Assessment of global wetlands using a conceptual framework of entropy and climate extremes

Abstract

Wetlands are highly sensitive ecosystems whose stability is strongly influenced by rainfall variability and extremes. While previous studies have examined wetland shrinkage and precipitation extremes separately, this study uniquely integrates entropy-based metrics, Standardized Variability Index using Apportionment Entropy (SVIAE) and Marginal Entropy (SVIME), with 12 Standardized extreme precipitation indices to assess hydroclimatic risk across 2,490 Ramsar wetlands worldwide. Using high-resolution precipitation datasets and CMIP6 climate projections, we analysed historical (1951 - 2024) and future (2025 - 2100) scenarios under SSP 245 and SSP 585 pathways. Results reveal a clear rise in monthly rainfall variability (SVIAE), especially under SSP 585, in areas including Africa, South Asia, and West Asia; in contrast, yearly variability (SVIME) remains stable, masking critical intra-annual instability. Extreme indices (e.g., R95pTOT, Rx5) show significant intensification under SSP 585, with more than 40% of wetlands falling into high-risk zones for unpredictability and rainfall intensity. Arid wetlands, despite low rainfall, face increasing flash-flood risks due to more intense and erratic rainfall events. These findings emphasize that increasing rainfall does not guarantee stability; rather, the combination of variability and extremes amplifies wetland vulnerability. This study provides a novel, integrated framework for identifying climate-sensitive wetlands and guiding adaptive conservation planning. Keywords: Ramsar wetlands, Entropy, Rainfall variability, Precipitation extremes, Climate projections.