Highlights • Farming-pastoral ecotone (FPE) accounted for approximately 1/5 of China’s total land area. • FPE patterns and driving forces changed diversely in time and space. • The implementation of ecological protection policies has reversed the westward-shifting trend for FPE. Abstract The farming-pastoral ecotone (FPE), defined as the mosaic of transition zone between traditional farming and pastoral regions, is sensitive to climate change and human disturbance. Extensive farming activities within and along FPEs have led to alarming environment degradation in China in the past several decades. Many ecological protection policies have been deployed to improve the structure and function of current FPEs. However, the changes in national FPE patterns as a result of farming activities and ecological protection policies have rarely been quantified using a robust dataset. Therefore, in this study we quantified two-decades of FPE change patterns in China using spatial autocorrelation and spatial clustering methods, along with land use data at 10 year intervals from 1990 to 2010. The results show that the derived FPEs in the north, middle, and south sections along the Hu’s Line underwent remarkable spatio-temporal changes. The north and middle FPEs shifted from the southeast to northwest during the period of 1990–2000, mainly because of extensive farming activities. However, this trend slowed in the north FPE, and reversed in the middle FPE in the 2000s, mainly attributed to the deployment of ecological protection policies. As there are limited farming activities in mountainous terrains, the south FPE did not show notable changes compared with the north and middle FPEs. The PFE changes caused predominantly by extensive agricultural activities and ecological protection policies were then further quantified through transition matrix analyses between FPEs, farming areas (FA), and pastoral areas (PA). Our study suggests that new FPE maps derived from satellite remote sensing could provide a straightforward methodology to quantitatively evaluate the effect of agricultural activities and environmental policies on vulnerable FPE regions.

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. Highlights • Re-define dust storm intensity (DSI) with frequency, duration and visibility. • This definition is easily used because the data used is available. • DSI was underestimated after 2000 using the traditional method in China. • There were four modes in the pattern of DSI changes in China in the past 30 years. • Temperature, wind speed and rainfall only explained 5.9% of changes in DSI.

Mountainous areas in China account for two‐thirds of the total land area. Due to rapid urbanization, rural population emigration in China's mountainous areas is very significant. This raises the question to which degree such population emigration influences the vegetation greenness in these areas. In this study, 9,753 sample areas (each sample measured about 64 square kilometers) were randomly selected, and the influences of population emigration (population pressure change) on vegetation greenness during 2000–2010 were quantitatively expressed by the multivariate linear regression (MLR) model, using census data under the condition of controlling the natural elements such as climatic and landform factors. The results indicate that the vegetation index in the past 10 years has presented an increasing overall trend, albeit with local decrease in some regions. The combined area of the regions with improved vegetation accounted for 81.7% of the total mountainous areas in China. From 2000 to 2010, the rural population significantly decreased, with most significant decreases in the northern and central areas (17.2% and 16.8%, respectively). In China's mountainous areas and in most of the subregions, population emigration has significant impacts on vegetation change. In different subregions, population decrease differently influenced vegetation greenness, and the marginal effect of population decrease on vegetation change presented obvious differences from north to south. In the southwest, on the premise of controlling other factors, a population decrease by one unit could increase the slope of vegetation change by 16.4%; in contrast, in the southeastern, northern, northeastern, and central area, the proportion was about 15.5%, 10.6%, 9.7%, and 7.5%, respectively, for improving the trend of NDVI variation.

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 76 m2 in 2000, but that the corresponding value was 106 m2 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.

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 76 m2 in 2000, but that the corresponding value was 106 m2 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.

Abstract The Heihe River is located in the arid zone of northwestern China. In its middle-reach region, irrigation agriculture is well developed. With rapid population growth and expansion of the cultivated land in this region, effective water resource use is vital for the sustainable development of the river basin and the increase of incomes from farming practices. In this study, based on farmer survey data, the input parameters of the CROPWAT model were modified, the water use amount was simulated after deducting the influences of climate, seeds, and irrigation systems, and the variation of economic efficiency of water use (EEWU) induced by crop structure adjustment from 2001 to 2012 was analyzed. The results show that simulations for evapotranspiration of maize based on the CROPWAT model are in accord with the observed data. From 2001 to 2012, due to changes in the regional crop structure, EEWU in the study area increased by about 40%. In the arid areas in northwest China, crop structure adjustment has a huge potential for improving EEWU and increasing incomes from farming practices. Highlights • Input parameters of the CROPWAT model were modified using field survey data. • Modeled evapotranspiration is consistent with observed data. • Agricultural structure in the study area has experienced drastic changes. • Effects of planting structure on water use efficiency after deducting the other factors. • Economic efficiency of water use increased by 40% due to the crop structure changes.

