Spatiotemporal patterns and influencing factors of urban ecological space availability in coastal cities of China during rapid urbanization

Urban ecological space (UES) is crucial to the sustainable development of cities and the improvement of human well-being. Rapid urbanization tends to lead to the fragmentation of urban ecological space and functional decline. China's coastal cities are developed regions with high urbanization levels and the unique geographical location makes them have two kinds of ecological spaces, namely marine ecological spaces (MES) and terrestrial ecological spaces (TES). During rapid urbanization, the spatiotemporal changes of the urban ecological space availability (UESA) and its driving factors in China's coastal cities are still unclear. For this, this work selected 53 coastal cities in China as the research samples and applied remote sensing monitoring data of land use to analyze the spatiotemporal patterns of the UESA under different travel modes (walking, public transport, and driving) from 1990 to 2015. Then, the spatial econometric model was applied to reveal the impact of urbanization on urban ecological space availability (UESA). The main research results show: (1) generally, the marine ecological spaces availability (MESA), terrestrial ecological spaces availability (TESA), and marine and terrestrial ecological spaces availability (MTESA) of the coastal cities in China showed an increasing trend from 1990 to 2015. With the increase in travel distance, the MESA, TESA, and MTESA in the coastal cities increased accordingly. (2) however, the spatial pattern of MESA in the coastal cities showed a significant heterogeneity, The hot spots of the MESA mostly appeared in coastal cities from Zhejiang to Fujian, and the cold spots were concentrated in the Liaoning, Hebei, and Shandong. (3) The TESA and MTESA in southern coastal cities were generally higher than that in northern coastal cities. (4) The expansion of the urban built-up area (UBUA) led to the improvement of the UESA in China's coastal cities. GDP and population density were positive factors affecting the TESA and MTESA. Our research can provide scientific planning basis for coordinating marine and terrestrial ecological space and optimizing territorial space planning, which is conducive to improving the life quality of residents and promoting sustainable urban development.