Identifying Biodiversity-Based Indicators for Regulating Ecosystem Services in Constructed Wetlands

Constructed wetlands (CWs) are nature-based solutions that integrate ecological processes for water purification, climate regulation, and biodiversity enhancement. However, biodiversity monitoring in CWs has often been underprioritized, limiting its recognition as a functional driver of ecosystem service performance. This study first developed the Biodiversity-based Ecosystem Service Index (BBESI), a hierarchical framework for evaluating biodiversity contributions to regulating services, and then systematically identified representative indicators from the literature to operationalize this framework. Following PRISMA 2020 guidelines, 39 studies spanning tropical, temperate, and arid climatic regions were reviewed across six ecosystem functions: pollutant removal, nutrient retention, biological uptake, carbon storage, greenhouse gas regulation, and microclimate control. Indicators were considered representative when they demonstrated clear functional relevance to CW ecosystem processes and were repeatedly supported across the reviewed studies. These included microbial diversity metrics, nutrient-cycling functional genes, plant–microbe functional complementarity, and vegetation structural attributes. Each indicator was mapped to the Essential Biodiversity Variables (EBV) framework, spanning Genetic Composition, Species Traits, Community Composition, Ecosystem Structure, and Ecosystem Function to provide a standardized basis for biodiversity assessment, using a rule-based assignment that prioritized the biological signal of each indicator rather than its functional category. Although all EBV classes were represented, this pattern reflects the available literature and is influenced by uneven reporting across microbial and plant indicators and across climatic regions, which limits broad generalization of indicator strength. The BBESI offers a transferable framework because its EBV-aligned structure and commonly measured indicators allow application across diverse CW designs and environmental contexts provided that multiple EBV co-signals are present rather than reliance on single-indicator measurements, with flexibility for future integration of various quantitative weighting approaches.