.
39.Ecosystem services response to urbanization in metropolitan areas Thresholds identification
Science of the Total Environment, 2017, 607: 706-714
Jian Peng*, Lu Tian, Yanxu Liu, Mingyue Zhao, Yi'na Hu, Jiansheng Wu
Abstract: Ecosystem service is the key comprehensive indicator for measuring the ecological effects of urbanization. Although various studies have found a causal relationship between urbanization and ecosystem services degradation, the linear or non-linear characteristics are still unclear, especially identifying the impact thresholds in this relationship. This study quantified four ecosystem services (i.e. soil conservation, carbon sequestration and oxygen production, water yield, and food production) and total ecosystem services (TES), and then identified multiple advantageous area of ecosystem services in the peri-urban area of Beijing City. Using piecewise linear regression, the response of TES to urbanization (i.e., population density, GDP density, and construction land proportion) and its thresholds were detected. The results showed that, the TES was high in the north and west and low in the southeast, and there were seven multiple advantageous areas (distributed in the new urban development zone and ecological conservation zone), one single advantageous area (distributed in the ecological conservation zone), and six disadvantageous areas (mainly distributed in the urban function extended zone). TES response to population and economic urbanization each had a threshold (229 person km− 2 and 107.15 million yuan km− 2, respectively), above which TES decreased rapidly with intensifying urbanization. However, there was a negative linear relationship between land urbanization and TES, which indicated that the impact of land urbanization on ecosystem services was more direct and effective than that of population and economic urbanization. It was also found that the negative impact of urbanization on TES was highest in the urban function extended zone, followed in descending order by that in the new urban development zone and ecological conservation zone. According to the detected relationships between urbanization and TES, the economic and population urbanization should be strengthened accompanied by slowing or even reducing land urbanization, so as to achieve urban ecological sustainability with less ecosystem services degradation.
Sustainability, 2017, 9(6)
Jiansheng Wu, Xin Lin, Meijuan Wang*, Jian Peng, Yuanjie Tu
Abstract: Drought vulnerability of agriculture is significant to economic development and sustainable food production. In this paper, we proposed a framework to evaluate the regional agricultural-eco environment in the face of drought caused by climate change. Based on a vulnerability scoping diagram (VSD) model, we built up a comprehensive system to evaluate the agricultural drought vulnerability of Yunnan Province in China. The model highlights the human-land relationship by considering both natural conditions and human activities. Twelve indicators were generated to construct three components of the model: exposure, sensitivity, and adaptive capacity. During the construction of the VSD model, the entropy and the analytic hierarchy process (AHP) comprehensive analysis method were adopted to generate the weights and to compute the composite index for each section. Furthermore, the factor analysis method was used to determine the dominant factors of different cities and the main indicators driving the system. The results indicated a spatial pattern that the vulnerability value was high on the eastern and western sides, but low in the middle of Yunnan Province. Most of the vulnerable regions were concentrated in remote areas. Indicators such as population density, irrigation level, annual average precipitation, cultivation land ratio, and difficulty of water supply were the main driving factors. This means that there is a deep connection between agricultural drought vulnerability and urbanization. The evaluation system developed during this research will provide guidance for drought mitigation in regions of complex terrain.
Urban Ecosystems, 2017, 20(3): 701-714
Liqing Zhang, Jian Peng, Yanxu Liu, Jiansheng Wu
Abstract: Landscape ecological security pattern (LESP) can effectively safeguard urban ecological security, which is vital for urban sustainable development. Previous studies have not adequately considered the ability to fulfill people’s demand for ecosystem services when identifying sources of LESP. To address this gap, we sought to develop a more comprehensive approach coupling ecosystem services supply and human ecological demand to construct LESP for Beijing–Tianjin–Hebei region. We proposed a new evaluation framework integrating ecosystem services importance assessment and landscape connectivity analysis with human ecological demand importance assessment to identify ecological sources. Afterwards, ecological corridors were identified using Minimum Cumulative Resistance model based on sources and resistance surface modified through nighttime light data. Combined with ecological sources and corridors, LESP for Beijing–Tianjin–Hebei region can be constructed. The ecological sources are mainly located in western Beijing and southwestern Chengde. The ecological source area totals 36,245.50 km2, accounting for 21.26% of the ecological land in Beijing–Tianjin–Hebei region. The ecological corridors cross the whole region, from northeast to southwest, similar to the direction of the Yanshan–Taihang Mountain Chain. All the national nature reserves and 91.4% of the provincial nature reserves are distributed within the LESP. The validity of our methodology is confirmed by the distribution of the nature reserves. This study adds new insights into the methodology of LESP construction, and its results provide information about local ecological characteristics that can provide an important reference for decision-making concerning urban planning and ecological conservation.
