|Other Abstract||Globalization, informatization and marketization have promoted the rapid development of China's economy, and the spatial pattern of cities and towns has undergone tremendous changes. Unlike Western developed countries, China's urbanization process has accelerated since the reform and opening up, and the development of urbanization in developed countries has been completed in just a few decades. In the process of urbanization, problems such as mindless land expansion, land abuse and ecological environment destruction have occurred, which seriously hinder the high-quality development of urbanization. However, due to various factors such as location, resource endowment and policy inclination, the economic development of China's coastal zone is extremely unbalanced, and there are obvious differences in the level of urbanization and the scale of urban land. Therefore, there is an urgent need to clarify the pattern of urban land expansion in China's coastal areas to provide reference and basis for scientific urban development planning and optimization of urban development layout, so as to promote the sustainable development of China's coastal regions.
In order to comprehensively understand the spatiotemporal characteristics of urban land in China's coastal zone, this study carried out the following works: (1) Based on several Landsat 8 remote sensing images covering China's coastal zone in 2020, the visual interpretation method was used to update and supplement the land use dataset of China's coastal zone from 2000 to 2015 already established by the research group to obtain the land use data set covering China's coastal zone from 2000 to 2020; (2) analyzed the spatial and temporal evolution characteristics of land use in China's coastal areas in terms of spatial and temporal changes in land use and land use transfer characteristics, revealed the "weight" of urban expansion in regional land use change, and obtained the land use sources of new urban land in China's coastal areas; (3) Based on multi-temporal urban land data, the spatiotemporal characteristics of urban land in China’s coastal zone are analyzed in detail from various perspectives, such as area change, spatial distribution, growth rate, expansion type and scale distribution; (4) We select coastal provinces and cities, such as Liaodong Peninsula, Jiaodong Peninsula, Yangtze River Delta, Guangdong, Hong Kong and Macao Bay Area, Hainan and Taiwan, as typical regions and analyze the spatial and temporal evolution of urban land in typical regions; (5) We analyze and discuss the factors influencing the spatial and temporal evolution of coastal urban land and typical regions in China from various aspects, such as resource endowment, population and economic growth and policy guidance. The main conclusions are as follows. The main conclusions are as follows.
(1) During 2000 to 2020, human activities have been active along the coast of China, and the proportion of human made wetland, urban land, rural settlement, and isolated industrial-mining have all shown an obvious increasing trend; forest, coastal wetlands, grassland, inland freshwaters, coastal saltwater and unused have all decreased to different degrees. Farmland, forest and rural settlement are the main sources of new urban land, and the total net inflow of all three to urban land accounted for more than 75% of the total area of new urban land during different periods.
(2) During 2000 to 2020, the area of coastal urban land in China increased from 11,473.88 km2 in 2000 to 29,453.60 km2 in 2020, with a new urban of 17,979.72 km2. However, different stages show obvious differences: during 2000 to 2010, the extent of urban land continued to expand, with a small number of "satellite" towns appeared in some areas, and the degree of intensive land use increased; during 2010 to 2015, due to the international and domestic economic situation, the incentive for urban land expansion is insufficient, the area of new urban land is significantly reduced and type of urban expansion changed from edge extension to infill; during 2015 to 2020, China's economic situation improves and its international status is further improved, and the area of urban land expansion reaches 5319.39 km2.
(3) There are obvious differences in the spatial and temporal evolution of urban land use in several typical coastal areas. For example, at the typical zone level: The Liaodong and Jiaodong peninsulas form point-axis town clusters by relying on transportation networks; the Yangtze River Delta The Yangtze River Delta forms a spatial cluster of cities and towns with a single core (Shanghai), a main-sub-center (Shanghai-Suzhou) linkage, and a multi-center (Hangzhou, Ningbo) axial development; the Guangdong-Hong Kong-Macao Greater Bay Area forms a highly clustered city and town cluster with a belt-like expansion along the bay, a cluster gathering, and a multi-core union; the spatial distribution of urban land in Hainan and Taiwan is constrained by the geographic environment, and urban land in the plains with low terrain is clustered.
(4) The factors which impact the spatial pattern of urban land in China's coastal zone are mainly topography, transportation location, population and economic growth, and policy guidance. Plains, terraces and hills, as well as areas near transportation axes, are more suitable for the emergence and development of cities and towns; population and economic growth lead to a shortage of urban land, and urban land expansion promotes population and economic agglomeration. The central and local governments guide the flow of resources through development strategies and regional planning to accelerate industrial transfer and market co-location, thus influencing the spatial evolution of urban land. Due to the influence of geographical location and policy inclination, during 2000~2020, the scale of urban land in Shanghai ranked first in China's coastal zone; Tianjin's second place position is gradually replaced by Suzhou, and other cities such as Dongguan, Qingdao, Shenzhen and Ningbo show a "catching up" status, while coastal cities such as Liaoning, Guangxi and Hainan are behind other coastal cities on the whole.
(5) The growth rate of urban land in large cities is generally higher than that of small and medium-sized cities, but the growth rate of urban land in small and medium-sized cities may be higher than that of large cities due to factors such as development strategies and planning formulated by the central and local governments during the critical period of rapid urban development.|