Urban expansion brought stress to food security in China: Evidence from decreased cropland net primary productivity

Unequal impacts of global urban-rural settlement construction on cropland and production over the past three decades

The world has experienced a rapid expansion of human settlements in both urban and rural areas in recent decades, yet the unequal impacts of this construction on global food security remain unclear. In this study, we delineated the global-scale expansion of urban-rural settlements at a fine resolution from 1985 to 2020 and quantified their uneven impacts on food security, focusing on the relationships between settlement types, cropland categories, and disparities in crop production. Our results showed that despite dramatic urbanization, rural settlements still constituted the majority of human settlement areas in 2020. Globally, cropland loss due to the expansion of rural settlements was 1.2 times greater than that caused by urbanization, while the associated yield loss was 1.5 times higher. Notably, urban-rural settlement expansion in Asia accounted for 61% of cropland loss and 64% of yield loss. Moreover, future scenarios predicted that Asia's urban-rural settlement expansion will continue to have the most significant impacts on the loss of cropland and yield throughout the 2030s. These results provide systematic evidence of the unequal impacts of urban-rural settlement construction on global cropland and food security.

The interplay and synergistic relationship between urban land expansion and urban resilience across the three principal metropolitan regions of the Yangtze River Basin

As global urbanization advances, the expansion of urban land has subjected cities to increasingly frequent and extensive external disturbances, often revealing limitations in disaster prevention and mitigation capacities, particularly in regions characterized by high urbanization, environmental degradation, and recurrent natural disasters. This study investigates the association between urban land expansion and urban resilience, developing a targeted analytical framework to assess their coupling and coordination. Leveraging remote sensing data on land use and socio-economic development indicators, we constructed a comprehensive evaluation index encompassing social, economic, ecological, and infrastructural dimensions. Examining three principal urban agglomerations in China's Yangtze River Basin, we analyzed the spatial-temporal dynamics and rates of change in urban land area and resilience levels from 2000 to 2020. A coupling coordination model was applied to assess the alignment between the rate of urban land expansion and resilience improvement, ultimately aiming to derive actionable policy recommendations. The results demonstrate that: (1) both the intensity and rate of urban land expansion across urban agglomerations in the Yangtze River Basin have declined, indicating a shift in urbanization focus from "land expansion" to "quality enhancement," with a slowdown in the conversion of agricultural to urban land. (2) Urban land expansion exhibits weak directionality, with land expansion occurring uniformly within the region. (3) On the whole, resilience levels in the Yangtze River Basin's urban agglomerations remain moderate or lower, although showing gradual improvement. (4) The coordination between urban land area and urban resilience across the basin is limited, with a declining alignment between urban land expansion and resilience enhancement rates, signaling an emerging imbalance. By assessing the coordination between urban land expansion and resilience, this study seeks to inform policy development on urban land management and resilience enhancement within the Yangtze River Basin's urban agglomerations.

Evaluation of farmland production potential in key agricultural production areas on the Qinghai-Tibet Plateau under multi-scenario simulation

Predicting changes in future land use and farmland production potential (FPP) within the context of shared socioeconomic pathways (SSPs) and representative concentration pathways (RCPs) is crucial for devising sustainable land use strategies that balance agricultural production and ecological conservation. Therefore, the Huangshui Basin (HSB) in the northeast Qinghai-Tibet Plateau is taken as the study area, and a LUCC-Plus-FPP (LPF) coupling framework based on the SSP-RCP scenarios is proposed to evaluate future land use patterns and FPP changes. On the basis of the predictions of land use changes from 2020 to 2070, the trade-offs in grain production resulting from bivariate changes in farmland and FPP under future scenarios are analyzed. The results indicate that the model has a high simulation accuracy for land use types, with an overall accuracy of 0.98, a kappa coefficient of 0.97, and a figure of merit value of 0.21. Under the SSP245 and SSP585 scenarios, built-up land increases significantly, by approximately 45.89 %. Farmland and grassland conversions contribute the most to increased built-up land. Farmland area consistently decreases by approximately 5 % across all scenarios. The protection of farmland in the study area is difficult to undertake and thus requires much attention. Moreover, under the SSP126 scenario, the FPP of most districts is greater than that in 2020, and the average FPP of the HSB from 2030 to 2070 is greater than that in 2020. In the SSP585 scenario, by 2070, the average FPP of all districts decreases to different degrees compared with that in 2020. Furthermore, the compensated farmland quantities and average FPPs under all the scenarios are significantly lower than the amount of occupied farmland. The results provide a theoretical foundation and data support for farmland protection decision-making and layout optimization in the Qinghai-Tibet Plateau.

Effects of environment and human activities on rice planting suitability based on MaxEnt model

Rice is one of the major food crops, and the study of suitable planting areas for rice plays an important role in improving rice yield and optimizing the production layout. This study used Maximum Entropy (MaxEnt) model to simulate and predict the distribution of suitable rice planting areas in China from 1981 to 2020 by combining the climate, soil, and human activities, analyzed the spatial and temporal changes of suitable rice planting areas in China, and determined the main factors affecting rice planting suitability. The results indicated that the main factors influencing the distribution of suitable planting areas for rice in China were gross domestic product (GDP), population density (Pop), and annual sunshine duration (Sun), with human activities playing a dominant role. The high suitable planting areas of rice were mainly distributed in Hubei, Hunan, Jiangxi, Anhui, Guangdong, southeastern Sichuan and western Guizhou. The total suitable planting areas for rice were 346.00 × 104 km2, 345.66 × 104 km2, 347.01 × 104 km2, and 355.57 × 104 km2 from 1981 to 1990, 1991 to 2000, 2001 to 2010 and 2011 to 2020, respectively. With the passage of time, the area of unsuitable areas for rice gradually decreased, and the area of medium suitable areas increased, with large changes in the area of high- and low-suitable areas. Moreover, due to the transfer of a large number of rural laborers to the cities in recent years, the tension between people and land caused by the population explosion has led to the increasing impact of Pop on rice suitable areas and the relatively weakening of the impact of GDP on rice production interventions. The results can be used to provide scientific evidence for the management of rice cultivation and food production safety, with a view to reducing the impacts of climate change on agricultural production in the context of global climate change.

Study of spatial spillover effects and threshold characteristics of the influence of urbanization on grain green production efficiency in China under carbon constraints

Food security is a basic guarantee for maintaining social stability, and improving green and healthy grain production is the way to promote food security. China is currently experiencing rapid urbanization that has an impact on grain production and security, with reduced arable land, environmental pollution, insufficient agricultural population, and inadequate resource allocation. How to deal with the relationship between urbanization and grain production becomes the key to solve this problem. Therefore, this study constructs an evaluation system of grain green production efficiency (GGPE) with non-expected output containing carbon emissions, and uses the super-efficient SBM model to measure the level of GGPE, and constructs a spatial econometric model to examine the spatial correlation and spillover effect of urbanization on GGPE; then constructs a panel threshold model to analyze the nonlinear threshold characteristics between urbanization and GGPE. It was found that (1) from 2000 to 2019, China's GGPE showed an overall upward trend, and the performance of GGPE varied among different provinces. (2) According to the results of the spatial econometric model, China's GGPE shows obvious spatial characteristics, and the level of urbanization not only directly affects regional GGPE but also can indirectly affect neighboring regions' GGPE through spatial spillover effects, and the indirect effects among regions are larger than the direct effects. (3) Spatial threshold effect results, there is a significant non-linear threshold characteristic of the impact of urbanization rate on GGPE. In terms of the influence effects of other variables, the influence of each variable on GGPE is roughly in the same direction as the influence under the spatial spillover effect, but the degree of influence is slightly different.

Research on the spatio-temporal coupling relationship between agricultural green development efficiency and food security system in China

Food security and agricultural green development are fundamental issues concerning the survival of mankind. To realize the coordinated development of them is of great significance to promote the green transformation of agriculture and ensure national food security. However, few studies have analyzed the coupling relationship between agricultural green development and food security. Therefore, this study complements the research on the coupling relationship between them. First, we use the agricultural panel data of 31 provinces in China from 2010 to 2021 to measure the agricultural green development efficiency and food security level by Super-SBM model and entropy weight method. Then, the coupling relationship and spatiotemporal evolution of the two are analyzed by coupling coordination degree model. The results show that, first of all, China's agricultural green development efficiency and food security level have improved overall, but there are regional differences. Secondly, the degree of coupling and coordination between the two is significantly improved, and most provinces develop from the break-in stage to the coordination stage, and the regional differences are relatively reduced. Finally, Beijing, Shanghai and other developed areas are mostly of the lagging food security type, Liaoning, Shandong and other major grain producing areas have reached a high degree of coordination, while Tibet, Qinghai and other western regions are still in the break-in stage. According to the development situation of different regions, corresponding suggestions are put forward. For regions with lagging food security type, the government should give full play to the application of science and technology in agriculture and promote green and low-carbon planting technologies. For regions with low coupling and coordination degree, the government should improve support policies and build a collaborative operation system, adjust planting structure to improve land utilization rate and food security level. Finally, the government should work together to build agricultural industrial parks and give full play to the leading role of competitive provinces to achieve common development.

