Composite indices for the comprehensive assessment of coastal wetlands: a global systematic review

Abstract Coastal wetlands are highly productive ecosystems and essential for human well-being, but severely threatened or impacted by anthropogenic pressure and climate change. In response to this condition, composite indices have been generated and applied as key tools for comprehensively assessing these systems, integrating biophysical, social, economic, and governance indicators. However, their use still presents a significant amount of methodological diversity, making it difficult and complicated to compare and standardize. This paper conducts an exhaustive systematic review of the scientific literature published worldwide in two decades to answer: What evidence exists on the use and construction of composite indices in the assessment of coastal wetlands? A total of 73 studies were selected from 2361 articles examined and retrieved from academic databases. The analyses focused on the conceptual frameworks used, the chosen indicators, the index construction methodologies, and spatial and temporal trends and knowledge gaps. The results show a sustained increase in the use of composite indices, especially in Asia and in mangrove ecosystems. We identified a total of 1288 unique indicators and 39 different conceptual frameworks, reflecting significant theoretical and methodological diversity. Biophysical indicators (n = 647) are overrepresented relative to Governance (n = 265), Social (n = 198), and Economic (n = 178) indicators. Furthermore, limited social participation in the assessment processes was detected. The conclusion is that a shift toward greater conceptual and methodological harmonization, incorporation of participatory approaches, and strengthening of the integration of social and governance dimensions is needed to improve the usefulness and legitimacy of composite indices in the sustainable management of coastal wetlands.