The surface urban heat island effect (SUHI) that occurs during rapid urbanization increases the health risks associated with high temperatures. Urban ecological land (UEL) has been shown to play an important role in improving urban heat stress, however, the impact of UEL interactions with the natural-anthropogenic environment on SUHI at the urban agglomeration-scale is less explored. In this study, the Google Earth Engine and GeoDetector were applied to characterize the spatiotemporal patterns of UEL and SUHI in the Guangdong-Hong Kong-Macao Greater Bay Area from 2000 to 2020 by extracting major built-up urban areas and quantifying the impacts of UEL and its interactions with the natural-anthropogenic factors on SUHI. The results show that the evolution of the UEL landscape structure exhibits clear spatiotemporal coupling with SUHI. Specifically, the UEL underwent a dispersion and degradation process in 2000-2015 and a convergence and restoration process in 2015-2020, the SUHI correspondingly transitioned from intensification and continuity to mitigation and contraction. The UEL landscape structure showed a notable impact on the SUHI reduction, and the dominance and richness of the patches explained an average of 19.95% and 16.03% of the SUHI, respectively. Moreover, the interaction between UEL and land urbanization rate and anthropogenic heat release had a dominant effect on SUHI, but this effect significantly declined from 2015 to 2020. With the implementation of ecological restoration projects, the interaction of UEL with topography rapidly increased and the SUHI gradually dominated by the joint interaction of UEL and natural-anthropogenic factors. A synthesis of the varying effects of several factors showed that the dynamic relationship between the development stages of the urban agglomeration's regional system and SUHI may conform to the Environmental Kuznets Curve. SUHI reduction strategies should therefore comprehensively optimize the rational allocation of UEL landscape structures and natural-human elements to promote the well-being of residents.

Administrative division is an important means of political power reorganization and management, resource integration and optimal allocation, which profoundly shapes the spatial layout of urban development in China. To clarify and compare differences between counties, county-level cities and municipal districts is the primary premise for the study of administrative division and urban development. This paper analyzes the institutional differences between counties and county-level cities, as well as counties, county-level cities and municipal districts, from the aspects of organizational structure, urban construction planning, land management, finance, taxation and public services. The research shows that the establishment of counties, county-level cities and municipal districts adapt to different levels and stages of economic and social development,and the conversion from county to county-level city and the conversion from county (or county-level city) to municipal district are both important transformation ways to change their administrative systems, which has different management system and operation pattern. At the same time, the transformation of county-level administrative region is also a “double-edged sword”, we should think about the administrative system as a whole to decide whether it should be adjusted, and effectively respond to the actual needs of local economic and social development.

An improved two-step floating catchment area method (I2SFCA) was developed to assess the spatial accessibility of ecological recreation spaces (ERSs) in the Pearl River Delta Region (PRDR), a mega-city region in the south of China. The results show that: (1) the modified 2SFCA model is more effective in evaluating the spatial accessibility of ERSs; (2) the accessibility of ERSs decreased generally from the marginal region to the core region, and the difference between the highest-value region and lowest-value region is quite great, suggesting a great unevenness of accessibility distribution of ERSs in the PRDR. The spatial structure optimization of PRDR should aim to provide adequate and fairly distributed ERSs to enhance residents’ quality of life.