City Size Research Articles

Cities Shape the Diversity and Spread of Nonnative Species

The globalization of trade and increased human mobility have facilitated the introduction and spread of nonnative species, posing significant threats to biodiversity and human well-being. As centers of global trade and human populations, cities are foci for the introduction, establishment, and spread of nonnative species. We present a global synthesis of urban characteristics that drive biological invasions within and across cities, focusing on four axes: (a) connectivity, (b) physical properties, (c) culture and socioeconomics, and (d) biogeography and climate. Urban characteristics such as increased connectivity within and among cities, city size and age, and wealth emerged as important drivers of nonnative species diversity and spread, while the relative importance of biogeographic and climate drivers varied considerably. Elaborating how these characteristics shape biological invasions in cities is crucial for designing and implementing strategies to mitigate the impacts of invasions on ecological systems and human well-being.

Time Varying Extremes

Abstract Standard extreme value theory implies that the distribution of the largest observations of a large cross section is well approximated by a parametric model, governed by a location, scale and shape parameter. The extremes of a panel of independent cross sections are all governed by the same parameters as long as the underlying distribution as well as the size of the cross sections are time invariant. We derive inference about these parameters, and tests of the null hypothesis of time invariance, under asymptotics that do not require the number of extremes or the number of time periods to increase. We further apply Hamiltonian Monte Carlo techniques to estimate the path of time-varying parameters. We illustrate the approach in four examples of U.S. data: damages from weather-related disasters, financial returns, city sizes and firm sizes.

Identification and Analysis of Peak Population Migration Patterns in the Beijing-Tianjin-Hebei Region Based on Complex Network Theory

Abstract. As a vital economic and population agglomeration area in China, the Beijing-Tianjin-Hebei region has attracted considerable attention regarding population migration issues. Population migration not only directly affects the population size and structure of cities within the region but also has profound implications for economic development, social stability, and urban planning. This study extends the analysis to the "Spring Festival Travel Rush" period, using population migration data from January to March in the years 2020 to 2022 as the basis. By employing complex network theory and relevant statistical indicators, the study explores the peak period population migration patterns and their variations in the Beijing-Tianjin-Hebei region. The research firstly identifies significant changes in population migration patterns in the Beijing-Tianjin-Hebei region around 2021 and analyzes the changing patterns. Secondly, network statistical indicators indicate hierarchical population migration patterns based on city tiers. Furthermore, cities with unique migration patterns are identified. Finally, based on an in-depth exploration of population migration patterns and their variations in the Beijing-Tianjin-Hebei region, the study provides suggestions and prospects for future urban planning and development, offering important references for addressing the challenges posed by population migration in the region.

Structural change in city systems evolution

AbstractThis paper analyzes city system dynamics, based on a theoretical framework relating interaction potentials to agglomeration economies and density externalities. It employs new historical time series data on population size of cities in Sweden over two centuries (1810–2010) and introduces two schematic growth factors: (i) the intra-city potential and (ii) the extra-city potential located in in rings encircling each city. The first factor is measured by each city’s population size, while the second is a vector of distance-discounted population size for each of a city’s urban rings. In this way, we can explain a city’s growth as a function of its interaction potential inside the city, as well as inside the first, second hand third ring. A robust finding is that cities with large ring potentials follow different development paths than those with small ring potentials. We also find clear evidence of structural change between the two centuries 1810–1910 and 1910–2010. In the first period, city growth is positively impacted by the size of the intra-city potential, whereas the same potential dampens or reduces the growth in the second period. Moreover, the ring potentials outside the city tend to switch from having negative growth stimulation in the first period to having positive stimulation in the second period.

