With the intensification of the impact of human activities and climate change on land surface system, the vulnerability of natural and human elements and the complex nature-society-economy system has changed. Theories and methods of integrated research of physical geography have been developed (Liu, 2014; Liu et al., 2014). In terms of research objects, it develops from the integration of natural elements and processes to the integration of natural and human elements and processes, and extends to the research of earth critical zones through interdisciplinary research. In the comprehensive research paradigm, nonlinear coupled feedback methodology has gradually replaced one-way linear correlation methodology, and analytical tools and data sources are increasingly diverse. In terms of research direction, the study of natural region system has been developed from static characterization to dynamic evolution (Wu et al., 2015). The research of land system science has developed from structure and driving force to near and tele-coupling and service formation mechanism. Studies of typical regional surface processes have tended to pattern-process coupling. The human-environment coupling system has developed from conceptual framework to evolutionary mechanism.

Since the beginning of the 21st century, China’s integrated physical geography has maintained the international advanced level. (1) Terrestrial regional system study: Merging ecosystem and climate change concepts, the natural regionalization turned to “ecological”, major advances have been made in the study of eco-geographical regional systems, and schemes of ecological geographical regionalization and climate change risk regionalization have been completed (Fu et al., 2017; Wu et al., 2017a; 2017b). The research on building a beautiful China led by Chinese physical geographers directly serves the national demands. (2) Land use/cover change and landscape ecology: Patterns and processes are developing towards ecosystem services and their tradeoff decisions and optimal regulation, the researches including quantification, driving mechanism, models, effect, sustainable land use and land ecological security etc. (3) Typical regional study: The coupling research model of physical geography pattern, process and service represented by the Loess Plateau has been established. The model of ecological-hydrologic-economic system of Heihe River has formed an integrated river basin research paradigm of integrating observation, model and decision making. (4) Technologies and methodologies applied in the discipline: Modern techniques of observation and analysis of remote sensing, geographic information system, geographical database, modeling, big-data mining support that the text description of changes of geographical phenomenon and qualitative analysis get improvement into generalizing abstraction, conceptual model, mechanism, diagnosis, and the combination of qualitative and quantitative development, promoted the causal connection with the process coupling research and projecting future trends. On the whole, a comprehensive research mode of physical geography with Chinese characteristics has been formed (Fu et al., 2016), which provides important scientific supports for major national and regional strategic requirements and decision-making (Zheng et al., 2015).

To reveal the geographical dynamic process and presents the quantitative results, Prof. Bingwei Huang proposed in the 1950s in the introducing knowledge and new technology from mathematics, physics, chemistry, biology, and other disciplines into geographical researches (Yang et al., 2010). He also suggested the surface experiments; physical, chemical, and biological processes; and material migration regularity and energy conversion in the surface to be the main subjects for geographical studies. Based on this, the physical geography in China began to pay attention to the in-situ field experiment and set up field experimental stations, which promoted the important transformation of geography from a single regional work to a combination of points, sections and regions, as well as from a qualitative description to a combination of qualitative and quantitative (Yang et al., 2010). And gradually the physical geography formed a sub-disciplinary of experimental geography to reveal the spatial and temporal differences of the ecological environments by means of locating observation analysis and experimental test analysis. In 1988, Chinese Academy of Sciences established a Chinese Ecosystem Research Network (CERN), which systematically standardized the in-situ observation indexes, including biota, climate, and soil, through a unified technical process, specification and implementation to obtain uniform observation items and data. At the same time, the ecosystem structure and function, and ecosystem pattern and process were undertaken continuous tracking and comparison, exploring the optimization model of ecosystem management (Sun, 2006), and modern experimental simulation of human-environment interaction. At the beginning of the 21st century, on the basis of observation of CERN by the Chinese Academy of Sciences, the project of the national ecosystem observation research network station construction was launched, which covered the main ecosystem types and the key areas, and consists of 18 state farmland ecological stations, 17 state forest ecological stations, 9 state grassland and desert ecological stations, 7 state water body and wetland ecological stations. This continuous work, led by physical geographers and landscape ecologists, has promoted China’s ecological construction and agricultural production technology level, as well as regional industrial development (Yu et al., 2013).

