Climate-connectivity-geography interactions govern the hydrologic vulnerability of geographically isolated wetlands

Geographically isolated wetlands (GIWs) are hydrologic keystones that sustain landscape water balance and ecosystem resilience, yet their persistence under intensifying climate variability remains poorly constrained. Here, we develop and test a Climate-Connectivity-Geography (C-K-G) diagnostic framework. For the first time, this framework conceptualizes and quantifies the interactive effects of climate forcing, groundwater connectivity, and geographic heterogeneity on GIW hydrologic vulnerability. We address this using a factorial ensemble of 936 high-resolution simulations (30 m grid, 30 min timestep; 1950-2099). These simulations couple six bias-corrected CMIP5 climate models, two groundwater-connectivity states, and geographic variation across three regions, 13 sites, and two landforms. Across scenarios, climate sets the magnitude of hydrologic vulnerability: median water levels under DryWarm decline to -157 cm-over 100 cm lower than WetCool. Connectivity increases median levels by 20-46 cm and dampens annual excursions, with the strongest buffering in structurally constrained settings. Geography organizes the spatial pattern and intensity of these responses. Synthesizing system behaviour, we delineate three reproducible regimes-connectivity-dependent, fluctuation-driven (annual ranges up to 175 cm), and self-stabilizing (rarely < -120 cm)-each representing a distinct hydrologic response mode to climatic forcing. The C-K-G framework provides a process-based, transferable foundation for diagnosing wetland persistence, quantifying resilience thresholds, and guiding hydrologically informed management under non-stationary climate.