Coastal regions are threatened by natural processes, such as erosion driven by storm surges and the effect of jetties, as well as by human behavior. The coastline of the Yellow River Delta (YRD) was monitored using the general high-tide line method, which combines Remote sensing (RS) and geographic information system (GIS) technology, using multi-spectral scanner (MSS), thematic mapper (TM), and enhanced thematic mapper plus (ETM+) images of the YRD from 1976 to 2014 as a data source. The results demonstrated that the shape and length of the YRD coastline has changed dramatically since 1976. The course of the Diaokouhe channel has resulted in mainly inland erosion in the north, and is primarily marine erosion; therefore, it was termed an erosion-type estuary. However, the coastline of the Qingshuigou course has moved seaward, demonstrating an accretion stage, and was therefore termed an accretion-type estuary. The coastline advanced forward before 1997 and shrank after 2003 in the southern part of the river mouth, which was due to the shift in the river mouth in 1996. It has continually extended outward in the northern part of the river mouth from 2003 onward. The coastline in the southern part of the river mouth has moved randomly, with the occurrence of both erosion and sedimentation caused by land reclamation and sea wave intrusion. In most cases, the coastline has extended offshore, especially in the northern part of the river mouth. The YRD coastline has changed frequently and rapidly from 1992 to 2014. The river mouth channel, river water and sediments, and precipitation were the major factors affecting the YRD. The YRD coastline was mainly in an accretion stage during flow periods. The erosion rate decreased and tended to be stable during a dry period. The coastline was basically stable when dry periods occurred over a long period. The location of Yellow River ports and sea erosion were the main factors driving coastline changes. The coastline was mainly influenced by the flow path of the Yellow River, with recent human activity also becoming a factor.
Coastal depth is an important research focus of coastal waters and is also a key factor in coastal environment. Dongluo Island in South China Sea was taken as a typical study area. The band ratio model was established by using measured points and three multispectral images of Landsat-8, SPOT-6 (Systeme Probatoire d'Observation de la Terre, No.6) and WorldView-2. The band ratio model with the highest accuracy is selected for the depth inversion respectively. The results show that the accuracy of SPOT-6 image is the highest in the inversion of coastal depth. Meanwhile, analyzing the error of inversion from different depth ranges, the accuracy of the inversion is lower in the range of 0-5 m because of the influence of human activities. The inversion accuracy of 5-10 m is the highest, and the inversion error increases with the increase of water depth in the range of 5-20 m for the three kinds of satellite images. There is no linear relationship between the accuracy of remote sensing water depth inversion and spatial resolution of remote sensing data, and it is affected by performance and parameters of sensor. It is necessary to strengthen the research of remote sensor in order to further improve the accuracy of inversion.
Land-use changes in coastal wetlands have led to a worldwide degradation of marine coastal ecosystems and a loss of the ecological services they provide. Ecological offsetting is a popular strategy and an effective mitigation measure for ecosystems that have been degraded, damaged, or destroyed and is critical for habitats where natural recovery is hindered. However, the current understanding of the theory and practice of ecological offsetting for coastal wetlands is extremely limited in many developing countries. We conducted a review of ecological offsetting for coastal wetlands projects and studies in China in 1979-2017 to explore the application and limitations of ecological offsetting theory. It was found that China's coastal ecological offsetting regime has recently entered a rapidly developing stage, with an increasing number of different types of offsetting projects conducted, but theoretical research lags behind practical applications. Considerable governmental, social, technological and ethical challenges remain to resolve. Coastal ecological offsetting schemes have been inconsistent in meeting conservation objectives or preventing net losses because of the challenges of ensuring they are fully consistent in practice (mainly in-kind offsets) and theory (mainly out-of-kind offsets). Ecological offsetting projects were primarily implemented by government, developers, and non-profit organizations. The available funding of coastal ecological offsetting projects is insufficient, which makes ecological offsetting a risky operation. Therefore, we propose strategies for improvement that integrate the consideration of theoretical and practical challenges in the offsetting process, while providing a scientific basis and directional guidance for the future practice of biodiversity conservation and environmental management.
Water supply services (WSSs) are critical for the regional water balance and water circulation, but relevant studies have not established the relationship between WSSs and human well-being. This research identifies the scope of areas that benefit from WSSs from an ecosystem service flow perspective. Moreover, the path and quantity of the flow of WSSs are simulated to provide a scientific theoretical basis for ecosystem service management and ecological compensation. The Dongjiang Lake Basin is a national priority river basin in China where ecological compensation pilot programmes concerning water resources are top priorities. Dongjiang Lake Basin experienced an increase and then a decrease in the overall supply of water, with an average net water supply of 1096-1500 mm for the years 1995, 2000, 2005 and 2010. The water demand increased each year in service beneficiary areas (SBAs), varying from 387 to 580 mm. Overall, Dongjiang Lake Basin met the net water demands of the actual SBAs in the lower reaches, but a gap in the water supply and demand emerged gradually. This research provides an understanding of the functional mechanisms for the provision, demand and flow of WSSs and provides a scientific theoretical basis for ecosystem service management and ecological compensation.
