Xiaoshu Cao’s research while affiliated with Shaanxi Normal University and other places

Since the Bonn 2011 conference, the “water-energy-food” (WEF) nexus has aroused global concern to promote sustainable development. The WEF nexus is a complex, dynamic, and open system containing interrelated and interdependent elements. However, the nexus studies have mainly focused on natural elements based on massive earth observation data. Human elements (e.g., society, economy, politics, culture) are described insufficiently, because traditional earth observation technologies cannot effectively perceive socioeconomic characteristics, especially human feelings, emotions, and experiences. Thus, it is difficult to simulate the complex WEF nexus. With the development of earth observation sensor technologies and human activity perception methods, geographical big data covering both human activities and natural elements offers a new opportunity for in-depth WEF nexus analysis. This study proposes a five-step framework by leveraging geographical big data mining to dig for the hidden value in the data of various natural and human elements. This framework can enable a thorough and comprehensive analysis of the WEF nexus. Some application examples of the framework, major challenges, and possible solutions are discussed. Geographical big data mining is a promising approach to enhance the analysis of the WEF nexus, strengthen the coordinated management of resources and sectors, and facilitate the progress toward sustainable development.

The joint landscape ecological risk as well as ecological corridors for ecological restoration area identification is of great significance to the past evolution and future development of landscapes. Ecological risks were assessed based on the landscape pattern and functional changes in Pengyang County in 2000, 2010, and 2020; ecological restoration areas were divided based on ecological risks and security pattern. Results showed that the ecological risk types in Pengyang County were mainly low risk from 2000 to 2010 and distributed in the central region, while the high-risk areas increased from 2010 to 2020 and were concentrated in the southern residential area. According to a comprehensive assessment of the landscape ecological risks, an ecological security pattern consisting of 17 ecological source points and 34 potential ecological corridors with an average length of 6.57 km was identified. Three ecological restoration areas were eventually identified: mining restoration areas, mountain restoration area, and urban restoration area. Our results would provide an important perspective for the sustainable development of regional natural landscape resources.

The vulnerability evolution of human settlements system on the micro-scale is a direct indicator of the local impact of global environmental change. Traditional agricultural areas are most vulnerable to climate and market changes. Due to the lack of historical statistics, micro-scale quantitative studies on the historical evolution of vulnerability are extremely scarce. From the perspective of the socio-ecological system, this study conducted field investigations along with quantitative assessment and an ethnographic approach to explore the vulnerability change of rural human settlements system since 1980 in Jia County, an agro-pastoral interlocking area. The study found that the vulnerability of natural, dwelling and social systems has continued to decrease, while human system vulnerability increased. At present, the RHSS is characterized by the poor quality of the river, a depressed rural population and a large gap between the rich and poor as weaknesses, and is characterized by sandstorm disaster reduction, more robust rural roads, adequate water for domestic use and high social security as strengths. Results revealed that ecological projects, increased precipitation, market changes, urbanization siphoning and farmer behaviors are key drivers to the vulnerability change since 1980. The study findings can be directly applied to rural revitalization strategies, vulnerability mitigation and adaptive management practices in China. In addition, the vulnerability evolution under multiple perturbations can provide guidance for settlement planning and construction in traditional agricultural areas among developing countries under global changes.

Linear cultural heritage—a heritage system spanning time and space—is a large-scale cultural settlement that accommodates various heritage types. Here, we comprehensively explored the Straight Road (Zhidao) of the Qin Dynasty in Shaanxi Province, China, as a gene of traditional cultural connotations and geographical features, and provided holistic conservation strategies and effective utilization paths. From an ecological security pattern perspective, 4399.89 km2 of ecological sources and 19 ecological nodes were identified based on the importance of four ecosystem services—carbon sequestration and oxygen release, water conservation, habitat maintenance, and soil retention. Then, 45 ecological corridors with a total length of 2938.49 km were determined using the minimum cumulative resistance model. The intersections of ecological corridors were distinguished and the key areas of cultural landscape construction were extracted by taking into account the spatial distribution of existing relics as well as the spatial network relationship of prohibited-development areas and existing gray corridors (roads), blue corridors (rivers), and green ecological corridors (shade zones, green belts, recreational greenways). A plan was proposed to construct 98.45 km2 of new parks (country parks: 28.38 km2, forest parks: 70.07 km2) and 101.26 km of new landscape corridors (urban type: 32.08 km, countryside type: 26.49 km, ecological type: 42.69 km). Multilevel landscape complexes should be built to form a functional and networked ecological–cultural spatial structure system. Findings of this study could provide ecological ideas for promoting the reservation and active utilization of linear cultural-heritage corridors on a regional scale.