Impact of the Coupling Coordination Degree of Human Capital and Infrastructure on High-Quality Economic Development: Empirical Evidence from Chinese Cities

China’s economy is transitioning from high-speed to high-quality development, making coordination between economic factors increasingly important. Human capital (HC) and infrastructure (INFRA) are important elements of economic development, and the coupling coordination of the two can have a non-negligible impact on regional economies’ high-quality development. Therefore, this study measures the coupling coordination degree (CCD) of HC and INFRA based on data of 184 prefecture-level cities in China from 2011 to 2019, and comprehensively examines the impact effect and mechanism of the CCD on high-quality economic development (HQED). The relevant results are threefold. (1) Compared with single factors, the degree of HC-INFRA CCD can promote HQED more efficiently. (2) A significant single-threshold effect is evident in the promotion of HQED by the degree of HC-INFRA CCD, and a smaller city size and more extensive higher education institutions promote a stronger threshold effect. (3) Factor allocation and factor efficiency are significant transmission mechanisms of the HC-INFRA CCD affecting HQED, and the mediating effect of the capital-labor force allocation path accounts for 66.28% of the total indirect effect. The results provide empirical evidence verifying that HC-INFRA CCD promotes HQED, along with insightful reference suggestions for formulating relevant macro policies and promoting high-quality urban economic development.

Impact of vegetation coverage and configuration on urban temperatures: a comparative study of 31 provincial capital cities in China

Urban vegetation plays a crucial role in regulating temperatures and heat waves in urban areas. However, the influence of vegetation coverage and its configuration on surface temperatures in different climate zones at a national scale is unclear. To address this, we utilized high-resolution data to detect spatial patterns for 31 provincial capital cities in China. We integrated day and night surface temperatures to determine the influence of vegetative coverage and configuration on urban temperatures across different climate zones and city sizes. Our study revealed that a subtropical monsoon climate and medium-sized cities had the highest vegetative coverage and shape complexity. The best connectivity and agglomeration of vegetation were found in a temperate monsoon climate and large cities. In contrast, small cities, especially those under a temperate continental climate, had low vegetation coverage, high fragmentation, and weak agglomeration and connectivity. In addition, vegetative coverage had a negative impact on daytime surface temperatures, especially in large cities in a subtropical monsoon climate. However, an increase in vegetation coverage could result in warming at night in small cities in temperate continental climates. Although urban vegetation configuration also contributed to moderating surface temperatures, especially at night, they did not surpass the influence of vegetation coverage. The effect on nighttime temperatures of the configuration of vegetation increased by 3–6% relative to that of daytime temperatures, especially in large cities in a temperate monsoon climate. The contribution vegetation coverage and configuration interaction to cooling efficiency decreased at night, especially in medium-sized cities in a temperate continental climate by 3–5%. In addition, this study identified several moderating effects of natural and social factors on the relationship between urban vegetation coverage and surface temperatures. High duration of sunshine, low humidity and high wind speed significantly enhanced the negative impact of vegetation coverage on surface temperatures. In addition, the moderating effect of vegetation coverage was more pronounced in low population density cities and high gross domestic product. This study enhances understanding of the ecological functions of urban vegetation and provides a valuable scientific basis and strategic recommendations for optimizing urban vegetation and improving urban environmental quality.

A machine learning algorithm to explore the drivers of carbon emissions in Chinese cities

As the world’s largest energy consumer and carbon emitter, the task of carbon emission reduction is imminent. In order to realize the dual-carbon goal at an early date, it is necessary to study the key factors affecting China’s carbon emissions and their non-linear relationships. This paper compares the performance of six machine learning algorithms to that of traditional econometric models in predicting carbon emissions in China from 2011 to 2020 using panel data from 254 cities in China. Specifically, it analyzes the comparative importance of domestic economic, external economic, and policy uncertainty factors as well as the nonparametric relationship between these factors and carbon emissions based on the Extra-trees model. Results show that energy consumption (ENC) remains the root cause of increased carbon emissions among domestic economic factors, although government intervention (GOV) and digital finance (DIG) can significantly reduce it. Next, among the external economic and policy uncertainty factors, foreign direct investment (FDI) and economic policy uncertainty (EPU) are important factors influencing carbon emissions, and the partial dependence plots (PDPs) confirm the pollution haven hypothesis and also reveal the role of EPU in reducing carbon emissions. The heterogeneity of factors affecting carbon emissions is also analyzed under different city sizes, and it is found that ENC is a common driving factor in cities of different sizes, but there are some differences. Finally, appropriate policy recommendations are proposed by us to help China move rapidly towards a green and sustainable development path.