Abstract City size is closely related to urban heat island intensity (UHII). To examine the relationship more accurately, it is necessary to eliminate the effects of landforms and climatic differences on urban heat islands (UHIs), through selecting settlement clusters in a large plain within a similar biome as the study area. This study selected 1124 land use clusters (cities, towns, and big rural settlements) and demarcated surrounding buffer areas; each buffer width equaled the radius of the clusters. The results showed that UHI increased with growth in cluster size, and the relationship could be described using a logarithmic function. For clusters with an area >2 km 2 , the city size accounted for about 60% of the variance in UHII during the night and only about 30% during the day. For clusters with areas of <2 km 2 , the uncertainty in the relationship increased significantly and the relationship became very weak. In addition, our study showed that daytime UHII was higher than nighttime UHII, particularly for large cities with a size >10 km 2 . Highlights • UHII: urban heat island intensity. • To examine the relationship under the ideal conditions between city size and UHII. • For cities over 2 km 2 , city size explained ∼60% of the variance in nighttime UHII. • Variations in daytime UHII were greater than those in nighttime. • To re-define the rural background of urban clusters.

Highlights • 5 megaregions witnessed rapid urban expansion in China, 1990–2010. • Significant differences in cluster growth across the 5 megaregions. • Urban clusters in the 5 megaregions all fitted closely to the rank-size rule. • Size distribution of the clusters became more uneven. • Policy implications for New Urbanization. Abstract 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.

Highlights • About a half of water uses for winter wheat are met by rainfall in the south, compared to a third in northern NCP. • A north–south shift of area sown to winter wheat was identified in the NCP during 1998–2011. • The shift of area resulted in decreased use of groundwater for winter wheat in the NCP. • The shift of area also resulted in increased proportion of green water in total water use in the NCP. • Large savings were made in the amount of irrigation water used for winter wheat in the Hebei Plain. Abstract The serious water scarcity and groundwater over-exploitation problems of the North China Plain (NCP) have aroused worldwide concerns. Achieving a reduction in agricultural water use is critical, because agriculture is the largest water consumer in the NCP. New solutions to these problems may lie in changes in the area sown to winter wheat across the NCP. In this study, the water footprint ( WF ) was applied as an aggregative indicator to evaluate the impact of the changing area sown to winter wheat. A Chinese version of the AEZ model, the China-AEZ model, was used for the evaluation. The results showed: (1) Green water plays a more significant role in winter wheat production in the southern part of the NCP than in the north; about a half of the water requirements for winter wheat are met by green water in the southern part of the NCP, compared to only a third in the north. (2) As a result of the north–south shift in the area sown to winter wheat during the period 1998–2011, the WF , the green water footprint ( WF green ) and the surface water footprint ( W F bl ue s ) for winter wheat increased, respectively, by 459 × 10 6 m 3 yr −1 (0.9%), by 973 × 10 6 m 3 yr −1 (4.2%) and by 47 × 10 6 m 3 yr −1 (0.5%), whereas the groundwater footprint ( W F bl ue g ) diminished by 561 × 10 6 m 3 yr −1 (3.4%). The contribution of green water also increased, from 46.3% in 1998 to 47.8% in 2011, concurrent with the changes in the area sown to winter wheat. (3) The Hebei Plain, in the northern part of the NCP, conserved 1856 × 10 6 m 3 yr −1 of blue water footprint ( WF blue ) for winter wheat during the period 1998–2011, equivalent to about one third of the total amount of water supplied by the Middle Route of the South-to-North Water Transfer Project (MRP) in 2010. By comparison, WF and its components all increased in the southern provinces of the NCP. The diminishing requirement for groundwater and the increasing role of green water in winter wheat production encourage policies aimed at the further optimization of agricultural land use and the achievement of integrated blue-green water management in the NCP.

