Mainstreaming the framework of ecosystem services to enhance China's policy implementation for sponge city development

China introduced sponge city development (SCD) as a policy initiative to address the complex, interlinked water challenges, such as urban pluvial flooding and water pollution, faced by urban development under climatic change and rapid urbanization. The initiative relies on low-impact development (LID) techniques to integrate ecosystem conservation and urban development, with the aim to maintain or restore natural landscapes and their water regulating capacity as a way to mitigate urban flooding and associated pollution while augmenting water supply. While the country prepares for SCD demonstration and upscaling after pilot implementation since 2014, the initiative is subject to a design deficit in policy implementation that has received little consideration in both the literature and the policy arena but that negatively affects the effectiveness of SCD and its long run impact as intended by the policy. In this paper, we examine the design deficit by mapping and analyzing the policy implementation for SCD in the framework of theory of change (TOC). We present key conditions for individual components in SCD implementation to deliver causal pathways from program inputs to long-term impacts, with identified issues characterizing the design deficit. We provide an overview of the literature on SCD to shed some light on current research while identifying knowledge gaps. The paper proposes and justifies the framework of ecosystem services as an innovative design tool to deliver a systematic approach needed to address the design deficit, paving the pathways for SCD from inputs to impacts fully developing the policy potential for green urban transition with resilience and sustainability.