The Impact of Smart City Policies on City Resilience: An Evaluation of 282 Chinese Cities

This study uses four dimensions, namely social resilience, economic resilience, infrastructure resilience, and ecological resilience, to construct an index system for urban resilience. The subject data came from the panel data of 282 prefecture-level cities in China from 2006 to 2020. We selected a multiperiod double-difference model to study the effects of smart city pilot policies on macro-urban resilience. By conducting parallel-trend tests and selecting appropriate robustness tests, this study drew the following relevant conclusion: smart city pilot policies can have a positive effect on the urban resilience level. These policies exert their influence by facilitating industrial structure upgrading, which plays a partial mediating role. Considering different city area distributions and city scales, smart city pilot policies can have significant heterogeneity in their enhancement of urban resilience. The effect is pronounced in the “east > central > west” states and is more likely to have a significant impact on small- and medium-sized cities. Therefore, promoting the scope of smart city pilots, strengthening the intermediary role of industrial structure upgrading, and implementing differentiated policies for different regions and city sizes are important for sustainable urban development.

Sustainable transportation infrastructure in Indian cities of different size-class: towards a research and policy agenda

Owing to the fact that the planning and management of urban transportation systems are convoluted ventures, a sound number of cities in India, especially those lacking strong institutional and financial means – principally small and medium-sized cities – have become incapable of efficiently addressing their transportation challenges. Drawing on a pan-India comparative research on 54 cities, the present study well-demonstrates a previously undetected relationship between size-class of Indian cities and their existing state of sustainable transport infrastructure development. The results speak in accordance with the notion that betterment in non-motorized and public transit infrastructure is typically associated with increasing size of cities. Accordingly, this research argues that with regard to the production of knowledge in the field of urban transportation and associated policymaking, academicians and planners can rethink and branch out the understanding of transport sustainability beyond big-metropolises of the country. This study, therefore, enunciates in support of the need for a small and medium-sized city-based research and policy agenda that can focus on eliminating the ‘sizism’ which has conventionally influenced urban theory and policymaking in India and has led to the condition of such cities as the least understood and perhaps least studied element of urban and regional transport systems.

“A Review Of The Study Of Estimation Of The Concentration Of Particulate Matter Over Chhatrapati Sambhajinager (M.S) City Using Remote Sensing”

India’s ongoing population explosion has imposed a great strain on the country’s environment. This rapid growth in population along with urbanization and industrialization has placed lot of pressure on India’s infrastructure and natural sources. Forests destruction, soil erosion, water pollution and lowering of the level’s quality continue to hinder economic development in under developed and rural region of India. The rapid urbanization and subsequently industrialization in India leads degrading environmental condition in metro cities in India. Chhatrapati Sambhajinager cannot be an exception Chhatrapati Sambhajinager is one of the most affected cities where air particulate matters (PM) have been registered at the levels more than 10 times our country’s legal limit (Ninawe et-al 2010). Despite of introducing legal policy measures in India air pollution remained major concern. In many urban areas including Chhatrapati Sambhajinager, there is high level of pollution. This cause increase in the levels of air pollution including deforestation that is causing human health hazards. In India aggravation of air pollution is owing to the rapid and growth in the size of cities. The movement of people from one place to other helped to Increase in consumption pattern, unplanned urban and industrial development is the main causes of air pollution in big cities of India that resulted the worst. (Chitale et-al 2010). In India, the most severe problem of environment comes in varied forms including vehicular emissions and unsaturated industrial smoke. This has resulted in bringing about adverse effect on population and cities are unable to implement pertinent pollution control mechanism. High concentration of pollution in India is not due to absence of a sound environment legal regime, but is due to lack of environmental enforcement at the local level. Regulatory reforms aimed to improving the air pollution problem in most of the metro cities. To my knowledge this might be the first attempt in Maharashtra, to produce high-resolution of particulate matter and gaseous NO2 and SO2 pollution surface, making use of remote sensing data (Kourase et-al 2010). The outcome of this research work will be made available to help expose health research in this polluted and densely populated region