36.Estimation of the PM2.5 health effects in China during 2000–2011
Environmental science and pollution research international, 2017, 24(11): 10695-10707
Jiansheng Wu, Jie Zhu, Weifeng Li, Duo Xu, Jianzheng Liu
Abstract: Exposure to fine particulate matter (PM 2.5 ) has been associated with mortality, but the extent of the adverse impacts differs across various regions. A quantitative estimation of health effects attributed to PM 2.5 in China is urgently required, particularly because it has the largest population and high air pollution levels. Based on the remote sensing-derived PM 2.5 and grid population data, we estimated the acute health effects of PM 2.5 in China using an exposure-response function. The results suggest the following: (1) The proportion of the population exposed to high PM 2.5 concentrations (>3502μg/m 3 ) increased consistently from 2000 to 2011, and the population exposed to concentrations above the threshold defined by World Health Organization (WHO) (>1002μg/m 3 ) rose from 1,191,191,943 to 1,290,562,965. (2) The number of deaths associated with PM 2.5 exposure increased steadily from 107,608 in 2000 to 173,560 in 2010, with larger numbers in the eastern region. (3) PM 2.5 health effects decreased in three pollution control scenarios estimated for 2017, i.e., the Air Pollution Prevention and Control Action Plan (APPCAP) scenario, the APPCAP under WHO IT-1 scenario (3502μg/m 3 ), and the APPCAP under WHO IT-3 scenario (1502μg/m 3 ), which indicates that pollution control can effectively reduce PM 2.5 effects on mortality.
35.Regional ecosystem health response to rural land use change A case study in Lijiang City, China
Ecological Indicators, 2017, 72: 399-410
Jian Peng*, Yanxu Liu, Tianyi Li, Jiansheng Wu
Abstract: Quantitative analysis of the response of ecosystem health to rural land use change is required to comprehend the human-nature coupling mechanism and to explore the process of global environmental change, which can interpret the ecological effects of regional land use and land cover change comprehensively. However, the existing regional ecosystem health assessment largely ignored either the internal connection of ecosystem health to land use patterns or the internal representation of ecosystem services to ecosystem health. Using Lijiang City of China as a study area, the average normalized difference vegetation index (NDVI), landscape metrics, and ecosystem elasticity coefficient based on different land use types were used as quantitative indicators. Then the coefficient of spatial neighboring effect was introduced to characterize the adjacency effect on ecosystem services, and to generate the index of integrated ecosystem health. The results showed the change of land use was close to 30% at county level from 1986 to 2006, and forest land was the primary land use type. With respect to the declining physical health of ecosystems in all the four counties, the integrated health experienced a slight increase in Lijiang County. The vast majority of towns’ ecosystem physical health and integrated health declined, while more than 70% of towns did not change distinctly. Ecosystem physical health had distinct influence on the integrated ecosystem health, and ecosystem vitality was the main factor affecting the condition of physical health. Emphasized in the interconnection of pattern and process, this study provided an ecosystem health approach to assessing the integrated ecological effects of regional land use change.
