic and climatic controls on erosion at variable spatial and temporal scales is essential to our understanding of the topographic evolution of the orogen. In this work, we quantified millennial-scale erosion rates deduced from cosmogenic 10Be and 26Al concentrations in 15 fluvial sediments from the mainstream and major tributaries of the Yarlung Zangbo River draining the southern Tibetan Plateau (TP). The measured ratios of 26Al/10Be range from 6.33 ± 0.29 to 8.96 ± 0.37, suggesting steady-state erosion processes. The resulted erosion rates vary from 20.60 ± 1.79 to 154.00 ± 13.60 m Myr-1, being spatially low in the upstream areas of the Gyaca knickpoint and high in the downstream areas. By examining the relationships between the erosion rate and topographic or climatic indices, we found that both topography and climate play significant roles in the erosion process for basins in the upstream areas of the Gyaca knickpoint. However, topography dominantly controls the erosion processes in the downstream areas of the Gyaca knickpoint, whereas variations in precipitation have only a second-order control. The marginal Himalayas and the Yarlung Zangbo River Basin (YZRB) yielded significantly higher erosion rates than the central plateau, which indicated that the landscape of the central plateau surface is remarkably stable and is being intensively consumed at its boundaries through river headward erosion. In addition, our 10Be erosion rates are comparable to present-day hydrologic erosion rates in most cases, suggesting either weak human activities or long-term steady-state erosion in this area.
This article explored China’s urban employment dynamics with particular focus on the city size effect. Big data derived from the largest recruitment website were used to examine the direct and indirect impacts of city size on employment demand by using mediating and moderating models. We also investigated the roles of the government and location factors which have seldom been considered in literature. Results showed that the concentration degree of new jobs is higher than that of stock employment and population across cities, implying a path dependency mechanism of job creation and employment expansion. Meanwhile, numerous job posts in inland central cities are probably a symptom of more even distribution of employment in future China. Econometric models further verified the significant correlation between city size and job creation. Moreover, industrial diversity, fixed asset investment, and spatial location have heterogeneous effects on employment demand in cities of different sizes and different levels of administration. These results can not only deepen our understanding of the crucial role of city size in urban employment growth but also demonstrate the future trend of labor and population geography of China. Policy implications are then proposed for job creation in cities of China and other developing countries.
As the world’s largest developing country, the ability of China’s agricultural resource utilization to effectively support the current and future food security goals has been affected by a variety of factors (e.g., transformed supply channels, tightening international situation and frequent emergencies) in recent years and has attracted extensive attention from the academic community subject to multiple factors. This study uses literature review, statistical analysis, and spatial analysis methods to systematically explore China’s food security situation in the context of farmland resource constraints. It is found that the demand-side pressures such as demographic changes, social class differentiation, and dietary structure adjustments derived from economic growth and rapid urbanization have placed extremely high expectations on food supply. However, the quantitative restrictions, utilization ways, and health risks of farmland resources on the supply side constitute a huge hidden concern that affects the stability of food production. Although China’s farmland protection system is undergoing a transition from focusing on quantity management to sustainable use, the matching and coordinating demand pressure and supply capacity for food security is unbalanced. Therefore, facing uncertain future development scenarios, policymakers should focus on building a resilient space for China’s farmland protection to withstand the interference of major emergencies. The existing farmland protection space policy can be integrated by establishing a national farmland strategic reserve system (based on resilient space), and further development of targeted use control measures for zoning, grading, and classification will help realize sustainable China’s farmland resources use.
With the advent of climate change, winter temperatures have been steadily increasing in the middle-to-high latitudes of the world. However, we have not found a corresponding decrease in the number of extremely cold winters. This paper, based on Climatic Research Unit (CRU) re-analysis data, and methods of trend analysis, mutation analysis, correlation analysis, reports on the effects of Arctic warming on winter temperatures in Heilongjiang Province, Northeast China. The results show that: (1) during the period 1961- 2018, winter temperatures in the Arctic increased considerably, that is, 3.5 times those of the Equator, which has led to an increasing temperature gradient between the Arctic and the Equator. An abrupt change in winter temperatures in the Arctic was observed in 2000. (2) Due to the global warming, an extremely significant warming occurred in Heilongjiang in winter, in particular, after the Arctic mutation in 2000, although there were two warm winters, more cold winters were observed and the interannual variability of winter temperature also increased. (3) Affected by the warming trend in the Arctic, the Siberian High has intensified, and both the Arctic Vortex and the Eurasian Zonal Circulation Index has weakened. This explains the decrease in winter temperatures in Heilongjiang, and why cold winters still dominate. Moreover, the increase in temperature difference between the Arctic and the Equator is another reason for the decrease in winter temperatures in Heilongjiang.
