Assessment of interactions between influencing factors on city shrinkage based on geographical detector: A case study in Kitakyushu, Japan

Abstract

The phenomenon of urban shrinkage is a growing global issue. Although urban shrinkage in Japan was mostly contributed to the aging population and low fertility, a comprehensive understanding of the influence mechanisms of shrinking cities in Japan is still challenging. Thus, a case study in Kitakyushu, Japan, one of Japan's largest shrinking cities, was conducted for quantitative analysis of the characteristics of urban shrinkage. Moreover, a geographical detector method was applied to reveal the interactive correlation between the influencing factors on urban shrinkage. This study investigated the spatial patterns of urban shrinkage in a complex context and explored the individual and interactive influences of urban demographic and morphological factors. We found that the duration of residents, underage population ratio, and aging population ratio were mostly correlated with population changes. The interactions between urban demographic and morphological factors were manifested as bivariate enhanced or nonlinear enhanced, which informed different types of people may have preferences for the urban morphology in the process of relocation. The findings provide useful information for understanding urban shrinkage at the local scale and help urban planners and policy-makers develop effective sustainable urban planning forms.