The land fallow policy was adopted by central and local governments to encourage the abandonment of water-intensive crops, such as winter wheat, in groundwater over-exploited areas. At the same time, since the 1990s, many households in the North China Plain (NCP) have chosen to replace the winter wheat and summer maize double-cropping system with the spring maize single-cropping system. Therefore, it is crucial to identify target land parcels for winter wheat abandonment and to design reasonable and proper standards for ecological compensation prior to the implementation of the land fallow policy in the NCP. In this study, multi-level logit models were used with household survey data in order to detect determinants across land parcel, household and village levels on household cropping system decisions; the opportunity costs for winter wheat abandonment were also calculated using cost–benefit analysis. The results show that: (1) land quality and irrigation condition at parcel level are two essential elements influencing household cropping system decisions. Nearly 70% of the total area of poor land and more than 90% of the total area of unirrigated land has suffered winter wheat abandonment. Target land parcels for the land fallow policy should be those that are irrigated and of high quality. (2) There were no significant differences between net profits from spring maize and summer maize under similar farming conditions, and the opportunity cost for winter wheat abandonment should be equal to the net profit of winter wheat. (3) The primary purpose of the land fallow policy is to induce groundwater recovery and restoration as a preliminary stage. A higher level of 350 yuan/mu is recommended as subsidy for ecological compensation at this stage. Later, the primary purpose of the policy should be a transition to a balance between exploitation and supplementation of water resources, and a lower level of 280 yuan/mu is recommended as a subsidy at this stage.

Rural areas under urban pressure (rural areas under pressure) in China face a growing conflict between the expansion of developed areas and the protection of cropland. The concentration of rural settlements has been embraced by local governments as a strategy to alleviate the conflict between these two land-use needs. This paper used Daxing District, Beijing, China as a case study to discuss the evolution of rural settlements in China over the past three decades and to consider the policy implications for rural settlement concentration. The results showed that: (1) over the past three decades, rural settlements have remained evenly distributed, and in 2007 each settlement had an average of 609 inhabitants; (2) the area of rural settlements has increased by approximately 100% because of various factors such as decreasing household size, increasing numbers of migrants, and improvements in living conditions; and (3) the shape of rural settlements has become more regular. These factors pose challenges to concentrating rural settlements. This study recommends that rural settlement concentration and restructuring should pay special attention to the economies of scale of market towns and large and merged villages, which can house larger populations and better accommodate industry in the future.

Highlights • Plot level and household level were both crucial in explaining farmers’ abandonment of winter wheat. • Winter wheat was more likely to be abandoned on plots with lower land quality and larger plot areas. • Winter wheat was less likely to be abandoned on plots with stable water availability. • Household non-agricultural income ratio played a positive role on farmers’ abandonment of winter wheat. • Household demographic characteristics also contributed significantly to farmers’ abandonment of winter wheat. Abstract Since the late 1990s, the North China Plain (NCP) has undergone large-scale shrinkage of area sown to winter wheat, accompanying with traditional double cropping system being replaced by spring corns. However, studies on the underlying determinants are rarely found. The goal of this paper is to detect the hierarchical determinants on farmers’ cropping system decisions. A case study was carried out in Xingzhuangzi village of Hebei province, and multi-level statistic models were constructed using household survey data. Results show that plot level and household level were both crucial in explaining farmers’ land use decisions: winter wheat was more likely to be abandoned on plots with lower land quality, unable to be irrigated, and with larger plot areas; at household level, both the non-agricultural income ratio and the land fragmentation played positive roles on farmers’ abandonment of winter wheat while the role of household agricultural labor availability was negative. There was also a nonlinear relationship between average age of households’ agricultural laborers and their cropping system decisions, and middle-aged farmers had a lower probability to abandon winter wheat. Overall, this paper provides empirical identification on hierarchical determinants of agricultural land use change in the NCP, and encourages policies aiming at adjustment of cropping systems, integration management of both surface and groundwater, and promotion of land transfer, in order to achieve the twin goals of ecological conservation and food security in water-scarce areas.