It is common to obtain the topography of tidal flats by the Unmanned Aerial Vehicle (UAV) photogrammetry, but this method is not applicable in tidal creeks. The residual water will lead to inaccurate depth inversion results, and the topography of tidal creeks mainly depends on manual survey. The present study took the tidal creek of Chuandong port in Jiangsu Province, China, as the research area and used UAV oblique photogrammetry to reconstruct the topography of the exposed part above the water after the ebb tide. It also proposed a Trend Prediction Fitting (TPF) method for the topography of the unexposed part below the water to obtain a complete 3D topography. The topography above the water measured by UAV has the vertical precision of 12 cm. When the TPF method is used, the cross-section should be perpendicular the central axis of the tidal creek. A polynomial function can be adapted to most shape of sections, while a Fourier function obtains better results in asymmetrical sections. Compared with the two-order function, the three-order function lends itself to more complex sections. Generally, the TPF method is more suitable for small, straight tidal creeks with clear texture and no vegetation cover.
Deep-water navigation channels in the tidal reaches of the lower Yangtze River are affected by water and sediment fluxes that produce complex shoals and unstable channel conditions. The Fujiangsha reach is particularly difficult to manage, as it has many braided channels within the tidal fluctuation zone. In this study, hydrologic and topographic data from the Fujiangsha reach from 2012 to 2017 were used to examine the variations in deposition and erosion, flow diversion, shoals, and channel conditions. Since the Three Gorges Dam became operational and water storage was initiated, the Fujiangsha reach has shown an overall tendency toward erosion. Channels deeper than 10 m accounted for 83.7% of the total erosion of the Fujiangsha reach during 2012-2017. Moreover, the dominant channel-forming sediments have gradually changed from suspended sediments to a mixed load of suspended and bed-load sediments. Deposition volumes of these sediments has varied significantly among different channels, but has mainly occurred in the Fubei channel. Furthermore, periodic variations in the Jingjiang point bar have followed a deposition-erosion-deposition pattern, and the downstream Shuangjian shoal mid-channel bar has been scoured and shortened. Approximately 44.0% of the bed load from the upstream Fujiangsha reach is deposited within the 12.5-m deep Fubei channel. The increased erosion and river flow from the Jingjiang point bar and the Shuangjian shoal during the flood season constituted 59.3% and 40.7%, respectively, of the total amount of siltation in the Fubei channel.
It is urgent and important to explore the dynamic evolution in comprehensive transportation green efficiency (CTGE) in the context of green development. We constructed a social development index that reflects the social benefits of transportation services, and incorporated it into the comprehensive transportation efficiency evaluation framework as an expected output. Based on the panel data of 30 regions in China from 2003-2018, the CTGE in China was measured using the slacks-based measure-data envelopment analysis (SBM-DEA) model. Further, the dynamic evolution trends of CTGE were determined using the spatial Markov model and exploratory spatio-temporal data analysis (ESTDA) technique from a spatio-temporal perspective. The results showed that the CTGE shows a U-shaped change trend but with an overall low level and significant regional differences. The state transition of CTGE has a strong spatial dependence, and there exists the phenomenon of “club convergence”. Neighbourhood background has a significant impact on the CTGE transition types, and the spatial spillover effect is pronounced. The CTGE has an obvious positive correlation and spatial agglomeration characteristics. The geometric characteristics of the LISA time path show that the evolution process of local spatial structure and local spatial dependence of China’s CTGE is stable, but the integration of spatial evolution is weak. The spatio-temporal transition results of LISA indicate that the CTGE has obvious transfer inertness and has certain path-dependence and spatial locking characteristics, which will become the major difficulty in improving the CTGE.
Baseflow is an important component of river or streamflow. It plays a vital role in water utilization and management. An improved Eckhardt recursive digital filter (IERDF) is proposed in this study. The key filter parameter and maximum baseflow index (BFImax) were estimated using the minimum smoothing method to improve baseflow estimation accuracy. The generally considered BFImax of 0.80, 0.50 and 0.25 according to the drainage basin’s predominant geological characteristics often leads to significant errors in the regions that have complex subsurface and hydrologic conditions. The IERDF improved baseflow estimation accuracy by avoiding arbitrary parameter values. The proposed method was applied for baseflow separation in the upstream of Yitong River, a tributary of the Second Songhua River, and its performance was evaluated by comparing the results obtained using isotope-tracer data. The performance of IERDF was also compared with nine baseflow separation techniques belonging to filter, BFI and HYSEP methods. The IERDF was also applied for baseflow separation and calculation of rainfall infiltration recharge coefficient at different locations along the Second Songhua River’s mainstream for the period 2000-2016. The results showed that the minimum smoothing method significantly improved BFImax estimation accuracy. The baseflow process line obtained using IEDRF method was consistent with that obtained using isotope 18O. The IERDF estimated baseflow also showed stability and reliability when applied in the mainstream of the Second Songhua River. The BFI alone in the river showed an increase from the upstream to the downstream. The proportion of baseflow to total flow showed a decrease with time. The intra-annual variability of BFI was different at different locations of the river due to varying climatic conditions and subsurface characteristics. The highest BFI was observed at the middle reaches of the river in summer due to a water surplus from power generation. The research provided valuable information on baseflow characteristics and runoff mode determination, which can be used for water resources assessment and optimization of economic activity distribution in the region.
