Abstract
1. In the context of a declining population, falling birthrates, and an aging population, the phenomenon of “spongification” in cities that expanded during the period of rapid economic growth has become an issue, especially since the 2010s. “Urban spongification” refers to the phenomenon of a considerable amount of unused and underutilized space, such as vacant lots and houses, occurring within a city in small site units, characterized by randomness in terms of time and space. Moreover, it is sometimes described as the movement of small lacunae randomly opening up inside a city while the size of the city remains the same. The City Planning Act and Building Standards Act govern Japan’s current land use and building regulation systems, which were enacted during the period of urban growth. Furthermore, these systems are based solely on the premise that urban areas would expand in an uncontrolled manner if left to market and natural forces. Regulatory measures, such as block and district zoning, development permits, and building permits, were thus used to check this expansion. Given that the government’s focus has been on how to regulate the “excessive use” of land, it has been unable to respond adequately to the spongification of land caused by neglect. (View PDF for the rest of the abstract.)