Since the beginning of the 21st century, sectoral physical geography research in China has kept pace with the international in several frontier fields, and the research in some key areas has gradually taken the lead in the world. Climatology studies have taken opportunities of global change, expanded the extension of research from geographical perspective, and finally characterized by more and more interdisciplinary features. Geomorphology has made remarkable progress in geomorphic genesis, national geomorphic type regionalization, digital geomorphic information acquisition and so on. Hydrological research has gradually entered the front level in the research of surface hydrological process, developed regional representative runoff and evapotranspiration models in China (Xia et al., 2004; Zhang et al., 2019) and remote sensing precipitation data products (He et al., 2020), and developed integrated simulation models for surface hydrological process under global change (Tang et al., 2019). Soil geography research has established a soil systematic classification system, carried out digital soil mapping, and established a Chinese soil database. Biogeographic research has closely focused on the two themes of global change and biodiversity, carried out research on key regions and key taxonomic groups, and kept pace with the world. The research on deserts, lakes and wetlands, glaciers and permafrost (especially cryosphere) and eco-hydrology has closely focused on the demands of the state, based on the frontier of disciplines, and achieved an overall breakthrough.

Human living-environment geography, as a sub-discipline of geographic science, is a featured inter-discipline of physical geography, human geography, anthropology, archaeology and etc., specializing in the study of changes of natural environment in which human beings lived, and the human-environment interaction. It involves two core elements, humans and environments, studying the evolution of the spatio-temporal patterns of natural environment, and the interaction between the development of human society and the natural environment in the past.

China’s research on human living-environment geography is currently at the forefront of the world. For example, the methodological and theoretical development in the studies of the “westerlies-dominated climate regime” of Holocene climate change in the mid-latitude Asian inland arid regions (Chen et al., 2008; 2019a), the staged uplift and convergence of the Tibetan Plateau, the formation and evolution of extreme environments, the evolution of the arid environment pattern in Asia (Lu et al., 2018), the expansion and contraction of desert and sandy land and its environmental effects, are in advanced positions (Chen et al., 2019c; 2021). At present, the human environment pattern is changing rapidly, driven by the rising research of carbon cycle and human origin and evolution worldwide. The comprehensive and systematic research on the dynamics of carbon pools in soil, vegetation and oceans, reveals global carbon pool/sink capacity, and explores the relationship between the changes of atmospheric CO₂ and global temperature. High-precision dating technology and gene sequencing technology reveals the temporal and spatial pattern of the key elements in physical geography, and the adaptation and influence of human behaviors. The diversification of geological documents and proxies for climatic and environmental reconstruction enables quantitative research; with the application of numerical simulation and big data technology, it brings a broad and comprehensive view of human survival

At the turn of the century, the concept of Anthropocentric paleoecology was proposed internationally (Dincauze et al., 2000). During its development, the understanding of human-environment relationship has evolved from simple linear to human-centered paleoecological system, reflecting the development process from phenomenon description to mechanism research in this discipline. Accordingly, the research content has also expanded from the single environmental reconstruction at an archaeological site, to the study on the dynamic relationships between milestones of human society evolution, such as origins of humans, agriculture, civilization, anthropocene, and the ecosystems in which they belonged. Methods and theories including dating technology, remote sensing technology, animal and plant remain analysis, isotope analysis, big data integration have been introduced into this research field, rejuvenate the traditional discipline, and brings new growth points and opportunities. Since the 21st century, the application of molecular biology techniques such as ancient DNA, ancient environment (sediment) DNA and ancient proteins has promoted in-depth research on the population diffusion, human society development and the geospheres interactions. In recent years, with the application of new methods, new techniques and new theories, China has made great progress in the human living-environment geography, focusing on the prehistoric human-environment interactions. These new achievements has deepened the understanding of the domestication of Asian crops, millets and rice, origin of millet and rice agricultures (Yang et al., 2012; Zuo et al., 2017), discovered that the transcontinental agricultural diffusion promoted the large-scale permanent occupation of the high-altitude Tibetan Plateau in the late Holocene (Chen et al., 2015), discovered that the extinct Denisovans, an Archaic Homo sapiens, lived in the northeastern part of the Tibetan Plateau 160,000 years ago (Chen et al., 2019b), and may have continued to live in this area until 45,000 years ago (Zhang et al., 2020). With the constant publications of new results, it has become an important sub-discipline in physical geography, aiming at exploring the livability of human living-environment during different periods and areas, and serving the sustainability of human and human societies.

In integrated physical geography, aim at the multi-spatio-temporal scale variation characteristics, and interaction effects of key land surface elements, the driving mechanism of land surface elements and pattern will be revealed, the dynamic concept will be introduced into the land surface natural region system, the dynamic change law will be explored, and the future evolution trend will be projected. This sub-discipline will understand the subject development trend and regularity especially emphasize on the earth’s surface system of land surface system research as the key point. It will solve the key scientific issues, such as the relationship change between the key elements caused by the variation of the key elements of land surface, and their coupling and synergistic effects in the different scales (e.g. local, regional and global) and the typical areas (e.g. southwest of the Qinghai-Tibet Plateau and the Loess Plateau, mountain, urban and metropolitan area, estuarine coastal zone, in key river valleys), based on deepening the research on natural geography and social elements and process. Integrated physical geography research will form the research paradigm of China.

