Improving urban ecological security pattern is an important measure to coordinate ecological protection and economic development and is of great significance for rational allocation of ecological resources and maximization of ecological effects. Taking Shenzhen City as the case study area, this study first identified the ecological function nodes, then the ecological function cost surface was generated according to the cost distance model and a shortest path network analysis was carried out. Finally, key patches and key ecological corridors were extracted. The results are as follows: (1) According to the calculated ecological resistance values of each landscape type, the resistance of forest is the smallest, and it is much smaller than the ecological resistance values of other landscape types. Therefore, forest is of great significance to the ecological security of the study area. (2) Ecological function cost gradient surface in Shenzhen City diverges around a key ecological function node, and the eastern region is lower than the western region. (3) The area and shape of the key patches are different, the large patches are mainly distributed in the eastern part, and the corresponding node levels are high. (4) Four key ecological corridors can be identified, and their locations are mostly within the basic ecological control line. But some parts of them do not fall within the basic ecological control line, therefore strict control is needed in these areas. (5) Core patches and key corridors are basically within the ecological control line, indicating that the ecological security of Shenzhen City is overall controllable. (6) Given that outer edges of some core patches and key corridors fall outside the ecological control line and are highly likely to withstand the risk of human interference, it is recommended that on the one hand, the scope of the ecological control line should be adjusted and the conflict parts should be included within the ecological control line. On the other hand, necessary supervision and protection should be carried out to prevent damage.

The Guangdong-Hong Kong-Macao Greater Bay Area with economic geographical advantages is deemed to be the growth point that captivated the world for its impetus to the global economy. This article focuses on the nine main cities of the Pearl River Delta, analyzing the mutual influences among industry-population-space during the rapid development process of this urban agglomeration by constructing a vector auto regressive model and impulse response function and variance decomposition analysis. The results show that: The absorption effect for population in the development of industry in the urban agglomeration of the Pearl River Delta faded in the late stage. The acceleration that industry benefitted from population aggregation weakened in the middle and late periods. The spatial expansion effects on population aggregation were limited and have become negative in the late period. It concludes that in general a short-term mutual promoting development mechanism between industry-population-space was formed, but a long-term mechanism is yet to be developed. In order to promote the development of the Greater Bay Area of Guangdong-Hong Kong-Macao, the urban agglomeration of the Pearl River Delta should attract highly-qualified workforce on the basis of industrial upgrading, plan spatial growth according to the population aggregation, and construct a multilevel synergistic industrial space with complementary products and services. With these measures, the overall aims are to strengthen the synergistic development among industry, population, and space and promote the development of the Greater Bay Area of Guangdong-Hong Kong-Macao.

Urban population data are the basic data in various social and economy fields, and high-resolution spatialized urban population data are of great importance for the research in such fields. In this article, multi-source remote sensing data were used to extract the urban impervious surface changes in the Guangdong-Hong Kong-Macao (GHM) Greater Bay Area at a spatial resolution of 30 meters from 2007 to 2015. The Dasymetric mapping method was used to spatialize the population at different times to a resolution of 30 meters. We finally estimated the gridded population density distribution of 30 meters resolution, and analyzed the spatiotemporal changes of the urban population in the GHM Greater Bay Area from 2007 to 2015. Validated with Google Earth time series high-resolution images, the accuracy of the derived urban impervious surfaces in GHM is generally above 80%. Using the county-level demographic data, the consistency between the estimated population and the statistical data in the GHM Greater Bay Area was analyzed, and the correlation coefficient (R²) was generally above 0.7. Finally, according to the spatial distribution of urban population and the change of population density, urban expansion and population increase patterns of different cities in the GHM Greater Bay Area were analyzed. The research shows that the urban population of the GHM has special spatiotemporal characteristics: (1) Stable population distribution is observed for Hong Kong and Macao, but other urban areas have experienced expansion of population to different extents and in different directions. The population expansion of Guangzhou, Shenzhen, and Dongguan is most obvious. (2) The spatial distribution of urban population in GHM shows multi-scale and multi-center characteristics. In general, the population of GHM is concentrated in the core area centered at the Pearl River Estuary. The Zhaoqing, Jiangmen, and Huizhou areas are sparsely populated. In the core area, the distribution of urban population shows the characteristics of multi-center distribution on both urban and metropolitan scales. Hong Kong and Guangzhou have multiple urban centers, while Hong Kong, Macao, Shenzhen, and Guangzhou are the centers of the GHM. These four centers can drive the overall development of the GHM Greater Bay Area.

The high-speed railways network provides rapid transit service for inter-city passenger movements. The integration between high-speed railways (HSR) station and urban (intra-city) public transport plays a vital role in regional formation. Based on the passengers' travel experience, this study developed a theoretical framework of passenger-centered integrated transport. Moreover, this framework was tested with results of observational surveys conducted at three important HSR stations along the Hong Kong-Shenzhen-Guangzhou HSR line. With regard to the proposal of fostering the Guangdong-Hong Kong-Macao Greater Bay Area, the findings underline the importance of fostering seamless intermodal integration in enabling the formation of the Greater Bay Area. The results show that the Hong Kong HSR station distinguishes itself by scoring high in the "lowest level integration of information" in a cosmopolitan setting. In terms of the "moderate level integration of facilities and services," both Hong Kong and Shenzhen HSR stations are well connected to nearby shopping malls to enhance the passenger experience. In terms of the "highest level of integration of ticketing and fares," Shenzhen and Guangzhou HSR stations have made better use of information and communication technologies in ticketing; yet, none of the three stations offer any fare integration. Based on the research findings, specific suggestions on improving intermodal transfers are put forward based on the three levels of the transport integration ladder.