Increasing human activities have greatly influenced the ecosystem and the use of ecological resources, and the unbalanced urban–rural development in China (urban and rural areas being two major bases of human activities) has always been accompanied by heterogeneous ecological effects. Human appropriation of net primary production (HANPP) is an integrated indicator quantifying the human domination of productivity and harvest in the biosphere. Identifying the unbalanced constraints of urban and rural development on HANPP has become necessary for improving human–land relationships. This study analyzed the spatial distribution and regional differentiations of the HANPP in China in 2015 and investigated how HANPP and its components responded to unbalanced regional urban–rural development. The results show that the total amount of HANPP was 2.68 PgC and gradually decreased from the southeast to the northwest of China in 2015, representing 60.33% of the NPPpot. In addition, HANPPluc, harvest through cropland, livestock grazing, and forestry contributed 60.70%, 29.86%, 8.53%, and 0.91%, respectively, to the total HANPP, with HANPPluc playing the dominant role in 21 provinces. There was a significant differentiation (p < 0.05) in the spatial distribution of HANPP (gC/m2), HANPPharv (gC/m2), and HANPPluc (gC/m2), especially between the Huanyong Hu Line and the western–eastern part of China, fundamentally resulting from uneven regional development. In addition, biomass production–consumption decoupling existed in most regions in China, 17 provinces were identified as consumption type, and a universal positive correlation (p < 0.05) was identified between the production–consumption ratio of occupied biomass and HANPPharv (%HANPP). Different drive mechanisms were found between urban–rural development and HANPP, and each HANPP index was more likely to be affected by urban economy (UE), rural population (RP), and rural agricultural technology (RA) in China. The higher regional average nighttime light intensity, the proportion of the built-up area, and the urban road area corresponded with a large HANPPluc value. Conversely, HANPP would decrease as the proportion of urban green spaces increased. Furthermore, HANPP (%NPPpot) and HANPP (gC/m2) mostly depended on the rural development index, while HANPPluc and HANPPharv were mainly controlled by urban and rural development, respectively. Our findings help understand, first, how unbalanced regional development influences human-induced biomass occupation, the comprehensive urban ecological construction, and rural ecological restoration and, second, that the overall planning of urban–rural integration development must be strengthened to face greater ecological pressures in the future.

Towns serve as the basic unit of implementation for comprehensive land consolidation and rehabilitation. The utilization of scaling law can provide a new perspective for construction land consolidation. From two perspectives of the town hierarchic system and the growth of a single town, this research applies the Rank-Size Rule and Allometric Scaling Law to analyze the scale structure, hierarchy and allometric scaling evolution relationship of population and construction land in the Loess Plateau at the town scale in 2000, 2010, and 2017. Furthermore, the consolidation potential of construction land is divided into five zones and puts forward recommendations for the comprehensive consolidation of the construction land. The results indicate: (1) The majority of towns have small or medium populations and 62% of the towns in the study show negative population growth. Geographically, the northern part has a smaller population size compared with the southern part. 96% of the towns show an increasing trend in the quantity of construction land, and the south and north parts of the study area have more construction land compared with the center part. The zone of the Valley Plain has the largest population size, and the zone of the Sandy and Desert Area has the largest quantity of construction land. (2) The rank-size distributions of both population and construction land comply with the power-law relation. The population hierarchy has changed from equilibrium to concentration, while the hierarchy of construction land shows an opposite pattern. So, the whole town hierarchic system of the Loess Plateau is gradually tending to the optimal distribution, which is the town hierarchic system gradually forming an ideal sequence structure. (3) The population-construction land relationship obeys the allometric scaling law, and the major allometric type is positive allometry. The human–land relationship tends to be coordinated, and the town system tends to be reasonable. The allometric scaling coefficient is not robust in different geographical areas, especially in Irrigated Agricultural Areas. Furthermore, 90% of the towns have weak coordination of human–land relationships, and 60% of the towns have a relatively faster growth rate of construction land than the relative growth (decline) rate of population. (4) The consolidation potential of construction land is divided into five types. High Consolidation Potential Area concentrates in the Eastern Loess Plateau, while Medium and Low Consolidation Potential Area concentrically distribute in the Western Loess Plateau. The Human–land Coordination Area has a small number and scattered spatial distribution. The land use of towns that are concentrated around prefecture-level cities or with unique resources is not intensive enough. The zoning of construction land consolidation potential based on the results of the allometric scale is in line with reality, and local governments should make use of the characteristics and trends of the town system to formulate planning schemes to promote the integrated development of urban and rural areas.

The multi-functional classification of landscape and the division of ecological development areas will provide an important reference for regional environmental development. Pengyang County in the multi-basin of the loess hilly region was taken as a research area. InVEST model, RUSLE model and landscape identification methods were used to estimate the crop production (CP), habitat quality (HQ), carbon sequestration (CS), water yield (WY) and soil conservation (SC) functions. Spearman’s rank correlation analysis was used to discuss the trade-off and synergy among multifunctionality. Geographically weighted regression models and principal component analysis were used to analyze the drivers of landscape functions. Integrated landscape spatial distribution, relationships, and spatial overlay were used for ecological zoning. Results showed that the CP function in the south of Pengyang County was significant, the CS function in the north was prominent, and the HQ function in the marginal areas was strong. The WY function in the south was higher than that in the north, and the SC function had the opposite trend. A synergistic relationship was found among CP and CS, WY, while HQ and WY, CS, CP were trade-off relationships. The DEM, slope, economic development and urbanization were the main factors that lead to differences in the distribution of landscape functions. Based on the number of landscape functions and the boundaries of administrative areas, Pengyang was divided into three ecological development zones, and the dominant functions of the three areas were HQ + SC, WY + CS, and WY + HQ, respectively.