The introduction of complexity science in urban geography has provided a new perspective to understand cities. Urban scaling law is one of the simple rules behind complex urban systems, which describes how urban indicators scale with urban population size within the system of cities. Social interaction-related urban indicators, such as GDP and innovation, super-linearly scale with urban population in a power law form, while infrastructure-related urban indicators, such as roads and gas stations, sub-linearly scale with population. Other urban indicators linearly scale with population, which are related to human individual needs, such as jobs and household electricity consumption. In this study, we first summarize the content and progress of urban scaling law during the past decade (2007-2020) from the following four aspects: the validation of urban scaling law, the explanation on the mechanism of urban scaling law, the application of urban scaling law, and the criticism of urban scaling law. We further compare the fundamental differences between the urban scaling law and urban allometric growth. Urban scaling law describes quantitative relationships between urban indicators and population size across cities, while urban allometric growth emphasizes the temporal growth of individual cities. Our analysis indicates that the cross-sectional urban scaling law cannot be applied to predict temporal trajectories of individual cities. Finally, we introduce the scale-adjusted metropolitan indicator (SAMI) for the evaluation of economic performance and urban land use efficiency in 291 Chinese cities, which is based on the theory of urban scaling law. The conventional evaluation of cities based on per capita indicators ignores the non-linear scaling relationship between urban indicators and population size. For example, the GDP per capita of large cities ranks high thanks to their advantages of population size. SAMI eliminates the influence of city size and can compare urban performance more objectively. Cities with higher SAMIs of GDP experience a higher efficiency in economic output (GDP) and they are concentrated in southeast coastal regions, middle reaches of the Yangtze River, and Xinjiang. On the contrary, cities in the northeastern China and Central China Plains experience a relatively low efficiency in economic output. Future studies are encouraged to focus on the mechanism of urban scaling law, the unified model for the evolving urban system across cities and over time, and the scaling law within cities.

High-quality development is the key measure to overcome the middle-income trap and join the advanced economy. With the deepening of reform and opening up, coastal areas have increasingly become the ballast of the economic growth, the center of national manufacturing, the frontier zone for building an innovative country, the pacesetter for constructing an open economy, and the demonstration window for green development. With typical characteristics of high-quality development, coastal areas will effectively drive the hinterland areas to the right track of high-quality development in order to form a strong support for the country's high-quality development, shaping a new pattern of coordinated regional development. According to the status quo and characteristics of high-quality development in coastal areas, this paper focuses on exploring outstanding problems of coastal areas as a whole and the northern, central and southern coastal areas in the process of high-quality development from five aspects of economic growth, industrial strength, innovation ability, opening up and green development. By analyzing realistic reasons for these problems, valuable references for the design of targeted high-quality development paths are designed. In the new era, coastal areas should grasp the historical opportunity of Beijing-Tianjin-Hebei coordinated development, Yangtze river delta integration, Guangdong-Hong Kong-Macao Greater Bay Area construction, follow to improve industry core competitiveness, mobilize the vitality of innovation, build high-standard open economy, deepen ecological conservation by combining strategies of industrial upgrading, independent innovation, opening up and ecological civilization. By the method of working in concert to promote high-quality development in the northern, central and southern coastal areas, the leading role of coastal areas can be consolidated.

The research perspective of land system science can provide a reference for the study of urban-rural integrated development promoted by land use transitions. Based on the review of the development of land system science, this paper discusses the theoretical framework concerning land use transitions affecting urban-rural integrated development guided by land system science, the influential ways and paths of land use transitions on urban-rural integrated development, and the measures of promoting urban-rural integrated development via adjusting and controlling land use transitions. Land system science is committed to monitoring land use change, explaining the driving forces and feedback mechanism, understanding the human-environment interactions occurring on land, and translating scientific findings on land system into solutions for sustainable land use. The operating of land system takes sustainable land use and human well-being as the criterions, and manifests as multi-dimensional effects of land use. Operating well the land system via scientifically adjusting and controlling land use transitions can affect the process of urban-rural integrated development. Land use transitions promote the integrated development of urban and rural areas under the effects of strengthening the whole and reinforcing weak links through four channels, i.e., efficiency improvement, value embodiment, development elements circulation and structure optimization. In order to promote the integrated development of urban and rural areas from the perspective of land system science, the adjustment and control of land use transitions need to reshape the land use rights system, to promote the integrated consolidation of territorial space, and to improve the management and control system of land use transitions.