Spatial patterns of urban expansion and cropland loss during 2017-2022 in Guangdong, China

Urban expansion often occurs at the expense of cropland loss, posing challenges to sustainable urban growth and food security. However, detailed investigations into urban expansion and cropland loss remain limited, particularly in regions with varying levels of urbanization. Here, we take Guangdong Province, China, as a case study to exemplify how urban expansion affects cropland using remotely sensed land use products. We adopted geospatial analysis, correlation indicators, and landscape metrics to uncover their spatial relationships at 10-m spatial resolutions. Results showed that urban areas increased by 6335 km2 while cropland decreased by 3780 km2 from 2017 to 2022. Notably, 41 % of newly expanded urban areas were from croplands, and 45 % of lost croplands were converted to urban areas. Western Guangdong experienced the largest extent of urban expansion and cropland loss, emerging as a hotspot region in recent years. Additionally, our analysis observed the increasing compactness of urban areas and the growing fragmentation of cropland landscapes over time. These findings shed light on the intricate dynamics between urban expansion and cropland loss in rapidly urbanizing regions, which provide valuable insights for sustainable urban development, agricultural practice, and land management in the future.

Asymmetric response of vegetation GPP to impervious surface expansion: Case studies in the Yellow and Yangtze River Basins

Terrestrial gross primary production (GPP) changes due to impervious surfaces significantly impact ecosystem services in watersheds. Understanding the asymmetric response of vegetation GPP to impervious surface expansion is essential for regional development planning and ecosystem management. However, the asymmetric response of vegetation GPP to the impacts of impervious surface expansion is unknown in different watersheds. This paper selected the Yellow River and Yangtze River basins as case studies. We characterized the overall change in GPP based on changes in impervious surface ratio (ISR), determined impervious surface expansion's direct and indirect impacts on GPP in the two watersheds, and further analyzed the asymmetric response of the compensatory effects of indirect influences on the impervious surface expansion in different watersheds. The results showed that: (1) The vegetation GPP decreased with increasing ISR in the Yangtze River Basin, while that in the Yellow River Basin first increased and then reduced. (2) The direct impacts of increased ISR reduced vegetation GPP, while the indirect impacts both had a growth-compensating effect. Growth compensation stabilized at approximately 0.40 and 0.30 in the Yellow and Yangtze River Basins. (3) When the ISR was 0.34-0.56, the growth compensation could offset the reduction of GPP due to direct impact and ensure that the background vegetation GPP was not damaged in the Yellow River Basin. In contrast, the background vegetation GPP was inevitably impaired with increased ISR in the Yangtze River Basin. Therefore, this study suggests that the ISR should be ensured to be between 0.34 and 0.56 to maximize the impervious surface of the Yellow River Basin without compromising the background vegetation GPP. While pursuing impervious surface expansion in the Yangtze River Basin, other programs should be sought to compensate for the loss to GPP.

Potential of technological innovation to reduce the carbon footprint of urban facility agriculture: A food-energy-water-waste nexus perspective

As an emerging form of agriculture, urban facility agriculture is an important supplement to traditional agriculture and one of the ways to alleviate the urban food crisis, but it may generate a high carbon footprint. A comprehensive assessment of urban facility agriculture is a necessity for promoting its low-carbon development. In this study, the carbon footprint of urban facility agriculture under four different technological innovation models was simulated by life cycle assessment and a system dynamics model for a carbon footprint accounting without considering economic risk. Case 1, as the basic case, is Household farm facility agriculture. Case 2 is the introduction of vertical hydroponic technology based on Case 1, Case 3 is the introduction of distributed hybrid renewable energy micro-grid technology based on Case 2, and Case 4 is the introduction of automatic composting technology based on Case 3. These four cases demonstrate the gradual optimization of the food-energy-water-waste nexus in urban facility agriculture. This study further uses the system dynamics model for carbon reduction potential considering economic risk to simulate the diffusion (promotion) scale and carbon reduction potential of different technological innovations. Research results show that with the superposition of technologies, the carbon footprint per unit land area is gradually reduced, and the carbon footprint of Case 4 is the lowest at 4.78e+06 kg CO₂eq. However, the gradual superposition of technologies will further limit the diffusion scale of technological innovation, thereby reducing the carbon reduction potential of technological innovation. In Chongming District, Shanghai, under theoretical circumstances, the carbon reduction potential of Case 4 is the highest at 1.6e+09 kg CO₂eq, but the actual carbon reduction potential is only 1.8e+07 kg CO₂eq due to excessive economic risks. By contrast, the actual carbon reduction potential of Case 2 is the highest with 9.6e+08 kg CO₂eq. To fully achieve the carbon reduction potential of technology innovation, it is necessary to promote the scale diffusion of Urban facility agricultural technology innovation by raising the sales price of agricultural products and the grid connection price of renewable electricity.

Environmental factors affecting honey bees (Apis cerana) and cabbage white butterflies (Pieris rapae) at urban farmlands

Rapid urbanization results in a significantly increased urban population, but also the loss of agricultural lands, thus raising a concern for food security. Urban agriculture has received increasing attention as a way of improving food access in urban areas and local farmers' livelihoods. Although vegetable-dominant small urban farmlands are relatively common in China, little is known about environmental factors associated with insects that could affect ecosystem services at these urban farmlands, which in turn influences agricultural productivity. Using Asian honey bee (Apis cerana) and cabbage white butterfly (Pieris rapae) as examples, I investigated how environmental features within and surrounding urban farmlands affected insect pollinator (bee) and pest (butterfly) abundance in a megacity of China during winters. I considered environmental features at three spatial scales: fine (5 m-radius area), local (50 m-radius area), and landscape (500 m-raidus and 1 km-radius areas). While the abundance of P. rapae increased with local crop diversity, it was strongly negatively associated with landscape-scale crop and weed covers. A. cerana responded positively to flower cover at the fine scale. Their abundance also increased with local-scale weed cover but decreased with increasing landscape-scale weed cover. The abundance of A. cerana tended to decrease with increasing patch density of farmlands within a landscape, i.e., farmland fragmentation. These results suggest that cultivating too diverse crops at urban farmlands can increase crop damage; however, the damage may be alleviated at farmlands embedded in a landscape with more crop cover. Retaining a small amount of un-harvested flowering crops and weedy vegetation within a farmland, especially less fragmented farmland can benefit A. cerana when natural resources are scarce.

Impact assessment of urbanization on vegetation net primary productivity: A case study of the core development area in central plains urban agglomeration, China

Rapid urbanization process has a negative or positive impact on vegetation growth. Net primary productivity (NPP) is an effective indicator to characterize vegetation growth status. Taking the core development area of the Central Plains urban agglomeration as the study area, we estimated the NPP and its change trend in the past four decades using the Carnegie-Ames-Stanford Approach (CASA) model and statistical analysis based on meteorological and multi-source remote sensing data. Meanwhile, combined with the urbanization impact framework, we further analyzed urbanization's direct and indirect impact on NPP. The results showed that the urban area increased by 2688 km² during a high-speed urbanization process from 1983 to 2019. As a result of the intense urbanization process, a continuous NPP decrease (direct impact) can be seen, which aggravated along with the acceleration of the urban expansion, and the mean value of direct impact was 130.84 g C·m^-2·a^-1. Meanwhile, urbanization also had a positive impact on NPP (indirect impact). The indirect impact showed an increasing trend during urbanization with a mean value of 10.91 g C·m^-2·a^-1. The indirect impact was mainly related to temperature in climatic factors. The indirect impact has a seasonal heterogeneity, and high-temperature environments of urban areas are more effective in promoting vegetation growth in autumn and winter than in summer. Among different cities, high-speed development cities have higher indirect impact values than medium's and low's because of better ecological construction. This study is of great significance for understanding the impact of urbanization on vegetation growth in the Central Plains urban agglomeration area, supporting urban greening plans, and building sustainable and resilient urban agglomerations.

