From the perspective of achieving sustainable development in the world and building a community with a shared future for humankind in the "Anthropocene", and considering the complexity of the Earth's surface system, various disasters facing humanity, and future challenges of resource shortages and environmental risks, we proposed the development of "geographical synergy"—the mechanism, process and dynamics of the Earth's surface system and regional sustainability—in order to realize the transformation of geographical research from the explanation of human-environment relationship to the design of human-environment synergy. We discussed the scientific and technological questions of modern geography from the perspectives of integrating natural and social units, natural resources and natural disasters, achievements and faults of humans, and coupling of dynamic and non-dynamic processes and systems. We proposed the metrics of "consilience degree" as a measure of the complexity of integrated disaster reduction system based on the understanding of disaster system and the mechanism, process and dynamics of hazard and disaster formation. Using the principles of synergetic tolerance, synergetic constraint, synergetic amplification and synergetic diversification, we proposed to build an integrated disaster risk governance consilience model under the leadership of governments and with enterprises as the main body and the full participation of communities, with multiple optimization objectives of social consent maximization, cost minimization, welfare maximization, and risk minimization. Finally, we elaborated on the synergy of human and nature through "changing nature appropriately", with a case study on the Dujiangyan irrigation system, which enabled the win-win pattern of disaster reduction and benefit making.

Since 2010, big data has played a significant role in various fields of science, engineering and society. The paper introduces the concepts of geographic big-data, the fourth paradigm and nonlinear complex geographic system, and discusses interactive relationships of these concepts. It is proposed that geographic big-data and the fourth paradigm would become a new opportunity to research on geography complexity. Then the paper discusses how to use the methods of geographic big-data and complexity science to examine geography complexity. For example, based on big-data, a series of indicators of statistical physics fields could be constructed to describe the complex nonlinear characteristics of the real geographic world. Deep learning, complex network and multi-agent methods can be used to model and simulate the complex nonlinear geographic systems. These methods are important for a better understanding of the complexity of geographic phenomena and processes, as well as the analysis, simulation, inversion and prediction of complex geographic systems. Finally, the paper highlights that the combination of geographic big-data and complexity science would be the mainstream scientific method of geography in the 21st century.

Neil Smith is among the most renowned academics in human geography and Marxist geography. Based upon uneven development theory, Smith has integrated both the categories in Marxist theory and those in geography such as seesaw movement of the capital, spatial integration and scale evolvement to propose an approach to the even development, which has enriched Marxist geography significantly. Smith mainly reckons geographical space as a means of production, a social product and an ensemble of spatial relations. Currently, there is still a lack of overall understanding of Smith's spatial Marxist theory, though introductions to parts of his theoretic tapestry have been made. The paper summarizes Smith's spatial Marxist theory and divides it into four aspects including space production, geographical scale, American imperialism and gentrification. Thus, the paper attempts to analyze the uneven development of geographical space, to interpret the complex interactive relations among society, space and geographical scales, to illustrate the logical connections of capital seesaw movement, American imperialistic expansion and gentrification, and to end with an analysis of seesaw movement of the capital in urban scale via rent gap theory. The paper aims to offer an outline of Marxist spatial theory and geography for domestic academia, as well as theoretical and methodological inspirations for urbanization transition and economic growth in China. Smith's spatial Marxist theory is under several criticisms, to which the paper has discovered justifications. Primarily, Smith focuses on socio-spatial problems under capitalist flexible accumulation regimes, hence the accusation of spatial-temporal limitations to the explanatory power. Besides, remarks on Smith's production determinism are due to the production primacy and the effort to include political and ideological processes via cultural production inspired by Frankfurt school. Additionally, to answer queries about geographical scale, its major difference from other geographical terms is its nature as a social product that translates social divisions into spatial differentiations. Finally, Smith focuses on mediation role regarding urban ground rent to spare controversies on rent categories; hence the comment of neglecting Marxist ground rent theories. Four conclusions and policy suggestions accordingly are as follows. Firstly, high housing price is a form of secondary deprivation of labor and a potential source of social conflict in reproduction process. Long-term effective housing regulation requires public housing provision and rental right improvement. Secondly, multivariate supply of land boosts rental housing construction and meets urban dwelling needs. It may also help lower commercial housing price due to a mitigation of land scarcity. Thirdly, precautions against accumulation by dispossession of real estate developers should be taken in mature urbanized societies. Lastly, rent gap index based on price to rent ratio forecasted by hedonic price model may help stabilize housing market.

Since the 20th century, geography came into being with distinctive disciplinary characteristics by sustained effort of geographers. This paper puts forward predicament from cognitive and thought in the new era, and depicts new geographic characteristics from five aspects: new technology, new orders, new data, new approaches and new driving factors. According to new content of geo-regionality and new approaches of geo-comprehensiveness, the paper proposes that complexity research would be a successful new path in geography, and the complexity would be the third characteristic of geography. Then, the paper details some complex spatial patterns, complex time processes and complex spatio-temporal mechanisms in geography research. Based on the concept of a geographic complex system, this paper presents core issues and corresponding complex research tools. Finally, the paper puts forward new challenges and new requirements for geography in the new era.

Construction of the Belt and Road, an advocacy of China to promote win-win international cooperation in the new era, aims at building green, healthy, intellectual and peaceful Silk Road and ensuring joint development with the people of the countries along the Belt and Road. Systematic analysis on environmental characteristics, evolutionary tendency and future risk pattern is a scientific fundamental of sustainable development for the construction. Based on remote sensing monitoring and statistical analysis, this paper studies spatial-temporal characteristics of climate, topography, soil, hydrology, vegetation cover and production of terrestrial ecosystems. Taking the methodology of the classical integrated natural regionalization, the region is delineated into 9 sub-regions: Central and Eastern Europe, Mongolia and Russia, Central and Western Asia, Southeastern Asia, Pakistan, Bangladesh-India-Myanmar, Eastern China, Northwestern China and Tibetan Plateau. By combining modeling simulation with scenario projections, natural disaster assessment methodology is used to assess the risk of abrupt extreme events such as heat waves, droughts and floods in the next 30 years. And trend-baseline comparison method is applied to assess the risk of gradual change events in macro-ecosystems, food production, etc. Results show that, on the basis of the regional framework, the western Eurasia would show a warming trend; both sides of Tibetan Plateau are in high temperature and heat waves risk; cold-wet region of central and eastern Europe in high drought risk; monsoon area of Bangladesh, India and Myanmar as well as eastern China in high risk of flooding; the desert margin areas in high ecological fragile risk; the middle and low latitude areas in high risk of grain production.