Evolutionary overview of urban expansion based on bibliometric analysis in Web of Science from 1990 to 2019

Based on the Web of Science core collection database, this paper retrieves 1273 research papers on urban expansion published during the period of 1990-2019. Thematic evolutionary analysis, cluster analysis and SciMAT were used to identify the evolutionary path of urban expansion research. The results show that (1) in the past 20 years, the study of urban expansion has shown an upward trend. After 2013, it became a hot topic in academic research, and the number of documents increased sharply. (2) The themes of urban expansion research have mainly focuses on policy, landscape, land-use change, built-up environment and so on. Scholars from various fields have actively participated in the research, and the research results have been fruitful. (3) The interdisciplinary nature of the discipline determines that the research on urban expansion presents great differences in perspectives, scales, methods, and data. (4) The urban expansion field presents eight evolutionary paths in three research directions. The policy research and scale effect research of urban expansion represent the main thread of knowledge and will continue to be a research hotspot. The landscape ecology research of urban expansion has attracted much attention, and its research status has gradually increased, making it a research direction with the potential for development in this field. Moreover, there are regional differences in the thematic evolution paths between advanced and developing countries. Finally, the paper argues that scale issues, strengthening communication and integration within and between disciplines, introduction of new theories and methods, and model coupling will become the research directions that should be focused on in the future of urban expansion.