Spatial and structural characteristics of the ecological network of carbon metabolism of cultivated land based on land use and cover change: a case study of Nanchang, China

This paper explored the ecological network of CMCL (carbon metabolism of cultivated land) of Nanchang City from 2000 to 2020 to promote the low-carbon land management and China's dual carbon goals. We found that vertical and horizontal net carbon flow of cultivated land was negative during 2000-2020, and harmful carbon flow was mainly generated by the conversion of cultivated land to transportation and industrial land. Cultivated land contributed the most of the total carbon throughflow, accounting for 56.16%. Furthermore, exploitation and control relationships made maximal contribution to ecological relationships (45.83%), followed by competition relationships and mutualism relationships. In addition, ecological utility index showed the ecological network of CMCL is unhealthy. We suggest that it is necessary to achieve healthy and orderly operation of the ecological network of CMCL to reduce carbon emissions.

Carboxymethylcellulose reinforced starch films and rapid detection of spoiled beverages

The integrity of the packaging of a liquid foodstuff makes it difficult to detect spoilage. Therefore, it is important to develop a sensitive, fast and real-time material for liquid food detection. CMC, as lignocellulose derivatives and starch are widely used in the food industry. In this study, starch films with pH-responsive properties are successfully prepared from full-component starch and corn amylopectin (CA) by adding CMC. The effects of CMC on the mechanical properties, morphology characteristics, physical and chemical structures, stability and pH responsiveness of the starch films are analyzed. The starch/CMC-1.0 g composite films display good electrical conductivity and reduce the resistance of the composite film by two orders of magnitude. The composite films have pH response ability; in the simulation of orange juice spoilage experiment, the CA/CMC composite film has a more sensitive current response and was more suitable for the application to liquid food quality detection. Additionally, the starch/CMC composite films have potential applications for rapid detection and real-time monitoring of the safety of liquid food.

Slope climbing of urban expansion worldwide: Spatiotemporal characteristics, driving factors and implications for food security

The tendency of global urban expansion to be slope climbing has partly become possible with scarce cropland resources in plains. However, the scientific understanding of the quantity, intensity, pattern, and effect of the slope climbing of urban expansion (SCE) is minimal globally. In this study, we have attempted to quantify and evaluate global SCE from Suomi National Polar-orbiting Partnership (SNPP)-Visible Infrared Imaging Radiometer Suite (VIIRS)-like data and other auxiliary data. Results revealed that global SCE areas unevenly increased from 22,760 km² to 90,720 km² from 2000 to 2020, with an annual growth rate of 21.72%, in which low-environment cost type areas increased from 21,550 km² to 84,010 km² while high-environment cost type (HEC) areas increased from 1210 km² to 6710 km². One remarkable phenomenon is that China's SCE areas in 2020 were more than 11 times those in 2000. In addition, global SCE intensity increased by about 3.4-fold from 2000 to 2020 and the rapid growth of HEC intensity is concentrated in Asia and North America. SCE is mostly affected by urban population growth and terrain. Economic development also promotes its development to a certain extent. We also noted that global SCE potentially made a considerable contribution to saved cropland, saving about 46,747 km² with a theoretical increased grain yield of 25,020 × 10³ t. Our study provides timely and transparent monitoring of global SCE and offers new insights into sustainable urban development.

Ion-Modified Starch Film Enables Rapid Detection of Spoiled Fruit Juices

Juice, as a liquid foodstuff, is subject to spoilage and damage due to complications during transport and storage. The appearance of intact outer packaging often makes spoilage and damage difficult to detect. Therefore, it of particular importance to develop a fast, real-time material to evaluate liquid foodstuffs. In this paper, starch films with pH response characteristics are successfully prepared by inorganic ion modification by utilizing whole starch and amylopectin as raw materials. The mechanical properties, stability properties, hydrophilic properties and pH electrical signal response indices of the films are analyzed and measured. The films exhibit good electrical conductivity values with 1.0 mL of ion addition (10 mmol/L), causing the composite film to respond sensitively to solutions with varying pH values. In the test of spoiled orange juice, the full-component corn starch (CS) film has more sensitive resistance and current responses, which is more conducive for applications in the quality monitoring of juice. The results indicate that modified starch films can potentially be applied in the real-time monitoring of the safety of liquid foodstuffs.

Spatial Differences of Nutrient Adequacy in Coastal Areas of China

Ensuring nutrient adequacy for all is a common goal of the international community, but spatial difference is one of the barriers to its development. Exploring nutrient adequacy in coastal areas of China can help regions where food production systems and economic development systems are under mutual stress to reduce nutritional disparities and improve nutrition levels. This paper used the transformation food-to-nutrient model to calculate nutrient production and nutrient consumption in 11 coastal provinces of China and analyzed their spatial patterns, after which spatial differences in nutrient adequacy (including energy, protein and fat) were analyzed. The results showed that nutrient production and nutrient consumption in coastal areas of China showed significant spatial differences, in which nutrient production was mainly concentrated in land food, and the three provinces of Shandong, Jiangsu and Hebei contributed more. Guangdong had the highest nutrient consumption; in contrast, Shanghai, Tianjin, and Hainan had the lowest consumption. Nutrient adequacy was not optimistic, with fat being particularly significant, and nutrient surplus quantity was mainly concentrated in Shandong and Jiangsu and nutrient deficiency quantity was mainly concentrated in Guangdong. Overall, the study area had adequate levels of protein and was deficient in energy and fat levels, with surplus or shortage of 2.41 million tonnes, 2620 billion kcal and 9.97 million tonnes, respectively.

Spatiotemporal Differences, Dynamic Evolution and Trend of the Coupled Coordination Relationship between Urbanization and Food Security in China

Scientific assessment of the coupled coordination degree between urbanization and food security (CDUFS) revealed regional differences and sources. Dynamic evolution and trends are important references for achieving a coordinated interaction between high-quality urbanization and ensuring food security. Specifically, the CDUFS was measured using prefectural panel data in China from 2000 to 2019 and the coupling coordination degree model, which revealed its spatial correlation and differentiation. On this basis, in order to examine the spatiotemporal differences and evolution of the CDUFS, the Dagum-Gini coefficient and Kernel density estimation were innovatively used to analyze its regional differences and evolution distribution. The spatial Markov chain was further employed to examine the evolution trend of the CDUFS. The study found that the CDUFS showed a downward trend in fluctuation within the low coordination interval. There was a positive spatial correlation, with a more stable distribution pattern of high-high and low-low clusters. The regional differences in the CDUFS were obvious and the overall difference has expanded. The main source of regional differences among different food functional areas was inter-regional differences, followed by intra-regional differences. The regional difference between food main producing areas and food main marketing areas was the highest. The CDUFS shows a single-peak distribution; the imbalance between regions was still prominent with a left trailing phenomenon and no convergence. The CDUFS has the stability of maintaining the original state, and the probability of leapfrogging evolution is low in the short term. Finally, the geospatial effect plays an important role in the dynamic evolution of the CDUFS.

Quantitative Assessment of Climate Change Impact and Anthropogenic Influence on Crop Production and Food Security in Shandong, Eastern China

Food security plays an important role in maintaining national stability and sustainable development of human society, and its research has become a hot issue at present. Shandong is the main grain producing area in China, and its grain production plays an important role in national food security. Accordingly, this paper is based on the county climate change, grain yield, sown area, fertilizer use, total power of rural machinery, and total population data in Shandong Province from 1995 to 2020. The evolution process of the food security pattern was studied by the methods of spatial analysis and comprehensive evaluation, the influencing factors of food security were quantitatively analyzed, and the adaptive countermeasures to alleviate the food security risks in this region were discussed. The results show that: Grain production increased by 30.62% from 1995 to 2020. The total population and per capita food availability also increased. Since 2000, more than a quarter of counties have experienced a high risk of food insecurity. The spatial agglomeration of grain production was enhanced, and the local agglomeration characteristics were significantly different. The average temperature in the growing season, the sown area, and the total power of agricultural machinery had a significant positive impact on grain production, while the annual average temperature had a significant negative impact on grain production. Improving the food supply system, strengthening the protection of cultivated land, improving the efficiency of fertilizer utilization, and increasing investment in agricultural science and technology can effectively alleviate food security risks.