Climatology, geomorphology, hydrology, soil geography, biogeography and other sub-disciplines (Figure 1) will focus on major scientific issues such as climate change, desertification, soil erosion, attribution of hydrological change, temporal and spatial patterns and maintenance of biodiversity, and carry out fine description of and dynamic change of regional differentiations and key processes, multi-scale processes and mechanisms, and interaction between physical geographic elements from a global perspective. The research of deserts, lakes and wetlands, glaciers and permafrost (cryosphere) should deepen the fine mechanism research and expand to the coordinated development with related disciplines; at the same time, further focus on the quantitative research of service functions and disaster risk assessment and prevention for the demands of the states. In terms of regional research, based on the physical geographic features of Asian continent, the sectoral physical geography research will expand the research on individual physical geographic element in different regions of the world, and play a leading role in major scientific issues.

The study shall emphasize the reconstruction of the human living-environment and the human history in pivotal regions and crucial times, by developing geographical experimental technology and analytical methods at different spatio-temporal scales, improving dating techniques, discovering geological documents and proxies which can indicate shorter time scales (such as seasons, months, and days), inventing new methods for quantitative reconstruction of the paleoclimate, encouraging the application of biotechnologies in this field including biomarkers, ancient DNA, environmental (sediment) DNA and ancient proteins; developing quantitative and high-resolution reconstruction of human living-environment to explore mechanism and modes of the past human-environment interactions. developing big data simulation to integrate paleoclimate record data and model. Multi-proxy simulation of population, technology, economy, climate and environment on different ecosystems and different stages of social development shall be developed, to discuss the relationships between climate, resources and other environmental factors and the development of human societies, to predict future changes of climate patterns and human living-environment. The study of past human living-environment intends to break through the barriers between the fields of humanity and science, through time and across space, and to sustain the sustainability of human living-environment.

The priority development objectives are to deeply understand the mechanism of the interaction process of natural elements, to reveal the dynamic change law of the interaction process of natural elements, and to predict its future development trend through the study of the interaction mechanism of natural elements; based on the perspective of regional research, through the comprehensive research mode of “factor-process-pattern”, to improve the understanding of resources and environment in regional social and economic construction, and reduce the pressure on the environment; by accurately describing the process, driving mechanism and effect of land use/land cover change (LUCC), to construct a spatial dynamic prediction model based on pattern, process and effect to provide decision support for sustainable land use and spatial optimization; applying modern advanced technology, aiming at the future development scenario, and from the inner relationship between ecological environment and human well-being, to put forward scientific countermeasures to solve the obstacles to the sustainable development of social economy, so as to achieve effective regulation and management of natural resources and ecological environment.

Based on the important geographical elements in China, Asia and regions along the Belt and Road, the frontier issues such as the monsoon climate and westerly climate, the development of alpine permafrost and the great river development, as well as the dynamic changes of Asian water tower, the melting process of glaciers and permafrost in the High Asia and mountain regions under global warming, the changes of ecosystem in arid areas, and the hydrological processes of mountain oases, should be particularly focused on. At the same time, focusing on the major demands of the state in global change and ecological environment construction, carry out the fine description of the key processes of geographical elements through a variety of modern observation means, develop process-based models of different physical geographic element and their interactions, improve the prediction ability of the change trend of the earth system, and provide scientific and technological support for the sustainable social and economic development of countries and regions.

Preferentially, to study the extent, rate, rule and mechanism of changes in the past human environment patterns during the rise of Homo sapiens in Asia and the migrations of humans to East Asia, to explore the development of transcontinental exchanges and the civilization in East Asia, to clarify the spatial and temporal patterns and driving mechanisms of changes in climate, vegetation, lakes, dust storm, and land use in China since the beginning of Holocene, especially to pay attention to the new highlighted research field like Anthropocene to understand the history of human activities and their impact on human living-environment. By integrating the regional development models of natural and cultural processes in the past, it shall contribute to understanding the mechanism of human-environment interactions at different spatio-temporal scales, establishing the universal model of human-environment interactions, revealing and developing the scientific theory of the earth’s surface system, and providing the scientific basis for the sustainable development of human society.