The Guangdong-Hong Kong-Macao Greater Bay Area is one of the most urbanized city regions in the world. This study aimed to understand the development of the Guangdong-Hong Kong-Macao Greater Bay Area by applying the theoretical framework of mega-city region. We regarded the Guangdong-Hong Kong-Macao Greater Bay Area as a mega-city region and analyzed its spatial structure from four dimensions: intraregional boundaries, functional network, core area, and regional infrastructure integration. Four development trends were identified: (1) Boundary effect is reducing remarkably and border areas will grow rapidly inside the Greater Bay Area. (2) Industrial clusters become functional areas in a functional network, replacing cities to be the basic unit in global competition. (3) Two core areas can be identified, including the Guangzhou-Foshan core area and the Hong Kong-Shenzhen core area. (4) Rail transit station density tends to increase and a global transportation hub is emerging, which make it convenient for people in the Greater Bay Area to share transportation hub and public service facilities. In the end, the article presents a vision of spatial structure for the Guangdong-Hong Kong-Macao Greater Bay Area, concluding that this mega-city region will form a new structure of 'two cores and functional areas.'

The Guangdong-Hong Kong-Macao Greater Bay Area is a new geographical concept arising from the enhanced cooperation of the Pearl River Delta Economic Zone under China's Belt and Road Initiative. As a new global bay area, how to make a theoretical breakthrough in neoliberalism framework and explore the development pathway in line with the socialist market economic system is an important issue that policymakers and planners need to think about. Based on a systematic review of the existing theories in urban agglomeration, regional growth pole theory, the cluster theory in new economic geography, and the global production network theory, this article seeks for a theoretical framework and grounding for understanding the development issues in the Greater Bay Area. In line with the existing advantages of the Greater Bay Area, this article identifies the strategic positioning and development pathway for the area, and argues that creating a new development model of endogenous growth with indigenous innovation is the first development priority for the Greater Bay Area. That is, through deepening the cooperation between Guangdong, Hong Kong, and Macau under "one country, two systems, three tariff zone," the Greater Bay Area could first achieve the transformation and upgrading in advanced manufacturing industry and secure a strategic position as an important regional hub in the global production network. Second, the Greater Bay Area should also use its own strengths in education, scientific research, and international financial services to develop China's innovation hub and global financial center with strong property rights, compliance, and rule-based economic system.

Given the modern background of economic globalization, regional economic integration, new global economic development trends caused by modern technological reforms, the Belt and Road initiative, and the Guangdong-Hong Kong-Macao Greater Bay Area development strategy, there is a growing sense of urgency, necessity, and practical significance in achieving the joint development of the Guangdong-Hong Kong-Macao region. This requires an in-depth understanding and accurate grasp of the key scientific issues and important topics related to this task. This article argues that research related to the joint development of the Guangdong-Hong Kong-Macau region must be based on a regionally unified theoretical framework, "global-local" scale theory, and regional spatial interaction theory as its theoretical basis. In this regard, key scientific issues include the study of the theory of regional linkages of scale in Guangdong, Hong Kong, and Macau under the "One Country, Two Systems" framework, and the exploration of mechanisms, factors, models, and pathways governing linkages in the Guangdong-Hong Kong-Macau region. In so doing, this article proposes four important topics that can be considered with regard to the joint development of the Guangdong-Hong Kong-Macau region: (1) Research and exploration of unification/coordination theory in the Guangdong-Hong Kong-Macau region under the "One Country, Two Systems" framework; (2) Research related to the location and role of the Guangdong-Hong Kong-Macau region; (3) Research related to the multi-scale and multi-agent impact mechanisms and models for the linkages between Guangdong, Hong Kong, and Macau; (4) Research related to implementation pathways for the unified development of Guangdong, Hong Kong, and Macau.

Most recently, China has proposed the Belt and Road initiative in an effort to establish a form of multilateral trade cooperation mechanism. This initiative is meaningful for the construction of a healthy global economic structure and the breaking of US-initiated hegemony global economic structure. The notion of "Guangdong-Hong Kong-Macao Greater Bay Area" is a refresh regional concept developed exactly in such a context. In this sense, this notion is inevitably imbued with the meaning of political geography. This article therefore argues that studies related to the Guangdong-Hong Kong-Macao Greater Bay Area should not be limited to discussions within segregated practical disciplines, but considered on the macro-level, such as with the perspectives of political geography. In so doing, this article puts forward some suggestions from the lens of modern "vertical-horizontal" spatial management system, the integration of geo-cultures, and geo-economy. First, this article insists that the proposal of the concept of bay economy itself is a type of spatial management thoughts that stresses "upscaling." The development of the Guangdong-Hong Kong-Macao Greater Bay Area is under a rather complex and multi-scale space structure that should pay attention to the competitive and cooperative relations among different cities and regions. It is important to adjust the scale, in particular to the national scale to tackle problems faced in the process of integrating the development of the whole area. Second, this article argues that there is a potential for weakening the integration of various geo-cultures in the process of developing the Guangdong-Hong Kong-Macao Greater Bay Area. It is very important to discuss how to deal with the "identity crisis" between Hong Kong and the mainland of China, which, to a significant extent, provides stable social environment for the development of the Guangdong-Hong Kong-Macao Greater Bay Area. Third, this article argues that it is important to put the development of the Guangdong-Hong Kong-Macao Greater Bay Area into the framework of geo-economy, which underlines the importance of the requirement of the state power on economic development as well as the importance of economic development on power exercises. Finally, this article proposes an agenda to generate suggestions on the scientific development of the Guangdong-Hong Kong-Macao Greater Bay Area from multiple perspectives in other disciplines in the future.