Combined Effect of Biochar and Fertilizers on Andean Highland Soils before and after Cropping

Although a number of works present biochar as a promising material for improving the quality of degraded soils, only a few show the effect of this material in soils from the Andean highlands. The objective of this work was twofold: (a) to study the effect of two types of biochars on two agricultural soils commonly found in the Andean highlands (Andisol and Inceptisol) and the corresponding soil–biochar–fertilizer interactions, and, (b) to assess the response to biochar of two vegetable crops (lettuce and radish) grown in succession in a simulated double-cropping system. Biochar was produced at 400 °C and 500 °C, for 1 h (B400 and B500, respectively), using hardwood residues. Properties of biochar that could potentially affect its interaction with soil and water (e.g., functional groups, surface area, elemental composition) were assessed. Experiments were conducted to test for main and interaction effects of biochar type, soil type, and the addition of NPK fertilizer on the soils’ characteristics. Bulk density and water content at field capacity and permanent wilting point were affected by two-way interactions between biochar and soil type. Biochar impacted bulk density and water retention capacity of soils. Higher available water content was found in soils amended with B400 than with B500, which is a consequence of the higher hydrophilicity of B400 compared to B500. After the lettuce crop was planted and harvested, the soil pH was unaffected by the biochar addition. However, after the second crop, the pH in the Inceptisol slightly decreased, whereas the opposite was detected in the Andisol. The CEC of the Inceptisol decreased (e.g., from 36.62 to 34.04 and from 41.16 to 39.11 in the control and in the Inceptisol amended with B400 only) and the CEC of the Andisol increased (e.g., from 74.25 to 90.41 in the control and from 79.61 to 90.80 in the Andisol amended with B400 only). Inceptisol amended only with biochar showed decrease of radish weight, while a large increase was found in B400 + fertilizer Inceptisol (i.e., from 22.9 g to 40.4 g). In Andisol, the weight of radish after the second crop increased in less proportion (i.e., from 43 g in the control to 59.7 g in the B400 + fertilizer Andisol), showing a visible positive impact of B400. The results suggest that biochar produced at 400 °C performs better than biochar produced at 500 °C because B400 apparently promotes a better environment for bacteria growth in the soils, as a consequence of more OH available groups in B400 and its better interaction with water and the fertilizer.

Comprehensive Analysis of Grain Production Based on Three-Stage Super-SBM DEA and Machine Learning in Hexi Corridor, China

Food security is always a pressing agenda worldwide. The grain production in many areas has decreased due to the reduction in agricultural research funding and infrastructure investment. In this paper, we employed the Extreme-Tree algorithm to determine the main effectors in grain production in Hexi Corridor, Gansu, China, during 2002–2018. First, we applied the three-stage super-SBM DEA to precisely assess agricultural production. Then, we used the Extremely randomized trees algorithm to quantify the importance of each factor. Our results show that the variant of average efficiency score at the first stage was minimal. After removing the influence of environmental factors on production efficiency, the more accurate efficiency score was decreasing from 2002 to 2018. The R2 value of the Extra-Tree model was 0.989 in the grain production analysis. Our research shows that grain production in the Hexi Corridor was controlled by human-driven but not nature-driven during our research period. Based on the importance attribution analysis of each model, it showed that the importance of human-driven investment occupied 93.7% of grain production. The importance of nature-driving was about 6.3%. Accordingly, we proposed corresponding opinions and suggestions to government and growers.

Urbanization in China drives farmland uphill under the constraint of the requisition-compensation balance

The slope is an important objective attribute of farmland that changes with the evolution of its spatial pattern. A growing area of plain farmland is being occupied by built-up land owing to rapid urbanization, while the newly added are sloping and terrace farmland under the constraint of the requisition-compensation balance. Researchers have focused on the horizontal spatial redistribution of farmland quantity while ignoring vertical variations in its slope, which is critical for its overall quality. Based on data on land use classification in China from 1990 to 2019, this study uses land use change trajectory as well as trend and driver analyses to identify the impact of urbanization on change in the slope of unstable farmland. The results show the following: (1) The area of unstable farmland accounted for ~20% of all farmland, with its slope increasing from 5.77° in 1990 to 6.25° in 2019 due to conversion in land use. (2) Variation in the slope of unstable farmland had significant heterogeneity, with regions undergoing a significant increase concentrated in the east and those undergoing monotonous decline not spatially clustered. (3) Farmland development and built-up land occupation have driven increases in the slope of unstable farmland with a relatively balanced effect, whereas the trend of increasing has been mainly suppressed by farmland marginalization. (4) The area of urban land expanded by 158,446.70km² during 1990-2019, 24.15% of which was due to encroachment on farmland with a slope of 1.31°. Farmland development with a slope of 6.98° helped replenish 90.30% of the occupied area. This combined process has led to unstable farmland uphill under the constraint of the requisition-compensation balance. The results here can provide a reference for the protection and sustainable utilization of farmland.

Phenological Shifts of the Deciduous Forests and Their Responses to Climate Variations in North America

Forests play a vital role in sequestering carbon dioxide from the atmosphere. Vegetation phenology is sensitive to climate changes and natural environments. Exploring the patterns in phenological events of the forests can provide useful insights for understanding the dynamics of vegetation growth and their responses to climate variations. Deciduous forest in North America is an important part of global forests. Here we apply time-series remote sensing imagery to map the critical dates of vegetation phenological events, including the start of season (SOS), end of season (EOS), and growth length (GL) of the deciduous forests in North America during the past two decades. The findings show that the SOS and EOS present considerable spatial and temporal variations. Earlier SOS, delayed EOS, and therefore extended GL are detected in a large part of the study area from temporal trend analysis over the years, though the magnitude of the trend varies at different locations. The phenological events are found to correlate to the environmental factors and the impact on the vegetation phenology from the factors is location-dependent. The findings confirm that the phenology of the deciduous forests in North America is updated such as advanced SOS and delayed EOS in the last two decades and the climate variations are likely among the driving forces for the updates. Considering that previous studies warn that shifts in vegetation phenology could reverse the role of forests as net emitters or net sinks, we suggest that forest management should be strengthened to forests that experience significant changes in the phenological events.

Impacts of Land Use Changes on Net Primary Productivity in Urban Agglomerations under Multi-Scenarios Simulation

Land use is closely related to the sustainability of ecological development. This paper employed a patch-generating land use simulation (PLUS) model for the multi-scenario simulation of urban agglomerations. In addition, mathematical analysis methods such as Theil-Sen Median trend analysis, R/S analysis, Getis-Ord Gi* index and unary linear regression were used to study the temporal and spatial evolution characteristics of net primary productivity (NPP) for the impact of land use changes on NPP in urban agglomerations from 2000 to 2020 and to forecast the future trend of NPP. The results indicate that urban expansion is obvious in the baseline scenario and in the ecological protection scenario. In the scenario of cropland protection, the urban expansion is consistent with the land use plan of the government for 2035. The NPP in Beijing decreased gradually from northwest to southeast. The hot spot areas are concentrated in the densely forested areas in the mountainous areas of northwest. The cold spot areas are mainly concentrated in the periphery of urban areas and water areas. The NPP will continue to increase in forest and other areas under protection and remain stable in impervious surfaces. The NPP of Beijing showed a strong improvement trend and this trend will continue with the right ecological management and urban planning of the government. The study of land use in urban agglomeration and the development trend of vegetation NPP in the future can help policymakers rationally manage future land use dynamics and maintain the sustainable development of urban regional ecosystems.

Assessing the sustainability of ecosystems over fourteen years of cultivation in Longnan City of China based on emergy analysis method

Currently, the contradiction between the limited resources of China's cultivated ecosystems and population growth is becoming increasingly evident, and the negative impacts on the environment and human activities need to be curbed. Therefore, it is crucial to quantify the sustainability of cultivated ecosystems and determine these driving factors that affect their development. This study used the emergy method to quantify the input/output flow and sustainable development of the cultivated land ecosystem in Longnan City, combined with the logarithmic mean divisia index decomposition analysis (LMDI) method to evaluate the driving factors of sustainable development in the region. The results demonstrate that from 2004 to 2017, the total emergy input and output of Longnan City showed an upward trend, and non-renewable resources (N) were always in a dominant state in the total emergy (T) input, and their proportion rose from 59.69% to 66.92%. The emergy sustainability index (ESI) is less than 1, and the environmental pressure of the system is relatively higher. Comprehensive emergy production ratio (EPR), emergy investment ratio (EIR), the renewable fraction (R%), emergy yield ratio (EYR) and environmental load ratio (ELR), showed that the agricultural ecological economy in Longnan still has great development potential, and clean energy should be developed as far as possible to replace fossil fuels in future planning. LMDI results showed that the intensity factor ΔY^'A is the main driving factor for the positive development of ESI. The government's ecological protection requirements can reduce waste emissions through reasonable farming system and advocating the use of organic fertilizer, so as to achieve the purpose of improving crop yield. Vigorous development of green ecological agricultural production patterns can improve the sustainability of arable ecosystems. This study can provide a theoretical basis for the sustainable development of cultivated ecosystems and the formulation of related agricultural production measures.

