Ecosystem service assessments across cascade levels: typology and an evidence map

The ecosystem service (ES) cascade framework describes the process by which benefits from ecosystems are delivered to human society. In the recent decade, there has been a growing body of studies on ES mapping and assessment at multiple cascade levels. However, the terms and concepts used for characterizing ES cascade components differ widely across studies. Herein we present an evidence map for these studies and aim to reveal their similarities and differences and guide future research. First, we propose a concise and operational version of the ES cascade framework with three key components – supply, flow, and demand – to clarify and standardize these components. Then, we categorize related studies into three categories: supply-demand (Category 1), supply-flow-demand (Category 2), and spatial ES flow (Category 3). These three categories can well represent research on this topic at different levels, with cascade levels ranging from supply-demand to supply-flow-demand, and with research scope ranging from a given region (Category 1–2) to interregional linkages (Category 3). After establishing these standardized categories, we conducted a literature search, screening, and an evidence mapping. In total, 131 studies were selected and fit into the three proposed research categories (Category 1: 68; Category 2: 28; Category 3: 35). Results showed a growing research interest in ES mapping and assessments over the past decade, as well as the heterogeneous distribution of publications across geographic regions. We demonstrated their similarities and differences in terms of studied ES, research methods for analyzing the relationships between ES components, spatial and temporal scales, and research purposes. The ES research categories proposed in this study provide a meaningful framework for retrospection and improvement in future research design. Such evidence mapping can also help researchers approach a more holistic view of the characteristics of different categories of studies and their respective potentials and challenges, particularly when considering management and policy decisions with different purposes and conditions.