Historical thematic maps and remote sensing data were applied to address spatiotemporal dynamics of land use/land cover (LULC) changes and its impact on wetlands sustainability based on eight LULC datasets from 1954 to 2015 in Baoqing County, Northeast China. This study demonstrated that LULC drastically changed in the past six decades due to conversion of wetlands, woodland, and grassland into cropland. The cropland was 578.8 km2 in 1954, accounting for 5.8% of the area in Baoqing County, and it increased to 54.3% in 2015, which was nearly equivalent to 9.4 times of that in 1954. Cropland increased 4843.6 km2 from 1954 to 2015 with average increased area of 79.4 km2/yr. The conversion of wetlands was the main reason for cropland increase (49.7%), and woodland (18%) and grassland (16.3%) conversion were other reasons. Results also revealed that 78% of wetlands were lost during the past six decades, of which 91.2% were converted cropland. Population increasing (population across Baoqing in 2015 was 7.8 times of that in 1949), agricultural technology development was the main reason for cropland increase, institutional and economic policies also played important roles for cropland dynamics, particularly paddy field influenced by market price. Agricultural development has caused severe wetlands degradation both in area and functionality, and still being the major threads for wetlands sustainable development. Several suggestions concerning the future land use policy formulation and wetlands sustainability were proposed. They are adjusting the ‘food first’ agricultural policy, reinforce management for wetlands nature reserves, creating infrastructure for the rational use of surface and groundwater, harnessing the degraded cultivated land.
The Jiapigou gold mine area, located in the upper reaches of the Songhua River, was the first and largest artisanal gold mine once in China, and it used to be prominent in two marking years (1870 and 1974). Jiapigou area had a gold mining history of more than 190 years, which was first opened in 1820. Gold extraction with algamation was applied as the dominant method of excavation from 1940 to 2008, and a total of more than 100 t of gold were extracted from the mine using this method and it was estimated that 100-200 t Hg were released, thus causing severe mercury environmental pollution in the mining area. In the experimental campaigns of this study, in situ air and soil Hg concentrations and air-soil Hg fluxes were measured from April 2009 to December 2011. The results showed that in the study area the total gaseous mercury (TGM) concentration exhibited remarkable spatial and temporal distribution patterns, i.e. the TGM gradually decreased following the increase in distance to gold mining sites in space, and the values in spring, summer and autumn were elevated by 1-2 orders of magnitude in comparison with those in winter. Furthermore, at other sampling sites the total soil mercury (TSM) concentration in spring was higher than that in autumn, except for the contrary laws demonstrated at the Erdaogou mining site. However, in spring and winter the Hg flux between air and soil was under the control of different environmental factors, and the characteristics were clear and distinct. In spring the Hg flux between air and soil was directly under the control of solar irradiation, and the releasing process was predominant with a remarkable positive correlation to solar irradiation. Nevertheless, in winter the Hg fluxes were indirectly under the control of solar irradiation, which caused thermal inversion due to the thick snow cover. The depositing process was predominant and the correlations between Hg flux and air temperature was remarkably negative, and there was a positive correlation between Hg flux and solar irradiation.
Soil organic matter (SOM) is an important parameter related to soil nutrient and miscellaneous ecosystem services. This paper attempts to improve the performance of traditional partial least square regression (PLSR) model by considering the spatial autocorrelation and soil forming factors. Surface soil samples (n=180) were collected from Honghu City located in the middle of Jianghan Plain, China. The visible and near infrared (VNIR) spectra and six environmental factors (elevation, land use types, roughness, relief amplitude, enhanced vegetation index, and land surface water index) were used as the auxiliary variables to construct the multiple linear regression (MLR), PLSR and geographically weighted regression (GWR) models. Results showed that:1) the VNIR spectra can increase about 39.62% prediction accuracy than the environmental factors in predicting SOM; 2) the comprehensive variables of VNIR spectra and the environmental factors can improve about 5.78% and 44.90% relative to soil spectral models and soil environmental models, respectively; 3) the spatial model (GWR) can improve about 3.28% accuracy than MLR and PLSR. Our results suggest that the combination of spectral reflectance and the environmental variables can be used as the suitable auxiliary variables in predicting SOM, and GWR is a promising model for predicting soil properties.