Spatiotemporal Patterns of Cultivated Land Quality Integrated with Multi-Source Remote Sensing: A Case Study of Guangzhou, China

Scientifically revealing the spatiotemporal patterns of cultivated land quality (CLQ) is crucial for increasing food production and achieving United Nations Sustainable Development Goal (SDG) 2: Zero Hunger. Although studies on the evaluation of CLQ have been conducted, an effective evaluation system that is suitable for the macro-regional scale has not yet been developed. In this study, we first defined the CLQ from four aspects: soil fertility, natural conditions, construction level, and cultivated land productivity. Then, eight indicators were selected by integrating multi-source remote sensing data to create a new CLQ evaluation system. We assessed the spatiotemporal patterns of CLQ in Guangzhou, China, from 2010 to 2018. In addition, we identified the main factors affecting the improvement of CLQ. The results showed that the CLQ continuously improved in Guangzhou from 2010 to 2018. The area of high-quality cultivated land increased by 13.7%, which was mainly distributed in the traditional agricultural areas in the northern and eastern regions of Guangzhou. The areas of medium- and low-quality cultivated land decreased by 8.1% and 5.6%, respectively, which were scattered throughout the whole study area. The soil fertility and high productivity capacity were the main obstacle factors that affected the improvement of CLQ. Simultaneously, the obstacle degree of stable productivity capacity gradually increased during the study period. Therefore, the targeted improvement measures could be put forward by applying biofertilizers, strengthening crop management and constructing well-facilitated farmland. The new CLQ evaluation system we proposed is particularly practical at the macro-regional scale, and the results provided targeted guidance for decision makers to improve CLQ and promote food security.

Adaptive Management of Cultivated Land Use Zoning Based on Land Types Classification: A Case Study of Henan Province

Cultivated land serves as an important resource to ensure national food security, and how to allocate cultivated land reasonably and sustainably is an urgent problem that needs to be solved at present. Therefore, identifying land cultivability from the basic attributes of land and carrying out adaptive management measures in different zones is an effective way. Taking Henan province as a case study area, we proposed a research scheme for the adaptive management of cultivated land use zoning based on land types. First, a three-level land types classification system at the provincial level was established from five aspects—climate, topography, geology, soil properties, and hydrological conditions—and then Henan was divided into 39 first-level units, 4358 second-level units, and 6446 third-level units. On this basis, the changes in the status of land use in Henan province from 2009 to 2018 were analyzed from the four aspects of cultivated land utilization, population, grain yield, and GDP. The amount of cultivated land decreased, while the economy grew, the population increased, and grain yield increased, indicating that it is urgent to pay attention to the problem of cultivated land, and it is necessary to identify the potential space of cultivated land and manage and protect it reasonably. Based on the land types, evaluation of cultivability was carried out, the results showed that the degree of cultivability from high to low presented a transitional spatial distribution state from the east and the south to the middle, the north, and the west. Then superimposing the status of land use, six types of protection and management zones were proposed, and management suggestions were adaptively analyzed. The ideas and methods proposed in this study can be adapted to manage and utilize cultivated land from the perspective of sustainable utilization, which is of great significance for ensuring food security.

Spatial heterogeneity of changes in cropland ecosystem water use efficiency and responses to drought in China

Understanding cropland ecosystem water use efficiency (eWUE) responses to drought is important for sustainable water resource management and food security. Today in China, the spatiotemporal patterns of eWUE and responses to drought across different cropland classes remain poorly quantified. In this study, we characterized the spatial temporal variability in cropland eWUE and response to drought in China from 1982 to 2017 using the satellite-retrieved evapotranspiration (ET), gross primary production (GPP), and self-calibrating Palmer Drought Severity Index (scPDSI), in conjunction with the Global Food Security-support Analysis Data product for Crop Dominance (GFSAD1KCD) data. Results indicated that (1) mean annual cropland eWUE had a spatial range from 0 to 9.94 g C kg-1 H2O, with higher values (2.06 g C kg-1 H2O) in class 4 (rainfed: wheat, rice, and soybeans dominant), whereas the lowest eWUE (1.58 g C kg-1 H2O) occurred in class 2 (irrigated mixed crop 1: wheat, rice, barley, and soybeans). (2) Annual eWUE, GPP, and ET values for croplands in China increased significantly between 1982 and 2017. Class 1 (irrigated wheat and rice) had the highest trend of 0.011 g C kg-1 H2O yr-1, and class 6 (rainfed: corn and soybeans) had the lowest of 0.0007 g C kg-1 H2O yr-1. Apart from class 4, annual GPP and ET were enhanced in most cropland classes from 1982 to 2017 (p<0.01). (3) Rainfed croplands generally had higher eWUE, GPP, and ET values than irrigated croplands. Except for rainfed cropland eWUE, all other cropland variables increased significantly (p<0.001) from 1982 to 2017. (4) Correlation analysis found that the 19.66% (15.62%) of cropland had significant negative (positive) correlations between eWUE and current-year scPDSI. The legacy effects of drought on cropland eWUE indicated that previous and current-year drought impacts on cropland eWUE were in the same direction. Our results provide insights into variability in cropland eWUE and its response to drought in China, where there is a growing demand for agricultural water resource management.

Assessing the Effectiveness for Achieving Policy Objectives of Land Consolidation in China: Evidence from Project Practices in Jiangsu Province from 2001 to 2017

Land consolidation (LC) is an important measure taken to increase the quantity and productivity of farmland while reducing land fragmentation and ensuring food security. However, long-term land consolidation project (LCP) practices are rarely analyzed to assess the effectiveness for achieving current policy objectives of LC in China. Taking the practices of LCPs in Jiangsu Province from 2001 to 2017 as a case study, we used the spatial self-related analysis, the consistency analysis, and the redundant analysis (RDA), and found that the construction scale and the investment amount of LC in Jiangsu Province displayed varying trends, and that the newly increased farmland rate is clearly divided into three stages and gradually decreases. The newly increased farmland area, the investment funds, and reserved land resources for farmlands are not spatially synchronized in Jiangsu Province. Only the positive relationship between the LC rate and the Normalized Difference Vegetation Index (NDVI) growth rate continue to rise. The earlier stage of land consolidation projects (LCPs)’s practices is mainly affected by natural and social factors, and the late stage is mainly affected by economic and strategic factors. Finally, a new implementation scheme framework of LC planning has been proposed. This framework provides reference for top-level design, planning, and management of LC policies at the national level in China and other developing countries.

Assessing the impact of land surface temperature on urban net primary productivity increment based on geographically weighted regression model

Urbanization had a huge impact on the regional ecosystem net primary productivity (NPP). Although the urban heat island (UHI) caused by urbanization has been found to have a certain promoting effect on urban vegetation NPP, the factors on the impact still are not identified. In this study, the impact of urbanization on NPP was divided into direct impact (NPP_dir) and indirect impact (NPP_ind), taking Kunming city as a case study area. Then, the spatial heterogeneity impact of land surface temperature (LST) on NPP_ind was analyzed based on the geographically weighted regression (GWR) model. The results indicated that NPP, LST, NPP_dir and NPP_ind in 2001, 2009 and 2018 had significant spatial autocorrelation in Kunming based on spatial analytical model. LST had a positive impact on NPP_ind in the central area of Kunming. The positively correlation areas of LST on NPP_ind increased by 4.56%, and the NPP_ind caused by the UHI effect increased by an average of 4.423 gC m^-2 from 2009 to 2018. GWR model can reveal significant spatial heterogeneity in the impacts of LST on NPP_ind. Overall, our findings indicated that LST has a certain role in promoting urban NPP.

The Impacts of Farmland Loss on Regional Food Self-Sufficiency in Yangtze River Delta Urban Agglomeration over Last Two Decades

Food security is essential for human survival and sustainable development. Due to rapid urbanization and industrialization, the farmland loss in Yangtze River Delta Urban Agglomeration (YRDUA) has threatened food security. Thus, this study intended to quantify the farmland loss and assess its impacts on food security in the YRDUA from 2000 to 2020 at three scales based on the Google Earth Engine platform. Our results show that the area of farmland in YRDUA is decreasing at a rather high speed in the past 20 years and the trend is getting worse. At the urban agglomeration scale, there was a farmland deficit of 0.44 million ha in 2000, followed by larger farmland deficits in 2010 and 2020. At the city scale, Shanghai had the largest scarcity of farmland. At the urban subgroup scale, Subgroup I in the west and Subgroup II in the north always maintained an oversupply of farmland, while Subgroup III in the east and Subgroup IV in the south faced serious food security problems. Our study suggests that farmland must be protected in YRDUA in order to ensure food self-sufficiency and promote regional sustainability.

