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Soil organic carbon (SOC) is one of the most important soil attributes responsible for the sustainable maintenance of soil quality. In recent years, cropland withdrawal (CWD) (i.e., conversion into natural landscapes) in China has become a remarkable phenomenon of land use changes, driven by the spontaneous cropland abandonment by rural households and government‐led conversion of cropland to forest and grassland. The CWD may affect SOC content and storage in China. Therefore, this study estimated the variation in SOC caused by CWD between 1990 and 2018 based on the grid data of land use and soil organic matter (SOM). The results showed that CWD had a significant effect on SOC. (1) From 1990 to 2018, the total area of CWD was about 358 × 103 km2, an area that represented about 20% of the total area of cropland in China in 1990. In addition, within the total area of CWD, the proportions represented by the conversion of cropland to forest and grassland were the highest, reaching 58% and 39%, respectively. The former was mainly distributed in the southern part of China, especially in the southwestern mountainous area. The latter was largely concentrated in the northern part of China, especially in the Loess Plateau; (2) From 1990 to 2018, the average SOC content of CWD increased by about 10%, representing an increase of 193 Tg in soil organic carbon storage (SOCS). This is equivalent to six times the carbon emissions from agricultural land in China in 2019; (3) Among eight agricultural regions in China, the middle‐lower Yangtze Plain had the largest area of CWD, which accounted for 19.9% of the total CWD of the whole country. [ABSTRACT FROM AUTHOR]

The booming animal-sourced foods consumption is a crucial factor driving regional land carbon loss due to the expanded feed use, especially in countries with rapid economic growth. Here, we contribute to revealing the land carbon loss of increased animal-sourced foods consumption in China. Results show that animal-sourced foods consumption in China increased significantly during 2000–2020, especially for beef, dairy and poultry which increased by more than 200 %. As a result, land carbon loss of animal-sourced foods consumption in China has increased by approximately 42 % during the period. Spatially, land carbon loss of animal-sourced foods consumption in most eastern provinces intensified, while that in most western areas declined. The rise of animal-sourced foods consumption per capita was the prominent positive driver for the increase of land carbon loss, while the decline of land carbon loss intensity was the most negative factor. Overall, the booming consumption for animal-sourced foods in China had the dual effects on promoting human dietary and triggering land carbon loss. Therefore, it is essential to formulate strategies for coordinating animal-sourced foods demand and land carbon conservation. • Land carbon loss (LCL) of animal-sourced foods (ASF) consumption was detected. • ASF consumption in China increased significantly during 2000–2020. • LCL of ASF consumption in China increased by 42 % during 2000–2020. • Generally, LCL of ASF consumption increased in east, while declined in west. • The rise of ASF consumption per capita was the most positive driver for LCL rise. [ABSTRACT FROM AUTHOR]

Abstract: Cultivated land has been undergoing significant spatial shift during the last 2 decades in China, according to land‐use data derived from the Landsat Thematic Mapper. Based on soil organic matter data and yield data at county level, we developed a constant crop yield dataset at pixel level with a resolution of 1 km. Using this dataset, this paper quantitatively evaluates average crop yield change due to cultivated land spatial shift at national and regional levels. The results show that (a) at national level, the average crop yield per unit area decreased by 1.99% during the period 1990–2010. The main reason for this is that built‐up areas occupied a significant amount of high‐yield cultivated land whereas low‐yield land converted in ecologically vulnerable areas. (b) In spite of 77.2 thousand km2 cultivated land was converted to built‐up areas, especially in areas with high economic value, such as Huang–Huai–Hai Plain, 329.4 thousand km2 land was converted to cultivated land, especially in Northeastern and Northwestern China. (c) The quality gap between cultivated land converted to built‐up areas nationally and new cultivated land regionally suggests that the loss of 1 km2 of cultivated land converted to built‐up area would, to achieve equivalency, need to be compensated by 1.54 km2 of new land in Xinjiang, or more in Northeastern China. However, cultivated land expansion in these areas may cause land degradation and a series of ecological environment problems. [ABSTRACT FROM AUTHOR]