The trajectory, pattern, and mechanism of the human-land co-evolution process is a critical issue in the field of human geography. The pattern of human-environment interaction has varied significantly during different phases of human evolution, suggesting a series of changes in the driving force of human-land co-evolution. Although a variety of underlying mechanisms specific to the key periods of human history (e.g., Paleolithic, Neolithic, Bronze, and historical ages) have been intensively investigated, there are still significant gaps in the widely accepted model of the fundamental law that governs human-land co-evolution across human history. In this paper we propose the Fulcrum Cognitive Model (FCM), with the objective of disentangling the mechanism of human-land co-evolution. The FCM focuses on the equilibrium between the natural ecosystem and human social system, which can be disturbed by both climatic/environmental change and human activities, and restored by an adjustment of the human social system. Moreover, we propose a "quantitative-change equilibrium pattern" and "qualitative-change equilibrium pattern" on the basis of FCM, to further describe the mechanism of past human-land co-evolution in different contexts. In the former pattern, a new equilibrium between the natural ecosystem and human social system is rebuilt by the corresponding changes in population size, without a shift in the fulcrum position. In contrast, in the latter pattern, societies improve their social resilience to the deterioration of the living environment through social and/or technological changes. In this case, the fulcrum position of the original equilibrium shifts and the pattern of human-environment interaction is transformed. Social resilience is gradually strengthened during the evolutionary process and the dominant influencing factor moves from natural causes towards anthropogenic factors. To test its feasibility, we applied the model to the changing patterns of the human-land relationship in Shanxi, Shaanxi, and Henan provinces in central north China between the Yangshao period (~5000-3000 BCE) and Zhou Dynasty (1046-256 BCE), based on a comprehensive analysis of updated archaeological and paleoclimatic data. The results suggested that the mechanism controlling the human-land relationship during ~4000-2600 BCE and 2600-256 BCE could be explained by the "quantitative-change equilibrium pattern" and "qualitative-change equilibrium pattern", respectively. The mechanism of human-land co-evolution in the past is very complicated and the interaction of these two patterns may vary in terms of its spatiotemporal scale, which will require further study in the future.

Understanding the changes of physical and human geographical environment during the past 2000 years in China is beneficial to establish the position, direction, focus areas, and initiatives of "Beautiful China" construction. In this paper, we integrated the results published in research papers, summarized the general characteristics of geographical environment changes in the history, and explored the implications of these changes on the construction of ecological civilization. The results implied that historical changes in China's land surface had been mainly manifested by the multi-scale quasi-periodic fluctuations and regional differentiation of climate, the fragmentation of the Loess Plateau, the expansion of desertified land in the northern regions, the gradual migration of delta coasts, the large scale shrinkage of lake systems especially in the Yellow River and the Yangtze River basins, and the decline in area of forests and the grasslands of northern China. Meanwhile, the economic and social changes were prominently reflected in the population growth and pattern changes, the migration of economic center to the southeast, the expansion of cultivated land to the periphery, and the transportation network evolution. From the above results, we could achieve the following enlightenments: in the future, the deserts in the northern region would still exist, and the lake systems in the middle and lower reaches of both the Yellow River and the Yangtze River were difficult to restore. The grain transportation from the south to the north disappeared in the history. But there was still much room for improvement in the coverage rate of forests, the transportation network could still achieve a higher level, and at the same time, we must mitigate the risk from climate change in the coastal cities.

