Salinity-induced global pattern of atmospheric water constraints on mangrove photosynthetic activity revealed by time series Sentinel-2 data

• Global analysis reveals salinity regulates VPD constraints on mangrove photosynthesis. • Coupling Sentinel-2 red-edge with climate and salinity data quantifies mangrove responses. • Dry-climate and high-salinity mangroves are most vulnerable to future warming and drying. Atmospheric drought stress limits mangrove photosynthetic activity, and this constraint can be further amplified by high salinity, yet their combined global effects remain poorly understood. Here, we integrated multi-source Earth observation and geoinformation datasets, including Sentinel-2 red-edge position (a proxy for canopy photosynthetic activity), vapor pressure deficit from TerraClimate, seawater salinity from Copernicus reanalysis, to investigate how salinity regulates the sensitivity of mangrove photosynthesis to atmospheric drought stress during 2019–2023. Datasets were harmonized and analyzed through reproducible geoinformation workflows at 10 m–0.5° resolutions, enabling large-scale coupling analyses between remote sensing proxies and climate drivers. We found that drought stress constrained mangrove photosynthetic activity worldwide, with stronger limitations in tropical savannahs than in tropical rainforests. Marine mangroves exposed to persistent high salinity were more sensitive than estuarine mangroves influenced by freshwater inflow. These results reveal a global pattern in which salinity amplifies atmospheric water constraints on mangrove photosynthesis. Mangroves in dry climates and high-salinity habitats are therefore most vulnerable to future warming and drying. Our findings confirm that integrating multi-source satellite observations with geoinformation analysis provides an effective, large-scale approach for assessing vegetation vulnerability and identifying conservation priorities in climate-sensitive mangrove ecosystems.