The Science of the total environment, 2017, 586: 457-465
Weifeng Li, Qiwen Cao, Kun Lang, Jiansheng Wu*
Abstract: Rapid urbanization has significantly contributed to the development of urban heat island (UHI). Regulating landscape composition and configuration would help mitigate the UHI in megacities. Taking Shenzhen, China, as a case study area, we defined heat source and heat sink and identified strong and weak sources as well as strong and weak sinks according to the natural and socioeconomic factors influencing land surface temperature (LST). Thus, the potential thermal contributions of heat source and heat sink patches were differentiated. Then, the heterogeneous effects of landscape pattern on LST were examined by using semiparametric geographically weighted regression (SGWR) models. The results showed that landscape composition has more significant effects on thermal environment than configuration. For a strong source, the percentage of patches has a positive impact on LST. Additionally, when mosaicked with some heat sink, even a small improvement in the degree of dispersion of a strong source helps to alleviate UHI. For a weak source, the percentage and density of patches have positive impacts on LST. For a strong sink, the percentage, density, and degree of aggregation of patches have negative impacts on LST. The effects of edge density and patch shape complexity vary spatially with the fragmentation of a strong sink. Similarly, the impacts of a weak sink are mainly exerted via the characteristics of percent, density, and shape complexity of patches.
Remote Sensing of Environment, 2016, 184: 316-328
Jiansheng Wu, Fei Yao, Weifeng Li*, Menglin Si
Abstract: Satellite-based remote sensing data have been widely used in estimating ground-level PM 2.5 concentrations as it can provide spatially detailed information. Most modern satellite-based PM 2.5 estimates use statistical models that demand dense PM 2.5 monitoring networks. As the national PM 2.5 monitoring networks in China were not finished until the end of 2012, the research related to PM 2.5 is relatively unsubstantial. To further improve the accuracy and application of remote sensing based estimation models for PM 2.5 and take advantage of the newly established networks, we employed a time fixed effects regression model and geographically weighted regression model to develop a spatiotemporal statistical model that estimated ground-level PM 2.5 concentrations in Beijing–Tianjin–Hebei. The time fixed effects regression model used the aerosol optical depth (AOD) data from the VIIRS (Visible Infrared Imaging Radiometer Suite) instrument as the major predictive variable along with several other dependent variables, including some factors uncommonly discussed in previous literature, i.e., the satellite-derived NO 2 concentrations of the previous day (NO 2 _Lag) and four directional wind vectors, and estimated day-by-day ground-level PM 2.5 surfaces. The geographically weighted regression model used the residuals from the time fixed effects regression model as the dependent variable and the AOD value as the independent variable. Through adding the estimated residuals back to previous surfaces, we obtained the final prediction maps of ground-level PM 2.5 concentrations in Beijing–Tianjin–Hebei with a spatial resolution of 602km02×02602km. The results were as follows. i). The spatiotemporal statistical model performed satisfactorily in that it successfully captured both the temporal and spatial variations in the PM 2.5 –AOD relationships. The coefficient of determination (R 2 ), mean prediction error (MPE), and root-mean-square error (RMSE) were 0.88301, 8.133102μg/m 3 , and 13.057402μg/m 3 , respectively, during model fitting and 0.71889, 12.271202μg/m 3 , and 19.292702μg/m 3 , respectively, during model validation. ii). Incorporating the NO 2 _Lag in the time fixed effects regression model significantly improved the model's performance and it played a positive role in ground-level PM 2.5 concentrations. Replacing the simple wind speed with four directional wind vectors was helpful for the model's performance. iii). Meteorological factors and land use characteristics significantly affected the PM 2.5 –AOD relationships. The temperature and surface relative humidity (SRH) played a positive role, whereas the rainfall, planet boundary layer height (PBLH), average relative humidity in the PBLH (RH_PBLH), four directional wind vectors, and normalized difference vegetation index (NDVI) played a negative role. iv). The prediction maps revealed that fine particle pollution in Beijing–Tianjin–Hebei is severe and the pollution pattern presents relatively strong seasonal heterogeneity and southeast–northwest spatial heterogeneity.