Sewage leakage challenges urban wastewater management as evidenced by the Yangtze River basin of China

Sewage leakage, including uncollected, collected but exfiltrated, and collected but discharged with stormwater in combined sewer overflows, becomes a key challenge to clean water around the world. This study proposed a mass balance model to quantify sewage leakage and analyzed its influencing factors. Approximately 56% (53%–59%) of domestic total nitrogen loads in the Yangtze River basin of China leak out without treatment, two-thirds are exfiltrated or overflowed, significantly impacting receiving water quality. Cities with higher precipitation have greater leakage, indicating overflows are important. Pipe density has limited impact, showing higher importance of pipe quality over quantity. The per capita leakage rate first increases with city size and then decreases, showing the economies of scale. Yet uneven distribution of population and economy within megacities leads to greater leakage. Hence, separated sewage systems of rainwater and wastewater, regular maintenance and adapting centralized and decentralized systems are recommended, tailored to city-specific leakage characteristics.

Specific Technologies of Aviation Rescue and Firefighting Operations over the Years

The twentieth century was a period of rapid development in aviation. It was a time of great progress in the construction of aircraft, the development of ground infrastructure and the improvement of qualifications of aviation personnel. Over the years, aviation has gone from cruise flights in simple aircraft to transatlantic flights, complex aircraft with hundreds of passengers on board. Military aviation can operate at speeds exceeding the speed of sound and in all weather conditions. The infrastructure of large airports has reached the size of cities. Over the past century, the development of aviation has been followed by changes in the organization and equipment of rescue and fire-fighting services. The public does not accept the loss of human life or large-scale material damage and environmental damage. In the search for effective extinguishing agents and methods of administering them, people began to look for ways other than field fire services. Specialized firefighting units have appeared at airports, which are designed for specific rescue and firefighting operations on aircraft and infrastructure. For many years, attempts have been made to select special rescue and firefighting technologies capable of improving the effectiveness and safety of operations. Quite quickly, the car was chosen as the means of transport for airport rescue services. But over time, the need was recognized for it to have different characteristics and equipment than a vehicle for village and town safety units. As a result of various experiments, unusual technical solutions designed to solve basic problems specific to airports were developed. Equally interesting was the path to determining the best fire extinguishing agents and their means of administration. From hand-held fire extinguishers to remote-controlled cannons administering thousands of liters or kilograms of extinguishing agents over a long distance. The publication provides information on the history and development of basic firefighting technologies specific to aviation and some pointers to the future.

When market access gains do not spur urban growth

Abstract We revisit the natural experiments of division and unification of Germany. The negative shock to local market access following the division of Germany led to a fast and strong downward adjustment of the size of West German cities near the new border. In contrast, the positive shock of reunification did not lead to any change in their relative size. Even three decades after reunification, no convergence can be observed. We show that local subsidies to East Germany could have contributed to this asymmetry in time.

Influence of Nutrition, Lifestyle Habits, and Socio-Demographic Determinants on Eating Disorder Symptoms in the Spanish Young Adult Population: A Cross-Sectional Nationwide Survey.