Guangdong Province, as one of China’s fast-developing regions, an important manufacturing base, and one of the national first round low-carbon pilots, still faces many challenges in controlling its total energy consumption. Coal dominates Guangdong’s energy consumption and remains the major source of CO2. Previous research on factors influencing energy consumption has lacked a systematic analysis both from supply side (factors related to scale, structure, and technologies) and demand side (investment, consumption, and trade). This paper develops the logarithmic mean Divisia index (LMDI) method that focuses on the supply side and the structural decomposition analysis (SDA) method that focuses on the demand side to systematically identify the key factors driving coal consumption in Guangdong. Results are as follows: (1) Supply side analysis indicates that economic growth has always been the most important factor driving coal consumption growth, while energy intensity is the most important constraining factor. Industrial structure and energy structure have different impacts on coal consumption control during different development phases. (2) Demand side analysis indicates that coal is consumed mainly for international exports, inter-provincial exports, fixed capital formation, and urban household. (3) Industries with the fastest coal consumption growth driven by final demand have experienced significant shifts. Increments in industrial sectors were mainly driven by inter-provincial exports and urban household consumption in recent years. (4) Research on energy consumption in subnational regions under China’s new development pattern of “dual circulation” should not only focus on exports in the context of economic globalization but also pay more attention to inter-provincial exports on the background of strengthened interregional connections.
Mountainous landscapes are particularly vulnerable and sensitive to climate change and human activities, and a clear understanding of how ecosystem services (ES) and their relationships continuously change over time, across space, and along altitude is therefore essential for ecosystem management. Chongqing, a typical mountainous region, was selected to assess the long-term changes in its key ES and their relationships. From 1992 to 2018, the temporal variation in water yield (WY) revealed that the maximum and minimum WYs occurred in 1998 and 2006, which coincided with El Niño-Southern Oscillation and severe drought events, respectively. Soil export (SE) and WY were consistent with precipitation, which reached their highest values in 1998. During this period, carbon storage (CS) and habitat quality (HQ) both decreased significantly. ES in Chongqing showed large variations in altitude. Generally, WY and SE decreased with increasing altitude, while CS and HQ increased. For spatial distribution, WY and SE showed positive trends in the west and negative trends in the east. In regard to CS and HQ, negative trends dominated the area. Persistent tradeoffs between WY and soil conservation (SC) were found at all altitude gradients. The strong synergies between CS and HQ were maintained over time.
The study of temperature change in major countries of the world since the 1980s is a key scientific issue given that such data give insights into the spatial differences of global temperature change and can assist in combating climate change. Based on the reanalysis of seven widely accepted datasets, which include trends in climate change and spatial interpolation of the land air temperature data, the changes in the temperature of major countries from 1981 to 2019 and the spatial-temporal characteristics of global temperature change have been assessed. The results revealed that the global land air temperature from the 1980s to 2019 varied at a rate of 0.320°C/10a, and exhibited a significantly increasing trend, with a cumulative increase of 0.835°C. The mean annual land air temperature in the northern and southern hemispheres varied at rates of 0.362°C/10a and 0.147°C/10a, respectively, displaying significantly increasing trends with cumulative increases of 0.828°C and 0.874°C, respectively. Across the globe, the rates of change of the mean annual temperature were higher at high latitudes than at middle and low latitudes, with the highest rates of change occurring in regions at latitudes of 80°-90°N, followed by regions from 70°-80°N, then from 60°-70°N. The global land surface air temperature displayed an increasing trend, with more than 80% of the land surface showing a significant increase. Greenland, Ukraine, and Russia had the highest rates of increase in the mean annual temperature; in particular, Greenland experienced a rate of 0.654°C/10a. The regions with the lowest rates of increase of mean annual temperature were mainly in New Zealand and the equatorial regions of South America, Southeast Asia, and Southern Africa, where the rates were <0.15°C/10a. Overall, 136 countries (93%), out of the 146 countries surveyed, exhibited a significant warming, while 10 countries (6.849%) exhibited no significant change in temperature, of which 3 exhibited a downward trend. Since the 1980s, there have been 4, 34 and 68 countries with levels of global warming above 2.0°C, 1.5°C and 1.0°C, respectively, accounting statistically for 2.740%, 23.288% and 46.575% of the countries examined. This paper takes the view that there was no global warming hiatus over the period 1998-2019.
Droughts are the most frequent natural disaster in regions at the margins of the East Asian summer monsoon (EASM), which pose threats to agriculture, the economy, and human lives. However, the limitations of only approximately 60 years of meteorological observations hamper our understanding of the characteristics and mechanisms of local hydroclimate. Trees growing in the marginal region of the EASM are usually sensitive to moisture variations and have played important roles in past hydroclimatic reconstructions. Here, a 303-year tree-ring-width chronology of Pinus tabulaeformis from Mt. Lama, which is located in the junction of the Liaoning Province and Inner Mongolia, China, was used to reconstruct the May-August Palmer drought severity index (PDSI) in the marginal region of the EASM. The transfer function explains 48.0% (or 47.2% after adjusting for the loss of the degrees of freedom) of the variance over the calibration period from 1946 to 2012. A spatial correlation analysis demonstrates that our PDSI reconstruction can represent the drought variability on the northernmost margin of the EASM. The winter Asian polar vortex area index showed a delayed impact on the summer EASM precipitation in the following year.