Population change is a key variable that influences climate change, ecological construction, soil and water use, and economic growth. Census data are always point data, whereas planar data are often required in scientific research. By using nighttime light (NTL) images and land use data, combined with the fifth and sixth census data of China at the county level, we carried out spatial matching on the population of each county, respectively, and established population density diagrams of China for 2000 and 2010, which had a spatial resolution of 1 × 1 km. The method proposed in this paper is relatively simple and has a high simulation precision. The results showed that during the first ten years of the 21st century, there are some remarkable characteristics in Chinese population spatial pattern change: 1) the “disappearance” of intermediate-density regions; namely, areas with a population density between 500 and 1500 persons/km 2 have decreased by 41% during the ten years; 2) continuous growth of high-density regions; namely, areas with a population density of more than 1500 persons/km 2 have increased by 76%; 3) an expansion tendency of low-density regions similar to high-density regions. [ABSTRACT FROM AUTHOR]

Megaregions have become the principal geographic units for countries to participate in the global economy, which is often a composite of numerous urban clusters which are distributed in different cities. In China, a megaregion is regarded as a key urbanization platform, according to the National Plan on New Urbanization published in 2014. In this context, it is imperative to understand the spatial patterns of and the changes occurring in megaregions. For instance, what are the universal rules or differences related to urban cluster growth between different megaregions in the process of rapid urbanization, and are there differences in the growth of urban clusters with different sizes? Focusing on these issues, this study discusses the uneven growth of clusters in five of the largest megaregions in China using the rank-size rule, based on land-cover data interpreted from time-series satellite imagery during the period 1990–2010. The results show that the cluster size distribution of each of these megaregions obeyed the rank-size rule, and the size distribution of the clusters became more uneven and was tilted toward larger clusters between 1990 and 2010. These factors should be considered in the implementation of the National Plan on New Urbanization in China and the designation of urban macro planning and urban layout optimization in other countries those are experiencing rapid urbanization. [ABSTRACT FROM AUTHOR]

Many studies have demonstrated the efficient extraction of the spatial extent of urban areas from Defense Meteorological Satellite Program/Operational Linescan System imagery using a fixed thresholding technique. These studies may underestimate and overestimate the extents of small and large cities, respectively. To overcome this problem, a new intensity gradient (IG) and vegetation fractional coverage (VFC) method is developed for identifying cities or towns, principally based on the assumption that there is a border around a city at which the nighttime light intensity decreases sharply. Using this method, the spatial extents of urban areas for two of the biggest countries in the world, namely China and the United States, were extracted in 2010. The urban areas thus identified are compared with the urban areas interpreted from Landsat Thematic Mapper imagery, and the results show that there is a significant linear relationship between the former and latter areas. This demonstrates that the IG/VFC model is effective for efficiently extracting the extent of urban areas from nighttime light imagery. [ABSTRACT FROM PUBLISHER]

As the utmost component of water utilization, irrigation water use (IWU) has raised extensive concerns of academics who devoted to achieve regional water security. IWU per unit area of cropland varies across regions due to changing natural physical factors; thus, cropland spatial location change would drive regional total IWU variation even if the total area of cropland remains unchanged. Here, based on CROPWAT model and multi-source data, we estimated the IWU change caused by cropland spatial shift in China. Results show that cropland centroid in China moved to the northwest by approximately 56 km during 1990–2015, leading to national IWU increase by about 18 billion m3 (7.3%). By region, IWU in the northwest enhanced the greatest with nearly 23 billion m3, which was mainly caused by the high IWU per unit area of cropland (759–810 mm) which was more than five times as the national average. Furthermore, irrigation water productivity in the northwest (0.66 kg/m3) was relatively low, which was only 15% of the national average. Therefore, for alleviating water-grain contradiction, emphasis should be placed on raising yield and declining IWU per unit area on existing croplands rather than reclaiming new cropland in the northwest, which requires advanced production and irrigation technologies to be prioritized for the northwest. This research could provide valuable references for policymaking in order to achieve regional sustainable land-water management. • Irrigation water use (IWU) change by cropland spatial shift in China was studied. • IWU increased by about 7% due to cropland spatial shift in China during 1990–2015. • The national IWU rise was mainly caused by cropland increase in the northwest. • IWU per unit area of cropland in northwest was over 5 times the national average. • Advanced irrigation technologies were suggested to be prioritized in northwest. [ABSTRACT FROM AUTHOR]

