Urban green infrastructure: perspectives on life-cycle thinking for holistic assessments

This article discusses the application of life-cycle thinking (LCT) methods for holistic urban green infrastructure (UGI) assessments to inform and enhance urban sustainability decision-making. It draws upon scientific and grey literature to present the key concepts and emerging LCT methodology developments within the urban green infrastructure evaluation context. Key methodological challenges are identified and discussed: the issues of (i) defining "green infrastructure" and (ii)"urban" boundaries, achieving (iii) the full representation of the broad range of UGI benefits and impacts (iv) over its whole life cycle, as well as (v) accounting for the wide variety of UGI types, their combinations and (vi) inherently dynamic nature, (vii) high performance dependency on climatic and other local conditions, and also, the challenges related to (viii) the monetisation of costs and benefits for comprehensive economic evaluation as well as (ix) the issues of city-scale assessments. Further methodology development and data needs for the adaptation of LCT methods for urban green infrastructure assessments are outlined. Four guiding principles are proposed: alignment with global urban sustainability goals, integration of ecosystem services accounting, harmonisation with existing LCA and LCC standards, and co-creation. The article concludes that urban green infrastructure is a novel field of application of LCT methods and differs considerably from traditional uses due to a range of methodological challenges specific to the inherent characteristics of urban green infrastructure. These need to be addressed in order to close the knowledge gaps and better understand the holistic value and performance of urban green infrastructure to enable evidence-based decision-making.