Identifying urban rewilding opportunity spaces in a metropolis: Chongqing as an example

The worldwide urbanization has resulted in a massive loss of natural habitats, which is threatening biodiversity and socio-ecological sustainability. Urban rewilding is a strategy aiming to restore the complexity, autonomy and self-sustainability of urban ecosystems by interlinking ecological processes while minimizing or gradually reducing human disturbances. The benefits of urban rewilding are widely acknowledged; however, there remains a knowledge gap concerning the identification of suitable locations for urban rewilding and the methodologies for assessing the rewilding potential of urban areas. In this study, we proposed an approach that can be used to accurately identify urban rewilding opportunity spaces (UROS, the existing wildness areas and spaces offering ecological conditions conducive to the establishment of new urban wildness), by integrating data on spatial heterogeneity, biodiversity and human disturbance. UROS in Chongqing, China was evaluated and mapped at the city-wide scale, with a subsequent validation of the UROS results through an assessment of species richness of spontaneous herbaceous communities, which serve as the pioneer species in rewilding processes. The results revealed a positive correlation between high-scoring UROS and increased species richness of spontaneous herbs, thus confirming the feasibility of the UROS assessment method. Eleven primary types of UROS were identified, with the majority displaying scattered or linear distributions. Most very high-scoring UROS are characterized by expansive woodland expanses situated on the outskirts of high-density built-up areas and substantial water bodies within the built-up urban areas. Notably, nearly half of the UROS encompass areas of 900 m2 or less, underscoring the importance of urban rewilding initiatives targeting not only the preservation of extensive UROS with robust connectivity but also the revitalization of fragmented UROS with limited areas situated within central urban regions. The methodology is applicable to offer insights and spatial guidance in the execution of urban rewilding initiatives and biodiversity conservation efforts, contributing to sustainable regional development in the context of rapid urbanization.