Eating disorders represent a complex and multifaceted public health challenge, highly prevalent among young people. Background and Objectives: To examine the prevalence of eating disorders in the Spanish young adult population aged 18-30 years, and their correlation with various eating habits and lifestyle factors. Materials and Methods: A descriptive, cross-sectional survey was carried out using a non-probabilistic snowball sample. The valid and reliable NutSo-HH Scale was employed to collect data on nutrition, lifestyle, and health habits. Results: Data were collected from 9692 Spanish young adults, of which 101 (1.04%) were diagnosed with anorexia nervosa and 71 (0.73%) with bulimia nervosa. The prevalence of anorexia and bulimia was significantly higher (p < 0.001) in women than in men, regardless of socio-demographic variables such as educational level, income, region, and size of city of residence. A considerable percentage of participants showed possible symptoms of eating disorders. Nutritionally, individuals with eating disorders consumed less fast food and fried or ultra-processed food but tended to consume coffee and energy drinks more frequently. Additionally, sleep quality and duration were more adversely affected in individuals with eating disorders compared to the general population. Sedentary lifestyles did not significantly differ between those with eating disorders and healthy individuals, though physical activity increased in people with bulimia. Conclusions: The interplay between young adults' dietary habits, lifestyle factors, and mental health underscores the urgent need for targeted interventions to effectively address these complex public health challenges.

Impact of city size on self-employment behavior: Evidence from Chinese migrants

Self-employment is an important approach for migrants to gain a foothold in cities and improve their economic and social welfare. This study investigates the relationship between city size and migrants’ self-employment behavior using data from the 2011–2018 CMDS and macro-statistical sources. We find that in the Chinese context, larger cities correlate with an increased likelihood of migrants engaging in self-employment. These results persist under various methodological checks, including alternative estimation methods, sample screening techniques, and addressing concerns about endogeneity. Market potential and diversified agglomeration emerge as important channels through which larger cities encourage migrants’ decisions to pursue self-employment. Moreover, the positive impact of larger cities is more pronounced among rural-to-urban migrants and own-account workers compared to urban-to-urban migrants and employers. This paper provides insights into high-quality development and migrant management strategies in large cities in China.

Radial analysis and scaling of housing prices in French urban areas

Urban scaling laws summarize how attributes evolve with city size. However, one limitation concerns the aggregate view of this approach, which leads to neglecting the internal structure of cities. This is an important issue regarding housing prices, given their significant variations across space. Based on a dataset compiling millions of real estate transactions over the period 2017–2021, we investigate the regularities of the radial (center-periphery) profiles of housing prices across cities, with respect to their size. Results are threefold. First, they corroborate prior findings in the urban scaling literature stating that largest cities agglomerate higher housing prices. Second, we find that housing price radial profiles scale in three dimensions with the power 1/5 of city population. After rescaling, great regularities between radial profiles can be observed, although some locational amenities have a significant impact on prices. Third, it appears that our approach with rescaled profiles fails to explain housing price variations in the city center across cities. In fact, prices near the city center rise much faster with city size than in the periphery. This has strong implications for low-income households seeking homeownership because prohibitive prices in the center may contribute to pushing them out into peripheral locations, especially in large cities.

Why Local Governments Set Climate Targets: Effects of City Size and Political Costs

AbstractCities increasingly address climate change, e.g. by pledging city-level emission reduction targets. This is puzzling for the provision of a global public good: what are city governments’ reasons for doing so, and do pledges actually translate into emission reductions? Empirical studies have found a set of common factors which relate to these questions, but also mixed evidence. What is still pending is a theoretical framework to explain those findings and gaps. This paper thus develops a theoretical public choice model. It features economies of scale and distinguishes urban reduction targets from actual emission reductions. The model is able to explain the presence of targets and public good provision, yet only under specified conditions. It is also able to support some stylized facts from the empirical literature, e.g. on the effect of city size, and resolves some mixed evidence as special cases. Larger cities chose more ambitious targets if marginal net benefits of mitigation rise with city size—if they set targets at all. Whether target setting is more likely for larger cities depends on the city type. Two types are obtained. The first type reduces more emissions than a free-riding city. Those cities are more likely to set a target when they are larger. However, they miss the self-chosen target. Cities of the second type reach their target, but mitigate less than a free-riding city. A third type does not exist. With its special cases, the model can thus guide further empirical and theoretical work.