Research on Identification of Multiple Cropping Index of Farmland and Regional Optimization Scheme in China Based on NDVI Data

The multiple cropping index of farmland is a significant characterization of land use intensity. Based on the NDVI data, this paper calculated the multiple cropping index of farmland in China using the S-G filtering method, and proposed an optimized regionalization scheme for the farmland use. The findings reveal that from 2000 to 2018, the multiple cropping index of farmland in China underwent the fluctuation of rising first, then falling and rising continuously, which was closely associated with the agricultural support policies enforced in China. Counties whose multiple cropping indexes decreased from 2009 to 2018 were mainly located in areas primarily producing grain, which exerted a greater influence on food security. The gap between the multiple cropping index and potential multiple cropping index of farmland is increasingly widening from north to south in China. Accordingly, four types of grain producing zones were delineated: key development zone, potential growth zone, appropriate development zone, and restricted development zone. Some suggestions, such as rotation, fallow, determination of yield by water and offsetting the quantity balance of farmland by increasing the multiple cropping index, are put forward based on different zones.

Cities are going uphill: Slope gradient analysis of urban expansion and its driving factors in China

Rapid urbanisation causes large urban conversions of natural and agricultural land to non-agricultural use. Research on urban expansion has typically disregarded gradient characteristics. The current study uses slope data calculated based on the Shuttle Radar Topography Mission Digital Elevation Model data set and multi-period land cover data derived from China's Multi-Period Land Use Land Cover Remote Sensing Monitoring data set to reveal the evolution of spatiotemporal patterns of vertical urban expansion in China from 1990 to 2015. A built-up land climbing index is specifically defined to measure the increasing use of land with slopes. A slope-climbing phenomenon has become increasingly apparent over time. Although built-up land with slopes below 5° accounts for over 85% of the total, this proportion has declined steadily from 89.53% in 1990 to 86.61% in 2015. The number of cities where built-up land was developed on high slopes (over 5°) increased from 150 to 238. Slope-climbing intensity spatially increased from north to south, and showed a "low-high-low" pattern from west to east. In addition, built-up land showed evident slope-climbing trend in areas with high variation in slope. Slope-climbing intensity was high for cities located in mountains and ethnic autonomous prefectures. Lastly, cities going uphill are subjected to the combined effects of natural environmental conditions and social factors. The average slope and population growth have significantly positive impact on slope-climbing intensity.

The Imprint of Built-Up Land Expansion on Cropland Distribution and Productivity in Shandong Province

Grain self-sufficiency is a national food security target of China. The way that built-up land expansion impacts upon cropland loss and food provision needs to be explored in the major grain producing areas. Shandong Province is an important agricultural food production region, which is also experiencing rapidly urbanizing. Here we assessed the spatiotemporal distribution of cropland loss due to built-up land expansion and landscape dynamics of cropland during 2000–2020, by using 30 m resolution land cover data. We also analyzed the potential yield change influenced by cropland loss. The results showed that the area of built-up land expanded by 5199 km2 from 2000–2010, and 11,949 km2 from 2010–2020. Approximately 95% of the new built-up land was from cropland during the two stages, and the primary mode of built-up land expansion was the edge expansion. The patch density and the patch size of cropland kept increasing and decreasing, respectively, and the aggregation index kept decreasing from 2000 to 2020, indicating increased cropland fragmentation. The proportion of occupied cropland with potential yield greater than 7500 kg/ha was 25% and 37% during the former and the latter period. Thus, higher quality cropland was encroached in the recent period. The findings could provide meaningful implications for making sustainable land use development strategies in the study area and other similar regions.

Spatial optimization of urban land and cropland based on land production capacity to balance cropland protection and ecological conservation

Cropland protection strategies have provided a strong contribution to limit cropland transformation worldwide. However, it negatively affects ecological land (e.g., forest, grassland, and wetland). Identifying a win-win approach for cropland protection and ecological conservation is important. Land use optimization plays a vital role in solving conflicts among land uses. Thus, in this research, taking China (mainland) as the study area, we optimized the spatial distribution of urban land and cropland to balance the requirement of cropland protection strategies and their negative effects on ecological land according to the spatial heterogeneity of land agricultural production capacity by using the LAND System Cellular Automata model for Potential Effects (LANDSCAPE). Specifically, we developed three optimization scenarios from compensational, occupancy, and occupancy and compensational sectors. We also developed one non-optimization scenario to remain comparable. Results show that compared with the non-optimization scenario, the reduced loss of ecological land in compensational, occupancy, and occupancy and compensational optimization scenario is 7180, 247, and 7277 km², respectively. Our research indicates that we should prioritize the quality of compensated cropland when developing cropland protection strategies and planning, considering the low efficiency of the occupancy optimization and the cost of policymaking and implementing.

High-Resolution Monitoring and Assessment of Evapotranspiration and Gross Primary Production Using Remote Sensing in a Typical Arid Region

Land surface evapotranspiration (ET) and gross primary productivity (GPP) are critical components in terrestrial ecosystems with water and carbon cycles. Large-scale, high-resolution, and accurately quantified ET and GPP values are important fundamental data for freshwater resource management and help in understanding terrestrial carbon and water cycles in an arid region. In this study, the revised surface energy balance system (SEBS) model and MOD17 GPP algorithm were used to estimate daily ET and GPP at 100 m resolution based on multi-source satellite remote sensing data to obtain surface biophysical parameters and meteorological forcing data as input variables for the model in the midstream oasis area of the Heihe River Basin (HRB) from 2010 to 2016. Then, we further calculated the ecosystem water-use efficiency (WUE). We validated the daily ET, GPP, and WUE from ground observations at a crop oasis station and conducted spatial intercomparisons of monthly and annual ET, GPP, and WUE at the irrigation district and cropland oasis scales. The site-level evaluation results show that ET and GPP had better performance than WUE at the daily time scale. Specifically, the deviations in the daily ET, GPP, and WUE data compared with ground observations were small, with a root mean square error (RMSE) and mean absolute percent error (MAPE) of 0.75 mm/day and 26.59%, 1.13 gC/m2 and 36.62%, and 0.50 gC/kgH2O and 39.83%, respectively. The regional annual ET, GPP, and WUE varied from 300 to 700 mm, 200 to 650 gC/m2, and 0.5 to 1.0 gC/kgH2O, respectively, over the entire irrigation oasis area. It was found that annual ET and GPP were greater than 550 mm and 500 gC/m2, and annual oasis cropland WUE had strong invariability and was maintained at approximately 0.85 gC/kgH2O. The spatial intercomparisons from 2010 to 2016 revealed that ET had similar spatial patterns to GPP due to tightly coupled carbon and water fluxes. However, the WUE spatiotemporal patterns were slightly different from both ET and GPP, particularly in the early and late growing seasons for the oasis area. Our results demonstrate that spatial full coverage and reasonably fine spatiotemporal variation and variability could significantly improve our understanding of water-saving irrigation strategies and oasis agricultural water management practices in the face of water shortage issues.

Spatial Evolution of Urban Expansion in the Beijing–Tianjin–Hebei Coordinated Development Region

Against the background of coordinated development of the Beijing–Tianjin–Hebei region (BTH), it is of great significance to quantitatively reveal spatiotemporal dynamics of urban expansion for optimizing the layout of urban land across regions. However, the urban expansion characteristics, types and trends, and spatial coevolution (including urban land, GDP, and population) have not been well investigated in the existing research studies. This study presents a new spatial measure that describes the difference of the main trend direction. In addition, we also introduce a new method to classify an urban expansion type based on other scholars. The results show the following: (1) The annual urban expansion area (UEA) in Beijing and Tianjin has been ahead of that in Hebei; the annual urban expansion rate (UER) gradually shifted from the highest in megacities to the highest in counties; the high–high clusters of the UEA presented an evolution from a “seesaw” pattern to a “dumbbell” pattern, while that of the UER moved first from Beijing to Tianjin and eventually to Hebei. (2) Double high speed for both UEA and UER was the main extension type; most cities presented a U-shaped trend. (3) Qinhuangdao has the largest difference between the main trend direction of spatial distribution of urban land, GDP and population; the spatial distribution of GDP is closer to that of urban land than population. (4) The area and proportion of land occupied by urban expansion varied greatly across districts/counties. BTH experienced dramatic urban expansion and has a profound impact on land use. These research results can provide a data basis and empirical reference for territorial spatial planning.

