Evaluating the benefits of urban green infrastructure: Methods, indicators, and gaps

Green infrastructure (GI) offers a promising solution for mitigating the adverse effects of climate change, but evaluating its effectiveness necessitates a comprehensive understanding of how that has been quantified in the literature. This study aims to review the methods (monitoring, remote sensing, and modelling) employed to assess the effectiveness of GI in urban areas for three ecosystem services: heat mitigation (cooling of air temperature), thermal comfort control, and air quality mitigation. The objectives include evaluating the suitability of these approaches across diverse scales, categorising the essential parameters, and identifying the strengths and limitations inherent in each method. Through a literature review, 126 research papers were selected for detailed analysis. Modelling was the dominant method for heat mitigation (45.6 %), thermal comfort (70 %), and air pollution (51.9 %). The main inputs for assessing these three ecosystem services by GI were: meteorological parameters used in monitoring or modelling, morphological parameters (describing vegetation, surface, and built-up area conditions), specified parameters depending on the evaluated benefit such as landscape metrics (for heat mitigation), personal factors (for thermal comfort), pollutant measures (for air pollution), and other parameters (e.g. building and traffic heat emissions). The application scale of each method was dependent on the instruments, satellite data, and simulation tools utilised. Monitoring methods were employed in studies ranging from street-scale to neighbourhood-scale, remote sensing methods covered city-scale to regional-scale assessments, and modelling studies spanned from street-scale to regional-scale analyses. These diverse methods used to assess the GI benefits each have individual strengths and limitations which need to match the context and objectives of the study.