Intention to adopt autonomous vehicles in China: a comparative study among residents in different-sized cities

ABSTRACT Transitioning to a fully Level-5 autonomous vehicle (AV) environment presents numerous challenges, notably influenced by public adoption intention. Previous studies have shown limitations in scope, population, and methodology. This study expands the Technology Acceptance Model to investigate AVs adoption intention across various city sizes in China. Through surveys in China, 2,662 responses were gathered in 2021 from mega, large, and small-to-medium cities. Using Multiple Indicators and Multiple Causes models, the study examines influencing factors on AVs adoption intention and population heterogeneities. Key findings emphasize the importance of adoption attitude, information provision, and perceived AV usefulness. Additionally, the impact of financial incentives, convenience, and several other factors varies across city sizes. The insights gained from the study can be utilized to develop more cost-effective policies and strategies tailored to different subgroups of the population to fully utilize the potential benefits of AVs while minimizing unintended consequences across diverse urban settings.

Carbon reduction effects of electric delivery vehicle adoption in Chinese cities: Gradient pattern and scenario analysis

China's carbon peak and neutrality targets pose major challenges for the transportation sector due to its significant contribution to carbon emissions. The analysis of the penetration process and impact of electric delivery vehicles (EDVs) in the urban delivery industry (UDI) is relatively poor compared with electric passenger vehicles. This study conducts a scenario analysis of the electrification process and carbon impact of delivery vehicles (DVs) in Chinese cities based on current data and policies. In the baseline scenario, the stock of urban DVs is predicted to reach 22.4 million in 2035, while the stock of EDVs will reach 7.8 million, representing 35 % of the total. Carbon emissions from DVs will decline from a peak of 120.5 Mt in 2022 to 101.4 Mt in 2035 due to the penetration of EDVs. The high electrification rate (HER) scenario will result in an additional 10 Mt of carbon emissions reduction in 2035 as 45 % of DVs are electric. Furthermore, the impact of electrification on carbon emissions shows a spatial gradient due to city size and local policies. With a better understanding of EDV adoption and energy-related carbon emissions in Chinese cities, suggestions are proposed to promote low-carbon transition of UDI in different types of cities.

Investigating Variations in Anthropogenic Heat Flux along Urban–Rural Gradients in 208 Cities in China during 2000–2016

Anthropogenic heat emissions, which are quantified as anthropogenic heat flux (AHF), have attracted significant attention due to their pronounced impacts on urban thermal environments and local climates. However, there remains a notable gap in research regarding the distinctions in the distribution of anthropogenic heat emissions (AHEs) along urban–rural gradients. To address this gap, the present study introduces a new concept—the anthropogenic urban heat island (ArUHI)—where the AHF within urban areas is higher than that in background areas. To quantitatively describe the magnitude and spatial extent of the ArUHI effect, two metrics—namely, ArUHI intensity (ArUHII) and ArUHI footprint (ArUHIFP)—are introduced. We conducted a comprehensive study across 208 cities in China to investigate the spatiotemporal patterns of AHF variations along urban–rural gradients during the period of 2000–2016. In addition, we explored how the complex interactions between land cover and building form components affect changes in the AHF along urban–rural gradients. Additionally, we analyzed how economic zones and city sizes alter the ArUHI intensity and ArUHI footprint. The results showed that 97% (201/208) of Chinese cities exhibited a significant ArUHI effect from 2000 to 2016. The modeled ArUHI intensity value exhibited a substantial increase of nearly fivefold, increasing from 5.55 ± 0.19 W/m2 to 26.84 ± 0.99 W/m2 over time. Regarding the spatial distribution of the ArUHI footprint, the analysis revealed that, for the majority of cities (86% or 179 out of 208), the ArUHI footprint ranged from 1.5 to 5.5 times that in urban areas. City sizes and economic zones yielded significant influences on the ArUHI intensity and ArUHI footprint values. Building forms were significantly positively correlated with AHF, with R2 values higher than 0.94. This study contributes to the understanding of ArUHI effects and their driving factors in China, providing valuable insights for urban climate studies and enhancing our understanding of surface urban heat island mechanisms.