Objective Against the backdrop of global aging, numerous researches have demonstrated that urban green spaces have potentially positive benefits on both mental and physical wellness and human well-being. Small and medium-sized fragmented green spaces in high-density built-up areas are both an integral part of urban space and an essential component of age-friendly urban design, and are thus closely linked to the promotion of active aging from the perspective of design practice. As China’s aging process accelerates, age-friendly green spaces are progressively becoming a current concern with various challenges across policy, research and practice. This research aims to systematically review the development trends, focuses and methods of the research on age-friendly green spaces over the past 20 years from a global perspective, and to elucidate the multifaceted transformations in the development process of age-friendly green spaces. The main research contents include the following two aspects: 1) Clarification of the evolution of research hotspots and research methods in age-friendly green spaces across the globe; 2) review of the future research and practical directions of age-friendly green spaces in China under the demands of age-friendliness, and exploration of appropriate assessment and optimization methods for age-friendly green spaces in the current and future development stages.

Methods This research focuses on the research of age-friendly green spaces after 2000. With Web of Science, CNKI and Scopus as paper databases, the research retrieves 8,156 research papers spanning the period from 2000 to 2023 that meet the criteria. Integrating dimensions such as publication quantity, policy events, spatial orientation, driving factors, and measurement indicators, the research explores the trends and changes in the research on age-friendly green spaces over time. Additionally, based on systematic literature review, 134 key papers about research methods are screened out. Through a detailed review of research methods, the research investigates the development and application of emerging methods.

Results The research development journey can be divided into 3 stages: Exploratory stage, developmental stage and flourishing stage. Through the analysis of global research distribution and hotspot development, the research finds that the countries under research exhibit variations in terms of location and stage, in addition to a diversity of research interests. China maintains close scholarly ties with other countries throughout this process. Simultaneously, extensive academic research has been conducted by Chinese scholars on age-friendly green spaces, including researches on age-friendly spatial patterns, analysis of physical activities in parks, design and evaluation of age-friendly parks, and assessment of both physical and mental health. For research content, the hotspots can be divided into 8 categories based on analyses from spatial and population aspects: Pocket park, park-based moderate to vigorous physical activity, active travel, community garden, park usage, self-rated health, age-friendly community and residential satisfaction. The research further explores the changes in research hotspots over 3 developmental stages. Research in the exploratory period focuses on the development of age-friendly theories and policies, as well as the practical application of such theories and practices. In the developmental stage, researchers concentrate on diverse types of green spaces and the demands of the aging population regarding both physical and mental health. In the flourishing stage, research topics have become varied and in-depth, including context-specific review of the COVID-19 pandemic, mental health concerns, and analysis of socio-environmental impacts. Furthermore, the research classify the research methods into 3 categories according to the attributes of the research objects: Spatial features evaluation, population perception assessment, and mixed research assessment. Increasingly innovative methods are adopted in the research on age-friendly green spaces because of the diversification of research themes. On the spatial level, the research focuses gradually expand from individual micro-spatial elements to macro-spatial patterns, guiding the macro-planning and design of age-friendly green spaces. Regarding the population perception assessment, both the objectivity and scientificity of research have been steadily improving. The sources of research data have been transformed from early field observations and scale statistics to quantitative indicator statistics. A range of more scientific scales and data collection techniques have arisen for various evaluation aims. This facilitates the bottom-up design method, whereby planners and designers base their designs on people’s demands. Future research on age-friendly green spaces should make greater use of the hybrid research approach, which combines the assessment of crowd perception with the review of spatial attributes.

Conclusion In summary, it is necessary for the research and construction of age-friendly green spaces to develop in line with the times and policies. Small and medium-sized green spaces in built-up areas have become highly accessible and comfortable for the elderly, and their utilization has increased dramatically, especially in recent years due to travel restrictions brought on by the COVID-19 pandemic and the widespread embrace of aging-in-place concepts. This has also promoted researchers to explore age-friendly green spaces at both spatial and population levels. Moreover, the current manifold coexistence of research themes propels the continual integration of emerging research methods in the review of age-friendly green spaces. Looking ahead, the research and practice direction of age-friendly green spaces in China will be guided by the friendly whole-process design practice, the exploration of multiple covariates from a holistic perspective, the comprehensive and differentiated evaluation, and the technological leadership for emerging methods. These initiatives will also foster the application of assessment and optimization methods better suited for China.