Abstract: In the process of studying dust-storm events, we have to face an important scientific problem: How to define dust-storm intensity (DSI)? This study provides a comprehensive definition of DSI in terms of the frequency, duration, and visibility of dust storms, and uses it to measure the trend of annual changes in dust-storm activities. With dust-storm data from 186 meteorological observation stations in China, the trend in DSI was studied for the period 1980–2007. This trend differs from those based on the frequency of dust storms, which are often used in the literature. In this study, average DSIs after 2000 were underestimated using frequency alone to measure the dust activities, compared with those before 2000. According to the spatiotemporal distribution, there are four modes of change in DSI over the period, namely a significantly decreasing trend, an increasing trend, a mode in which dust storm activity remained constant, and a two-peak mode. [Copyright &y& Elsevier]

Highlights: [•] Rural settlements have remained evenly distributed in Daxing. [•] Rural settlements were getting more regular and compact. [•] Role of market towns should be emphasized in rural development. [•] Larger settlements and settlements which have merged should be emphasized. [•] Controlling industrial land growth is important for rural land use. [ABSTRACT FROM AUTHOR]

Abstract: In China, some people believe that urban land has a large potential for absorbing more of the urban population, while others think that urban population density is very high, and has already caused many urban problems. The population density of 135 major cities is studied by using the city population data (Shiren kou) from the Fifth Census of China in 2000. The data included the floating population who lived in cities for more than 6 months/year, so it could more closely reflect the real size of the urban population. Land-use data were obtained from a digital map interpreted from remotely sensed data collected in 2000. The results show that urban population density was fairly high in China and the average urban land per capita of these cities was only about 76m2 in 2000, but that the corresponding value was 106m2 if it was calculated with the non-agricultural population. Moreover, urban population density varied greatly between cities: from 4×103 to 22×103/km2. Regression results show the differences in urban population density were strongly related to six independent variables, including wage per capita, city size and shape index of urban land, etc. The policies derived from the results deserve more attention in the new land-use planning with the target year of 2020 in China. [Copyright &y& Elsevier]

With significant economic development in the last decade in China, urban land has increasingly expanded and encroached upon arable land in the last decade. Although many papers have analyzed the characteristics of urban land expansion, relatively less attention has been paid to examining the different expansion features of different-tier cities at a regional level. This paper analyzes the spatio-temporal differences of urban land expansion and arable land loss among different-tier cities of the BTH (Beijing–Tianjin–Hebei) region in China in the 1990s, and identifies social, economic, political and spatial factors that led to these differences. Based on urban land change data determined by interpreting Landsat Thematic Mapper (TM) imagery, it was found that the urban land area in the BTH region expanded by 71% between 1990 and 2000. Different-tier cites, however, had enormous differences in urban development, such as speed of urban land expansion, speed of urban land per capita growth, and so on. These differences were closely related to rapid economic development, strict household registration systems, urban development guidelines (chengshi fazhan fangzhen), and national land use policies. Of all the new urban land, about 74% was converted from arable land, and there was a general tendency for smaller cities to have higher percentages. One of the important reasons for this result is that urban land is highly correlated with arable land in spatial distribution. [Copyright &y& Elsevier]

Urban forests are vitally important for sustainable urban development and the well-being of urban residents. However, there is, as yet, no country-level urban forest spatial dataset of sufficient quality for the scientific management of, and correlative studies on, urban forests in China. At present, China attaches great importance to the construction of urban forests, and it is necessary to map a high-resolution and high-accuracy dataset of urban forests in China. The open-access Sentinel images and the Google Earth Engine platform provide a significant opportunity for the realization of this work. This study used eight bands (B2–B8, B11) and three indices of Sentinel-2 in 2016 to map the urban forests of China using the Random Forest machine learning algorithms at the pixel scale with the support of Google Earth Engine (GEE). The 7317 sample points for training and testing were collected from field visits and very high resolution images from Google Earth. The overall accuracy, producer's accuracy of urban forest, and user's accuracy of urban forest assessed by independent validation samples in this study were 92.30%, 92.27%, and 92.18%, respectively. In 2016, the percentage of urban forest cover was 19.2%. Nearly half of the cities had an urban forest cover between 10% and 20%, and the average percentage of large cities whose urban populations were over 5 million was 24.8%. Cities with less than half of the average were mainly distributed in northern and western parts of China, which should be focused on in urban greening planning. [ABSTRACT FROM AUTHOR]

