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Now showing items 1 - 6 of 6

  • The population in China's earthquake-prone areas has increased by over 32 million along with rapid urbanization

    He, Chunyang   Huang, Qingxu   Dou, Yinyin   Tu, Wei   Liu, Jifu  

    Accurate assessments of the population exposed to seismic hazard are crucial in seismic risk mapping. Recent rapid urbanization in China has resulted in substantial changes in the size and structure of the population exposed to seismic hazard. Using the latest population census data and seismic maps, this work investigated spatiotemporal changes in the exposure of the population in the most seismically hazardous areas (MSHAs) in China from 1990 to 2010. In the context of rapid urbanization and massive rural-to-urban migration, nearly one-tenth of the Chinese population in 2010 lived in MSHAs. From 1990 to 2010, the MSHA population increased by 32.53 million at a significantly higher rate of change (33.6%) than the national average rate (17.7%). The elderly population in MSHAs increased by 81.4%, which is much higher than the group's national growth rate of 58.9%. Greater attention should be paid to the demographic changes in earthquake-prone areas in China.
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  • How Did Urban Land Expand in China between 1992 and 2015? A Multi-Scale Landscape Analysis

    Xu, Min   Liu, Zhifeng   Dou, Yinyin  

    Effective and timely quantification of the spatiotemporal pattern of urban expansion in China is important for the assessment of its environmental effects. However, the dynamics of the most recent urban expansions in China since 2012 have not yet been adequately explained due to a lack of current information. In this paper, our objective was to quantify spatiotemporal patterns of urban expansion in China between 1992 and 2015. First, we extracted information on urban expansion in China between 1992 and 2015 by integrating nighttime light data, vegetation index data, and land surface temperature data. Then we analyzed the spatiotemporal patterns of urban expansion at the national and regional scales, as well as at that of urban agglomerations. We found that China experienced a rapid and large-scale process of urban expansion between 1992 and 2015, with urban land increasing from 1.22 x 10(4) km(2) to 7.29 x 10(4) km(2), increasing in size nearly fivefold and with an average annual growth rate of 8.10%, almost 2.5 times as rapid as the global average. We also found that urban land in China expanded mainly by occupying 3.31 x 10(4) km(2) of cropland, which comprised 54.67% of the total area of expanded urban land. Among the three modes of growth-infilling, edge expansion, and leapfrog-edge expansion was the main cause of cropland loss. Cropland loss resulting from edge expansion of urban land totalled 2.51 x 10(4) km(2), accounting for over 75% of total cropland loss. We suggest that effective future management with respect to edge expansion of urban land is needed to protect cropland in China.
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  • Urban expansion brought stress to food security in China:Evidence from decreased cropland net primary productivity

    He, Chunyang   Liu, Zhifeng   Xu, Min   Ma, Qun   Dou, Yinyin  

    Cropland net primary productivity (CNPP) is a crucial indicator of grain productivity and food security. However, assessments of the impact of urban expansion on the CNPP in China have been inadequate owing to data limitations. In this paper, our objective was to assess the impact of urban expansion on the CNPP in China from 1992 to 2015 in a spatially explicit manner. We first obtained the CNPP before urban expansion between 1992 and 2015 in China using the Carnegie-Ames-Stanford Approach (CASA) model. We then assessed the impact of urban expansion on the CNPP from 1992 to 2015 at multiple scales (the whole country, agricultural zones, and urban expansion hotspots) by combining the CNPP before urban expansion with the urban land coverage time series extracted from multi-source remotely sensed data. We found that the total loss of the CNPP due to urban expansion from 1992 to 2015 was 13.77 TgC, which accounts for 1.88% of the CNPP before urban expansion in China. This CNPP loss resulted in a 12.45-million-ton decrease in grain production in China, corresponding to a reduction in the mean annual grain self-sufficiency rate of 2%. Therefore, we concluded that rapid urban expansion from 1992 to 2015 caused stress to China's food security. We suggest that it is still vital for China to effectively protect cropland to improve the urbanization level to 60% by 2020. (C) 2016 Elsevier B.V. All rights reserved.
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  • Quantifying the heat flux regulation of metropolitan land use/land cover components by coupling remote sensing modeling with in situ measurement

    Kuang, Wenhui   Dou, Yinyin   Zhang, Chi   Chi, Wenfeng   Liu, Ailin   Liu, Yue   Zhang, Renhua   Liu, Jiyuan  

    Quantifying the effects of urban land use/land cover with regard to surface radiation and heat flux regulation is important to ecological planning and heat stress mitigation. To retrieve the spatial pattern of heat fluxes in the Beijing metropolitan area, China, a remote sensing-based energy balance model was calibrated with synchronously measured energy fluxes including net radiation, latent heat flux (LE), and sensible heat flux (H). Our model calibration approach avoided the uncertainties due to subjective judgments in previous empirical parameterization methods. The land surface temperature (LST), H, and Bowen ratio () of Beijing were found to increase along the outskirt-suburban-urban gradient, with strong spatial variation. LST and H were negatively correlated with vegetation fraction cover (VFC). For example, the modern high-rise residential areas with relatively higher VFC had lower H and than the traditional low-rise residential areas. Our findings that indicate thermal dissipation through vegetation transpiration might play an important role in urban heat regulation. Notably, the thermal dissipating strength of vegetation (calculated as LE/VFC) declined exponentially with increased VFC. For the purpose of heat stress regulation, we recommend upgrading the traditional low-rise residential areas to modern high-rise residential areas and focusing urban greenery projects in areas whose VFC<0.1, where the heat regulating service by urban vegetation could be twice as effective as in other places. Key Points
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  • Rapid Urban Land Expansion in Earthquake-Prone Areas of China

    Huang, Qingxu   Meng, Shiting   He, Chunyang   Dou, Yinyin   Zhang, Qiang  

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  • A comparative analysis of urban impervious surface and green space and their dynamics among 318 different size cities in China in the past 25 years

    Dou, Yinyin   Kuang, Wenhui  

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