Spatiotemporal Dynamics of Net Primary Productivity in China’s Urban Lands during 1982–2015

The rapid urbanization process has threatened the ecological environment. Net primary productivity (NPP) can effectively indicate vegetation growth status in an urban area. In this paper, we evaluated the change in NPP in China and China’s urban lands and assessed the impact of temperature, precipitation, the sunshine duration, and vegetation loss due to urban expansion on NPP in China’s three fast-growing urban agglomerations and their buffer zones (~5–20 km). The results indicated that the NPP in China exhibited an increasing trend. In contrast, the NPP in China’s urban lands showed a decreasing trend. However, after 1997, China’s increasing trend in NPP slowed (from 9.59 Tg C/yr to 8.71 Tg C/yr), while the decreasing trend in NPP in China’s urban lands weakened. Moreover, we found that the NPP in the Beijing–Tianjin–Hebei urban agglomeration (BTHUA), the Yangtze River Delta urban agglomeration (YRDUA), and the Pearl River Delta urban agglomeration (PRDUA) showed a decreasing trend. The NPP in the BTHUA showed an increasing trend in the buffer zones, which was positively affected by temperature and sunshine duration. Additionally, nonsignificant vegetation loss could promote the increase of NPP. In the YRDUA, the increasing temperature was the main factor that promoted the increase of NPP. The effect of temperature on NPP could almost offset the inhibition of vegetation reduction on the increase of NPP as the buffer zone expanded. In PRDUA, sunshine duration and vegetation loss were the main factors decreasing NPP. Our results will support future urban NPP prediction and government policymaking.

Global cropland intensification surpassed expansion between 2000 and 2010: A spatio-temporal analysis based on GlobeLand30

Cropland expansion and intensification are the two main strategies for increasing food production. Here, we investigated the spatio-temporal patterns of global cropland expansion and intensification between 2000 and 2010 using the GlobeLand30 dataset. In doing so, we first analyzed the expansion and loss of global cropland at different spatial scales. Second, we quantified cropland intensification from the perspective of output and mapped its global spatial distribution. Third, nine coupled patterns of cropland expansion and intensification were identified, and the contributions of these two strategies to global crop production were finally estimated and compared. The results show that global cropland increased slightly (2.19%) during 2000-2010, with the American continent having the largest net increase (0.21 million km²) and Africa having the highest magnitude of increase (7.42%) as well as the most substantial spatial variation. Among the world's top ten countries with the largest cropland areas, China was the only country which experienced cropland decrease, while cropland in Brazil and Argentina increased the most. Moreover, we found that Brazil ranked first in cropland intensification, followed by China, India and Ukraine. More than one-third of countries' cropland had stable area and moderate intensification, suggesting that agricultural land systems did not cause significant environmental harm globally during this period. Ten countries (e.g., Brazil and Algeria) experienced significant cropland expansion as well as a high level of intensification, suggesting that they could be major contributors to global crop production as well as environmental change. Cropland expansion largely boosted crop production improvement in Asia, while cropland intensification was the dominant factor for crop production in Europe and America. Overall, cropland intensification contributed much more than expansion to improving global agricultural production during 2000 and 2010. Our results gain a comprehensive overview of spatio-temporal patterns of global cropland expansion and intensification, which can provide helpful insights for the international community and individual countries to better guide land use planning, adjust agricultural structure and coordinate food trade so as to achieve a sustainable development of agriculture.

Establishment of an integrated decision-making method for planning the ecological restoration of terrestrial ecosystems

Ecological restoration of terrestrial ecosystems facilitates environmental protection and enhances sustainable development of land resources. With increasingly severe land degradation, new and effective methods must be developed for the restoration of ecological functions. In this study, we developed a regional risk assessment approach to support the planning of ecological restoration of a terrestrial ecosystem located in the Daye area in central China. The study area was divided into six sub-regions where ecological risks were characterized by building a non-linear model to represent ecological interactions among the risk components there. Socio-economic conditions in the areas were evaluated and presented using an analytic hierarchy process. Assessment of different stakeholders there was conducted based on multiple-criteria decision analysis. Then, integrated assessment was performed using the technique of order preference for an ideal solution. We divided the degraded land in Daye into areas with different priorities for restoration or rectification and presented corresponding sequential time intervals for the action. The results are as follows: (i) the top priority rectification areas (totaling 358 km²) are mainly distributed in northeast and northwest regions; (ii) the high priority rectification areas are concentrated in the central region spanning 226 km²; (iii) the medium priority rectification areas comprised a large amount of arable and forest land spanning 605 km²; and (iv) the low priority rectification areas cover the rest part of the Daye area spanning 195 km². The assessment tool was proven to be useful in planning regional ecological restoration in terrestrial ecosystems.

Does Social Capital Help to Reduce Farmland Abandonment? Evidence from Big Survey Data in Rural China

At a time when COVID-19 is sweeping the world, farmland abandonment is obviously not conducive to solving food security problems. Since the formal institutions of local government in China have not been effective in the reduction of farmland abandonment, this study aims to explore whether informal institutions can help mitigate this problem. Based on big survey data from 8031 farmer households in 27 provinces in mainland China, this study uses an econometric model to investigate the quantitative impact of social capital on farmland abandonment, and to analyze the channels through which that impact manifests itself. The empirical results point to the following conclusions: (i) Social capital, as a key informal institution, can help reduce farmland abandonment. More specifically, after controlling for other variables, for every unit increase in social capital, the proportion of farmland abandonment can be predicted to drop by 7.17 percentage points. (ii) Both off-farm employment and farmland rent are channels for the impact of social capital on farmland abandonment. However, social capital’s effect on increasing farmland abandonment via the promotion of off-farm employment is small when compared with its effect on reducing farmland abandonment via the promotion of farmland rent. This study’s conclusions may help generate new ideas for reducing farmland abandonment. At the same time, the study may provide a sound, empirical basis for policies aimed at reducing the negative impact of COVID-19 on food security while also revitalizing rural areas.

Systemic Design for Food Self-Sufficiency in Urban Areas

This article adopts a systemic approach to address the problem of the operationalization of relationships between actors conducive to food self-sufficiency in urban areas. Through the use of Social Network Analysis (SNA), the literature on urban agriculture was analyzed, detecting eight key trends and topic areas. This information was used to design a generic recursive organizational structure with the identification of the key roles and functions for management and governance in the multi-level and multi-stakeholder relationships of a sustainable urban self-sufficient food production system, inspired by the principles of complexity management and organizational cybernetics. Methodologically, this is the first application that combines the exploratory capability of SNA and the recursive structure of the Viable System Model (VSM) to propose applicable organizational structures in any urban area, suggesting a new route for the study and application of systemic thinking in the development of urban agriculture schemes. However, due to the conceptual nature of this work, this study opens a discussion on how we can rethink interactions to seek continuous adaptation in food self-sufficiency, provide tools that foster inclusion, and adapt to every context to support the relevant actors and academics in urban agriculture.

Observed Vegetation Greening and Its Relationships with Cropland Changes and Climate in China

Chinese croplands have changed considerably over the past decades, but their impacts on the environment remain underexplored. Meanwhile, understanding the contributions of human activities to vegetation greenness has been attracting more attention but still needs to be improved. To address both issues, this study explored vegetation greening and its relationships with Chinese cropland changes and climate. Greenness trends were first identified from the normalized difference vegetation index and leaf area index from 1982–2015 using three trend detection algorithms. Boosted regression trees were then performed to explore underlying relationships between vegetation greening and cropland and climate predictors. The results showed the widespread greening in Chinese croplands but large discrepancies in greenness trends characterized by different metrics. Annual greenness trends in most Chinese croplands were more likely nonlinearly associated with climate compared with cropland changes, while cropland percentage only predominantly contributed to vegetation greening in the Sichuan Basin and its surrounding regions with leaf area index data and, in the Northeast China Plain, with vegetation index data. Results highlight both the differences in vegetation greenness using different indicators and further impacts on the nonlinear relationships with cropland and climate, which have been largely ignored in previous studies.