International Journal of Remote Sensing, 2016, 37(13): 3125-3142
Jiansheng Wu, Tong Wang, Kuangyi Pan, Weifeng Li, Xiulan Huang
Abstract: In early 2008, forest ecosystems in southern China suffered damage due to a severe ice storm disaster. The area and degree of forest damage caused by the ice storm was assessed using Satellite Pour l鈥橭bservation de la Terre (SPOT)-Vegetation images for Guangdong Province acquired between 1999 and 2008. By using the maximum value composition method and image thresholding techniques, the forest vegetation loss, expressed as the change in net primary productivity (NPP) and two indicators (I1, I2), was estimated. The damage threshold was determined by comparing the standard deviation of pixels of the undamaged areas in 2008 and other years without any disaster, which was 10%. The area of damaged forest vegetation was 47,670 km2, with the northern Guangdong Province most seriously affected. The total loss of NPP for forest vegetation was 50,578,055 t (DW) year鈭1, with 52 counties (43.7%) suffering forest vegetation damage. Evergreen coniferous forest was most widely affected, but evergreen broad-leaved forest was the most severely damaged vegetation type. Terrain topography influenced the damage to forest vegetation, which was found to increase with increasing elevation and slope gradient. The range and degree of damaged forest determined by remote-sensing data is consistent with the extent of the ice storm, indicating that this study provides a new approach for rapid assessment of forest disasters at a regional scale.
Environmental Science and Pollution Research, 2016, 23(2): 1428-1440
Jiansheng Wu, Jing Song, Weifeng Li, Maokun Zheng
Abstract: Accumulation of heavy metals in agricultural land and their ecological risks are key issues in soil security studies. This study investigated the concentrations of six heavy metals—copper (Cu), zinc (Zn), lead (Pb), nickel (Ni), and chromium (Cr) in Shenzhen’s agricultural lands and examined the potential hazards and possible sources of these metals. Eighty-two samples from agricultural topsoil were collected. Potential ecological risk index was used to calculate the potential risk of heavy metals. Principal component analysis (PCA) was applied to explore pollution sources of the metals. Finally, Kriging was used to predict the spatial distribution of the metals’ potential ecological risks. The concentrations of the heavy metals were higher than their background values. Most of them presented little potential ecological risk, except for the heavy metal cadmium (Cd). Four districts (Longgang, Longhua, Pingshan, and Dapeng) exhibited some degree of potential risk, which tended to have more industries and road networks. Three major sources of heavy metals included geochemical processes, industrial pollutants, and traffic pollution. The heavy metal Cd was the main contributor to the pollution in agricultural land during the study period. It also poses the potential hazard for the future. High potential risk is closely related to industrial pollution and transportation. Since the 1980s, the sources of heavy metals have evolved from parent rock weathering, erosion, degradation of organics, and mineralization to human disturbances resulting in chemical changes in the soil.
30.Spatiotemporal patterns of remotely sensed PM2.5 concentration in China from 1999 to 2011
Remote Sensing of Environment, 2016, 174: 109-121
Jian Peng*, Sha Chen, Huiling Lu, Yanxu Liu, Jiansheng Wu
Abstract: Air pollution in the form of fine particulate matter, or PM 2.5 , can decrease human life expectancy and increase the overall mortality rate. Based on a time series of remotely sensed PM 2.5 concentrations, this study analyzed the spatiotemporal patterns of this crucial pollutant in China from 1999 to 2011 using trend analysis and standard deviation ellipse analysis, and carried out a health risk assessment of human exposure to PM 2.5 . The results showed that PM 2.5 concentrations increased significantly from 1999 to 2011 in China, especially in the central and eastern parts of the country. The proportion of areas with PM 2.5 concentrations higher than 3502μg/m 3 increased year by year, and the areas with PM 2.5 concentrations lower than the annual primary standard of 1502μg/m 3 decreased continuously. The areas most polluted by PM 2.5 were south of Hebei, north of Henan and west of Shandong provinces, with changes in the overall spatial distribution of the pollutant occurring faster along a south–north axis than along an east–west axis, and also faster along an east–south axis than along a west–north axis. Based on the PM 2.5 concentrations in China from 1999 to 2011, a two-tier standard (level-I and level-II) was proposed for delineated areas to assist in nationwide air pollution control. It was also found that the proportion of the population exposed to PM 2.5 concentrations greater than 3502μg/m 3 increased year by year, and increased faster than the proportion of population exposed to PM 2.5 concentrations in the range 15–3502μg/m 3 . The health risk in the central and eastern areas of the country was the highest. Based on these results, PM 2.5 pollution poses an increasingly serious risk to human health across China and there is an immediate need to implement its regional control. In addition, more attention should be paid at the national scale in terms of pollution risk, rather than focusing narrowly on a city scale.
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