Integrated physical geography will study on the interaction between natural elements and their effects on land surface pattern formation; the coupling of natural and human elements and their impacts on social economy; ecosystem services generated by the integration of nature, human and ecosystem; and regional integrated human-environment coupling system and sustainable development. Key directions in the future include: (1) the coupling mechanism and regional effect of key elements of land surface, exploring the multi-scale interaction of natural elements in land surface and the formation mechanism of land surface pattern; (2) risk formation mechanism and its comprehensive impact on social economy under changing environment, social and economic response mechanism of regional climate change, ecological services and social economy long-term effects caused by land surface pattern change; (3) the evolution mechanism of ecosystem services driven by LUCC and its resource and environmental effects, the coupling mechanism of LUCC and socio-economic system, and the resource and environmental effects brought by regional ecosystem service flows; (4) the safe operation space and optimal development pathway of human-environment coupling system in China, exploring the response of natural ecosystem and socio-economic system to the trade-off decisions and management measures of ecosystem services, and exploring the optimal development pathway of human-environment coupling system oriented by the Sustainable Development Goals of the United Nations; (5) in-situ observation system of natural environment, observing the interaction between the environment and human activities, in order to quantitatively support the in-depth understanding of the human-environment interaction.

Sectoral physical geography will give further extension of the advantages of pattern and process research. In the future, it will deeply explore the mechanism of earth surface pattern and process by integrating different physical geographic elements, so as to better serve regional sustainable development. The key directions in the future include: (1) Processes and regulations of the earth critical zone: describe and characterize the complex topographic process and the coupling relationship between underground and aboveground processes at different spatio-temporal scales, and study how the ecosystem services and their dynamics in different physical geographic regions are regulated by aboveground and aboveground processes; (2) Simulation of global change and earth surface process: carry out comprehensive observation from both space and ground, reveal the earth surface process change under the background of global change, develop earth surface process model, and realize the simulation and prediction of future environmental change and sustainable development in key regions concerning the demands of state; (3) Land-cover changes and its climate effects in typical areas caused by human activities, carry out research on the feedback and mechanism of the mutual-transformation between forests, grasslands, farmland and water bodies to the climate system, and evaluate the climate effect of major regional projects; (4) Multi-scale eco-hydrological process and water resource threshold of regional human activities, carry out research on the coupling and integration between eco-hydrological, biogeochemical and socio-economic models, and reveal the water resource threshold of regional economic and social development; (5) Vegetation-soil system process and restoration of degraded ecosystem, carry out research on the change of vegetation-soil system process in the process of ecosystem degradation and restoration, and understand the degradation mechanism of different ecosystems such as forest, grassland, lake and wetland; (6) Monitoring of surface processes and ecological and environmental effects of special surface units and spheres, carry out systematic measurement of wind erosion erodibility of different ground types in different regions, establish the relationship between erodibility and wind erosion factors, study the impact mechanism of human activities and climate change on the evolution of lake and wetland system, and quantitatively analyze the impact and action mechanism of cryosphere change from global and regional scales.

The core of geographic science is human-environment relationship. The modern human-environment relationship in every region succeeded from the evolution of the past. Tracing its evolution trajectory could benefits further research. The future research will focus on: (1) The evolution of environment patterns and early human dispersals in Asia, including studying the formation and changes of geomorphological and climatic patterns, the dispersal route of Homo erectus in the Old World, the history, evolution process, subsistence strategies of early humans in the Asian continent and their impacts on the ecological patterns. (2) The dispersal of Homo sapiens and environment changes in the Old World, including discussing the dispersal route and subsistence strategies of modern Homo sapiens in Asia, the westerly climate and Asian monsoon climate changes since the last glacial period, the vegetation pattern changes since the last glacial period, and the impact of severe climate fluctuations on the spread of Homo sapiens and subsistence strategies, the impact of modern Homo sapiens dispersal on continental-scale ecological patterns and regional flora and fauna, and the sedentism of Homo sapiens on the Tibetan Plateau. (3) The origins and spreads of agriculture and monsoon-westerly changes. This topic includes study on the origin and spread of millet and rice farming in East Asia, the impetus of early plant domestication and climate change, the evolution of the East Asian monsoon and the formation of prehistoric East Asian agricultural patterns, the cultural exchanges between East Asian crops and West Asian crops, early agriculture development on the Tibetan Plateau, population dispersals, monsoon-westerly interaction and natural landscape changes on the Tibetan Plateau. (4) Civilization evolution and environmental change, including studying the climatic background of social complexity in East Asia and the origin of civilization, the environmental background of the succession of human societies in prehistoric and historical periods, the history of the Silk Road on the Tibetan Plateau, quantitative reconstruction of paleoclimate and mechanism simulation, the changes of climate and vegetation under the influence of human activities. (5) Anthropocene research, including through the integrated research of geology, geography, atmospheric science, ecology, social science and other disciplines, studying the starting time of the Anthropocene, constructing the history of disturbance magnitude and relative changes of rate by natural forces and human forces, and pushing forward the development of earth system science and earth science.