Accurate mapping of soil salinity and recognition of its influencing factors are essential for sustainable crop production and soil health. Although the influencing factors have been used to improve the mapping accuracy of soil salinity, few studies have considered both aspects of spatial variation caused by the influencing factors and spatial autocorrelations for mapping. The objective of this study was to demonstrate that the ordinary kriging combined with back-propagation network (OK_BP), considering the two aspects of spatial variation, which can benefit the improvement of the mapping accuracy of soil salinity. To test the effectiveness of this approach, 70 sites were sampled at two depths (0-30 and 30-50 cm) in Ningxia Hui Autonomous Region, China. Ordinary kriging (OK), back-propagation network (BP) and regression kriging (RK) were used in comparison analysis; the root mean square error (RMSE), relative improvement (RI) and the decrease in estimation imprecision (DIP) were used to judge the mapping quality. Results showed that OK_BP avoided the both underestimation and overestimation of the higher and lower values of interpolation surfaces. OK_BP revealed more details of the spatial variation responding to influencing factors, and provided more flexibility for incorporating various correlated factors in the mapping. Moreover, OK_BP obtained better results with respect to the reference methods (i.e., OK, BP, and RK) in terms of the lowest RMSE, the highest RI and DIP. Thus, it is concluded that OK_BP is an effective method for mapping soil salinity with a high accuracy.
The parameter bp in the tuo-omega (τ-ω) model is important for retrieving soil moisture data from passive microwave brightness temperatures. Theoretically, bp depends on the observation mode (polarization, frequency, and incidence angle) and vegetation properties and varies with vegetation growth. For simplicity, previous studies have taken bp to be a constant. However, to reduce the uncertainty of soil moisture retrieval further, the present study is of the dynamics of bp based on the SMAPVEX12 experimental dataset by combining a genetic algorithm and the L-MEB microwave radiative transfer model of vegetated soil. The results show the following. First, bp decreases nonlinearly with vegetation water content (VWC), decreasing critically when VWC becomes less than 2 kg/m2. Second, there is a power law between bp and VWC for both horizontal and vertical polarizations (R2=0.919 and 0.872, respectively). Third, the effectiveness of this relationship is verified by comparing its soil-moisture inversion accuracy with the previous constant-bp method based on the HiWATER dataset. Doing so reveals that the dynamic bp method reduces the root-mean-square error of the retrieved soil moisture by approximately 0.06 cm3/cm3, and similar improvement is obtained for the calibrated SMAPVEX12 dataset. Our results indicate that the dynamic bp method is reasonable for different vegetation growth stages and could improve the accuracy of soil moisture retrieval.
As the construction sector is a major energy consumer and thus a significant contributor of CO2 emissions in China, it is important to consider carbon reduction in this industry. This study analyzed six life-cycle stages and calculated the life-cycle CO2 emissions of the construction sector in 30 Chinese provincial jurisdictions to understand the disparity among them. Results show that building materials production was the key stage for carbon reduction in the construction sector, followed by the building operation stage. External variables, e.g., economic growth, industrial structure, urbanization, price fluctuation, and marketization, were significantly correlated with the emission intensity of the construction sector. Specifically, economic growth exhibited an inverted U-shaped relation with CO2 emissions per capita and per area during the period examined. Secondary industry and land urbanization were negatively correlated with CO2 emission intensity indicators from the construction sector, whereas tertiary industry and urbanization were positively correlated. Price indices and marketization had negative effects on CO2 emission intensity. The policy implications of our findings are that cleaner technologies should be encouraged for cement providers, and green purchasing rules for the construction sector should also be established. Pricing tools (e.g., resource taxes) could help to adjust the demand for raw materials and energy.
As is well known, clouds impact the radiative budget, climate change, hydrological processes, and the global carbon, nitrogen and sulfur cycles. To understand the wide-ranging effects of clouds, it is necessary to assess changes in cloud cover at high spatial and temporal resolution. In this study, we calculate global cloud cover during the day and at night using cloud products estimated from Moderate Resolution Imaging Spectroradiometer (MODIS) data. Results indicate that the global mean cloud cover from 2003 to 2012 was 66%. Moreover, global cloud cover increased over this recent decade. Specifically, cloud cover over land areas (especially North America, Antarctica, and Europe) decreased (slope=-0.001, R2=0.5254), whereas cloud cover over ocean areas (especially the Indian and Pacific Oceans) increased (slope=0.0011, R2=0.4955). Cloud cover is relatively high between the latitudes of 36°S and 68°S compared to other regions, and cloud cover is lowest over Oceania and Antarctica. The highest rates of increase occurred over Southeast Asia and Oceania, whereas the highest rates of decrease occurred over Antarctica and North America. The global distribution of cloud cover regulates global temperature change, and the trends of these two variables over the 10-year period examined in this study (2003-2012) oppose one another in some regions. These findings are very important for studies of global climate change.
