Downscaling SSP-consistent global spatial urban land projections from 1/8-degree to 1-km resolution 2000–2100

Long-term, spatial urban land projections that simultaneously offer global coverage and local-scale empirical accuracy are rare. Recently a set of such projections was produced using data-science-based simulations and the Shared Socioeconomic Pathways (SSPs). These projections update at decadal time intervals from 2000 to 2100 with a spatial resolution of 1/8 degree, while many socio-environmental studies customarily run their analysis and modelling at finer spatial resolutions, e.g. 1-km. Here we develop and validate an algorithm to downscale the 1/8-degree spatial urban land projections to the 1-km resolution. The algorithm uses an iterative process to allocate the decadal amount of urban land expansion originally projected for each 1/8-degree grid to its constituent 1-km grids. The results are a set of global maps showing urban land fractions at the 1-km resolution, updated at decadal intervals from 2000 to 2100, under five different urban land expansion scenarios consistent with the SSPs. The data can support studies of potential interactions between future urbanization and environmental changes across spatial and temporal scales.

Spatiotemporal Characteristics of Urban Land Expansion and Population Growth in Africa from 2001 to 2019: Evidence from Population Density Data

Africa has been undergoing a rapid urbanization process, which is critical to the achievement of the 11th Sustainable Development Goal (SDG11). Using population density data from LandScan, we proposed a population density-based thresholding method to generate urban land and urban population data in Africa from 2001 to 2019, which were further applied to detect the spatiotemporal characteristics of Africa’s urbanization. The results showed that urban land and urban population have both grown rapidly in Africa, which increased by about 5.92% and 4.91%, respectively. The top three countries with the most intense urbanization process in Africa are Nigeria, the Democratic Republic of the Congo, and Ethiopia. The coupling relationship index of urban land expansion and population growth was 0.76 in Africa during 2001–2019. Meanwhile, the total proportion of uncoordinated development types at the provincial level was getting higher, which indicated an uncoordinated relationship between urban land expansion and population growth in Africa. Cropland, grassland, rural land, and forests were the most land-use types occupied by urban expansion. The proportion of cropland, grassland, and forests occupied was getting higher and higher from 2001 to 2019. The extensive urban land use may have an impact on the environmental and economic benefits brought by urbanization, which needs further research.

Land-Use Change and Health Risks in the Process of Urbanization: A Spatiotemporal Interpretation of a Typical Case in Changzhou, China

China has undergone rapid urban expansion in recent decades. At the same time, environmental pollution and its risk to public health have increased. However, the relationship between urban land-use changes and health is ambiguous and insufficiently understood. Based on a typical city-scale case—namely, Changzhou, China—this research aimed to interpret the evolution of health risks alongside land-use change during the process of urbanization. We gathered data from multiple sources, including population mortality data, socioeconomic data, remote-sensing images, data for the points of interest of enterprises, and relevant information on environmental health events and cancers. The results showed that Changzhou’s urbanization was typical insofar as it was characterized by massive growth in industry, a rapid increase in the urban population, and urban land expansion. Health risks related to environmental pollution increased considerably with urban land expansion over time, and they increased with proximity to the pollution. The results from a generalized linear model confirmed that Changzhou’s urbanization triggered increasing health risks. Our study interpreted the relationship between urban land expansion and health risks from a spatiotemporal perspective. It can be used as a reference for urban planning and policymaking with regard to urban environmental health.

EVALUATION ON URBAN LAND EXPANSION QUALITY OF QINGDAO CITY FROM 2010 TO 2018

With the process of people moving from rural to urban area, the urban land boundary expanded significantly. In this paper, the urban land areas of Qingdao were extracted by using remote sensing images from 2010 to 2018. The spatiotemporal pattern of urban expansion in Qingdao city was revealed. Furthermore, the land cover type of the urban expansion area and urbanization rate were also analyzed to study the quality of urban expansion in different counties. It has shown that over 95% land cover types are impervious in the build-up areas of Qingdao, e.g. Shibei and Shinan district. However, there are more forest and water land exist in the suburban counties. The urban land expansion rate and people urbanization rate are highly related.

Analysis of Spatial and Temporal Changes and Expansion Patterns in Mainland Chinese Urban Land between 1995 and 2015

China has experienced greater and faster urbanization than any other country, and while coordinated regional development has been promoted, urbanization has also introduced various problems, such as an increased scarcity of land resources, uncontrolled demand for urban land, and disorderly development of urban fringes. Based on GIS, remote sensing data, and spatial statistics covering the period 1995–2015, this study identified the patterns, as well as spatial and temporal changes, with respect to urban land expansion in 367 mainland Chinese cities. Over this study period, the area of urban land in mainland China increased from 3.05 to 5.07 million km2, at an average annual growth rate of 2.56%. This urban land expansion typically occurred the fastest in medium-sized cities, followed by large cities, and then small cities, with megacities and megalopolises exhibiting the slowest expansion rates. Nearly 70% of the new urban land came from arable land, 11% from other built land, such as pre-existing rural settlements, and 15% from forests and grasslands. When considering marginal-, enclave-, and infill-type expansion patterns, growth in >80% of the 367 cities surveyed was dominated by marginal expansion patterns. Marginal and enclave expansion patterns were found to be becoming more prevalent, with infill-type expansion being seen less. The results of this study provide a theoretical basis and data support for urban spatial planning, the protection of farmland, and the promotion of urban land use efficiency, and can be used as guidance for regional urbanization planning.

Impacts of high-speed rail development on urban land expansion and utilization intensity in China

Urban land expansion (ULE) is a crucial factor for socioeconomic and environmentally sustainable development. However, nowadays, the unprecedented scale of high-speed railway (HSR) construction in China could exert an important influence on ULE. This manuscript first reveals the influence mechanism of HSR on ULE and then employs difference-in-difference (DID) models to investigate this effect based on the data of 280 prefectures and above level cities of 2001-2016. We analyze that HSR exerts a joint effect on ULE from the territorial and local levels and then affects urban land-use intensity (ULUI). HSR opening and HSR station distance both have notably positive effects on ULE, with elastic coefficients of 4.1% and 0.5%, respectively. HSR opening and HSR station distance also both exert positive effects on ULE of the central, eastern region cities and large cities of China, while for the western region and small to medium cities, they are not significant. The impact of HSR station distance on ULUI is negative with a significance level of 0.073, while the impact of HSR opening on ULUI is not significant. Lastly, relevant policy implications are proposed to alleviate urban land waste and spatial disequilibrium under the context of HSR building. This study can provide an important basis for sustainable urban land allocation.