Ecological homogenization and convergence in urban ecosystems: A global synthesis of biotic, abiotic, and ecosystem dimensions

Urban ecological homogenization and convergence describe the increasing similarity among cities in species composition and environmental conditions at both regional and global scales. Although widely used, these terms are inconsistently defined in the literature, contributing to mixed findings and limited clarity about their applications. This study addresses the issue by systematically reviewing 255 peer-reviewed publications, conducting a qualitative analysis of terminology usage, and applying a hierarchy-of-hypotheses framework to assess the support for urban ecological homogenization. The qualitative analysis of terminology use supports “ecological homogenization” as the most inclusive term, encompassing a broad scope of urban ecological patterns. Research on this topic has steadily grown from 1999 to 2024, yet geographic representation remains uneven, with regions such as Africa, Central Asia, and Southeast Asia underrepresented. To better understand the multifaceted nature of these concepts, this study categorized the literature into four dimensions: biotic, abiotic, ecosystem-level, and sociocultural. Within each, previous findings were synthesized across multiple spatial scales and habitat types. While 62 % of studies supported urban ecological homogenization or convergence, confirmation varied by scale and category, but not by terminology used. This synthesis identifies emerging research themes and offers recommendations for improving conceptual clarity and interdisciplinary integration. The findings provide a more holistic understanding of urban ecological change and inform urban planning and management, such as designing green spaces to preserve native biodiversity, mitigating soil and microclimate homogenization, and guiding infrastructure development to reduce ecological uniformity across cities.