Exploring key characteristics of performance indicators for green infrastructure assessment

The growing importance of green infrastructures (GIs) is attributed to their multifaceted positive economic, societal, and environmental impacts. By utilizing performance indicators (PIs) and conducting thorough evaluations, stakeholders can maximize the positive outcomes of GI projects. PIs are crucial for measuring effectiveness, informing decision-making, ensuring accountability and transparency, and optimizing resource allocation. This study delves into the evaluation of 41 PIs recommended by commonly used GI assessment guidelines. It examines the availability of standards for interpreting assessed PI values and defines metrics such as the scope of application and measurability to assess the associated usefulness and resource requirements for each PI. By exploring interpretative standards, the study identifies a need for the development of well-established international standards for 23 PIs. Nevertheless, 18 out of 41 PIs are ready to be utilized for interpretative purposes and can be integrated into the current performance assessment guidelines. In addition, 85 % of the studied PIs exhibit an intermediate or broad scope of application, signifying their versatile applicability across various GI typologies and spatial scales. Moreover, although a measurability assessment reveals diverse associations between PIs considering their budgetary requirements, it highlights the moderate to substantial resources needed for the data collection of more than half of them (ranging from 51 % to 98 %), based on the approach used for calculating measurability. The study advocates for the integration of these critical elements into existing performance assessment local, regional, national and transnational guidelines. Accordingly, decision-making in GI asset management will be improved, and resource allocation will be optimized.