In recent years, the large scale and frequency of severe air pollution in China has become an important consideration in the construction of livable cities and the physical and mental health of urban residents. Based on the 2016-year urban air quality index (AQI) data published by the Ministry of Environmental Protection of China, this study analyzed the spatial and temporal characteristics of air quality and its influencing factors in 338 urban units nationwide. The analysis provides an effective scientific basis for formulating national air pollution control measures. Four key results are shown. 1) Generally, air quality in the 338 cities is poor, and the average annual values for urban AQI and air pollution in 2016 were 79.58% and 21.22%, respectively. 2) The air quality index presents seasonal changes, with winter > spring > autumn > summer and a u-shaped trend. 3) The spatial distribution of the urban air quality index shows clear north-south characteristic differences and a spatial agglomeration effect; the high value area of air pollution is mainly concentrated in the North China Plain and Xinjiang Uygur Autonomous Region. 4) An evaluation of the spatial econometric model shows that differences in urban air quality are due to social, economic, and natural factors.
As an important constitute of land consolidation, high-standard basic farmland construction is an important means to protect the quantity, quality and ecological environment of cultivated land. Its target not only lies in the increase of cultivated land quantity, but also the improvement of cultivated land quality, agricultural production conditions and ecosystem environments. In the present study, the quality evaluation method and construction arrangement of cultivated land were explored to facilitate the process of decision-making and implementation for high-standard basic farmland construction (HSBFC) with administrative village as the unit. Taking the land comprehensive improvement project area in Quzhou County, Handan City, Hebei Province as a case study, the whole process of the study comprised of three steps:1) establishment of the evaluation model of cultivated land quality uniformity based on regional optimum cultivated land quality, and construction of the uniformity evaluation index system from the aspects of soil fertility quality, engineering quality, spatial quality and eco-environment quality, according to the new concept of cultivated land quality; 2) calculation of cultivated land quality uniformity by grading indicators, assigning scores and weighting sums, exploring the local homogenization characteristics of regional cultivated land quality through spatial autocorrelation analysis, and analyzing the constraints and transformative potential of barrier factors; 3) arrangement of HSBFC according to the principle of concentration, continuity and priority to the easy operation. The results revealed that the value of farmland quality uniformity for the administrative villages in the study area was between 7.76 and 21.96, and there was a difference between various administrative villages. The regional spatial autocorrelation patterns included High-High (HH), Low-Low (LL), High-Low (HL) and Low-High (LH). These indicate that regional cultivated land quality has local homogenization characteristics. The most restrictive factors in the study area were the medium and low transformation difficulty indexes, including soil organic matter content, farmland shelterbelt network density, field regularity and scale of the field. In addition, there were also high transformation difficulty indicators in some areas, such as sectional configuration. The project area was divided into four partitions:major construction area, secondary construction area, general construction area, and conditional construction area. The cultivated land area of each subarea was 1538.85 ha, 1224.27 ha, 555.93 ha, and 1666.63 ha, respectively. This comprised of 30.87%, 24.56%, 11.15% and 33.42% of the total project area, respectively. The evaluation model and index system could satisfy the evaluation of farmland quality and diagnosis of obstacle factors to facilitate the subsequent construction decision. The present study provides reference for the practice of regional HSBFC, and a new feasible idea and method for related studies.
A quantitative approach to the national geopolitical influence is helpful to provide a reference for national sustainable development on the international stage, based on describing national diplomatic capacity and overseas influence. Herein, this study proposes a complex geopolitical influence model, considering the affected nations' response. The geopolitical influences of great power in the affected nation are correlated with overall strength, the acceptance degree of the affected nation to the great power and the distance between both sides. Then, the geopolitical influences of China and the US in Southeast Asia countries are empirically analyzed from 2005 to 2015. The geopolitical influence of China in Southeast Asia has been largely growing for the past decades, accompanying with a constant trend of the US' effects. It is believed that China and the US can coexist peacefully in Southeast Asia to promote the regional development, and jointly create an open, inclusive and balanced regional cooperation architecture that benefits all nations in this region and great powers, through mutual political trust and economic beneficial cooperation. This study may contribute to advancing the policy debate and determining the optimal cooperation in pledging commitment to a new and sustainable model of great power relationship among the various regional geopolitical options.
As a result of rapid urbanization in China, urban sprawl has increased rapidly, and land-use regulation and smart urban growth are equally important. Spatial function regionalization can provide the scientific groundwork for the regulation of land use and protection. This paper probes the system of evaluation indices and applies the methods of spatial analysis and classification clustering to the calculation of the ecologically significant value and economically significant value in each evaluation unit. After use of a classification matrix integrated by the two significant values, city space can be divided into four functional types, namely, feasible development area, moderate development area, moderate conservation area and prohibited exploiting area, and these are the basis for spatial development and control.
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