Recording Urban Land Dynamic and Its Effects during 2000–2019 at 15-m Resolution by Cloud Computing with Landsat Series

Cities, the core of the global climate change and economic development, are high impact land cover land use change (LCLUC) hotspots. Comprehensive records of land cover land use dynamics in urban regions are essential for strategic climate change adaption and mitigation and sustainable urban development. This study aims to develop a Google Earth Engine (GEE) application for high-resolution (15-m) urban LCLUC mapping with a novel classification scheme using pan-sharpened Landsat images. With this approach, we quantified the annual LCLUC in Changchun, China, from 2000 to 2019, and detected the abrupt changes (turning points of LCLUC). Ancillary data on social-economic status were used to provide insights on potential drivers of LCLUC by examining their correlation with change rate. We also examined the impacts of LCLUC on environment, specifically air pollution. Using this approach, we can classify annual LCLUC in Changchun with high accuracy (all above 0.91). The change detection based on the high-resolution wall-to-wall maps show intensive urban expansion with the compromise of cropland from 2000 to 2019. We also found the growth of green space in urban regions as the result of green space development and management in recent years. The changing rate of different land types were the largest in the early years of the observation period. Turning points of land types were primarily observed in 2009 and 2010. Further analysis showed that economic and industry development and population migration collectively drove the urban expansion in Changchun. Increasing built-up areas could slow wind velocity and air exchange, and ultimately led to the accumulation of PM2.5. Our implement of pan-sharpened Landsat images facilitates the wall-to-wall mapping of temporal land dynamics at high spatial resolution. The primary use of GEE for mapping urban land makes it replicable and transferable by other users. This approach is a first crucial step towards understanding the drivers of change and supporting better decision-making for sustainable urban development and climate change mitigation.

Impacts of cropland expansion on carbon storage: A case study in Hubei, China

When cropland expansion encroaches on ecological land (e.g., forest, grassland, wetland), it seriously affects carbon storage which plays an important role in global climate change. Taking Hubei as the study area, this study explored the effects of cropland expansion on carbon storage in both 2000-2010 and 2010-2030 in different scenarios by using the Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) model and the LAND System Cellular Automata model for Potential Effects (LANDSCAPE). The results showed that cropland expansion led to a massive loss of carbon storage (1.76 Tg C) during 2000-2010, which is expected to continue during 2010-2030 in different scenarios. The loss is predicted to be 3.70 Tg C in the Business-As-Usual scenario and be 0.88 Tg C in the Requisition-Compensation Balance of Cropland Policy scenario. Noticeably, the loss of carbon storage due to cropland expansion was 1.12 times more than that due to urban expansion during 2000-2010. For the period of 2010-2030, the loss of carbon storage caused by cropland expansion is predicted to be 3.89 times more than that caused by urban expansion in the Business-As-Usual scenario, while the losses caused by cropland expansion and urban expansion are predicted to be almost equal in the Requisition-Compensation Balance of Cropland Policy scenario. The main cause of carbon storage loss due to cropland expansion is that it leads to the considerable loss of forest and wetland. This study highlights the importance of considering the loss of carbon storage caused by cropland expansion when conducting cropland protection policies and land use planning.

Probing Influence Factors of Implementation Patterns for Sustainable Land Consolidation: Insights from Seventeen Years of Practice in Jiangsu Province, China

Land consolidation is a key measure in the implementation of agricultural sustainability and has a strategic importance in farmland fragmentation reduction and rural revitalization. In order to understand spatiotemporal patterns of land consolidation implementation and their influences at a large scale, a comprehensive evaluation of 1046 land consolidation projects was conducted in Jiangsu Province, China. The results of this study showed that the construction scale (CS) and investment amount (IA) rose in waves in Jiangsu province during the period 2001–2017, while the newly increased farmland rate (NIFR) continued to decline. Spatial patterns of land consolidation aggregated, whereas the scale and the kernel density of the newly increased farmland area (NIFA) was differentiated in different time periods. In addition, the regional differentiation was significant. The gravity center of CS, IA, and NIFA moved with an overall trend from South Jiangsu to North Jiangsu, and finally stopped at the Li-Xia River plain area in North Jiangsu. The key factors that promoted land consolidation included natural farmland quality and the proportion of the primary industry production in GDP. The potential of NIFA, the farmland production amount, and the income of the financial transferring payment were also important factors. Spatial patterns were initially influenced by natural conditions and were later influenced more significantly by economic and policy conditions. In the future, differentiated land consolidation policy oriented by public involvement should be formulated to improve new frameworks of system implementation, as well as to provide evidence for spatial configuration, district cooperation, policy adjustment, and the systematic improvement of sustainable land consolidation.

Spatial Analysis of Socio-Economic Driving Factors of Food Expenditure Variation between Provinces in Indonesia

Food security has become one of the global challenges; therefore, monitoring food consumption is required. As food consumption is a resultant of food availability at an affordable price, food expenditure actually is a key indicator to assess food security policy. Particularly, the link of food expenditure with socio-economic factors based on the perspective of spatial connectivity should be understood as nowadays food supply and demand between regions are increasingly connected. This study aims to define socio-economic driving factors of food expenditure that considering spatial connectivity between provinces in Indonesia. Data of household food expenditure and socio-economic factors by province including urbanization level, economic growth, gross domestic regional product (GDRP) per capita, poverty severity index, and unemployment rate were used. The preliminary test on the spatial correlation of food expenditure showed a significant result; thus, a spatial regression approach was employed. The results showed that declining food expenditure did not simply indicate increasing prosperity. Larger income disparity among the poor has become crucial to detect lower food expenditure caused by a lack of income. In addition, the increasing unemployment rate was followed by increasing food expenditure. Despite economic growth, increasing GDRP per capita and urbanization contributing to declining food expenditure, both poverty and unemployment are the main issues that threaten household’s ability to afford food. Furthermore, the effect of food expenditure in the neighboring region is also significant, but it shows a contradictory relationship as food expenditure in a region is decreasing when food expenditure in its neighbors is increasing, and vice versa. Therefore, reducing disparities in economic growth, GDRP per capita, urbanization, poverty, and unemployment rate between provinces is also crucial to support more equal food expenditure as well as to achieve the second goal of SDG’s (Sustainable Development Goals) in improving food security.

Severe drought events inducing large decrease of net primary productivity in mainland China during 1982-2015

The analysis of the impact of drought events on terrestrial net primary productivity (NPP) is significant to understand the effects of droughts on regional/global carbon cycling. During the past three decades, terrestrial ecosystems in mainland China have been frequently impacted by drought events. However, quantitative analyses of the variation of NPP induced by droughts are still not enough. Therefore, this study explored the response of NPP to drought events from 1982 to 2015 based on the standardized evapotranspiration deficit index (SEDI) and an NPP dataset obtained from the Carnegie-Ames-Stanford Approach model. We first identified drought events and analyzed the characteristics of drought events using a three-dimensional clustering algorithm. Subsequently, we determined the NPP variations in the drought-affected areas during the droughts and explored the correlation between the NPP variation and the drought characteristics. The results showed that 152 persistent drought events lasting at least 3 months were identified. Most events had durations between 3 and 5 months, and 19 events lasted >9 months. A negative NPP was detected in >60% of the drought-affected areas during long-term (>6 months) and severe (>4 × 10⁶ km² month) drought events and the total NPP showed a clear decrease during these events. In general, strong drought events reduced the total NPP by >30 TgC in the Northern Region, South Region, Southwest Region, and Northeast Region. The substantial decrease was mainly caused by the NPP anomaly from April to September. The NPP responses to drought events exhibited differences due to different drought characteristics. Although a high proportion of the drought-affected areas experienced a decrease in NPP during most short-term (<5 months) and less severe droughts (<2 × 10⁶ km² month), the total NPP did not exhibit a large change during these events.

Optimising land use allocation to balance ecosystem services and economic benefits - A case study in Wuhan, China

The optimisation of land use allocation plays an important role in sustainable land use planning. It is crucial to realise the synergy between economic development and ecosystem conservation by optimising land use allocation. In this study, we developed a method to optimise land use allocation to balance ecosystem services and economic benefits based on the spatial difference of both ecosystem services value (ESV) and land use efficiency, based on the LAND System Cellular Automata model for Potential Effect (LANDSCAPE). In the optimisation model, spatial difference of ESV was represented by the parameter of resistance, while spatial difference of land use efficiency was expressed as the parameter of asynchronous rate of transition. Subsequently, land use allocation was optimised based on spatial difference of resistances and asynchronous rates. Taking Wuhan as the study area, the proposed optimisation model was used to conduct the optimisation of land use allocation during 2010-2020. Results showed that: economic benefits would increase by 444.77 million US$, while losses of ESV would decrease by 142.55 million US$ by optimisation of land use allocation. This indicated that the optimal allocation of land use based on spatial difference of ESV and land use efficiency can increase economic benefits at lower cost of ESV. In conclusion, it is feasible to allocate land resources to balance ecosystem services and economic benefits based on the differences of ESV and land use efficiency. This study highlights that taking the spatial difference of both ESV and land use efficiency into consideration is helpful for a sustainable land use planning.