Due to the indivisibility of agricultural machinery in production, limited farm sizes have reduced mechanization efficiency and increased the cost of grain production in China. As a result, the development of a moderate-scale farming system has been proposed by academic communities and policy makers. However, it is still hotly debated how to determine a moderate farm scale. We offer a new perspective on the costs of machinery services. This manuscript employs the threshold model and uses the nationally representative data from the 2015 China Rural Household Panel Survey (CRHPS) to investigate the role of farm size expansion relative to per area machinery services expenditures (PAMSE). The empirical results reveal that there is a nonlinear relation between the farm size and PAMSE. Specifically, farm size expansion can reduce the PAMSE by improving mechanization efficiency in all cases, while the magnitude of cost-saving is progressively reduced in the process of farm scale expansion. In particular, a 1 mu (1 mu = 1/15 ha) increase in the farm scale could only lead to a 0.3% decrease in the PAMSE when the farm size exceeded 50 mu, which indicates that 50 mu is a minimum efficient farm scale to achieve most economies of scale. Therefore, we suggest that persistent efforts should be devoted to improving farmland circulation efficiency and developing scale farms. More importantly, governmental supporting policies, such as agricultural subsidies, need to attach more importance to these large farms. [ABSTRACT FROM AUTHOR]

Agricultural land carbon opportunity cost (COC) characterizes potentials for carbon sequestration through ecosystem restoration, which is a critical component for formulating nature-based solutions to mitigate climate change. Yet existing relevant estimates still stayed at global scale, lacking estimates at national and provincial scale. Here, we integrated multi-source downscaled data to estimate the magnitude of land COC for 20 categories of crops and livestock in 30 provinces of China. Results show that beef got the highest land COC with about 29% of the national total, and COC per unit production of beef was much higher than that of other products. The high beef-induced COC was primarily caused by vast amount of grass feed consumed by beef cattle, resulting in native forest land being cleared into grazing land. Moreover, both land COC and crops yield per unit area of cropland enhanced with latitude decrease, but the increase rate of the former was much higher than that of the latter. Therefore, improving utilization efficiency of existing grazing land and raising yields per unit area of existing croplands in low-latitude provinces, rather than clearing new native forest land into grazing land and cropland, would have great functions on declining national total land COC for agricultural products. The research could also contribute to discussions of local tradeoffs between land carbon storage and agricultural production and then inform climate mitigation strategies. • Land carbon opportunity cost (COC) by province-product in China was estimated. • Sichuan, Hunan, and Guangxi had the largest capacity to restore carbon. • Beef production contributed the most (29%) of national total COC. • Land COC per unit yield enhanced substantially with decreasing latitude. • Tradeoffs between carbon stock and agricultural production needs to be discussed. [ABSTRACT FROM AUTHOR]

The spatiotemporal change of cultivated land can exert significant effects on food production and the associated water consumption. The quantification of these effects is meaningful for guiding relevant policies. However, few studies have explored systematic methods assessing changes of food production and water consumption and the relations between them, caused by cultivated land change. This study developed new spatially explicit datasets for constant food crop yield and constant food crop water consumption, combining agricultural statistical data, the China-AEZ model, and the GIS spatial analysis method, and estimated the impact of cultivated land change on food crop production, food crop water consumption and food-water relations characterized by two major indicators, i.e., crop water productivity (CWP) and green water proportion (GWP), in China during 1990–2015. The results showed that the increase of approximately 0.80% in cultivated land area in China resulted in a decrease of approximately 0.37% in average food crop yield per unit area, an increase of approximately 1.97% in blue water consumption per unit area (ET blue), and continuous decreases in both total water consumption per unit area (ET a) and green water consumption per unit area (ET green), with overall rates of 2.41% and 3.11%, respectively, at the national scale from 1990 to 2015. Concurrently, the average CWP continuously increased with an overall rate of 2.06%, while the average GWP continuously decreased with an overall rate of 0.86% at the national scale. A low-level coupling trend of food-water relations was concluded, together with a negative environmental effect. The food-water relations were getting even worse in major cultivated land expansion areas and during the later period of 2000–2015. The findings of this study can be useful for providing a deep understanding of food-water relations corresponding to cultivated land change and giving suggestions for the sustainable development of cultivated land and the integrated management of water resources. Unlabelled Image • We developed new spatially explicit datasets for constant food crop yield and constant food crop water production in China. • Cultivated land change resulted in a rough decrease in average food crop yield in China during 1990–2015. • Cultivated land change resulted in decreases in average ET a and ET green a, and an increase in ET blue in China during 1990–2015. • Cultivated land change resulted in an increase of average CWP and a decrease in average GWP in China during 1990–2015. • Cultivated land change resulted in a low-level coupling food-water relations, with a negative environmental effect in China. [ABSTRACT FROM AUTHOR]