Beautiful China Initiative (BCI) aims at sustainable development with blue sky and green land, lucid waters and lush mountains, prosperous society and rich people, and harmony between humans and nature. The BCI is a Chinese practice to implement the SDGs 2030 of the United Nations, and an important method to promote the harmonious development between humans and nature and to win the gold and silver mountains by maintaining clear waters and green mountains. Geography, an applied cross-discipline serving the country's socio-economic development, has comprehensive and regional characteristics. Geographers shoulder the historical mission of building a beautiful China, and are duty-bound to take the lead in becoming pioneers and practitioners of the BCI. The theory of pericoupling and telecoupling between humans and nature is the theoretical foundation of the BCI. The interdisciplinary and comprehensive integration of geography is the practical means for the BCI. The complex system simulation and optimization of geography provide a scientific tool for coupling ways between humans and nature of the BCI. The main coupling ways for geography to promote the BCI include: carry out major scientific and technological projects and coupling demonstrations; perform dynamic assessment and monitoring of the coupled human and natural systems for the BCI; draw up the strategic coupling roadmap and the action plan of the 14th Five-Year Plan (2021-2025) for the BCI; build a concept of beautiful land to comply with the objectives of the National Territorial Space Plan of China; develop a comprehensive regionalization of coupled human and natural systems in accordance with local conditions, and build a group of beautiful urban agglomerations and national parks; undertake pilot projects for the construction of Beautiful China and summarize the regional coupling models for the BCI. These coupling paths will ensure that the whole country and each of its provincial-level region are getting closer to the target according to the schedule and roadmap for building a beautiful China, and diverse regions will achieve the overall goals in the competition.

Agricultural and rural modernization is the general goal of the implementation of the rural revitalization strategy. The scientific formulation of the rural revitalization planning is related to the implementation effect of the national rural revitalization strategy. How to establish the basic theory of rural revitalization and develop the methods of rural revitalization planning have become important tasks of academic research and government decision-making. This paper constructed the theoretical model and method system of rural revitalization planning, tried to carry out the main function-oriented zoning, dominant type classification and principal purpose classification of rural regional system, and established the spatial system of rural revitalization planning and its optimal adjustment scheme. This system was applied to the overall rural revitalization planning in Yanchi County of Ningxia. By establishing the principle of rural revitalization planning that sticks to ecological priority, adaptation to local condition, industrial support and urban-rural integration, it put forward that the priority should be given to the development of rural professional cooperation organizations and the mixed economy of villages and towns, and the acceleration of the construction of advantageous industrial system characterized by the industrialization of tan-sheep, day lily, and minor cereals, and highlighted by the wisdom of eco-cultural tourism. Moreover, it was encouraged to give prominence to the position of the central town in space, and form the village organism and housing industry coordination body with the county seat and three key towns as the center of integrated industry development. The typical case study of Yanchi County has shown that the main contents and technical points of rural revitalization planning were embodied in the following four aspects: (1) determining the overall orientation of rural revitalization planning, and clarifying the phased development mode, key areas; (2) developing the county area based on the main function-oriented zoning, leading type classification and main purpose classification system, and exploring the territorial pattern and differentiation rules; (3) establishing the county development mode and industrial system, formulating coordination schemes of different main function-oriented zones, and revealing the spatial configuration and structural relationship of different dominant types; (4) exploring the local association and hierarchical system of each dominant type in its scale and level. The main task of implementing the rural revitalization planning is to promote the formation of a new pattern of urban-rural development with factors gathering, reasonable structure and orderly space in accordance with the objective requirements of "industrial prosperity, ecological livability, rural civilization, effective governance and prosperous life". China is facing great differences in rural development and many problems in transformation. Regional disparities and urban-rural differences determine the complexity, diversity and differences of rural governance and rural revitalization planning. China's rural transformation-urban and rural integration-rural revitalization-high quality development will become the major development logic and new normal in the future. The research on rural revitalization planning in the new era should focus on the overall situation of regional coordination and urban-rural integration, and solve the practical problems of "rural disease", so as to serve the national rural revitalization planning and scientific decision-making.